Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Soybeans R4 crop stage, the stage of growth is known as end of pod elongation, the approximate days to maturity is 37, and the water use to maturity is 9.0 inches. For Soybeans R5 crop stage, the stage of growth is known as beginning of seed enlargement, the approximate days to maturity is 29, and the water use to maturity is 6.5 inches.  For Soybeans R6 crop stage, the stage of growth is known as end of seed elongation, the approximate days to maturity is 18, and the water use to maturity is 3.5 inches.  For Soybeans R6.5 crop stage, the stage of growth is known as leaves begin to yellow, the approximate days to maturity is 10, and the water use to maturity is 1.9 inches.  For Soybeans R7 crop stage, the stage of growth is known as beginning maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the approximate days to maturity for soybeans in the R4 crop stage, the stage of growth that is known as end of pod elongation?

Answer: 37

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: Applying nitrogen fertilizer or crop protection products through a center pivot is an efficient and effective method. In fact, it is a well-documented best management practice to apply nitrogen fertilizer as close to the time the corn will use it to get the most efficient use of the fertilizer. Most of the products are injected into the pivot with a fixed rate injection pump. So, how does one figure the pumping rate to set the pump at, and what about the change the end gun causes when it's turned on and off? We will discuss both challenges in this article.

Question: how are products like nitrogen fertilizer injected into the pivot?

Answer: with a fixed rate injection pump

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: 3) Center Pivot - The pivot will take a little more time to go through.  Start by checking each tower:  Check tire pressure and condition, check driveline knuckles for wear, drain water from gearboxes and top off with appropriate gear oil, visually inspect the tower box and the alignment system and then check operation.

Question: where should you start checking when ensuring your center pivot system is functional?

Answer: Start by checking each tower

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: Nebraska is a groundwater-rich state, thanks in part to the High Plains Aquifer. Many people are familiar with the High Plains Aquifer (also sometimes called the Ogallala aquifer), but fewer people know that there are other aquifers in the state. In fact, Nebraska has seven secondary aquifers, which are much smaller in areal extent than the High Plains Aquifer and generally have poorer water quality, but are nonetheless important in places where the High Plains Aquifer and shallow sand gravel deposits are absent.

Question: what types of aquifers are smaller in areal extent than the high plains aquifer and generally have worse water quality?

Answer: secondary aquifers

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Many irrigators apply more water than necessary toward the end of the irrigation season because the crop is using less water per day. The crop is getting more mature and the days are getting shorter and cooler. The average crop water use rate drops from around 2.1 inches per week at silking to only about 1.2 inches per week by the full dent stage. This 40% reduction requires irrigators to adjust their thinking about how much water needs to be applied each week.

Question: what is the average crop water use at silking?

Answer: 2.1 inches per week

Melvin, S. (2017). Predicting Late-Season Irrigation Needs. UNL Water. https://water.unl.edu/article/agricultural-irrigation/predicting-late-season-irrigation-needs


Context: When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.02, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.96. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.03, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.94. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.04, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.92. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.05, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.91. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.06, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.89. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.07, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.87. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.08, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.86. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.09, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.84. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.1, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.83. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.11, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.81. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.12, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.8. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.13, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.78. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.14, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.77. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.15, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.76. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.16, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.74. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.17, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.73. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.18, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.72. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.19, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.71. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.2, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.69.

Question: what is the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) when the ratio of the end gun throw (Rg) to the pivot length (R) is 0.14?

Answer: 0.77

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: These six categories were determined because the soil water level where deep percolation losses of water and nutrients slows to a low rate in a silt loam soil is about 70 cb; thus, it is recommended to keep at least one of the sensors in the second or third foot in this range or dryer. Yield losses would not be expected until all the sensors were approaching 140 cb, making the 70 cb level very achievable without any chance of causing yield loss. Field capacity in a silt loam is about 30 cb, so the goal is not to refill the soil above this level with irrigation in the second or third foot.

Question: how many categories were formed because the soil water level where deep percolation losses of water and nutrients slows to a low rate in a silt loam soil that is about 70 cb?

Answer: six

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Soil Sensor Install Tips: While other tasks may seem more pressing, early installation of sensors is critical to ensure their proper operation during the later critical growth phases. Early installation helps to minimize root damage, allows time for sensors to acclimate to read actual soil water conditions instead of water within the sensor or slurry, and gives a better chance for proper soil contact.

Question: what does the early installation of soil sensors give a better chance for with regard to soil contact?

Answer: gives a better chance for proper soil contact

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: The description of a zone or nozzle control VRI system is that the sprinklers are pulsed on and off and pivot speed may vary and that irrigation management zones may be any shape or size. Considerations for this VRI system are that has greatest flexibility in application, it is more expensive, and may require additional maintenance and management effort. Example uses include avoiding application on irregularly- shaped uncropped areas for water surfaces. It can also vary irrigation on irregularly- shaped management zones as needed to maximize yield and profits.

Question: what is a description of a zone or nozzle control VRI system?

Answer: the sprinklers are pulsed on and off and pivot speed may vary and that irrigation management zones may be any shape or size

Barker, J. B. (2017). Considerations in Adopting Variable Rate Irrigation for Center Pivots and Lateral Systems. http://extensionpublications.unl.edu/assets/pdf/ec2000.pdf


Question: what is the approximate water use to maturity for soybeans in the R6.5 crop stage, the stage of growth that is known as leaves begin to yellow?

Answer: 1.9 inches

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: The analysis focused on dividing the fields into one of six categories based on the soil water levels in the heart of the season (July and August) and on Sept. 15. The six categories were developed based on the readings from the Watermark sensors. The sensors generate data reported in centibars and have a range from 0 (wet) to 240 (dryer) centibars (cb). Centibar is a unit of measure that refers to the force required by the plant to pull the water out of the soil and into the plant. Typically, installations use a set of three sensors, with one sensor installed at six to 12 inches, one at 18-24 inches, and one at 30-36 inches.

Question: what is the data range for Watermark sensors?

Answer: 0 (wet) to 240 (dryer) centibars (cb)

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Other secondary aquifers in eastern Nebraska include the Niobrara aquifer (230 wells, mostly in Cedar County), the Codell aquifer (70 wells in Knox and Boyd counties), and the Western Interior Plains Aquifer System. Only one active well is currently installed in the Western Interior Plains Aquifer System in Nebraska, but the aquifer system was a historic source of water to the Omaha area, and still supplies huge volumes of water to Iowa and other states to our east.

Question: What is one aquifer in eastern Nebraska that mostly supplies Cedar County?

Answer: Niobrara aquifer

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: For winter wheat in the boot/heading crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 1.30 inches and the estimated water use during the week of June 19-25, 2023 is 1.50 inches. For winter wheat in the soft dough crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 1.18 inches.

Question: what is the estimated water usage for winter wheat during the boot/heading crop growth stage during the week of June 12-18 in 2023?

Answer: 1.30 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: Knowing approximately, how much plant available water is remaining in the active root zone is critical for calculating the last few irrigations and will be referred to as the "remaining available water." The best method for determining the amount of remaining soil water is to use a soil water monitoring system.

Question: what is critical for calculating the last few irrigations?

Answer: how much plant available water is remaining in the active root zone

Melvin, S. (2019). Scheduling the Last Irrigations in a Year with Delayed Crop Maturity | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2019/scheduling-last-irrigations


Context: For sugarbeets in the 10-30% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.17 inches and the estimated water use during the week of June 19-25, 2023 is 1.20 inches. For sugarbeets in the 30-50% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.25 inches. For sugarbeets in the 50-70% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.40 inches.

