01 Nov Saving soil moisture
By John Walter/Agriculture.com 11/1/2012
In a postdrought year, soil moisture will take center stage for many farmers as they look ahead to next season. But in most years during a normal growing season, farmers experience soil moisture shortages through annual short-term droughts, according to Harold van Es, a Cornell University crop and soil expert, and author of the book Building Soils for Better Crops.
“Most field crop farmers will experience drought in most years,” says van Es, who took part in a research project funded by the Sustainable Agriculture Research and Education (SARE) program. A recent report from SARE, “Smart Water Use on Your Farm or Ranch,” looks at practices that can help you conserve water.
Soil management is a big part of any strategy that tries to deal with drought, the SARE work shows. And late last summer, farmers reported unusually adverse soil conditions.
“Just try to take a spade to the ground,” Jim Cullison, an Illinois farmer, told Agriculture.com. “It will just bounce off the surface like you are digging concrete.”
He and other growers debated the wisdom of tillage under such soil conditions.
“My agronomist told me the corn extracted so much microscopic water from the soil surface causing it to get so hard that we will probably need to wait until we get some moisture so we can pull the chisel through it,” Cullison said.
Research funded by the SARE program suggests it will be a good year to consider the value of soil organic matter, which is essential to soil water availability.
“As organic matter increases, soils develop more macropores. That happens because, as plant residue and other organic amendments decompose, sticky substances bind soil particles and create pore spaces between them. And, organic matter itself can hold water,” the SARE report states.
“You can change a soil’s pore-size distribution. And with that, you can change the water-holding capacity,” van Es says. “There’s more water available to plants when you have a well-structured soil than if it’s compacted.”
Strategies for increasing organic matter are well known. Applying manure or composts, seeding cover crops, and reducing tillage are all effective. Crop diversification is another approach.
Results from the SARE research are promising. By reducing tillage or lengthening the crop rotation, a 10% to 20% increase in the soil’s available water content can be achieved.
No-tillers report more drought resiliency in their soils. Steve Groff, a Pennsylvania farmer, is cited in the SARE report for his work with no-till and cover crops to improve soil quality.
“My crops seem to show drought stress a few days later than those around me,” he says.
Adding Organic Matter
There’s special need following drought for increased applications of organic matter to help offset reduced crop residue, says Eileen Kladivko, a Purdue University agronomist. Late last summer she recommended fall-planted cover crops.
“Cover crops will help the farmer recoup part of the fertilizer N investment from this season, and they will provide some benefits in improving soil organic matter and soil biological activity,” Kladivko says.
Once the cover crop window is past, another option would be to apply manure or other available materials, such as compost, she says.
“When there is poor crop yield, there may also be less crop residue. If there is less crop residue, then less organic matter is being put back into the soil to feed the microorganisms, to improve soil structure, and to protect against erosion,” she says.