# Topological Sustainability of Crop Water Requirements and Irrigation Scheduling of Some Main Crops Based on the Penman-Monteith Method

Authors: Waseem Asghar Khan; Jamshaid Ul Rahman; Mogtaba Mohammed; Ziyad Ali AlHussain; Murtada K. Elbashir
Journal: Journal of Chemistry
 (2021)

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## Abstract

The following method was used to apply the topology of the current study of evapotranspiration ETo, net irrigation demand, irrigation schedules, and total effective rain fall of different crop models: using the Food and Agriculture Organization's (FAO) CROPWAT 8.0 standard software and the CLIMWAT 2.0 tool and the FAO-56 Penman-Monteith approach to examine the variable topology of evapotranspiration ETo. Due to high temperatures in summer with an annual mean of 6.33 mm/day, the topological demonstration of reference evapotranspiration (ETo) increases from 2.84 mm/day in January to a maximum of 9.61 mm/day in July. Effective rainfall fluctuates from 0 mm to 53.4 mm. Total irrigation topological indices requirements were 308.3 mm/dec, 335.9 mm/dec, 343.6 mm/dec, 853 mm/dec, and 1479.6 mm/dec for barley, wheat, maize, rice, and citrus, respectively. The physical topological indices due to low demand in winter and high demand in summer, the total net irrigation, and gross irrigation for clay loamy soils for wheat (210.6 mm and 147.4 mm), barley (176.6 mm and 123.6 mm), citrus (204.5 mm and 143.2 mm), and maize (163.9 mm and 114.7 mm), but not for rice. This topology demonstrates that wheat has 4, barley has 4, citrus has 12, maize has 4, and rice crop has 12 irrigation schedules in a year.


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## Body

## 1. Introduction

The topology of agricultural technology development for wheat, rice, maize, citrus, and barley in Saudi Arabia faces enormous challenges, which are average of arid areas described with water shortage, low precipitation, and above average evapotranspiration requirement. The greatest source of irrigation water is acquired from groundwater. The farming segment expended more than 85% of water ingesting, which achieved more than 23 billion m3 in 2012; see [1]. An efficient and precise assessment of CWR is necessary for preparing, constructing, operating, and controlling farm systems due to a rise in the demand of water with time. Precise assessment of CWR can assist to sustain cost-effective utilization of water reserves for irrigation. Evapotranspiration (ET) performs the most important part in topological sustainability of irrigation water [2].Groundwater is an important source of freshwater of strategic importance for a country’s and its people’s long-term development. Management of water resources has become a hot topic in recent years, with the goal of ensuring sustained quality and availability while also meeting economic and social development objectives [3, 4].Under conditions of limited water resources, the CROPWAT model can help improve useful suggestions for increasing yield production [5]. It enables the expansion of irrigation practice suggestions, the design of irrigation timetables under various water allocation requirements, and the estimation under rainfed or shortfall irrigation conditions. The approximate yield reduction is caused by water pressure and climate factors. According to the modeling results, the significant yield decline occurred in the embryonic stage in both rainfed and watered situations [6, 7].CROPWAT and CLIMWAT softwares are used by many researchers for the estimation of CWR, and irrigation pattern and preparation. These tools were built by the “Food and Agriculture Organization” (FAO) for assisting researchers in water irrigation investigations and irrigation sustainability [7–11]. CLIMWAT is a climate data bank that works in conjunction with software application CROPWAT. CROPWAT uses meteorological data from over 5000 climate stations across the world to determine agricultural water requirements, irrigation source, and planning for a range of crops. Aimed at the stations in its database, CLIMWAT delivers lengthy-term monthly base values of the climatical limitations required for the Penman-Monteith method computation of evapotranspiration: mean relative humidity, mean high daily temperature, mean minimum daily temperature, mean sunshine hours, mean wind speed, and monthly total and effective rainfall [9, 12]. In the current analysis, the IWR and irrigation scheduling of rice, maize, citrus, barley, and wheat in Qassim region, Saudi Arabia, were investigated using the CLIMWAT and CROPWAT models.


