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www.ia.nrcs.usda.gov

to protect groundwater sources of drinking water

Cropland Conservation Practices

United States Department of Agriculture

Natural Resources Conservation Service

Des Moines, Iowa

Ninety-two percent of Iowa’s public water systems use 

groundwater as their source. Rainwater is the source of 

much of this water, helping to recharge much of Iowa’s 

groundwater. Landowner and farm operator decisions 

impact water quality, safety, treatment costs, and even 

drive the need to find alternative water sources to replace 

contaminated public and private water supplies.

Impacted wells could be on your farm, which provide 

water for your family or livestock. The well may supply a 

rural water system or serve your neighbors in a nearby 

community. Fields in your operation might have been 

identified as part of a public well’s source water capture 

zone, possibly for a well already showing signs of 

contamination.

When developing the production and conservation systems for your farm, consider how to best prevent polluting groundwater through fertility and agronomic activities. NRCS staff and your local soil and water conservation 

district (SWCD) are available to help you make decisions 

to sustain your operation and protect drinking water 

sources. To build your strategy: 

1. Use nutrient management to avoid exceeding the 

nitrogen needs of the crop and to optimize N use 

efficiency.

2. Trap nitrogen using cover crops.

3. Build a resilient N management system using multiple 

conservation strategies and improve your soil’s health.

Consider installing the following conservation practices 

to improve drinking water quality while meeting your 

production objectives.
Conservation Practice Description Key Points Decision

Nutrient Management (590): 4R Nutrient Management Plan

The 4Rs of nutrient management – apply the Right nutrient source at the Right rate 

at the Right time in the Right 

place – to improve nutrient use 

efficiency by the crop and to 

minimize nutrient losses to the 

surface and groundwater.

•Apply the plan to optimize 

production using Iowa State 

University recommendations

•Consider how changing one 

“R” impacts others.

•Account for all nutrient 

sources

•Keep records

•Update plan as needed

Field #

Nutrient Management (590): Right Source

Determine the nitrogen, 

phosphorus, potassium and 

other nutrient needs based 

on crop requirements and soil 

properties. Examples: swine 

or poultry manure, alfalfa or 

clover rotation, or nitrapyrin 

for fall applied anhydrous.

Select the Right nutrient 

source, considering:

•what the crop needs

• cost

• availability

•method of delivery

• environmental risk

Field #

Nutrient Management (590): Right Rate

Match application rates with 

crop requirements. Use soil 

testing, crop history, in-season 

testing, crop nutrient budgets 

and adaptive management to 

determine application rates.

Use ISU recommendations to 

select the Right rate:

•Use the Corn Nitrogen Rate 

Calculator to determine the 

recommended Maximum 

Return to Nitrogen rate.

•Apply P and K based on the 

soil test.

Field #

Nutrient Management (590): Right Time

Synchronize nutrient availability with crop demand and 

reduced environmental risk. 

•Consider applying nitrogen in 

the spring.

•Consider a split application of 

N based on testing.

• For fall applied anhydrous 

ammonia and high 

ammonium manures, apply 

when daily soil temperatures, 

at a 4-inch depth, are 50 

degrees and trending colder.

Field #

Nutrient Management (590): Right Place

Place and keep nutrients 

where the crop can get to 

them, where nutrients are least 

likely to leave the field, and efficiency in maximized.

•Inject or incorporate nutrients 

to prevent runoff

•Place the nutrients where the 

crop’s roots can efficiently get 

to them.

Field #

to protect groundwater sources of drinking water

Cropland Conservation Practices
Conservation Practice Description Key Points Decision

Nutrient Management (590): Soil Sampling

Take soil samples typically six 

inches deep. For one sample, 

take 15-20 soil cores representing the sample area. A sample 

represents a maximum 10-acre 

area, smaller for precision ag.

•Determines nutrient, pH, and 

organic matter content.

•Agronomic interpretations 

determine recommended P, K, 

and lime application rates.

•Used to determine risk of P 

runoff.

