Nutrient Management: Accounting For Nitrogen Credits from Legumes and Manure
alternative practice names:
Nitrogen credits refer to the amount of nitrogen available to crops from organic sources, such as legumes, manure, or crop residues. By accounting for these natural nitrogen sources during nutrient management planning, farmers can reduce the application of commercial nitrogen fertilizers while still meeting crop nutrient requirements. Key sources of nitrogen credits include:
Legumes: Crops like alfalfa, soybeans, and clover fix atmospheric nitrogen through a symbiotic relationship with soil bacteria, leaving nitrogen in the soil for subsequent crops. This residual nitrogen can be used by the next crop in rotation, reducing the need for synthetic nitrogen fertilizers.
Manure: Manure contains both inorganic nitrogen, which is immediately available, and organic nitrogen, which mineralizes over time. The rate of nitrogen release depends on factors such as temperature, moisture, and microbial activity, with warmer and moist conditions accelerating the mineralization process. Research shows that roughly one-third of the nitrogen from manure is typically available to crops within the first year, with the remainder being released more gradually over subsequent years (Van Kessel et al. 2002).
Crop residues: Residues from previous crops, such as grass, corn, or wheat, can also contribute to nitrogen in the soil through decomposition, providing additional nitrogen credits.
Residual nitrogen, the portion of organic nitrogen not immediately available to plants, becomes accessible over time through a process known as microbial mineralization. This gradual release provides a steady supply of nutrients, which often aligns well with the nitrogen demands of crops such as grains and forages throughout the growing season. The amount of nitrogen made available depends on several factors, including the species of legume used, how the previous crop or cover crop was terminated, the composition and properties of the manure, and environmental conditions like temperature and moisture.
When used, in what regions in the U.S. is the practice found:
Northwest, West, Upper Midwest, Southwest, Northeast, Southeast
FARM SIZE
When used, typically found on farms of the following sizes:
All Sizes

Practice Benefits
Cost savings: By properly accounting for the nitrogen provided by legumes and manure, farmers can reduce their use of commercial fertilizers, which lowers input costs.
Increased yield stability: Organic nitrogen sources, such as legumes and manure, release nitrogen slowly over time, providing a steady supply of nutrients that promotes consistent crop growth and yield stability.

Implementation Insights
Site-specific or Farm-specific requirements

In most cases, there are no specific site or farm requirements.
Required Capital Expenditures (CapEx)

There are no capital expenditures associated with this practice.
Required Operational Expenditures (OpEx)

Agronomy support: Farmers can collaborate with agronomists to refine their nutrient management plans, ensuring that all relevant factors, such as previous legume crops and manure application history, are considered. Farmers should inquire about how nitrogen rate recommendations are calculated. Understanding whether the recommendations are based on a Pre-Sidedress Nitrate Test (PSNT), a deep soil test (which is more common in arid areas), or other methods helps farmers make more informed decisions.
Soil testing: Soil testing can be a valuable tool for farmers looking to refine nitrogen application rates, although nitrogen levels fluctuate due to microbial activity, temperature, and moisture, making it difficult to obtain accurate readings at any single point in time. While soil nitrogen test results can be accurate, they should be interpreted with caution, particularly in rain-fed regions where conditions are more variable. Consistent testing over time helps farmers gain confidence in their results and improve nutrient management. Using other diagnostic tools can enhance reliability and decision-making. In rain-fed areas, the PSNT can be used to estimate nitrogen requirement at the time of sidedessing in corn fields. In arid regions, deeper soil tests (1-2 feet) require more effort but can provide critical information about nitrogen availability for better recommendations. Combining these approaches allows for optimized nitrogen use and improved crop yields.
Implementation Considerations

