Cover crops as nitrogen source

Christina Curell, Michigan State University Extension - April 01, 2015

Learn how cover crops can produce Nitrogen for your fields.

Cover Crops can be used to produce Nitrogen. The following charts rates legumes as a nitrogen source and gives nitrogen production from common cover crop species.

The reasons why farmers use cover crops are as varied as the number of species that can be used as a cover crop. Traditionally cover crops were used for erosion control but in the past few years’ cover crops have been used for other purposes.

Nitrogen is necessary for all plant growth. Legumes have the ability to “fix” nitrogen from the air and store it in nodules in their roots. This nitrogen can be released or use by subsequent crops.

The following chart rates typical legume cover crops grown in Michigan for its nitrogen fixation tendencies. Do not confuse nitrogen scavenging for nitrogen fixing. These are different concepts that will be addressed and I will address them in a subsequent article.

Excellent	Very Good	Good	Fair
Berseem Clover	Crimson Clover
Cowpea	Red Clover
Field Pea
Hairy Vetch
Sweet Clover
White Clover

Chart information taken from Managing Cover Crops Profitably third edition, SARE Handbook Series 9.

There have been many research studies conducted to determine how much nitrogen cover crops produce. There are many factors that determine how much nitrogen can be credited to cover crop. For that reason a large range for nitrogen credit is given, see chart below. It is very important to take a good soil sample if you plan to use cover crops as a nitrogen source. It is also advisable to follow up with a plant tissue analysis to ensure that you have enough nitrogen for production.

Cover Crop	Lb./A *
Mustard	30-120
Radish	50-200
Rapeseed	40-160
Berseem Clover	75-220
Cowpea	100-150
Crimson Clover	70-130
Field Pea	90-150
Hairy Vetch	90-200
Red Clover	70-150
Sweetclover	90-170
White Clover	80-200

* Total Nitrogen from the entire plant

Chart information taken from Managing Cover Crops Profitably third edition, SARE Handbook Series 9.

For more information or to help decide what cover crop will be best for your farm contact Michigan State University Extension educators Christina Curell, curellc@anr.msu.edu or Paul Gross, grossp@anr.msu.edu. More information can also be found at the Midwest Cover Council website.

This article was published by Michigan State University Extension. For more information, visit https://extension.msu.edu. To have a digest of information delivered straight to your email inbox, visit https://extension.msu.edu/newsletters. To contact an expert in your area, visit https://extension.msu.edu/experts, or call 888-MSUE4MI (888-678-3464).