## 2. Methodology and Materials

### 2.1. Working Area

Al-Qassim Province, as shown in Figure1, is located at the heart of Saudi Arabia, geographically at the center of the Arabian Peninsula. The total population of this region is 1370727 and the total area of this region is 58046 km2. This region is an agricultural asset of Saudi Arabia. The total cultivated area is 453099 m2, the total harvest area is 427050.1 m2, and the total production is 236505 (ton) [13]. The average minimum and maximum temperatures are 16.5°C and 31.4°C in 2019. The average humidity, wind, and sunshine of this region are 30%, 238 km/day and 8.1 per hour, respectively. The latitude and longitude of Qassim are 26°30’N and 43°76’E with an altitude of 650 m. The average rainfall of Qassim is 183 mm [14–16].Figure 1
(Color) Experiential area location of Al-Qassim Region, Saudi Arabia [13].


### 2.2. Topology of FAO Penman-Monteith Method to Estimate Reference Evapotranspiration (ETo)

FAO-56 Penman-Monteith method to estimate (ETo) at standard climatological measurements of sunlight, air temperature, humidity, and wind velocity is used in the calculation. The weather measurements are needed at 2 m above an extensive surface of green grass, shadowing the ground and being not short of water, to maintain the integrity of the computations and strength of this method to predict evapotranspiration perfectly under every climatic situation [2, 17]:(1)ETo=0.408ΔRn−G+γ900/T+273u2es−eaΔ+γ+0.34u2,where γ is psychrometric constant (kPa/°C), es−ea is saturation vapour pressure deficit (kPa), ea is actual vapour pressure (kPa), es is saturation vapour pressure (kPa), ET0 is reference evapotranspiration (mm/day), Δ is slope vapour pressure curve (kPa/°C), Rn is net radiation at the crop surface (MJ/m2 day), u2 is wind speed at 2 m height (m/s), T is air temperature at 2 m height (°C), and G is soil heat flux density (MJ/m2 day).In Table1 results in column 9 show that the ETo gradually increases from nearly 2.84 mm/day in January to the highest worth of approximately 9.61 mm/day in Jul. Then it again declines steadily to 2.97 mm/day in December as shown in Table 1 and Figure 1. The maximum ETo rises from 5.26 to 6.98 mm/day in April. The average yearly ETo was 6.33 mm/day in 2019.Table 1
The date of low temperature =Tmin (°C); high temperature Tmax (°C); humidity (%); wind speed (km/day); sunshine (hour); radiation (MJ/m2/day) and reference evapotranspiration = ETo (mm/day); and rainfall (mm) and effective rainfall = Peff (mm) (source: Statistical Yearbook, Ministry of Planning, 2019).
MonthTmin °CTmax °CTmean °CHumidity %Wind km/daySun hoursRadiation MJ/m2/dayETo mm/dayRainfall (mm)Effective rainfall (USDA S. C. method) (mm)January6.518.412.45522166.813.42.8418.017.5February8.221.614.9432167.916.73.7710.09.8March12.326.419.35362596.717.55.2659.053.4April16.930.923.931302719.66.9837.034.8May2236.929.45243028.322.48.7944June23.740.532.11625910.325.59.4700July24.541.432.951625910.225.29.6100August24.441.132.75132161024.28.600September22.439.430.9171738.520.66.9600October17.233.925.55232168.217.86.3144November12.425.819.138216815.24.3720.019.4December7.820.113.95512165.411.32.9731.029.5Total183172.3Average16.531.423.95302388.119.16.33In Table1, the maximum effective rainfall was 53.4 mm in November, 2019, although it was zero in June to September and between 4 mm and 37 mm in the other months of year 2019. The total twelve-month effective rainfall was expected to be 172.3 mm. There are various approaches to estimate the effective rainfall, e.g., fixed percentage 80%, dependable rain (FAO/AGLW method), empirical formula, and no rainfall. But, in this study, we use the US Agriculture Department of Soil Conservation Service (USAD S. C.) method which has developed a technique for determining effective rainfall using long-term meteorological and soil quality data. Perusing 50 years of rainfall information at 22 experimental stations representing various meteorological and soil conditions resulted in a complete analysis. Each day, the soil moisture balance was calculated by subtracting consumptive usage from the previous day’s balance and adding effective rainfall or irrigation. The soil input rate and rainfall intensities are not taken into account in this method to avoid a high level of complexity [2].USAD S. C. Method:(2a)effective rainfallPeff=rainfall∗125−0.2∗rainfall125if rainfall≤250,and(2b)effective rainfallPeff=125−0.1∗rainfall if rainfall≥250.


