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Residue boosts yield when water is limitedNebraska First-year results of a three-year study currently in progress 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, while similar plots with the residue scraped off yielded 172 bushels per acre--a 25 bushel per acre difference, said Simon van Donk, UNL irrigation engineer. Van Donk said that the study was begun last year on 40 by 40 foot plots that had been planted to soybeans for the previous three years. The soybean residue remained on half the plots and the other half was scraped clean to create a bare 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. On the bare-surface plots, the corn was visibly stressed more and earlier than on the residue-covered plots. In late August and September, that corn dried out and turned yellow and 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. 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. For more about producing more with less water, be sure to attend one of the Irrigation Strategies Field Tours now in progress throughout West Central Nebraska (http://water.unl.edu/irrigationtournews) or register for the Great Plains Conference on Improving Crop Water Productivity Sept. 18, at the West Central Research and Extension Center in North Platte http://events.unl.edu/extension/2008/09/18/28717/. For dates and places of Irrigation Field Tours, contact Steve Melvin at 308-367-4424 and to register for the Great Plains Conference, call Linda Lehmann at 308-696-6727. 8/25/08 Date: 8/20/08
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