Water conservation

Benefits of cover crops extend to dry areas

Comparison of grazed and ungrazed portions of a cover crop field in Alexander, KS. This study focused on semi-arid environments like the Great Plains in the United States. Credit: Augustine Obour

Cover crops do more than just cover soil. They offer a range of benefits, such as the ability to reduce soil erosion and improve soil health. They can help attract pollinators, repel pests, turn into “green manure” or can be used as livestock feed.

A new study shows that the benefits of cover crops extend even into semi-arid areas. This review has just been published in the Journal of the Soil Science Society of Americaa publication of the Soil Science Society of America.

“A lot of the research data we have on cover crops comes from regions with high rainfall,” says Humberto Blanco, principal investigator at the University of Nebraska at Lincoln. “Thus, questions remain about the ecosystem services provided by cover crops in drier regions.”

Some skeptics have argued that growing cover crops in drier areas might use too much water. This, in turn, could reduce subsequent yields of food crops. But research concludes that this is not necessarily the case.

“We found that cover crops can improve most ecosystem services in low water content environments,” says Blanco. “In the majority of cases, these improvements have no negative effects on food crop yields.”

To determine how well cover crops work in semi-arid areas, Blanco and his colleagues collected and analyzed the limited number of studies on cover crops in dry regions. They focused on studies of the large semi-arid plains in the United States.

Benefits of cover crops extend to dry areas

Yearling cattle grazing on spring planted cover crops in a field in Alexander, KS. Cover crops are often used as livestock feed. Credit: Augustine Obour

The researchers examined cover crops in relation to several ecosystem services. These included the amount of organic carbon in soils, soil microbial properties, weed management, and food crop yields, among others.

One of the main soil characteristics that the researchers focused on was soil organic carbon.

“Soil organic carbon is the catalyst for many other changes in soil properties and soil services,” says Blanco. “Soils in water-limited regions are often low in organic carbon.”

Researchers found that in dry areas, cover crops increased soil organic carbon levels almost 60% of the time.

“This buildup of organic carbon is essential for these soils,” says Blanco. Indeed, soil organic carbon is the food source for many soil organisms, such as microbes. Ultimately, these soil organisms play a vital role in maintaining healthy and fertile soils.

Cover crops also suppress weeds in dry areas. This is particularly important because several weed species are resistant to current herbicides. Weed suppression by cover crops has a knock-on effect of increasing water conservation and preventing soil erosion.

Benefits of cover crops extend to dry areas

A cover crop field after four days of grazing by yearling cattle in Alexander, KS. Even when grazed, a significant portion of the cover crops remains on the fields. Cover crop roots persist even when grazed, which holds soils together and provides many benefits. Credit: Augustine Obour

“Herbicide-resistant weeds can drive tillage in typically no-till systems,” says Blanco. “This can reduce the water conservation capacity of these agroecosystems.” Plowing can also make soils more susceptible to erosion.

Cover crops also provide food for livestock in dry areas. “Grazing or haying cover crops can improve net yields without negating soil benefits,” says Blanco. Indeed, even when grazed, a significant portion of cover crops remains in the fields. Additionally, the roots of cover crops persist even when grazed, which keeps soils together and provides many benefits.

The study found that cover crops can reduce food crop yields in some cases. These cases generally coincided with intermittent drought conditions. Water availability for cover and food crops declined during these years.

“Adjusting crop rotations and the use of cover crops to adapt to weather conditions is key,” says Blanco. “Farmers in drier areas may not be able to plant a cover crop every year. They can target wet years when cover crops can be successful.”

Blanco aims to continue its research on cover crops in drylands.

“Long-term research is key to identifying the lasting effects of cover crops,” he says. “Yet, long-term research data on cover crops in arid and semi-arid areas is virtually absent from the literature.”

Impacts of cover crop planting dates on soil properties after 4 years

More information:
Humberto Blanco-Canqui et al, Can cover crops improve soil ecosystem services in water-limited environments? A review, Journal of the Soil Science Society of America (2021). DOI: 10.1002/saj2.20335

Provided by the American Society of Agronomy

Quote: Benefits of Cover Crops Extend to Dry Areas (March 1, 2022) Retrieved March 1, 2022 from https://phys.org/news/2022-03-benefits-crops-areas.html

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