### 2.3. Crop Water Requirement (CWR) or Crop Evapotranspiration (ETc)

The quantity of rainwater necessary by the harvest throughout the spell is specified as crop water necessity.ETc is calculated by the crop factor tactic whereby the consequence of the numerous climate circumstances is combined into ETo and the crop properties into the crop factor and reference crop evapotranspiration ETo which can be investigated by the following relation [8, 18]:(3)s=Kc×ETo,where Kc, called crop coefficient introduced by [2, 7, 19] varying according to crop time of season (days or weeks after planting) at different stages as shown in Figure 2, is basically the ratio of the ETc to ETo. This coefficient incorporates the impacts of four necessary measures that characterize the crop from source grassland, i.e., reflectance of the soil surface, crop height, evaporation from soil, and resistance canopy. In growth spell, four different phases of crop growth are considered, i.e., initial stage, crop development stage, mid-season stage, and late season stage [2, 20].Figure 2
The relationship between crop coefficient =Kc and time of season, which varies according to crop time of season (days or weeks after planting) at different stages [7]: crop coefficient initial (20% of seasonal time from A to B); crop coefficient development (50% of seasonal time from B to C); crop coefficient mid-season (70% of seasonal time from C to D), and crop coefficient late-season (100% of seasonal time from D to E).


### 2.4. Topology of Net Irrigation Water Requirement (NIWR)

NIWR for each crop is calculated by using the following formula:(4)NIWR=ETc−Peff.


## 2.1. Working Area

Al-Qassim Province, as shown in Figure1, is located at the heart of Saudi Arabia, geographically at the center of the Arabian Peninsula. The total population of this region is 1370727 and the total area of this region is 58046 km2. This region is an agricultural asset of Saudi Arabia. The total cultivated area is 453099 m2, the total harvest area is 427050.1 m2, and the total production is 236505 (ton) [13]. The average minimum and maximum temperatures are 16.5°C and 31.4°C in 2019. The average humidity, wind, and sunshine of this region are 30%, 238 km/day and 8.1 per hour, respectively. The latitude and longitude of Qassim are 26°30’N and 43°76’E with an altitude of 650 m. The average rainfall of Qassim is 183 mm [14–16].Figure 1
(Color) Experiential area location of Al-Qassim Region, Saudi Arabia [13].