Variability in mineralization rates: The rate at which nitrogen mineralizes from organic matter depends on numerous factors, including temperature, moisture, soil texture, and microbial activity. These factors fluctuate over time, making it difficult to predict nitrogen availability consistently. Warm, moist conditions typically accelerate mineralization, but drought or cold conditions can slow the process significantly.
Timing unpredictability: The release of nitrogen from organic materials often doesn’t align perfectly with crop demand. For example, nitrogen can mineralize during periods when crops are not actively growing, such as early spring or fall. This can result in nitrogen losses through leaching or runoff, particularly in temperate or rain-fed regions.
Environmental factors: Climate conditions, such as rainfall and temperature patterns, greatly influence nitrogen mineralization. In arid or drought-prone areas, mineralization may be slow, while in wetter regions, the risk of nitrogen leaching can increase if mineralization occurs when crops are not present to absorb it.
Financial Considerations and Revenue Streams
PROFIT POTENTIAL
Reducing commercial nitrogen application by accounting for nitrogen credits from manure and legumes will reduce input expenses.
FEDERAL COST-SHARE PROGRAM
Funding is available for this practice through USDA's Natural Resources Conservation Service (NRCS) Environmental Quality Incentives Program (EQIP).
Related EQIP Practice Standard: Nutrient Management (590).
Notes:
Check with the local NRCS office on payment rates and practice requirements relevant to your location.
A Nutrient Management Plan (NMP) may be required to receive implementation funding for this practice.
Additional Resources
Article: Field-Specific Nitrogen Fertilization Adjustments (University of California-Davis)
Article: Include Last Year's Nitrogen Credits in Your Fertility Plan This Year (University of Minnesota)
Article: Nitrogen Release from Cover Crops (Sustainable Agriculture Research and Education)
Article: The 5 R's of Precision Agriculture (South Dakota State University)
Factsheet: Nitrogen Credits from Manure (Cornell University)
Factsheet: Nitrogen Credits from Red Clover as Cover Crop Between Small Grains and Corn (Cornell University)
Factsheet: Soybean N Credits (Cornell University)
Tool: Calculating Manure Nitrogen Credits from Prior Years (University of Maryland)
Tool: Manure/Legume Credits (University of Wisconsin-Madison)
Tool: Nitrogen Input Credits (University of California-Davis)

Environmental Impacts
REDUCES FARM GREENHOUSE GAS FOOTPRINT
By accurately accounting for nitrogen contributions from legumes and manure during nutrient management planning, farmers reduce their use of commercial nitrogen fertilizer, thus reducing the greenhouse gases associated with its production. Commerial fertilizers are energy-intensive to produce and contribute to greenhouse gas (GHG) emissions during manufacturing. Additionally, when nitrogen is not overapplied, the risk of nitrous oxide emissions is also minimized.
See research highlights below:
According to Ma et al. (2012), rotations with legumes such as alfalfa or soybean reduced the carbon footprint of maize production due to increased productivity, with maize following legumes at 100 kg N/ha resulting in up to 42% lower GHG emissions and 46% lower carbon footprint compared to maize monoculture treated with 200 kg N/ha.
IMPROVES WATER QUALITY
Estimating nitrogen contributions from residual soil organic nitrogen and other organic nitrogen sources, such as manure and legume crops, during nutrient planning allows farmers to better match crop nitrogen needs without over-application. This minimizes the risk of excess nitrogen leaching into groundwater or running off into surface water.
REFerences

Alignment with FARM Program
FARM Environmental Stewardship (ES) V2-V3 Alignment
FARM ES Version 3 includes an optional crop module, allowing users to enter their crop management. Users can enter which crops are being planted on certain fields, allowing for farms to reflect their unique practices in the model.
Contents
We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights.
We're always eager to update the website with the latest research, implementation insights, financial case studies, and emerging practices. Use the link above to share your insights.
Nitrogen credits refer to the amount of nitrogen available to crops from organic sources, such as legumes, manure, or crop residues. By accounting for these natural nitrogen sources during nutrient management planning, farmers can reduce the application of commercial nitrogen fertilizers while still meeting crop nutrient requirements. Key sources of nitrogen credits include:
Legumes: Crops like alfalfa, soybeans, and clover fix atmospheric nitrogen through a symbiotic relationship with soil bacteria, leaving nitrogen in the soil for subsequent crops. This residual nitrogen can be used by the next crop in rotation, reducing the need for synthetic nitrogen fertilizers.
Manure: Manure contains both inorganic nitrogen, which is immediately available, and organic nitrogen, which mineralizes over time. The rate of nitrogen release depends on factors such as temperature, moisture, and microbial activity, with warmer and moist conditions accelerating the mineralization process. Research shows that roughly one-third of the nitrogen from manure is typically available to crops within the first year, with the remainder being released more gradually over subsequent years (Van Kessel et al. 2002).
Crop residues: Residues from previous crops, such as grass, corn, or wheat, can also contribute to nitrogen in the soil through decomposition, providing additional nitrogen credits.
Residual nitrogen, the portion of organic nitrogen not immediately available to plants, becomes accessible over time through a process known as microbial mineralization. This gradual release provides a steady supply of nutrients, which often aligns well with the nitrogen demands of crops such as grains and forages throughout the growing season. The amount of nitrogen made available depends on several factors, including the species of legume used, how the previous crop or cover crop was terminated, the composition and properties of the manure, and environmental conditions like temperature and moisture.
Practices and technologies
Nutrient Management: Accounting For Nitrogen Credits from Legumes and Manure
alternative practice name: