Organic Fertilizer and Cover Crop Calculators

These free online tools allow you to compare the nutrient value and cost of cover crops, organic and synthetic fertilizers and compost in acre and 1,000 ft2 units. You can use them to estimate nitrogen supplied by cover crops and organic fertilizers, and develop well balanced and cost effective nutrient management programs for your farm. The resources provide cover crop sampling instructions and describe some of our research into cover crop nitrogen release. Developed by Nick Andrews, Dan Sullivan, Jim Julian and Kristin Pool.

Select a calculator based on your preferred units:

This version makes calculations on a per acre basis.

Use these worksheets to calibrate cover crop seeders.


This quick guide illustrates the main steps used to sample cover crops and use the calculator, the records sheet identifies the information needed to use the calculator.

This PNW Extension Publication explains how to sample cover crops, introduces a shortcut method for estimating cover crop plant-available nitrogen (PAN) release, describes the science behind cover crop PAN estimates, and uses on-farm case studies to address other frequently asked questions about cover crop PAN.

This OSU Extension Publication describes the research conducted to develop the mineralization models used in the Calculator. 

This work was sponsored by Western Sustainable Agriculture Research and Education (projects FW06-301 and FW09-328) and Oregon Tilth, Inc.

We also thank Stutzman Environmental ProductsConcentrates Inc.Wilbur-Ellis Company, and Bridgewell Resources for supporting this work with their donations.