August 22, 2008 

First-year results of a three-year study in west central Nebraska show a substantial increase in corn yield on plots with residue compared with those without, said a UNL specialist.

Corn planted on plots with soybean residue yielded an average of 197 bushels per acre in 2007, while similar plots with the residue scraped off yielded 172 bushels per acre — a 25 bushel per acre difference, said Simon van Donk, Extension irrigation engineer at the West Central Research and Education Center at North Platte.

Van Donk said the study was started last year on 40-by-40 ft plots that had been planted to soybeans for the previous three years. The soybean residue was kept on half the plots and scraped off the other half to leave a bare soil surface.

"We grew corn to see how residue would affect water balance and crop yields," van Donk said. "We didn't find much difference in soil water content between the two kinds of plots, but we did see a big difference in yield at the end of the season."

All the plots received the same treatment, including a limited amount of water in order to stress the crop. If the crop on the residue-covered plots had more water, it should do better than the bare-surface plots and that's what happened. Corn in the bare-surface plots was visibly stressed more and earlier than corn in the residue-covered plots. In late August and September, the bare-surface corn dried out and turned brown much sooner than the crop on the residue-covered plots.

Because there was more evaporation on the bare-surface plots, there was less moisture for transpiration, an essential function of plant growth, van Donk said. The physical effects that cause the increased evaporation include more energy from the sun reaching the bare surface and more movement of air at the bare soil surface. Also, without residue to slow run-off from intense rain or intense irrigation, there is less infiltration to provide water for crops.

Another benefit of leaving residue on cropland is reduced erosion both by water and by wind, van Donk said.

"If the same tillage practices were in use during the recent drought as were being used during the 1930s, we would have seen much more wind erosion and dust storms than we did," he said.

Faith Colburn
Communication Specialist
West Central REC