Healthy soil does much more than hold plants upright on the surface of the earth. It is a mix of mineral bits and old plant particles teeming with microbes to form a mysterious and complex web of life scientists are just beginning to understand.

While scientists use high technology to study heathy soil – painstakingly counting soil worms and bugs, sequencing the DNA of soil bacteria, for example – some farmers know intuitively whether the soil is healthy just by walking on it.

Scott Park is a first-generation Meridian, Calif., farmer. “When I step on a field and it feels like a road, something is wrong,” he said. “If it feels like a marshmallow or sponge, that's good.”

Managing crop residues to essentially make them disappear has been the norm in California agriculture.

But a growing body of research, and experience with conservation tillage on thousands of acres of Central Valley farmland, is showing that reducing tillage and leaving crop residues on the soil surface can improve water use efficiency.

“Crop residues are an inevitable feature of agriculture,” Jeffrey Mitchell, cropping systems specialist in the Department of Plant Sciences, UC Davis, wrote in the April-June 2012 issue of California Agriculture journal....

The amount of California farmland being cultivated using conservation tillage techniques is continuing to expand, according to a survey by California’s Conservation Agriculture Systems Institute (CASI).

The survey tallies silage and grain corn; small grains for hay, silage and grain; tomatoes, cotton, dry beans, and melons managed as no-till, strip-till, ridge-till and mulch-till – which leave at least 30 percent of residue from the previous crops on the soil surface – in the nine-county Central Valley region. In 2010, such conservation tillage accounted for about 14 percent of the crops’ total acreage, an increase from about 10 percent in 2008. The survey also found that minimum tillage practices – which reduce the overall...

UC scientists presented recent additions to the growing body of research on conservation tillage in California at the second annual Twilight Conservation Tillage and Cropping Systems field day last month, demonstrating progress in agricultural systems that will help farmers cut production costs, reduce soil disturbance and save water.

UC scientists and their partner farmers are conducting research that addresses the current needs of the San Joaquin Valley agricultural industry and research that is looking to the future by anticipating changes that may need to be negotiated in coming decades.

During the field day at UC's West Side Research and Extension Center in...