Using Forage Quality Testing to Predict Nitrogen Replacement Value of Cover Crops

Project Overview

Project Type: Graduate Student
Funds awarded in 2010: $9,967.00
Projected End Date: 12/31/2011
Grant Recipient: South Dakota State University
Region: North Central
State: South Dakota
Graduate Student:
Faculty Advisor:

Annual Reports


  • Agronomic: corn


  • Crop Production: cover crops, no-till, nutrient cycling
  • Production Systems: general crop production
  • Soil Management: nutrient mineralization

    Proposal abstract:

    Cover crops can provide environmental and economic benefits. To broaden their use it is essential to be able to demonstrate and quantify the economic benefits of cover crops to make planting them more attractive to the farmer. Depending on their rate of breakdown, cover crops can have positive or negative effects on nitrogen (N) availability for the following crop. As N fertilizer costs climb, the incentive increases for an improved ability to predict cover crop effects on N availability for the following crop. This is an important consideration for optimum management of N in the cropping system. We propose to evaluate the use of familiar forage tests including acid detergent fiber (ADF), neutral detergent fiber (NDF), and crude protein (CP) to predict the cover crops effect on N availability. Cover crop forage test results will be compared to the cover crop residue N mineralization rates observed in a controlled laboratory setting and in a field study. On a field plot scale various cover crops will be planted following the harvest of winter wheat in an on-farm study. Forage quality testing will be done on the cover crops. The cover crops will be followed by corn fertilized with a range of N rates the next year. The yield and N response of the corn will be evaluated on each cover crop plot and compared to cover crop biomass and forage analysis to see what relationships can be made. The goal of this research is to provide a tool to help producers quantify the benefits of cover crops in terms of N credit for the following crop by using familiar and readily available forage testing on the cover crops. This will aid the producer when considering the value of different cover crops on their farm.

    Project objectives from proposal:

    For each cover crop a Nitrogen Fertilizer Equivalent (NFE)value will be determined. That is, the amount of N that was taken up in the cover crop and made available through mineralization to the following corn crop. This NFE will be compared to the fiber tests of the cover crops to determine the extent of the relationship between fiber content and NFE.

    Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.