Decision Support to Reduce the Nitrogen Yield Gap in Organic Agriculture
Project Director
Jason P. Kaye
Year Funded
2020
Award Number
2020-51300-32178
Funded Institution
Pennsylvania State University
Grant Program
OREI (Organic Agriculture Research and Extension Initiative)
USDA NIFA Report
Project Overview
This project refined an existing decision support tool for optimizing fertilizer N rate for corn production to cover the range of agricultural soils across Pennsylvania and to account for N contributions from soil organic matter (SOM) and cover crop residues. Project objectives included:
(1) Agronomic validation – multisite N rate field trials with corn grown after various cover crops and in a wide range of soil textures and SOM levels.
(2) Biogeochemical validation – lab studies with soils collected from 36 fields across PA and southern NY to test model assumptions about soil and microbial carbon-to-nitrogen (C:N) ratios and humification efficiency (% of residue carbon converted to soil organic carbon).
(3) Outreach, tool testing, and tool delivery – farmers tried out the tool and provided feedback. The tool was fine-tuned and expanded to identify the economic optimum nitrogen rate (EONR) based on fertilizer costs and farmgate price for corn.
The improved model uses measured soil C:N (rather than an assumed value of 10:1), and considers % sand, % clay, and summertime precipitation, all of which affect N cycling and crop N availability. Cover crop N credit is determined by biomass N and C:N ratio. The tool now includes a cover crop look-up table based on analyses of 1,200 cover crop samples so that users do not need costly and time-consuming N measurements to estimate cover crop N contribution. The updated tool demonstrated substantially improved accuracy in predicting corn yield response to N and pinpointing the EONR.
Farmer Takeaways
(1) An updated fertilizer nitrogen (N) rate decision support tool for corn production in Pennsylvania is now available online (see Farmer resources below).
(2) The tool accounts for N released from soil organic matter (SOM) and cover crops, considering soil texture, soil carbon-to-nitrogen (C:N) ratio, and summertime rainfall.
(3) The tool was developed with farmer input and was tested on multiple organic farms representing a range of soil textures and SOM levels.
(4) Users enter data on soil texture, SOM, soil C:N ratio, cover crops, fertilizer cost ($/lbN) and corn price ($/bu). The model predicts unfertilized corn yield and N fertilizer response curve and recommends an economic optimum N rate.
Project Outputs
Nitrogen Decision Support Tool for Corn | Penn State
Article: Soil Organic Matter and Cover Crop-based Nitrogen Recommendations for Corn | Penn State
Arrington, K. E., Ordóñez, R. A., Rivera-Ocasio, Z., Luthard, M., Tierney, S., Spargo, J., Finney, D., Kaye, J. P., & White, C.M. (2024). Improving a nitrogen mineralization model for predicting unfertilized corn yield. Soil Science Society of America Journal,88(3), 905-920.
Zhang, Z, J.P. Kaye, B.A. Bradley, J.P. Amsili, V. Suseela. (2022). Cover crop functional types differentially alter the content and composition of soil organic carbon in particulate and mineral-associated fractions. Global Change Biology 28: 5831-5848.
White, C.M., Finney, D.M., Kemanian, A.R., and Kaye, J.P. (2020). Modeling the contributions of nitrogen mineralization to yield of corn. Agronomy Journal.