Building Soils for Better Crops, p101

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Building Soils for Better Crops, 3rd Edition
Sustainable Agriculture Research and Education (SARE).

The publication can be downloaded from SARE’s web site.
Sustainable Agriculture Research and Education – Publications – Building Soils for Better Crops, 3rd Edition.
To obtain paper copies, contact SARE.

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* Front Cover.
* Contents.
* About the Authors.
* About SARE.
* Preface.
* Introduction.
* 1.Healthy Soils.
* 2.Organic Matter: What It Is and Why It’s So Important.
* 3.Amount of Organic Matter in Soils.
* 4.The Living Soil.
* 5.Soil Particles, Water, and Air.
* 6.Soil Degradation: Erosion, Compaction, and Contamination.
* 7.Nutrient Cycles and Flows..
* 8.Soil Health, Plant Health, and Pests.
* 9.Managing for High-Quality Soils: Organic Matter, Soil Physical Condition, Nutrient Availability.
* 10.Cover Crops.
* 11.Crop Rotations.
* 12.Animal Manures for Increasing Organic Matter and Supplying Nutrients.
* 13.Making and Using Composts.
* 14.Reducing Erosion and Runoff..
* 15.Preventing and Lessening Compaction.
* 16.Reducing Tillage.
* 17.Managing Water: Irrigation and Drainage.
* 18.Nutrient Management: An Introduction.
* 19.Management of Nitrogen and Phosphorus.
* 20.Other Fertility Issues: Nutrients, CEC, Acidity, and Alkalinity.
* 21.Getting the Most from Routine Soil Tests.
* 22.How Good Are Your Soils? Field and Laboratory Evaluation of Soil Health.
* 23.Putting It All Together.
* Glossary.
* Resources.
* Index.
* Back Cover.

Chapter 10
Cover Crops
Where no kind of manure is to be had, I think the cultivation of lupines will be found
the readiest and best substitute. If they are sown about the middle of September in a poor soil,
and then plowed in, they will answer as well as the best manure.
—Columella, 1st century, Rome

Cover crops have been used to improve soil and
the yield of subsequent crops since antiquity. Chinese
manuscripts indicate that the use of green manures is
probably more than 3,000 years old. Green manures
were also commonly used in ancient Greece and Rome.
Today, there is a renewed interest in cover crops, and
they are becoming important parts of many farmers’
cropping systems.
Three different terms are used to describe crops
grown specifically to help maintain soil fertility and
productivity instead of for harvesting: green manures,
cover crops, and catch crops. The terms are sometimes
used interchangeably and are best thought of from the
grower’s perspective. A green manure crop is usually
grown to help maintain soil organic matter and increase
nitrogen availability. A cover crop is grown mainly to
prevent soil erosion by covering the ground with living
vegetation and living roots that hold on to the soil. This,
of course, is related to managing soil organic matter,
because the topsoil lost during erosion contains the
most organic matter of any soil layer. A catch crop is
grown to retrieve available nutrients still in the soil following
an economic crop and prevents nutrient leaching
over the winter.
Sometimes which term to use is confusing. We usually
have more than one goal when we plant these crops
during or after our main crop, and plants grown for one
of these purposes may also accomplish the other two
goals. The question of which term to use is not really
important, so in our discussion below, the term cover
crop will be used.
Cover crops are usually killed on the surface or
incorporated into the soil before they mature. (This
is the origin of the term green manure.) Since annual
cover crop residues are usually low in lignin content and
high in nitrogen, they decompose rapidly in the soil.
Photo by Tim McCabe

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