Question: what is the estimated water usage for sugarbeets in the 10%30% cover crop growth stage during June 19-25, 2023?

Answer: 1.20 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: A review of soil water data logs from farmers in the Upper Big Blue Natural Resources District indicates irrigators tend to overwater more in wetter years than dry ones. On very dry years like 2022, many farmers apply about the right amount of water. However, some still over irrigate, and some tend to under-irrigate.

Question: on very dry years like in 2022 do farmers typically apply the correct of water?

Answer: many farmers apply about the right amount of water

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Question: what is the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) when the ratio of the end gun throw (Rg) to the pivot length (R) is 0.13?

Answer: 0.78

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: Each time the user logs in and selects a field, the program will make a prediction regarding the need for irrigation (Figure 3), using up-to-date weather data for that field and other crop and soil information the user provided at field registration. When the user irrigates a field, the irrigation date and amount must be entered into the program so the next prediction will reflect the irrigation.

Question: what does CornSoyWater use to make irrigation need predictions?

Answer: using up-to-date weather data for that field and other crop and soil information the user provided at field registration

Yang, H. (2017). CornSoyWater: An Online App to Aid in Irrigation Management | UNL Water. https://water.unl.edu/article/agricultural-irrigation/cornsoywater-online-app-aid-irrigation-managemen


Context: The top foot will go above field capacity (30cb) after every irrigation or heavy rain. However, if the second foot gets above 30 cb, it would indicate that over-irrigation is occurring. The data in the chart indicated that the field was this dry on a given day and not how many days the soil was drier than 70 cb. The 70 cb level is equal to about 70% of plant available water (PAW) and stress should not start until below 50% of PAW during the summer and 40% in late August and September. Soil types such as those with high sand or clay content would require different levels other than 30 and 70 cb.

Question: what should plant stress not start below in the summer and in late August and September?

Answer: 50% of PAW during the summer and 40% in late August and September.

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Corn R2 crop stage, the stage of growth is known as blister, the approximate days to maturity is 45, and the water use to maturity is 10.5 inches. For Corn R4 crop stage, the stage of growth is known as dough, the approximate days to maturity is 34, and the water use to maturity is 7.5 inches. For Corn R4.7 crop stage, the stage of growth is known as beginning dent, the approximate days to maturity is 24, and the water use to maturity is 5.0 inches. For Corn R5 crop stage, the stage of growth is known as 1/4 milk line, the approximate days to maturity is 19, and the water use to maturity is 3.75 inches. For Corn R5 crop stage, the stage of growth is known as 1/2 milk line - full dent, the approximate days to maturity is 13, and the water use to maturity is 2.25 inches. For Corn R5 crop stage, the stage of growth is known as 13/4 milk line, the approximate days to maturity is 7, and the water use to maturity is 1.0 inches. For Corn R6 crop stage, the stage of growth is known as physiological maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the approximate days to maturity for corn in the R5 crop stage, the stage of growth that is known as 1/4 milk line?

Answer: 19

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Question: what is the approximate days to maturity for corn in the R5 crop stage, the stage of growth that is known as 13/4 milk line?

Answer: 7

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: 2023's Exceptional Drought Reviewing several soil water logs from central Nebraska, many fields were left a little drier than normal after 2022's harvest. Plus, with many areas of the state getting very little precipitation from October through May, many fields have needed some irrigation to get the crop established and growing well through the vegetative stage. It all depends on the amount of water stored in the soil.

Question: what resulted in many fields in Nebraska needing some irrigation to get the crops established and growing well through the vegetative stage?

Answer: many areas of the state getting very little precipitation from October through May,

Melvin, S., Power, C., Daigh, A., & Taghvaeian, S. (2023). Early Season Irrigation During Drought. UNL CropWatch. https://cropwatch.unl.edu/2023/early-season-irrigation-during-drought


Context: Table II. Total available water in top 4 feet if soil is at field capacity and minimum balances at physiological maturity. For fine sands, the available water in 1 foot of soil at 100% of available water is 1.0 in/ft, the available water in top 4 feet at 100% of available water is 4.0 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 1.6 in/ft. For loamy sands, the available water in 1 foot of soil at 100% of available water is 1.1 in/ft, the available water in top 4 feet at 100% of available water is 4.4 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 1.8 in/ft. For sandy loams, the available water in 1 foot of soil at 100% of available water is 1.4 in/ft, the available water in top 4 feet at 100% of available water is 5.6 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 2.2 in/ft.

Question: what is the amount of available water in units of (in/ft) for sandy loam soils at 100% of available water in 1ft of soil?

Answer: 1.4 in/ft

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Question: what is critical to ensure soil sensors proper operation during the later critical growth stages?

Answer: early installation of sensors

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Question: what is the estimated water usage for sugarbeets in the 30%-50% cover crop growth stage during June 12-18, 2023?

Answer: 0.25 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Question: How many wells are in the Codell aquifer?

Answer: 70

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: To learn more about the secondary aquifers of Nebraska, download the Conservation and Survey Division publication titled 'An Overview of Secondary Aquifers in Nebraska' available at http://digitalcommons.unl.edu/conservationsurvey/138. Questions regarding western Nebraska aquifers may be directed to xxxxx xxxxxx atxxxxxxxxxxxxx; questions regarding eastern Nebraska aquifers may be directed to xxxx xxxxxx atxxxxxxxxxxxxx.

Question: who can questions regarding western Nebraska's aquifers be directed to?

Answer: xxxxx xxxxxx

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: To identify possible issues developing with pressure regulators and/or sprinklers record and observe your system's flow rate and pressure over time, looking for changes. For further information on irrigation management, visit the Agricultural Irrigation section of Water.unl.edu.

Question: for more information on irrigation management where can an irrigator visit?

Answer: the Agricultural Irrigation section of Water.unl.edu

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: Chadron wells average about 350 feet deep, and the majority (64%) are used for domestic supply, but livestock and irrigation wells account for 15% and 12% of the wells, respectively. The biggest challenge to using the Chadron aquifer is poor water quality.

Question: what percentage of wells in the Chadron aquifer are used for irrigation?

Answer: 12%

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: To determine the actual cost, we would recommend the use of the IrrigateCost app. The app, which is available for both Apple and Android products, allows users to input their specific information such as acres irrigated, pumping lift, system PSI, pump and pivot life, and inches applied as well as related costs such as for the well and engine, labor, energy, district fees, and taxes. The app then calculates total irrigation cost as well as total ownership and total operating costs.  It also breaks down costs by irrigation well, pump, gear head, pump base, diesel engine and tank and system and calculates per acre annual cost and per acre-inch annual cost.

Question: what does the IrrigateCost app calculate using the specific information and related costs?

Answer: calculates total irrigation cost as well as total ownership and total operating costs

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: Calculating the amount of water needed from rain and irrigation for the crop to reach maturity becomes important after early August. The objective is to leave the field as dry as possible without lowering the yield.

Question: when does calculating the amount of water needed from rain and irrigation for the crop to reach maturity become important?

Answer: after early August.

Melvin, S. (2019). Scheduling the Last Irrigations in a Year with Delayed Crop Maturity | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2019/scheduling-last-irrigations


Context: The conclusion is that many irrigators could save money, water and nitrogen by using data from irrigation scheduling systems to make data-driven decisions to help them feel confident they are getting optimal yields without putting on extra water just for insurance purposes. Otherwise, irrigators follow their natural tendencies to put on about the same amount of water as in the past and just slightly adjust it for dry or wet years. For more information on yield losses, take time to read the following NebGuide: Plant Growth and Yield as Affected by Wet Soil Conditions Due to Flooding or Over-Irrigation.

