No-till crop yields can exceed what you might expect given the nutrient and water supply, says Randy Anderson, a research agronomist USDA-ARS North Central Agricultural Research Laboratory in Brookings, S.D.
He offers this example:
Ralph Holzwarth, Gettysburg, S.D., has averaged 150 bushel per acre on corn his farm for the past six years.
"We were surprised with this yield, as corn yields in eastern South Dakota (Brookings County) averaged 140 bushels per acre during this same time interval," Anderson says. "One reason for our surprise is that yearly precipitation in Gettysburg is 5 inches less than in Brookings County A second reason is that Holzwarth plants corn at 22,000 plants per acre, compared to 32,000 plants per acre in Brookings County."
Holzwarth's corn produces 7% more grain with 5 inches less water and 10,000 fewer plants per acre.
An individual corn plant on his farm produces 45% more grain than a corn plant in Brookings County.
Extra moisture accounts for some of the gain, Anderson says.. Before adopting no-till, Holzwarth followed a winter wheat-corn-fallow rotation where corn yielded about 70 bushels per acre. He noticed an immediate increase in corn yield when he started no-tilling 20 years ago, because not tilling and keeping residue on the soil surface increased water supply for crop growth.
A second gain in corn yield occurred when Holzwarth diversified his rotations to reduce plant diseases.
"Crops generally yield more when grown less frequently," Anderson says. "His rotations now include four to six crops. One typical rotation is winter wheat-corn-dry pea-corn-soybean-oat In contrast, producers in Brookings County grow mainly corn and soybean in a tillage-based system."
Holzwarth also noted another jump in corn yield when he grew dry pea in front of corn.
"Dry pea increases corn yield by improving its resource-use-efficiency," Anderson says. "Also, we believe that changes in the soil microbial community contribute to improved corn yield," Anderson says. "One favorable change may be increased mycorrhizae levels. Mycorrhizae are fungi that attach to corn roots and improve crop absorption of nutrients and water in soil."