## 2.2. Topology of FAO Penman-Monteith Method to Estimate Reference Evapotranspiration (ETo)

FAO-56 Penman-Monteith method to estimate (ETo) at standard climatological measurements of sunlight, air temperature, humidity, and wind velocity is used in the calculation. The weather measurements are needed at 2 m above an extensive surface of green grass, shadowing the ground and being not short of water, to maintain the integrity of the computations and strength of this method to predict evapotranspiration perfectly under every climatic situation [2, 17]:(1)ETo=0.408ΔRn−G+γ900/T+273u2es−eaΔ+γ+0.34u2,where γ is psychrometric constant (kPa/°C), es−ea is saturation vapour pressure deficit (kPa), ea is actual vapour pressure (kPa), es is saturation vapour pressure (kPa), ET0 is reference evapotranspiration (mm/day), Δ is slope vapour pressure curve (kPa/°C), Rn is net radiation at the crop surface (MJ/m2 day), u2 is wind speed at 2 m height (m/s), T is air temperature at 2 m height (°C), and G is soil heat flux density (MJ/m2 day).In Table1 results in column 9 show that the ETo gradually increases from nearly 2.84 mm/day in January to the highest worth of approximately 9.61 mm/day in Jul. Then it again declines steadily to 2.97 mm/day in December as shown in Table 1 and Figure 1. The maximum ETo rises from 5.26 to 6.98 mm/day in April. The average yearly ETo was 6.33 mm/day in 2019.Table 1
The date of low temperature =Tmin (°C); high temperature Tmax (°C); humidity (%); wind speed (km/day); sunshine (hour); radiation (MJ/m2/day) and reference evapotranspiration = ETo (mm/day); and rainfall (mm) and effective rainfall = Peff (mm) (source: Statistical Yearbook, Ministry of Planning, 2019).
MonthTmin °CTmax °CTmean °CHumidity %Wind km/daySun hoursRadiation MJ/m2/dayETo mm/dayRainfall (mm)Effective rainfall (USDA S. C. method) (mm)January6.518.412.45522166.813.42.8418.017.5February8.221.614.9432167.916.73.7710.09.8March12.326.419.35362596.717.55.2659.053.4April16.930.923.931302719.66.9837.034.8May2236.929.45243028.322.48.7944June23.740.532.11625910.325.59.4700July24.541.432.951625910.225.29.6100August24.441.132.75132161024.28.600September22.439.430.9171738.520.66.9600October17.233.925.55232168.217.86.3144November12.425.819.138216815.24.3720.019.4December7.820.113.95512165.411.32.9731.029.5Total183172.3Average16.531.423.95302388.119.16.33In Table1, the maximum effective rainfall was 53.4 mm in November, 2019, although it was zero in June to September and between 4 mm and 37 mm in the other months of year 2019. The total twelve-month effective rainfall was expected to be 172.3 mm. There are various approaches to estimate the effective rainfall, e.g., fixed percentage 80%, dependable rain (FAO/AGLW method), empirical formula, and no rainfall. But, in this study, we use the US Agriculture Department of Soil Conservation Service (USAD S. C.) method which has developed a technique for determining effective rainfall using long-term meteorological and soil quality data. Perusing 50 years of rainfall information at 22 experimental stations representing various meteorological and soil conditions resulted in a complete analysis. Each day, the soil moisture balance was calculated by subtracting consumptive usage from the previous day’s balance and adding effective rainfall or irrigation. The soil input rate and rainfall intensities are not taken into account in this method to avoid a high level of complexity [2].USAD S. C. Method:(2a)effective rainfallPeff=rainfall∗125−0.2∗rainfall125if rainfall≤250,and(2b)effective rainfallPeff=125−0.1∗rainfall if rainfall≥250.


## 2.3. Crop Water Requirement (CWR) or Crop Evapotranspiration (ETc)

The quantity of rainwater necessary by the harvest throughout the spell is specified as crop water necessity.ETc is calculated by the crop factor tactic whereby the consequence of the numerous climate circumstances is combined into ETo and the crop properties into the crop factor and reference crop evapotranspiration ETo which can be investigated by the following relation [8, 18]:(3)s=Kc×ETo,where Kc, called crop coefficient introduced by [2, 7, 19] varying according to crop time of season (days or weeks after planting) at different stages as shown in Figure 2, is basically the ratio of the ETc to ETo. This coefficient incorporates the impacts of four necessary measures that characterize the crop from source grassland, i.e., reflectance of the soil surface, crop height, evaporation from soil, and resistance canopy. In growth spell, four different phases of crop growth are considered, i.e., initial stage, crop development stage, mid-season stage, and late season stage [2, 20].Figure 2
The relationship between crop coefficient =Kc and time of season, which varies according to crop time of season (days or weeks after planting) at different stages [7]: crop coefficient initial (20% of seasonal time from A to B); crop coefficient development (50% of seasonal time from B to C); crop coefficient mid-season (70% of seasonal time from C to D), and crop coefficient late-season (100% of seasonal time from D to E).