Question: what will using data from irrigation scheduling systems help irrigators feel more confident about?

Answer: they are getting optimal yields without putting on extra water just for insurance purposes.

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Soil Moisture Monitoring In this drought year, many irrigated fields have very little subsoil moisture, while other portions of Nebraska have experienced significant rains over the last month. With irrigation, any grower can can over-irrigate early and create a wet spring. The most reliable method to know when and how much to irrigate is to monitor soil moisture at multiple depths. Keep in mind that when irrigation is applied with a center pivot an inch at a time on the soil surface, the top foot will stay very wet all summer.

Question: what is the most reliable way to know when and how much a grower should irrigate?

Answer: monitor soil moisture at multiple depths

Melvin, S., Power, C., Daigh, A., & Taghvaeian, S. (2023). Early Season Irrigation During Drought. UNL CropWatch. https://cropwatch.unl.edu/2023/early-season-irrigation-during-drought


Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Dry Beans R5 crop stage, the stage of growth is known as early seed fill, the approximate days to maturity is 35, and the water use to maturity is 7.0 inches. For Dry Beans R6 crop stage, the stage of growth is known as mid-seed fill, the approximate days to maturity is 25, and the water use to maturity is 4.2 inches. For Dry Beans R7 crop stage, the stage of growth is known as beginning maturity, the approximate days to maturity is 15, and the water use to maturity is 2.0 inches. For Dry Beans R8 crop stage, the stage of growth is known as harvest maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the water use to maturity for dry Beans R5 crop stage or the stage of growth that is known as early seed fill?

Answer: 7.0 inches

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: Average percent of fields by year fitting into the six categories. The dry years 2020, '21 and '22 are different than the other years. In 2020, out of 39 reports, 64% were ranked good, 21% were fair, 0% were wet late, 3% were wet early, 5% were wet all season, and 8% were very wet all season.

Question: In 2020 out of 39 reports, what percentage of Nebraska fields were considered wet early?

Answer: 3%

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: In a dry year, aerial imagery can be a useful tool to help identify systematic patterns (i.e., rings) within a field as a result of water stress from poor uniformity. However, in high rainfall areas (i.e., low irrigation requirements) aerial imagery may not be able to visually identify differences in the crop canopy. In these instances, it's recommended that catch cans be used to evaluate application uniformity. Evenly distribute cans of equal size across the system, measure the depth of water applied, and compare to identify areas of nonuniform water application.

Question: what are recommended to be used in high rainfall areas to evaluate irrigation application uniformity?

Answer: catch cans

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: Variable rate irrigation or VRI is 'the ability to spatially vary water application depths across a field to address specific soil, crop, and/or other conditions' (Evans and others, 2013). This technology has many potential uses that might enhance farm profitability, irrigation water productivity (i.e., yield produced per unit of irrigation water applied), and water quality.

Question: what is VRI defined as?

Answer: the ability to spatially vary water application depths across a field to address specific soil, crop, and/or other conditions

Heeren, D., Barker, J. B., Lo, T. H., Melvin, S., Martin, D., & Luck, J. (2017). Considerations in Adopting Variable Rate Irrigation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/considerations-adopting-variable-rate-irrigation


Question: what is the minimum balance for water in the top 4ft of the loamy sand soil at 40% of available water?

Answer: 1.8 in/ft

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: Determine the average rainfall per week for the remaining weeks of crop growth and add it into the prediction of how much water may be needed from irrigation. This number should be recalculated each week until the crop is mature. Use Figures 2 and 3 to determine the average rainfall per week in August and in September for central Buffalo County. The chart shows that, on average, central Buffalo County gets 0.60 inch of rain per week in August and 0.55 inch per week in September. The crop is expected to continue growing for three weeks in August and two weeks in September. Remaining available water at maturity is 5.25 inches. The you subtract the average august rain for three weeks which is 1.80 inches. Then you subtract the average September rain for 2 weeks which is 1.10 inches. This gives us that the water we need after accounting for average rain is 2.35 inches. The chart predicts that if average rainfall is received over the next five weeks, only 2.35 inches of irrigation would be needed to mature the crop.

Question: how often should the average rainfall per week for the remaining weeks of crop growth be recalculated?

Answer: each week until the crop is mature

Barker, J. B. (2017). Considerations in Adopting Variable Rate Irrigation for Center Pivots and Lateral Systems. http://extensionpublications.unl.edu/assets/pdf/ec2000.pdf.


Context: The difference in cost between the two scenarios is $14.61 per acre.  With 130 acres irrigated the total annual savings from using sensors would equal $1,899.30. From this total we would have to subtract the cost of the sensors. A typical range for sensor prices is as low as $175 for systems with NRD cost share up to $1,500 per year for subscription based services. Therefore, the net savings from using sensors for a 130 acre center pivot could range from $400 to $1,700 per year.

Question: what is the typical range for sensor prices in Nebraska?

Answer: as low as $175 for systems with NRD cost share up to $1,500 per year for subscription based services

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: Check for proper operation by making sure there is not any water squirting from the side of any regulators.  This is a sign that the rubber bladder has failed.  Keep in mind that sprinklers and pressure regulators do have a life span.  If your system is approaching 10 years old you might need to take a closer look at them.  Uniformity of water application can suffer greatly if your sprinkler package is out of date.

Question: what has failed if water is squirting from the side of the regulators?

Answer: the rubber bladder has failed

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: The program also will show an up-to-date summary of: Amount of available water in soil root zone. Available water in soil root zone at planting. Total rainfall since planting. Total irrigation amount. Total crop water use (i.e., actual ET). Total water losses (non-ET losses)

Question: what does the CornSoyWater program provide and up to date summary of?

Answer: Amount of available water in soil root zone. Available water in soil root zone at planting. Total rainfall since planting. Total irrigation amount. Total crop water use (i.e., actual ET). Total water losses (non-ET losses)

Yang, H. (2017). CornSoyWater: An Online App to Aid in Irrigation Management | UNL Water. https://water.unl.edu/article/agricultural-irrigation/cornsoywater-online-app-aid-irrigation-managemen


Context: Average percent of fields by year fitting into the six categories. The dry years 2020, '21 and '22 are different than the other years. In 2018, out of 50 reports, 40% were ranked good, 18% were fair, 16% were wet late, 12% were wet early, 10% were wet all season, and 4% were very wet all season.

Question: In 2018 out of 50 reports, what percentage of Nebraska fields were considered wet all season?

Answer: 10%

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: Other secondary aquifers in eastern Nebraska include the Niobrara aquifer (230 wells, mostly in Cedar County), the Codell aquifer (70 wells in Knox and Boyd counties), and the Western Interior Plains Aquifer System. Only one active well is currently installed in the Western Interior Plains Aquifer System in Nebraska, but the aquifer system was a historic source of water to the Omaha area, and still supplies huge volumes of water to Iowa and other states to our east.

Question: what is one aquifer in eastern Nebraska that mostly supports Knox and Boyd counties?

Answer: Codell aquifer

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: The sand and sandstone units in the Brule Formation were deposited in ancient stream valleys and generally have higher porosity than the Brule siltstone that is common elsewhere in western Nebraska. More than 140 wells currently source all of their water from Brule sand-sandstone units and generally have good water quality.

Question: what were deposited in ancient stream valleys and generally have higher porosity than the Brule siltstone that is common elsewhere in western Nebraska?

Answer: sand and sandstone units in the Brule Formation

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: Support for People Wanting to Improve Their Irrigation Management For those who have not collected data in the past or would like to hone their scheduling skills, take some time now to figure out what will work best for your operation. Many resources are available to help. A great five-part video series on this topic can be found on the CropWatch YouTube channel at: How to Schedule Irrigations with Soil Water Data.

