Decision Support Tools

• Oregon State University Organic Fertilizer and Cover Crop Calculator – This downloadable spreadsheet uses models that predict nitrogen release from cover crops, organic fertilizers and compost that were developed in western Oregon. It also includes economic calculations that compare the cost and value of different amendments on your farm (website and downloadable spreadsheet)
• University of Hawaii Cover Crop Calculator – This online model predicts nitrogen release from cover crops based on research conducted at the University of Hawaii with predictions for Oahu, Hawaii, Kauai, Maui and Molokai (website)
• University of Idaho Cover Crop Nitrogen Model – This paper describes research done to develop a cover crop nitrogen release model in Idaho (article)
• Cover Crop Nitrogen Calculator (CC-NCALC) – This online model predicts models that predict nitrogen release from no-till cover crops in rain fed cropping systems using site-specific soil and weather data. It has not been tested in the western U.S. (website)

General

• Estimating Plant-Available Nitrogen Release from Cover Crops – This PNW Extension Publication describes cover crop sampling methods and research into cover crop nitrogen release and immobilization (Extension Publication)
• OSU Organic Fertilizer & Cover Crop Calculator: Predicting Plant-available Nitrogen – This publication describes the research supporting the mineralization models that predict nitrogen release from cover crops and organic fertilizers (Extension Publication)
• Cover Crop Effects on Light, Nitrogen, and Weeds in Organic Reduced Tillage – This research investigated the effects of cover crop type on biomass production, soil nitrate levels and light transmitted to the soil surface in reduced tillage organic crops in western Washington (Journal Article)
• The influence of cover crop variety, termination timing and termination method on mulch, weed cover and soil nitrate in reduced-tillage organic systems – This research investigated legume and grain cover crops terminated with a roller crimper and a roller crimper at different times in western Washington. They measured termination effectiveness, soil nitrate levels and weed populations (Journal Article – paywall) 
• Soil Nitrate Testing for Willamette Valley Vegetable Production (2019) EM9221 – This publication describes how to use in-season soil nitrate testing to adjust sidedress N fertilizer application rate to match crop N requirements based on research conducted in western Oregon (Extension Publication)
• Baseline Soil Nitrogen Mineralization: Measurement and Interpretation (2020) EM9281 – Cover crops and other organic amendments can increase the amount of nitrogen released from soil organic matter. This publication discusses some soil tests that can measure this relative change in soil health (Extension Publication)