Cover crops can help conserve moisture, says Kris Nichols, research soil microbiologist with the USDA Agriculture Research Service, Mandan, N.D.
“Cover crops can be an important part of keeping moisture in the soil because they keep that soil covered,” she says.
Below the soil’s surface, cover crops play a vital role in soil and plant health, too. “A green and growing cover feeds a whole web of soil organisms — much more than crop residue,” Nichols says.
Key Points
• Cover crops can be a help in drought, says USDA ARS scientist.
• Cover crops conserve moisture by protecting the soil.
• Cover crops help keep soil microbes alive during drought.
Most soil organisms are carbon-limited, making them dependent on plant material either directly or indirectly to obtain carbon. “In order to get that carbon, they have to trade something to the plant. Many times they are trading nutrients, which they acquire from the soil, and in some cases, they also trade water,” she says.
Stress reducers
Mycorrhizal fungi are an example. They are organisms made up of fine threads and filaments called hythae. Because these threads are so much smaller than plant roots, they have access to more soil and the nutrients or water it contains. For farmers who have been using cover crops for a few years and have built up their soil ecology, these same organisms will help reduce the amount of stress their plants succumb to during a drought.
“Many times during a drought, plants are not as much water stressed as they are nutrient stressed,” she says. “The way plants get nutrients from the soil to their roots is through water. In times of drought, plants will sometimes give off their own water supply to create a water fill around the roots so nutrients can travel.”
Plants growing in soils rich with mycorrhizae can take advantage of the fungi to help them obtain nutrients from the soil.
“The fungi can do this using much less water,” she says.
Soil rich with living organisms also has a soil structure that is more conducive to water retention.
“Organisms help form soil aggregates, which allow for better water absorption because there is more pore space between the soil for water as well as gas exchange,” she says.
Cover crops will grow during a drought, says Justin Fruechte, cover crop and forage specialist for Millborn Seeds, Brookings and North Sioux City, S.D.
“Most species have very fine seeds and require little moisture to germinate,” he says. “When planting into dry soil, be sure to close the furrow tightly, and that seed will wait for moisture.”
Source: Millborn Seeds
This article published in the October, 2012 edition of DAKOTA FARMER.
All rights reserved. Copyright Farm Progress Cos. 2012.
Cover Crops
Crop Management