Analyzing Trends in Nitrogen Applications and Management Practices
Using Data to Understand Adoption Patterns of Nitrogen Management Practices
Through the Nitrogen and Irrigation Initiative, we are using advanced statistical analysis to analyze trends in nitrogen application rates and adoption of nitrogen management practices in California. Using Irrigated Lands Regulatory Program data from the Central Coast and Central Valley, we are analyzing trends in nitrogen use and uptake across crops, farm sizes, and regions. The long-term goal of the work is to evaluate economic benefits and costs of adopting nitrogen management practices and inform improved education, extension, and research offerings.
Our first published study analyzed nitrogen use trends in Kings River region of the San Joaquin Valley, including nitrogen use across crop types and years.
Authors
Divya Prakash, Erik Porse, Mehdi Nemati, Rachel Shellabarger, Ariel Dinar
Citation
Prakash, Divya, Erik Porse, Mehdi Nemati, Rachel Shellabarger, and Ariel Dinar. "Adoption patterns of on-farm nutrient management practices and nitrogen application rates in California's Central Valley." California Agriculture 79, no. 2 (2025).
Abstract
Nitrogen fertilizers in irrigated agriculture improve cropland productivity, but contribute to groundwater contamination, air pollution, and greenhouse gas emissions. While California has implemented agricultural water quality regulations since the 1980s, targeted efforts to address nitrate contamination through nitrogen application reporting and management have been especially emphasized more recently under the Irrigated Lands Regulatory Program (ILRP). This study uses a unique, field-level dataset from the Kings River Water Quality Coalition (KRWQC) in California’s Central Valley to examine nitrogen management practices, including common combinations of practices (bundling), across crop types. The analysis draws on four years of data from Irrigation and Nutrient Management Plans (INMPs), detailing nitrogen application and management strategies. The results show that in 80% of fields across crops, between 50 and 300 pounds per acre (lbs/acre) of nitrogen is applied. Crop-level nitrogen applied minus nitrogen removed (A-R) values show substantial variation, with walnuts showing a nitrogen surplus (+ 65.5 lbs/acre) and alfalfa a significant deficit (– 424.5 lbs/acre). Many growers adopt multiple practices, with 26% of fields utilizing six practices and 24% using five. Such bundling may provide growers with more flexibility in managing nitrogen. Further research is needed to evaluate the effect of various nitrogen management practices on fertilizer application.