## 2.4. Topology of Net Irrigation Water Requirement (NIWR)

NIWR for each crop is calculated by using the following formula:(4)NIWR=ETc−Peff.


## 3. Discussion and Results

The region (Saudi Arabia), climatic location (Al-Qassim region), name of crop, sowing and harvesting period, and soil information were all included in the CROPWET and CLIMWAT package data (black clay soil). Once all data have been entered into the system, we calculate ETo using the Penman-Monteith method (equation (1)) and effective rainfall using the USDA S. C. method ((2a) and (2b)). The IWRs and effective rain of rice, wheat, citrus, maize (grain), and barley are shown in Tables 2–6. The CROPWAT program [9] was used to calculate all of the results. The crop’s scientific name, critical depletion, sowing and harvesting times, Kc value, rooting depth (m), yield response friction at various phases (beginning, growing, mid-season, and late-season), total number of days required for completion, and croup height (m) are shown in Tables 7–11.Table 2
Results shows CWR to rice at different stages; the total time taken from nursery/land preparation to end stage is 150 days approximately. Column 8 shows the results of IWR.
Year/Mon.DecadeStagesKcETc mm/dayETc mm/decEffective rainfall mm/decIWR mm/decNov.2Nure1.200.523.16.70Nov.3Nurs/LPr1.122.6826.87.8110.1December1Nurs/LPr1.063.5935.93.1122.8December2Initial1.093.1231.20.289.1December3Initial1.103.1534.70.634January1Dev1.113.1431.4130.3January2Dev1.153.1731.70.930.7January3Dev1.203.7040.72.538.1February1Mid1.234.2542.55.237.2February2Mid1.234.6346.37.139.1February3Mid1.235.2441.9537March1Mid1.235.8558.5157.5March2Late1.226.4264.2064.2March3Late1.176.8575.40.874.6April1Late1.137.2272.2468.2April2Late1.107.66231.720.1Total659.347.9853.0Table 3
CWR of wheat at different stages.
Year/Mon.DecadeStagesKcETc mm/dayETc mm/decEffective rainfall mm/decIWR mm/decDecember2Init0.30.865.26.50December3Init0.30.869.59.20.3January1Init0.30.858.57.11.4January2Dev0.381.0510.55.74.8January3Dev0.682.123.24.918.3February1Dev0.993.4334.32.531.8February2Mid1.184.4444.40.943.6February3Mid1.185.0440.46.533.8March1Mid1.185.6356.314.941.4March2Mid1.186.2262.220.741.5March3Late1.116.4671.117.753.4April1Late0.815.2252.21438.2April2Late0.523.6436.412.224.2April3Late0.332.57.52.63.2Total461.5125.2335.9Table 4
CWR of citrus at different stages.
Year/Mon.DecadeStagesKcETc mm/dayETc mm/decEffective rainfall mm/decIWR mm/decDecember2Init0.742.1212.76.53.1December3Init0.7222.19.212.9January1Init0.71.9719.77.112.7January2Init0.71.9219.25.713.5January3Init0.72.1623.84.918.9February1Init0.72.4224.22.521.7February2Dev0.72.6426.40.925.5February3Dev0.72.99246.517.4March1Dev0.73.3533.514.918.6March2Dev0.73.7137.120.716.4March3Dev0.714.1245.317.727.6April1Dev0.714.5345.31431.3April2Dev0.714.9549.512.237.3April3Dev0.715.3953.98.545.3May1Dev0.715.8758.73.954.8May2Mid0.716.3363.30.163.3May3Mid0.716.4771.2071.1June1Mid0.716.5965.90.165.7June2Mid0.716.7567.5067.5June3Mid0.716.7867.8067.8July1Mid0.716.8668.6068.6July2Mid0.716.9169.1069.1July3Mid0.716.6573.2073.2August1Mid0.716.3763.7063.7August2Mid0.716.1361.3061.3August3Mid0.715.7463.2063.2September1Mid0.715.353053September2Late0.745.0550.5050.5September3Late0.744.9249.20.149October1Late0.744.8648.60.548October2Late0.744.7247.20.846.4October3Late0.744.2246.52.743.8November1Late0.743.7374.932.1November2Late0.743.2232.26.725.6November3Late0.742.8828.87.721.1December1Late0.742.4924.99.415.5December2Late0.742.128.54.33.1Total1656.4172.51479.6Table 5
CWR of maize (grain) at different stages.
Year/Mon.DecadeStagesKcETc mm/dayETc mm/decEffective rainfall mm/decIWR mm/decDecember2Init0.30.865.26.50December3Init0.30.869.59.20.3January1Dev0.371.0610.67.13.5January2Dev0.631.7417.45.711.7January3Dev0.922.8331.14.926.2February1Mid1.184.0940.92.538.3February2Mid1.244.6646.60.945.7February3Mid1.245.2842.26.535.7March1Mid1.245.8958.914.944March2Late1.236.56520.744.2March3Late1.036.0166.117.748.5April1Late0.724.6146.11432.1April2Late0.453.1725.39.713.2Total464.9120.2343.6Table 6
