Cover Cropping Improves Soil Properties and Reduces Greenhouse Gas Emissions

The Issue

Diversifying crop rotations may be a means for reducing disease pressures and improving long-term productivity in California’s annual crop production valleys. Using “off-season” or intercrop cover crops might be a useful crop diversification strategy that also could add organic matter to the soil and improve soil function and quality. In general, farmers have little experience with cover-cropping practices and have been reluctant to use them.

What Has ANR Done?

Over the past several years, UC scientists Jeff Mitchell, William Horwath, Gene Miyao, and Johan Six worked to evaluate the impacts of adding winter cover crops to annual crop rotations in California’s San Joaquin and Sacramento Valley production regions. In a study initiated in 1999 at the UC West Side Research and Extension Center in Five Points, Calif., the use of triticale/rye/vetch cover crops increased soil carbon by an average of 4,000 pounds per acre after four years under standard tillage and by 4,456 pounds per acre in a conservation or reduced tillage system.
When projecting these results into the future to take into account the storage and emissions of various greenhouse gases such as CO2, CH4, and N2O, the cover-crop systems -- particularly when coupled with reduced tillage -- can reduce emissions significantly relative to today’s standard systems in which cover cropping and conservation tillage are not used. In addition, the use of subsurface drip systems may enhance the effects of cover crops and conservation tillage in reducing greenhouse gases.

The Payoff

Cover cropping shows benefits

This initial research shows a number of potential benefits to using cover crops in Central Valley annual-cropping systems, including the improvement of soil properties and the mitigation of greenhouse gas emissions. Researchers and farm advisors are busy developing more grower-friendly practices and systems. They are studying the use of subsurface drip or overhead low-pressure irrigation systems in cover-crop systems, the evaluations of various new cover crops and mixes, the timing of cover-crop establishment and termination, how to efficiently manage irrigation water resources in cover-crop systems, and more efficient means for cover-crop incorporation or management systems.

Contact

Jeff Mitchell, Cooperative Extension Specialist, UC Davis Department of Plant Sciences, mitchell@uckac.edu
William Horwath, Professor, UC Davis Department of Land, Air and Water Resources, wrhorwath@ucdavis.edu
Gene Miyao, Farm Advisor, Yolo, Solano and Sacramento Counties, emmiyao@ucdavis.edu