• Late Spring Soil Nitrate Test

Field #

Nutrient Management (590): Calibration

Calibrate equipment used to 

apply fertilizer and manure to 

assure that what you plan to 

apply is actually applied.

•Calibrate using scales when 

unit is full, empty, and acres 

covered.

•Properly plumb and 

maintain anhydrous ammonia 

applicators.

• Speak with your custom 

applicator to verify.

Field #

Cover Crop (340): Winter Hardy (e.g. cereal rye)

Winter hardy cover crops are 

planted into or after a cash 

crop to scavenge nutrients, 

reduce erosion, suppress 

weeds, provide winter grazing 

for livestock, and increase 

soil organic matter. Examples 

include rye, winter wheat, and 

hairy vetch.

• Select species that fit your 

cropping system.

• Learn from producers who 

have experience with cover 

crops.

•Have a plan to terminate the 

crop in the spring, so that it 

does not compete with your 

cash crop.

Field #

Cover Crop (340): Winter Kill (e.g. oats)

Winter killed cover crops are 

planted into or after a cash 

crop to scavenge nutrients, 

reduce erosion, and increase 

soil organic matter. Examples 

include oats, radishes, and 

turnips.

•Need to be planted early to 

have enough fall growth to 

make a difference.

•Do not require spring 

termination.

Field #

Cover Crop (340): Multiple Species

Planting a diverse mix of cover 

crops prior to or following 

harvest can improve the vigor 

of the cover crops, reduce 

compaction, feed livestock, 

and improve soil health.

• Experiment with new mixes 

of cover crops to improve 

management.

•As part of the conservation 

planning process, develop 

mixes to test in your operation 

that will meet your needs.

Field #

to protect groundwater sources of drinking water

Cropland Conservation Practices
Conservation Practice Description Key Points Decision

Conservation Crop Rotation (328): Perennials

Growing a perennial crop in the 

rotation reduces nitrate loss 

and soil erosion and improves 

soil health. Legume perennials fix nitrogen for future grain 

crops. Crop sequences can 

break weed and insect cycles 

and reduce the need for pesticides.

•Weather conditions and 

marketing considerations 

may affect year-to-year cropping decisions and require a 

change in scheduled rotation.

•Markets for perennial crops 

are needed.

Field #

Conservation Crop Rotation (328): Extended Rotations with Small Grains

Including small grains in your 

rotation reduces soil erosion, 

reduces nitrogen leaching, and 

improves soil health. Extended 

rotations also diversify a farming operation economically.

• Extending rotations can 

improve soil health. 

•Markets for small grain crops 

are needed.

Field #

Conservation Crop Rotation (328): Grazed Pasture

In a 6-7 year conservation crop 

rotation that includes perennials, livestock producers can 

optimize their land use by 

adding grazing to the rotation. 

Consecutive years of alfalfa or 

clover can provide essential 

livestock grazing.

•Alfalfa may require more 

intense management to 

attain desired yields.

•Consider no-till planting 

alfalfa after soybeans. This 

requires uniform planting 

depth, good soil to seed 

contact and a firm seedbed.

Field #

Integrated Pest Management (595)

Implement diverse management practices to limit agricultural pests and to reduce 

potential adverse effects on 

plant growth, crop production, 

human health, pollinators, and 

wildlife.

•Respond to cropping system 

and complex pest changes, 

and avoid the development of 

pest resistance.

•Periodically review your plan 

when the rotation changes or 

when new pesticides need to 

be used.

Field #

Filter Strip (393)

A strip or area of vegetation 

next to a stream, lake, or other 

water body that helps remove 

sediment, organic matter, and 

other pollutants from runoff 

and wastewater. Filter strips 

also provide cover for wildlife.

•Minimize the development of 

rills and small channels within 

filter areas to allow re-establishment of sheet flow.

•Maintain vigorous vegetation.

• Fence off livestock from filter 

strips.

Field #

to protect groundwater sources of drinking water

Cropland Conservation Practices