CWR of barley at different stages.
Year/Mon.DecadeStagesKcETc mm/dayETc mm/decEffective rainfall mm/decIWR mm/decDecember2Init0.30.865.26.50December3Dev0.310.899.89.20.6January1Dev0.561.5915.97.18.8January2Dev0.912.5255.719.4January3Mid1.173.639.64.934.7February1Mid1.184.0740.72.538.1February2Mid1.184.4344.30.943.4February3Mid1.185.0140.16.533.6March1Mid1.185.65614.941.1March2Late1.115.8558.520.737.8March3Late0.814.751.717.734April1Late0.483.0830.81416.8April2Late0.281.965.93.60Total423.4114.2308.3Table 7
Rice crop data at various stages.
Crop NameRiceScientific NameOryza sativaPlanting date (KSA)15th December, 2020Harvest date13th April, 2021Growth stageStagesNurseryLand prepInitialDevelopMidLateTotalTotalPuddlingLength (days)3020520304030150Kc dry values0.700.300.50⟶1.050.70Kc wet value1.201.051.10⟶1.201.05Rooting depth (m)0.10⟶0.600.60Puddling depth (m)0.40Nursery area (%)10Critical depletion0.200.20⟶0.200.20Yield response friction11.091.091.091.09Crop height (m)1Only for rice crop we added nursery and land preparation time and Kc wet value; results show that at nursery stage, the Kc dry values and Kc wet values are 0.70 and 1.20; at land preparation stage, the Kc dry values and Kc wet values are 0.30 and 1.05; at land preparation stage, the Kc dry values and Kc wet values are 0.30 and 1.05; at initial and developing stages, the Kc dry values and Kc wet values are 0.50 and 1.10; at mid-season stage, the Kc dry values and Kc wet values are 0.05 and 1.20; and at late season stage, the Kc dry values and Kc wet values are 0.70 and 1.05.Table 8
Wheat crop data at various stages.
Crop NameSpring WheatScientific NameTriticum aestivumPlanting date (KSA)15th December 2020Harvest date23rd April 2021StagesInitialDevelopMidLateTotalLength (days)30304030130Kc values0.30⟶1.150.30Rooting depth (m)0.30⟶1.201.20Critical depletion0.55⟶0.550.80Yield response friction0.400.600.800.40Crop height (m)1The Kc value at the initial and developing stage is 0.30; at mid-season stage, the Kc is 1.15, and at late season stage, the Kc value is 0.30.Table 9
The Citrus crop data at various stages.
Crop NameCitrus ca barsScientific NameRutaceaePlanting date (KSA)15/12/2020Harvest date14/12/2021StagesInitialDevelopMidLateTotalLength (days)609012095365Kc values0.70⟶.650.70Rooting depth (m)1.40⟶1.401.40Critical depletion0.50⟶0.500.50Yield response friction11111Crop height (m)4The Kc value at the initial and developing stage is 0.70; at mid-season stage, the Kc is 0.65; and at the late season stage, the Kc value is 0.70.Table 10
The maize grain crop data at various stages.
Crop NameMaize GrainScientific NameZea maysPlanting date (KSA)15/03/2020Harvest date17/07/2020StagesInitialDevelopMidLateTotalLength (days)20354030125Kc values0.30⟶1.200.35Rooting depth (m)0.30⟶1.001.00Critical depletion0.55⟶0.550.80Yield response friction0.400.400.300.501.25Crop height (m)2The Kc value at initial and developing stage is 0.30; at mid-season stage, the Kc is 1.20; and at late season stage, the Kc value is 0.35.Table 11
Barley crop data at various stages.
Crop NameBarleyScientific NameHordeum vulgarePlanting date (KSA)15/10/2020Harvest date11/02/2021StagesInitialDevelopMidLateTotalLength (days)15255030120Kc values0.30⟶1.150.25Rooting depth (m)0.30⟶1.101.10Critical depletion0.55⟶0.550.90Yield response friction0.200.600.500.401.00Crop height (m)1The Kc value at initial and developing stage is 0.30; at mid-season stage, the Kc is 1.15; and at late season stage, the Kc value is 0.25.Tables2–6 reveals the results of total irrigative water requirements (IWRs), total effective rainfall and crop evapotranspiration (ETc) of five crops (rice, wheat, citrus, maize, and barley) in Qassim region; KSA are according to