Can cover crops control weeds and save water too?

“Ten years ago, only about 10 million acres in the U.S. were planted with cover crops. Today that’s up to about 22 million acres, and the number is increasing by about 8% annually.” This is a quote from this article on the ancient farming practice of cover crops (click here for article). Certainly, organic farmers are familiar with and use cover crops and in our “Great Plains” region the Organic Farming Research Foundation has survey results that show over 85% of you use cover and green manure crops in your organic operation.

Because we use and need cover crops and because I give organic programs on cover crops, I try to read all the research I can and occasionally I find something that just “tickles the brain.” I accidentally came across a study done at New Mexico State University in Las Cruces entitled, “Fall-sown small grain cover crops for weed suppression and soil moisture management in an irrigated organic agroecosystem” in the journal Renewable Agriculture and Food Systems. (Click the image to read the study)

It is a very interesting read but in summary they conducted the trials over several years with many different cereals and found that the barley varieties gave the best weed suppression and least soil moisture losses. Here are a few quotes from the results:

In our study, earlier maturing varieties (‘Robust’, ‘UC603’) also displayed high levels of weed suppression. The apparent relationship between early maturity and weed suppression ability suggests that time to canopy closure is a significant cause of differences in weed suppression among barley varieties.

Our study demonstrated that a barley cover crop did not deplete the soil moisture, and during one season (2016–2017) actually conserved it following a long dry period (Figs 1 and 2). The beneficial ecosystems services demonstrated in this study may help reduce the hesitancy to incorporate cover crops into southwestern irrigated cropping systems.

The varieties ‘Robust’ and ‘UC603’ did an excellent job of weed suppression during two seasons. Thus, these barley varieties (‘Robust’ and ‘UC603’) are recommended for organic cropping systems in southern New Mexico and similar semi-arid environments.

These recommended barley varieties could fill the need for a ‘non-thirsty’ cover crop in the southwestern United States and play an important role in the effective management of weeds in organic production systems.

In summary the barley varieties they planted had far less weeds than in the unplanted control (less than 5 weeds per square meter (11 square feet)) and soil moisture in the unplanted control (bare ground) was consistently less than the soil moisture content in the barley plots. Not bad and something that should make us want to plant some barley!

Author: Bob Whitney, Regents Fellow & Extension Organic Specialist

Agriculturalist, extension educator and researcher, organic agriculture enthusiast and promoter, international program developer, Christian, husband, father and friend.

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