Question: what is the tittle of a great five-part video series on Youtube that can help growers with their irrigation management techniques?

Answer: How to Schedule Irrigations with Soil Water Data

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Percent of fields that became wetter moving from August to Sept. 15. The dry years 2020, '21 and '22 fields are much drier than the other years in the fall.  In the weighted average dry years, 2020, 2021, 2022, 42% of fields with soil in the 15-25 in zone became wetter from August to Sept. 15, 30% of fields with soil in the 25-36 in zone became wetter from August to Sept. 15, and 19% of fields with soil in both zones became wetter moving from August to Sept. 15.

Question: what percentage of fields with soil in the 15-25 inch zone became wetter from August to Sept. 15 in the dry years of 2020, 2021, and 2022?

Answer: 42%

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Value of Using Sensors to Manage Irrigation and Tips for Proper Installation: With planting wrapping up across the state, now is an excellent time to turn attention to soil water sensor and ETgage installations if they haven't already been completed.  Timely installation is important to gain the true benefits of sensors, leading to reduced irrigation costs, reduced chances of overwatering leading to anaerobic soil conditions, and less nutrient leaching.

Question: what can the timely installation of soil sensors lead to?

Answer: reduced irrigation costs, reduced chances of overwatering leading to anaerobic soil conditions, and less nutrient leaching

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: In general, about one-third of the irrigators in the study on the normal to wet years are doing a good job of applying the correct amount of water to minimize deep percolation of water and nutrients and save pumping costs while producing top yields. The other two-thirds could have saved money and water without lowering yield. In fact, about one-third could have saved a lot! On the other hand, about 60% to 80% are doing a good job during the dry years as shown in Table 1.

Question: what are two examples of benefits to irrigators if they apply the correct amount of water?

Answer: minimize deep percolation of water and nutrients and save pumping costs while producing top yields

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: To determine the actual cost, we would recommend the use of the IrrigateCost app. The app, which is available for both Apple and Android products, allows users to input their specific information such as acres irrigated, pumping lift, system PSI, pump and pivot life, and inches applied as well as related costs such as for the well and engine, labor, energy, district fees, and taxes. The app then calculates total irrigation cost as well as total ownership and total operating costs.  It also breaks down costs by irrigation well, pump, gear head, pump base, diesel engine and tank and system and calculates per acre annual cost and per acre-inch annual cost.

Question: what platforms is the IrrigateCost app available on?

Answer: Apple and Android products

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.02, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.96. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.03, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.94. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.04, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.92. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.05, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.91. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.06, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.89. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.07, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.87. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.08, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.86. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.09, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.84. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.1, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.83. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.11, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.81. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.12, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.8. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.13, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.78. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.14, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.77. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.15, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.76. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.16, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.74. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.17, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.73. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.18, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.72. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.19, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.71. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.2, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.69.

Question: what is the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) when the ratio of the end gun throw (Rg) to the pivot length (R) is 0.19?

Answer: 0.71

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Question: how can you check for proper operation of your irrigation system?

Answer: making sure there is not any water squirting from the side of any regulators

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: Soil Moisture Monitoring In this drought year, many irrigated fields have very little subsoil moisture, while other portions of Nebraska have experienced significant rains over the last month. With irrigation, any grower can can over-irrigate early and create a wet spring. The most reliable method to know when and how much to irrigate is to monitor soil moisture at multiple depths. Keep in mind that when irrigation is applied with a center pivot an inch at a time on the soil surface, the top foot will stay very wet all summer.

Question: in drought years what do many irrigated fields lack?

Answer: subsoil moisture

Melvin, S., Power, C., Daigh, A., & Taghvaeian, S. (2023). Early Season Irrigation During Drought. UNL CropWatch. https://cropwatch.unl.edu/2023/early-season-irrigation-during-drought


Context: Average percent of fields by year fitting into the six categories. The dry years 2020, '21 and '22 are different than the other years. In the weighted average dry years, 2020, 2021, 2022, 64% were ranked good, 11% were fair, 3% were wet late, 15% were wet early, 3% were wet all season, and 4% were very wet all season.

Question: what percentage of Nebraska fields were wet early in the dry years of 2020, 2021, and 2022?

Answer: 15%

Heeren, D., Barker, J. B., Lo, T. H., Melvin, S., Martin, D., & Luck, J. (2017). Considerations in Adopting Variable Rate Irrigation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/considerations-adopting-variable-rate-irrigation


Context: Percent of fields that became wetter moving from August to Sept. 15. The dry years 2020, '21 and '22 fields are much drier than the other years in the fall.  In 2019, 54% of fields with soil in the 15-25 in zone became wetter from August to Sept. 15, 54% of fields with soil in the 25-36 in zone became wetter from August to Sept. 15, and 38% of fields with soil in both zones became wetter moving from August to Sept. 15.

Question: what percentage of fields with soil in the 15-25 inch zone and 25-36 inch zone became wetter from August to Sept. 15 in 2019?

Answer: 38%

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Poor water distribution can result in over- and under-irrigated areas. Insufficient irrigation can reduce total biomass, grain yield, and grain quality; whereas, excessive irrigation can cause runoff, soil erosion, deep percolation of water and nutrients, and anaerobic soil conditions (plant oxygen stress). Consequently, poor water distribution can have a negative effect on a farm's net return as well as lead to potential environmental concerns (Rudnick and Irmak, 2015). Routine maintenance to improve and maintain high system uniformity and application efficiency is desired

Question: what are four outcomes as a result of excessive irrigation?

Answer: runoff, soil erosion, deep percolation of water and nutrients, and anaerobic soil conditions (plant oxygen stress)

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: If you need a refresher on how to prime the ETgage, please view the assembly video at http://water.unl.edu/cropswater/awmdnvideos. It is a good idea to replace the green covers and white wafers on a regular basis to ensure accurate readings, so if you don't have any on hand it may be a good idea to check with your local supplier.

Question: what's a good idea to replace on a regular basis to ensure accurate readings on the ETgage?

Answer: the green covers and white wafers

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: Both methods require the basic information for the pivot. All the needed details can be found on the sprinkler chart for the center pivot. The sprinkler chart is the documentation that came with the sprinkler package for the pivot and describes the basic layout of the pivot, water flow rate, pressure, size of each sprinkler, etc. If the current sprinklers on the pivot came with the machine when it was new, the pivot dealer should be able to provide a copy. Otherwise, ask the company that sold the current sprinkler package for it. If you do not have the sprinkler chart, then you will need to determine the needed data by measuring the pivot.

Question: who can provide a copy of the sprinkler chart if the current sprinklers on the pivot came with the machine when it was new?

Answer: the pivot dealer should be able to provide a copy

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Center pivot manufacturers have developed options to place the pressure sensor somewhere on the center pivot. Part of Brar's thesis research evaluated where the pressure sensor should be located to achieve maximum energy conservation.

Question: who's thesis research evaluated where the pressure sensor should be located on a center pivot system to achieve maximum energy conservation?

Answer: Brar's

Kranz, B. (2018). Economics of Variable Frequency Drives for Irrigation Pumps. UNL CropWatch. https://cropwatch.unl.edu/2018/economics-variable-frequency-drives-irrigation-pumps


Context: In addition to reducing pumping costs, when properly used to manage irrigation, sensors may also improve crop growth and yield by helping to avoid the detrimental effects of over watering on soil conditions and nutrient leaching.  As shown in NebGuide G1904 Plant Growth and Yield as Affected by Wet Soil Conditions Due to Flooding or Over-Irrigation, over irrigation of a Hastings silt-loam soil at the South Central Agricultural Laboratory near Clay Center reduced yields from 8 to 15 bushels per acre.