this order respectively:IWRs:(5)Barley308.3<Wheat335.9<Maize343.6<Rice853<Citrus1479.6.Total Effective Rainfall:(6)Rice47.9<Barley114.2<Maize120.2<Wheat125.2<Citrus172.5.Crop Evapotranspiration (ETc):(7)Barley423.4<Wheat461.5<Maize464.9<Rice659.3<Citrus1656.4.In Tables2–6 results reveal that 172.5% of effective rainfall has been recorded by citrus, 152.2% has been recorded by wheat, 120.2%, 114.2%, and 47.9% have been recorded by maize, barley, and rice, respectively, and Tables 12–16 shows the net irrigation mean and gross irrigation mean for clay loamy soils for wheat (210.6 mm and 147.4 mm), barley (176.6 mm and 123.6 mm), citrus (204.5 mm and 143.2 mm), and maize (163.9 mm and 114.7 mm), but not for rice crop. This analysis demonstrates that wheat has 4, barley has 4, citrus has 12, maize has 4, and rice crop has 12 irrigation schedules in a year. Figures 3–7 demonstrate the irrigation schedules of rice, wheat, citrus, maize, and barley, respectively [21].Table 12
Rice irrigation schedules, starting from the 25th of November and ending on the 13th of April of the next year.
DateDayStageEta (%)Puddl.Rain (mm)Ks (fract.)Percol.Depl. SM (mm)Net Gift (mm)Loss (mm)Depl. (mm)25-Nov−19PrePu90Prep00.904191.304010-Dec−4Puddl100Prep01049004014-Dec0Puddl100OK014.9054.304.323-Dec9Init100OK4.813.1095.50-4.510-Jan27Dev100OK013.10100.400.426-Jan43Dev100OK013.1095.30-4.79-Feb57Mid100OK013.1095.30-4.722-Feb70Mid100OK013.10100.800.88-Mar84Mid100OK013.1098.30-1.721-Mar97End100OK013.10100.100.12-Apr109End013.10100.800.813-AprEndEnd21380Depl.  = Depletion (mm); Percol. = percolation; Ks is the adjustment coefficient for water stress.Table 13
Wheat irrigation schedules.
DateDayStageRain (mm)Ks (fract.)Eta (%)Depl. (%)Net Irr. (mm)Deficit (mm)Loss (mm)Gr. Irr. (mm)Flow (L/s/ha)22-Jan8-FebDev011005698.800141.20.4224-Feb12-MarMid0110057136.800195.50.6931-Mar16-AprEnd0110061147.400210.60.723-AprEndEnd2110025Table 14
Citrus irrigation schedules.
DateDayStageRain (mm)Ks (fract.)Eta (%)Depl. (%)Net Irr. (mm)Deficit (mm)Loss (mm)Gr. Irr. (mm)Flow (L/s/ha)15-Dec1Init0110051142.10020323.56-Mar82Dev0110051141.900202.70.2925-Apr132Dev0110051142.600203.80.4720-May157Mid0110050140.400200.60.9311-Jun179Mid0110051143.600205.21.082-Jul200Mid0110051142.200203.21.1223-Jul221Mid011005114400205.61.1314-Aug243Mid0110051141.500202.11.068-Sep268Mid0110051142.400203.40.947-Oct297End0.3110051143.700205.20.8212-Nov333End0110051143.200204.50.6614-DecEndEnd01021Table 15
Maize irrigation schedules.
DateStageDayRain (mm)Ks (fract.)Depl. (%)Eta (%)Net Irr. (mm)Deficit (mm)Loss (mm)Gr. Irr. (mm)Flow (L/s/ha)12-JanDev29-Jan015510073.600105.20.4212-FebMid29-Feb0157100114.400163.40.6110-MarMid26-Mar0157100114.700163.90.7318-AprEndEnd0164100Table 16
Barley irrigation schedules.
DateDayStageRain (mm)Ks (fract.)Eta (%)Depl. (%)Net Irr. (mm)Deficit (mm)Loss (mm)Gr. Irr. (mm)Flow (L/s/ha)10-Jan27Dev011005693.500133.60.5711-Feb59Mid0110055121.1001730.6312-Mar88Mid0110056123.600176.60.713-AprEndEnd6.4110037Figure 3
Color reveals rice irrigation schedules showing depletion SAT (blue vertical lines pattern); depletion SM (red vertical lines pattern); SAT rootzone (dark blue line); TAM rootzone (dark green line); RAM rootzone (brown line); SAT puddle (blue thin line); and TAM puddle (green thin line).Figure 4
Color reveals the wheat irrigation schedules showing RAM (brown line); TAM (green line); and water depletion (red vertical line pattern).Figure 5
Color reveals the citrus irrigation schedules showing RAM (brown line); TAM (green line); and water depletion (red vertical line pattern).Figure 6
Color reveals the maize irrigation schedules showing RAM (brown line); TAM (green line); and water depletion (red vertical line pattern).Figure 7
Color reveals the barley irrigation schedules showing RAM (brown line); TAM (green line); and water depletion (red vertical line pattern).


