Putting your field data to work: New end-of-season assessment tool for nitrogen management of corn silage

Optimizing nitrogen (N) management in corn silage production can help improve dairy farm profitability while reducing its environmental footprint. However, managing N remains difficult. Assessment tools and key performance indicators that show us how well N was managed during the cropping season once harvest is completed can be useful for fine-tuning N use over time. Recent work at Cornell University shows end-of-season N balance assessments could be a useful tool to improve N management over time. Comparing individual field results with feasible targets can help farmers identify opportunities to refine N management and support field experimentation through N.Y.’s adaptive N management process.

CALCULATING A FIELD N BALANCE

A field balance is the difference between nutrients supplied to the crop, and what is removed with harvest (Figure 1). Available N supply is the sum of the plant-available N contributions from soil, previous crop N credits, fertilizer, and manure (organic and inorganic N that can vary depending on manure type, application method, and timing). These can be estimated based on farm records, manure analysis and book values for various inputs. Nitrogen removal can be derived by multiplying measured yield and average N content in the field (see details on how we derive these values for N.Y. in Agronomy Factsheet 125). The ratio of N removal to N supply (N removal/available N supply) is another valuable indicator of N use efficiency that can be calculated with the same data.

INTERPRETING THE RESULTS

Once the available N balance and N removal/available N supply are calculated for a field, the results can be compared with feasible target values. A recent study with 994 corn silage fields in N.Y. resulted in a new “Green Operational Outcomes Domain (GOOD)” framework (Figure 2). Fields performing inside the GOOD (green area in Figure 2) have an N removal/available N supply that is at least 50 percent, and a field available N balance of 142 lbs. N per acre or less. Fields placed outside of the GOOD display the largest opportunities for N management refinement.

As manure is a valuable soil amendment and source of N frequently used in dairies, the GOOD framework also considers how effectively manure N was used for corn production. Fields with spring manure injection or surface application followed by incorporation, display the most efficient use of N and are represented with green triangles (Figure 3, Fields 1 and 3). Fields with manure applications outside of the growing season (fall/winter) or surface application without incorporation in the spring (more inefficient manure N use) are represented with a red square (Figure 3, Fields 2 and 4). Field 1 in Figure 3 displays the most efficient use of N (low balance, and high manure N use efficiency). Field 4 shows the largest opportunities for improved N management (large N balance plus low manure N use efficiency). Field 2 shows a low N balance, at the expense of inefficient manure N use, with opportunities for refinement via spring manure injection or incorporation. Similarly, Field 3 shows effective manure N use, but large N balance, with the opportunity to reassess N supplied to the crop.

PRIORITIZING MANAGEMENT INTERVENTIONS

Once fields outside of the GOOD are identified, additional graphical tools can help prioritize fields for improvement and give insight into potential management alternatives at the field and farm levels. First, fields can be ranked based on increasing N balances, to check those with largest gap between N supplied and N removed, and re-assess nutrient availability from sod, manure, and fertilizer for the past season or identify where nitrogen may not be a yield-limiting factor (Figure 4). Second, fields can be represented in a graph of N balance (vertical axis) versus crop yield (horizontal axis) (Figure 5). Fields with consistent high N balances and yields lower than the farm average should show the greatest opportunities for N management change (quadrant three in red, Figure 5).

ASSESSMENTS IN CONTEXT

Farms can utilize readily available data from field management and corn silage yield to calculate N use efficiency indicators (available N balance and N removal/available N supply) and compare their performance to the GOOD feasible targets. Farms can also use this framework to compare their performance with other farms, or with records of the same farm across multiple years. In N.Y., the adaptive N management process encourages farmers to experiment with different N application rates with the responsibility to assess if additional N beyond land-grant university guidelines resulted in improved yield and N use efficiency. The field N balance assessment and GOOD framework were developed with farmers and farm consultants and a database of 994 corn silage fields in N.Y., and as a result, the N balance and the GOOD feasible limits were added as an additional end-of-season evaluation option in New York in January of 2025.

MORE INFORMATION

If you are growing corn silage in N.Y. and interested in running this assessment for your farm or want to learn more about the process, please reach out to Quirine Ketterings.

The research that resulted in the development of the GOOD framework was published in the following journal articles:

• Olivo, A.J., O.F. Godber, K. Workman, K.J. Czymmek, K. Reed, D.V. Nydam, and Q.M. Ketterings (2024a). Doing GOOD: defining a green operational outcomes domain for nitrogen use in NY corn silage production. Field Crops Research.
• Olivo A.J., K. Workman, and Q.M. Ketterings (2024b). Enhancing nitrogen management in corn silage: insights from field-level nutrient use indicators. Frontiers in Sustainable Food Systems 8.

Guidance documents on conducting field N balances and its use under the adaptive management process in N.Y. can be found here:

• Cornell Cooperative Extension Agronomy Fact Sheet #125: Field Nitrogen Balances for Corn Silage.
• Ketterings, Q.M., K. Workman, J. Hornesky, S. Latessa, R. Bush, B. Jordan, and G.L. Albrecht (2025). Adaptive Nitrogen Management for Field Crops in New York. Cornell University, Ithaca NY.

This article appeared in PRO-DAIRY's The Manager in March 2025. To learn more about Cornell CALS PRO-DAIRY, visit PRO-DAIRY.