Question: in addition to reducing pumping cost what can sensors help improve when used to manage irrigation?

Answer: crop growth and yield

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: University of Nebraska Extension irrigation scheduling recommendations encourage irrigators to allow the crop to continue using more and more of the stored soil water starting in August and continuing into September when the crop matures. The recommendation is to lower the soil water level from the usual summer water condition of a minimum of 50% plant available water in the top three feet of soil to 40% in the top four feet after the dough stage (R4) is reached. Thus, the stored soil water content should be significantly lower when the crop matures in September than earlier in August.

Question: what should the stored soil water content be in September when the plant matures, compared to early august?

Answer: significantly lower

Melvin, S., & Ingram, T. (2021). Scheduling the Last Few Irrigations of the Season Deserves More of Your Management Time Than Earlier Irrigations | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2021/scheduling-last-few-irrigations-season-deserves-more-your-management-time-earlier-irrigations


Context: Each time the user logs in and selects a field, the program will make a prediction regarding the need for irrigation (Figure 3), using up-to-date weather data for that field and other crop and soil information the user provided at field registration. When the user irrigates a field, the irrigation date and amount must be entered into the program so the next prediction will reflect the irrigation.

Question: each time a user logs in to CornSoyWater what does the program predict?

Answer: the need for irrigation

Yang, H. (2017). CornSoyWater: An Online App to Aid in Irrigation Management | UNL Water. https://water.unl.edu/article/agricultural-irrigation/cornsoywater-online-app-aid-irrigation-managemen


Context: Also, keep in mind the corn roots grow about an inch each day into soil that is at field capacity, providing much of the water the plants need for that day. Generally, irrigation needs to be delayed until the soil begins to dry down. Furthermore, research conducted in the North Platte area has shown that irrigation could be reduced by one to four inches, compared to a fully irrigated crop, during the vegetative period without a significant yield reduction and can stimulate deeper root growth. For more information, go to "Vegetative Growth Stage Irrigation, Is It Needed This Year?"

Question: for more information about the reduction of irrigation in the vegetative growth period of a crop where should a grow go?

Answer: Vegetative Growth Stage Irrigation, Is It Needed This Year?

Melvin, S., Power, C., Daigh, A., & Taghvaeian, S. (2023). Early Season Irrigation During Drought. UNL CropWatch. https://cropwatch.unl.edu/2023/early-season-irrigation-during-drought


Context: Chadron wells average about 350 feet deep, and the majority (64%) are used for domestic supply, but livestock and irrigation wells account for 15% and 12% of the wells, respectively. The biggest challenge to using the Chadron aquifer is poor water quality.

Question: what percentage of wells in the Chadron aquifer are used for domestic supply?

Answer: 64%

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: Percent of fields that became wetter moving from August to Sept. 15. The dry years 2020, '21 and '22 fields are much drier than the other years in the fall.  In 2022, 36% of fields with soil in the 15-25 in zone became wetter from August to Sept. 15, 20% of fields with soil in the 25-36 in zone became wetter from August to Sept. 15, and 18% of fields with soil in both zones became wetter moving from August to Sept. 15.

Question: what percentage of fields with soil in the 15-25 inch zone and 25-36 inch zone became wetter from August to Sept. 15 in 2022?

Answer: 18%

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Soybeans R4 crop stage, the stage of growth is known as end of pod elongation, the approximate days to maturity is 37, and the water use to maturity is 9.0 inches. For Soybeans R5 crop stage, the stage of growth is known as beginning of seed enlargement, the approximate days to maturity is 29, and the water use to maturity is 6.5 inches.  For Soybeans R6 crop stage, the stage of growth is known as end of seed elongation, the approximate days to maturity is 18, and the water use to maturity is 3.5 inches.  For Soybeans R6.5 crop stage, the stage of growth is known as leaves begin to yellow, the approximate days to maturity is 10, and the water use to maturity is 1.9 inches.  For Soybeans R7 crop stage, the stage of growth is known as beginning maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the approximate days to maturity for soybeans in the R5 crop stage, the stage of growth that is known as beginning of seed enlargement?

Answer: 29

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: The conclusion is that many irrigators could save money, water and nitrogen by using data from irrigation scheduling systems to make data-driven decisions to help them feel confident they are getting optimal yields without putting on extra water just for insurance purposes. Otherwise, irrigators follow their natural tendencies to put on about the same amount of water as in the past and just slightly adjust it for dry or wet years. For more information on yield losses, take time to read the following NebGuide: Plant Growth and Yield as Affected by Wet Soil Conditions Due to Flooding or Over-Irrigation.

Question: what can irrigators save by using data from irrigation scheduling systems?

Answer: money, water and nitrogen

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Many irrigators apply more water than necessary toward the end of the irrigation season because the crop is using less water per day. The crop is getting more mature and the days are getting shorter and cooler. The average crop water use rate drops from around 2.1 inches per week at silking to only about 1.2 inches per week by the full dent stage. This 40% reduction requires irrigators to adjust their thinking about how much water needs to be applied each week.

Question: why do many irrigators apply more water than necessary near the end of the season?

Answer: the crop is using less water per day.

Melvin, S. (2017). Predicting Late-Season Irrigation Needs. UNL Water. https://water.unl.edu/article/agricultural-irrigation/predicting-late-season-irrigation-needs


Context: Internal combustion engines need quite a bit more attention.  Change engine oil and all filters.  Check engine hours and refer to the manufactures service interval on valve adjustments and other service that may be needed.  It would also be a good idea to run the Nebraska Extension App IrrigatePump to see where your well stacks up against the Nebraska Pumping Plant Criteria.  This will give you an idea on the efficiency of the power unit and pump.  In the current economic climate we want to be as efficient as possible.

Question: after checking the engine hours what should be used as a reference for valve adjustments and other services that may be needed?

Answer: the manufactures service interval on valve adjustments and other service that may be needed.

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: The categories are as follows: Good - At least one sensor out of the three depths drier than 70 cb early and one sensor drier than 70 cb on 9/15. Fair - At least one sensor drier than 70 cb early and one sensor drier than 30 cb on 9/15. Wet Late - At least one sensor drier than 70 cb early but no sensor drier than 30 cb on 9/15. Wet Early - No sensor drier than 70 cb early, but one sensor drier than 30 cb on 9/15. Wet All Season - Both sensors measuring the second and third foot not drier than 70 cb all year, but one sensor between 30 to 70 cb on Sept. 15. Very Wet All Season - Both sensors measuring second and third foot not drier than 70 cb all year and no sensor drier than 30 cb on Sept. 15.

Question: what is the criteria for a field to be ranked "good" in terms of wetness?

Answer: At least one sensor out of the three depths drier than 70 cb early and one sensor drier than 70 cb on 9/15.

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: The key to knowing the correct setting for the chemigation pump is to determine how many acres per hour the pivot will cover at the desired irrigation application depth or rate. Chemigation injection pumps are calibrated in gallons per hour (gph). So, if you know how much product you want to apply per acre -e.g., 10 gallons/acre - and how many acres the pivot will irrigate per hour - e.g., five acres/hour - then you will know how many gallons per hour the pump will need to deliver.

Question: what unit are chemigation injection pumps calibrated in?

Answer: gallons per hour (gph)

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: Percent of fields that became wetter moving from August to Sept. 15. The dry years 2020, '21 and '22 fields are much drier than the other years in the fall.  In the weighted average dry years, 2020, 2021, 2022, 42% of fields with soil in the 15-25 in zone became wetter from August to Sept. 15, 30% of fields with soil in the 25-36 in zone became wetter from August to Sept. 15, and 19% of fields with soil in both zones became wetter moving from August to Sept. 15.

Question: what percentage of fields with soil in the 15-25 inch zone and 25-36 inch zone became wetter from August to Sept. 15 in the dry years of 2020, 2021, and 2022?

Answer: 19%

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: So, if we want to apply 8.5 gallons/acre of 32% UAN (30 lbs/acre N) with a pivot irrigating 5.7 acres/hour, the pump would need to be set to pump 48.5 gph.  Example:  8.5 g/acre x 5.7 acre/hr = 48.5 gph  The pump would need to be set to deliver 48.5 gph to apply the planned 30 lbs/acre.

Question: if an irrigator wants to apply 8.5 gallons/acre of 32% UAN (30 lbs/acre N) with a pivot irrigating 5.7 acres/hour what would the pump need to be set to in units of gph?

Answer: 48.5 gph

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: The description of a speed control VRI system is that its application rate is varied by changing the speed of the pivot and that the irrigation management zones are pie slice shaped. Considerations for the speed control VRI system are that it is relatively inexpensive - many picot panels are capable without additional investment. It also needs no special hardware on the sprinklers. Example uses of it are if spatial variation lines up well with pie slices, varying application based on topography (e.g. reduced application on low spots) if it lines up pie slices, multiple crops or varieties under one pivot, and on-farm research.

Question: what is a description for a speed control VRI system?

Answer: its application rate is varied by changing the speed of the pivot and that the irrigation management zones are pie slice shaped

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: Table II. Total available water in top 4 feet if soil is at field capacity and minimum balances at physiological maturity. For loam, very fine sandy loam, or silt loam topsoil which is silty clay loam or silty clay subsoil, the available water in 1 foot of soil at 100% of available water is 2.0 in/ft, the available water in top 4 feet at 100% of available water is 8.0 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 3.2 in/ft. For loam, very fine sandy loam, or silt loam topsoil which is medium textured subsoil, the available water in 1 foot of soil at 100% of available water is 2.5 in/ft, the available water in top 4 feet at 100% of available water is 10.0 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 4.0 in/ft.

Question: what is the available water in 1ft of soil at 100% of available water for loam, very fine sandy loam, or silt loam topsoil which is medium textured subsoil?

Answer: 2.5 in/ft

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.02, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.96. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.03, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.94. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.04, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.92. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.05, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.91. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.06, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.89. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.07, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.87. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.08, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.86. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.09, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.84. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.1, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.83. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.11, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.81. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.12, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.8. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.13, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.78. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.14, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.77. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.15, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.76. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.16, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.74. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.17, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.73. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.18, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.72. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.19, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.71. When the ratio of the end gun throw (Rg) to the pivot length (R) is 0.2, the the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) is 0.69.

Question: what is the pivot speed with the end gun on (Se) compared to the speed with the end gun off (S) when the ratio of the end gun throw (Rg) to the pivot length (R) is 0.08?

Answer: 0.86

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: How does CornSoyWater work in the background? CornSoyWater uses crop simulation models (Hybrid-Maize for corn and SoySim for soybean) to predict crop growth, development, crop water use, and soil water balance. Based on the location of the field, the program automatically determines the weather station that is closest to the field in the weather station network, and the soil texture for the field.

Question: what crop simulation model does CornSoyWater use for soybean?

Answer: SoySim

Yang, H. (2017). CornSoyWater: An Online App to Aid in Irrigation Management | UNL Water. https://water.unl.edu/article/agricultural-irrigation/cornsoywater-online-app-aid-irrigation-managemen


Context: The two different speeds can be achieved by a simple setup in the computer pivot panel. The degree of rotation at which the end gun turns on, the program simply slows the speed down and then returns it to the faster speed at the time the end gun turns off. The idea is that we want the pivot to cover a constant number of acres per hour. The key is to know how to calculate the slower speed.

Question: what does the computer pivot panel program do?

Answer: slows the speed down and then returns it to the faster speed at the time the end gun turns off

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Context: Thus, the pivot should operate at a 90% timer setting when the end gun is off and slow to 77.4% when it is on to apply the 30 lbs/acre nitrogen both when the end gun is off, as well as when it is on. The water application will be different - 0.29 inches when the end gun is off and about 0.33 inches when it is on - but the nitrogen rate will remain the same with the constant injection rate pump. The concept behind this method is that the pivot will irrigate the same number of acres per hour, thus the lower cost fixed-rate injection pump will work correctly.

Question: what should the timer setting of the pivot irrigation system be operating at to apply 30 lbs/acre nitrogen when the end gun is on?

Answer: 77.4%

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: Predicting how much rain the field will receive is difficult, but if you do not plan for the possibility of rain, it is easy to apply too much irrigation water. Figures 2 and 3 show the long-term weekly average rainfall for August and September in Nebraska.

Question: what becomes easy to do if you do not plan for the possibility of rain?

Answer: apply too much irrigation water

Melvin, S. (2019). Scheduling the Last Irrigations in a Year with Delayed Crop Maturity | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2019/scheduling-last-irrigations


Context: For alfalfa in the stage 4 crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 1.22 inches and the estimated water use during the week of June 19-25, 2023 is 2.05 inches. For alfalfa in the maturity crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 1.30 inches. For alfalfa in the full cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 1.18 inches.

Question: what is the estimated water usage for alfalfa during the stage four crop growth stage during the week of June 19-25 in 2023?

Answer: 2.05 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: VFDs are electronic monitor and control systems that alter the speed of pump rotation by adjusting the frequency of the electricity delivered to the motor. It turns out that the motor cares little about what frequency the power is and the speed of the motor changes linearly with the change in frequency.

Question: what does the speed of a VFD motor change linearly with?

Answer: the change in frequency

Kranz, B. (2018). Economics of Variable Frequency Drives for Irrigation Pumps. UNL CropWatch. https://cropwatch.unl.edu/2018/economics-variable-frequency-drives-irrigation-pumps


Context: Soil Sensor Install Tips: If you are installing Watermark sensors, remember to check them before installation to ensure that they are reading properly. When dry, sensors should read 199 kPa. After soaking in water for 10-15 minutes, sensors should read between 0-10 kPa. Values higher than this likely indicate that the sensor needs to be replaced. Before you go to the field to install Watermark sensors, be sure to put the sensors in water and install them wet to eliminate air in the sensor.

Question: before going to the field to install Watermark sensors what should be done to eliminate air in the sensor?

Answer: be sure to put the sensors in water and install them wet

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: The Dakota aquifer (formally called the Maha Aquifer) is by far the largest of these secondary aquifers, supplying all of the water to more than 3,400 wells in eastern Nebraska. Seventy-five percent of these wells are domestic, although in places the aquifer is capable of supplying a sufficient volume of water for irrigation and commercial use. The biggest limitation to using the Dakota aquifer is potentially high salt concentrations.  Geologists think the salty water probably moves into the Dakota aquifer from underlying rocks, a hydraulic condition that is increased by heavy pumping.

Question: what aquifer supplies water to nearly 3400 wells in eastern Nebraska?

Answer: The Dakota aquifer

Divine, D. (2017). An Overview of Secondary Aquifers in Nebraska | UNL Water. https://water.unl.edu/article/agricultural-irrigation/overview-seondary-aquifers-nebraska


Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Corn R2 crop stage, the stage of growth is known as blister, the approximate days to maturity is 45, and the water use to maturity is 10.5 inches. For Corn R4 crop stage, the stage of growth is known as dough, the approximate days to maturity is 34, and the water use to maturity is 7.5 inches. For Corn R4.7 crop stage, the stage of growth is known as beginning dent, the approximate days to maturity is 24, and the water use to maturity is 5.0 inches. For Corn R5 crop stage, the stage of growth is known as 1/4 milk line, the approximate days to maturity is 19, and the water use to maturity is 3.75 inches. For Corn R5 crop stage, the stage of growth is known as 1/2 milk line - full dent, the approximate days to maturity is 13, and the water use to maturity is 2.25 inches. For Corn R5 crop stage, the stage of growth is known as 13/4 milk line, the approximate days to maturity is 7, and the water use to maturity is 1.0 inches. For Corn R6 crop stage, the stage of growth is known as physiological maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the approximate water use to maturity for corn in the R6 crop stage, the stage of growth that is known as physiological maturity?

Answer: 0.0 inches

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view


Context: For corn in the V4 crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.21 inches and the estimated water use during the week of June 19-25, 2023 is 1.30 inches. For corn in the V6 crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.41 inches. For corn in the V8 crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.60 inches.

Question: what is the estimated water usage for corn in the V4 crop growth stage during June 12-18, 2023?

Answer: 0.21 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: The top foot will go above field capacity (30cb) after every irrigation or heavy rain. However, if the second foot gets above 30 cb, it would indicate that over-irrigation is occurring. The data in the chart indicated that the field was this dry on a given day and not how many days the soil was drier than 70 cb. The 70 cb level is equal to about 70% of plant available water (PAW) and stress should not start until below 50% of PAW during the summer and 40% in late August and September. Soil types such as those with high sand or clay content would require different levels other than 30 and 70 cb.

Question: what will go above field capacity after every irrigation or heavy rain?

Answer: The top foot

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: This is important for two reasons. First, it's important to provide room to store free offseason precipitation. In most years even the drier Nebraska Panhandle sees enough precipitation to fill the soil water profile. (On heavier soils it may take only 4 or 5 inches to refill to field capacity; sandy soils would only take 2-3 inches.)

Question: what is important to leave storage room for in the offseason?

Answer: offseason precipitation.

Melvin, S. (2017). Predicting Late-Season Irrigation Needs. UNL Water. https://water.unl.edu/article/agricultural-irrigation/predicting-late-season-irrigation-needs


Context: The key to early water management is to apply irrigation only when it is needed to get the crop off to a good start, while keeping in mind over-irrigation enables crop input losses. Precision water and nitrogen management can help guide your early season irrigation decisions.

Question: what can help guide early season irrigation decisions?

Answer: Precision water and nitrogen management

Melvin, S., Power, C., Daigh, A., & Taghvaeian, S. (2023). Early Season Irrigation During Drought. UNL CropWatch. https://cropwatch.unl.edu/2023/early-season-irrigation-during-drought


Context: University of Nebraska Extension irrigation scheduling recommendations encourage irrigators to allow the crop to continue using more and more of the stored soil water starting in August and continuing into September when the crop matures. The recommendation is to lower the soil water level from the usual summer water condition of a minimum of 50% plant available water in the top three feet of soil to 40% in the top four feet after the dough stage (R4) is reached. Thus, the stored soil water content should be significantly lower when the crop matures in September than earlier in August.

Question: what is the usual summer condition in Nebraska soils?

Answer: a minimum of 50% plant available water in the top three feet

Melvin, S., & Ingram, T. (2021). Scheduling the Last Few Irrigations of the Season Deserves More of Your Management Time Than Earlier Irrigations | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2021/scheduling-last-few-irrigations-season-deserves-more-your-management-time-earlier-irrigations


Context: Soil Sensor Install Tips: As plants mature, later installation can lead to poorer readings as a result of root damage, residual water in the sensor or slurry, and more challenging installation given soil conditions. Because of these disadvantages, early installation of sensors is highly recommended.

Question: as the plant matures what can late field installation of soil sensors lead to?

Answer: poorer readings as a result of root damage, residual water in the sensor or slurry, and more challenging installation given soil conditions

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Question: what is the estimated water usage for corn in the V4 crop growth stage during June 19-25, 2023?

Answer: 1.30 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: The 2017 growing season started with warm dry planting conditions, followed by significant rain delays in May in many parts of the state, and a summer of intermittent weeks of hot and cool temperatures. The net result is that crops may mature over a longer period than usual this fall. Fortunately, the following procedure for making end-of-season irrigation decisions is based on crop maturity stage rather than the calendar.

Question: what is the net result of the growing season starting with warm dry planting conditions, followed by significant rain delays in May, and a summer of intermittent weeks of hot and cool temperatures in the state of Nebraska?

Answer: crops may mature over a longer period than usual this fall.

Melvin, S. (2017). Predicting Late-Season Irrigation Needs. UNL Water. https://water.unl.edu/article/agricultural-irrigation/predicting-late-season-irrigation-needs


Context: Once the system is up to pressure it is a good idea to check the system for leaks and operation of the sprinklers.  If you find missing or inoperable sprinklers refer to the sprinkler chart that was developed for the system to find the correct replacement.  If the system is on rolling or hilly terrain, regulators are also needed for uniform application and definitely should be checked.

Question: what is it a good idea to check for once the irrigation system is up to pressure?

Answer: check the system for leaks and operation of the sprinklers

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: The description of a zone or nozzle control VRI system is that the sprinklers are pulsed on and off and pivot speed may vary and that irrigation management zones may be any shape or size. Considerations for this VRI system are that has greatest flexibility in application, it is more expensive, and may require additional maintenance and management effort. Example uses include avoiding application on irregularly- shaped uncropped areas for water surfaces. It can also vary irrigation on irregularly- shaped management zones as needed to maximize yield and profits.

Question: what are some considerations that should accounted for zone or nozzle control VRI systems?

Answer: as greatest flexibility in application, it is more expensive, and may require additional maintenance and management effort

Barker, J. B. (2017). Considerations in Adopting Variable Rate Irrigation for Center Pivots and Lateral Systems. http://extensionpublications.unl.edu/assets/pdf/ec2000.pdf


Context: Pressure differences along the system can be attributed to elevation change and pipeline friction losses. When the sprinkler design flow rate varies by at least 10% for more than 15% of the system due to pressure differences, the use of pressure regulators is encouraged.

Question: under what sprinkler design flow rate variations are the use of pressure regulators encouraged?

Answer: 10% for more than 15% of the system due to pressure differences

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: There is increasing pressure on our water resources. Concerns about natural ecosystems and the sustainability of groundwater withdrawals are heightening. Domestic and international competition for water between different users is increasing. Agricultural demand by a global population growing both in number and in wealth is rising.

Question: whats happening to concerns about natural ecosystems and the sustainability of groundwater withdrawals?

Answer: heightening

Heeren, D., Barker, J. B., Lo, T. H., Melvin, S., Martin, D., & Luck, J. (2017). Considerations in Adopting Variable Rate Irrigation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/considerations-adopting-variable-rate-irrigation


Context: The broken gooseneck on this pivot, as shown in the video, is one cause of non-uniform water application. Walking the irrigation span to visually inspect it can help identify issues before crop yield is affected.

Question: what can be done to help visually identify irrigation issues before the crop yield is affected?

Answer: Walking the irrigation span

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: Table II. Total available water in top 4 feet if soil is at field capacity and minimum balances at physiological maturity. For fine sands, the available water in 1 foot of soil at 100% of available water is 1.0 in/ft, the available water in top 4 feet at 100% of available water is 4.0 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 1.6 in/ft. For loamy sands, the available water in 1 foot of soil at 100% of available water is 1.1 in/ft, the available water in top 4 feet at 100% of available water is 4.4 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 1.8 in/ft. For sandy loams, the available water in 1 foot of soil at 100% of available water is 1.4 in/ft, the available water in top 4 feet at 100% of available water is 5.6 in/4 ft, and minimum balance in top 4 feet at 40% of available water is 2.2 in/ft.