## 4. Conclusion

The goal of this study was to determine IWRs and crop coefficients for wheat, barley, citrus, maize, and rice in the Qassim region. Penman-Monteith’s model estimated an average evapotranspiration of 6.33 mm/day. Citrus had more regular irrigation and evapotranspiration schedules than the four crops in this sequence, as shown by the above results:(8)Barley308.3<Wheat335.9<Maize343.6<Rice853<Citrus1479.6,and the order of effective rainfall of all crops is(9)Rice47.9<Barley114.2<Maize120.2<Wheat125.2<Citrus172.5.In these results, “ETo has increased from 2.84 mm/day to 9.61 mm/day, while effective rainfall has increased from 0 mm to 53.4 mm. For barley, wheat, maize, rice, and citrus, the overall IWRs were 308.3 mm/dec, 335.9 mm/dec, 343.6 mm/dec, 853 mm/dec, and 1479.6 mm/dec, respectively. Except for rice, total net irrigation and total gross irrigation for clay loamy soils are 210.6 mm and 147.4 mm, 176.6 mm and 123.6 mm, 204.5 mm and 143.2 mm, and163.9 mm and 114.7 mm, respectively, due to low demand in winter and high demand in summer. Wheat, barley, citrus, maize, and rice have irrigation schedules of 4, 4, 12, 4, and 12, respectively”, according to the data. Tables2–6 show the novelty of this work.



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*Source: 8552547-2021-11-22.xml*