Question: what is the amount of available water in units of (in/ft) for loamy sands at 100% of available water in the top 4ft of soil?

Answer: 4.4 in/4 ft,

Melvin, S. (2023a). How to Determine the Chemigation Injection Pump Setting for a Center Pivot with the End Gun Off and On. UNL CropWatch. https://cropwatch.unl.edu/2023/how-determine-chemigation-injection-pump-setting-center-pivot-end-gun-and


Question: what is the field capacity value?

Answer: (30cb

Melvin, S. (2023). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: Poor water distribution can result in over- and under-irrigated areas. Insufficient irrigation can reduce total biomass, grain yield, and grain quality; whereas, excessive irrigation can cause runoff, soil erosion, deep percolation of water and nutrients, and anaerobic soil conditions (plant oxygen stress). Consequently, poor water distribution can have a negative effect on a farm's net return as well as lead to potential environmental concerns (Rudnick and Irmak, 2015). Routine maintenance to improve and maintain high system uniformity and application efficiency is desired

Question: what are three outcomes as a result of insufficient irrigation?

Answer: otal biomass, grain yield, and grain quality

Rudnick, D. (2016). Sprinkler Irrigation System Maintenance for Improved Uniformity and Application Efficiency | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2016/sprinkler-irrigation-system-maintenance-improved-uniformity-and-application-efficiency


Context: Average percent of fields by year fitting into the six categories. The dry years 2020, '21 and '22 are different than the other years. In 2018, out of 50 reports, 40% were ranked good, 18% were fair, 16% were wet late, 12% were wet early, 10% were wet all season, and 4% were very wet all season.

Question: In 2018 out of 50 reports, what percentage of Nebraska fields were considered wet late?

Answer: 16%

Ingram, T. (2017). Is Your Irrigation System Ready For the Season? | UNL Water. https://water.unl.edu/article/agricultural-irrigation/your-irrigation-system-ready-season


Context: Determine the average rainfall per week for the remaining weeks of crop growth and add it into the prediction of how much water may be needed from irrigation. This number should be recalculated each week until the crop is mature. Use Figures 2 and 3 to determine the average rainfall per week in August and in September for central Buffalo County. The chart shows that, on average, central Buffalo County gets 0.60 inch of rain per week in August and 0.55 inch per week in September. The crop is expected to continue growing for three weeks in August and two weeks in September. Remaining available water at maturity is 5.25 inches. The you subtract the average august rain for three weeks which is 1.80 inches. Then you subtract the average September rain for 2 weeks which is 1.10 inches. This gives us that the water we need after accounting for average rain is 2.35 inches. The chart predicts that if average rainfall is received over the next five weeks, only 2.35 inches of irrigation would be needed to mature the crop.

Question: on average how much rain (inch) per week does central buffalo county receive in August?

Answer: 0.60 inch

Barker, J. B. (2017). Considerations in Adopting Variable Rate Irrigation for Center Pivots and Lateral Systems. http://extensionpublications.unl.edu/assets/pdf/ec2000.pdf.


Context: The Extremely Dry Winter/Spring 2022-23 Leaving the soil as dry as possible without lowering yields saves money on pumping costs and leaves room to store offseason precipitation. Most years, adequate precipitation will be received from October through May to refill the soil profile on fields that were fully irrigated the previous year in the entire state. A lot of years, even in the Panhandle, the two to four inches of recharge that fully irrigated fields can hold will be received from rainfall or snowfall. In addition to financial savings, leaving the soil drier will help reduce harvest delays due to mud if rain is received in the fall.

Question: what does leaving the soil as dry as possible without lowering yields leave room to store?

Answer: offseason precipitation

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: To illustrate this, let's look at some data from the Upper Big Blue NRD. The NRD requires growers in six areas that have an increased median nitrate-nitrogen level in the groundwater, to use soil water monitoring equipment in one irrigated field and report the data collected annually. Most of the producers impacted by this rule use Watermark sensors that measure soil matric potential; thus, this study has largely focused on Watermark data for easy comparison. The soils in the NRD are mostly a silt loam or similar soil texture, making the field-to-field data comparable as well. The assumption was made that the farmers using Watermark sensors would represent all irrigators in the area. To protect privacy, the NRD removes names from the information prior to group analysis; therefore, the location for each field is an unspecified area in the Upper Big Blue NRD.

Question: what does the Upper Big Blue NRD require growers in six areas that have an increased median nitrate-nitrogen level in the groundwater to use and report??

Answer: soil water monitoring equipment in one irrigated field and report the data collected annually

Melvin, S. (2023c). Study Reviews Farmer Irrigation Scheduling Tendencies in Dry Years. UNL CropWatch. https://cropwatch.unl.edu/2023/study-reviews-farmer-irrigation-scheduling-tendencies-dry-years


Context: For sugarbeets in the 10-30% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.17 inches and the estimated water use during the week of June 19-25, 2023 is 1.20 inches. For sugarbeets in the 30-50% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.25 inches. For sugarbeets in the 50-70% Cover crop growth stage the estimated water use during the previous week of June 12-18, 2023 is 0.40 inches.

Question: what is the estimated water usage for sugarbeets in the 10%-30% cover crop growth stage during June12-18, 2023?

Answer: 0.17 inches

Stone, G., & Qiao, X. (2023). Estimated Crop Water Use for June 19-25, 2023 | CropWatch | University of Nebraska–Lincoln. https://cropwatch.unl.edu/2023/estimated-crop-water-use-june-19-25-2023


Context: In addition to reducing pumping costs, when properly used to manage irrigation, sensors may also improve crop growth and yield by helping to avoid the detrimental effects of over watering on soil conditions and nutrient leaching.  As shown in NebGuide G1904 Plant Growth and Yield as Affected by Wet Soil Conditions Due to Flooding or Over-Irrigation, over irrigation of a Hastings silt-loam soil at the South Central Agricultural Laboratory near Clay Center reduced yields from 8 to 15 bushels per acre.

Question: how can sensors help improve crop growth and yield?

Answer: by helping to avoid the detrimental effects of over watering on soil conditions and nutrient leaching

Nygren, A. (2017). Value of Using Sensors to Manage Irrigation and Tips for Proper Installation | UNL Water. https://water.unl.edu/article/agricultural-irrigation/value-using-sensors-manage-irrigation-and-tips-proper-installation


Context: Table I. Normal water requirements for corn, grain sorghum, soybeans, and dry beans between various stages of growth and maturity in Nebraska. For Dry Beans R5 crop stage, the stage of growth is known as early seed fill, the approximate days to maturity is 35, and the water use to maturity is 7.0 inches. For Dry Beans R6 crop stage, the stage of growth is known as mid-seed fill, the approximate days to maturity is 25, and the water use to maturity is 4.2 inches. For Dry Beans R7 crop stage, the stage of growth is known as beginning maturity, the approximate days to maturity is 15, and the water use to maturity is 2.0 inches. For Dry Beans R8 crop stage, the stage of growth is known as harvest maturity, the approximate days to maturity is 0, and the water use to maturity is 0.0 inches.

Question: what is the approximate days to maturity for dry Beans R5 crop stage or the stage of growth that is known as early seed fill?

Answer: 35

Yonts, C. D., Melvin, S., & Eisenhauer, D. E. (2008). Predicting the Last Irrigation of the Season. UNL Extension Publications. https://extensionpubs.unl.edu/publication/g1871/html/view