Purdue News
Purdue News
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March 16, 2004 Fumed over no-till? 'Revenge' won't be sweet, agronomist saysWEST LAFAYETTE, Ind. - Disgusted with your no-till crop yields this past fall? Don't take it out on your soil this spring, said a Purdue University agronomist. Before farmers resort to "revenge tillage," they should know that yield differences between no-till and conventional tillage were near average in 2003 field trials, said Tony Vyn, Purdue Extension cropping systems specialist. The unusually high stress that corn and soybean crops were under from a cool, damp spring and soggy July was no harder on untilled trial plots than those plowed prior to planting, Vyn said. He added that crop rotation plays a greater role in soybean yield gains than do tillage practices. "In replicated experiments in 2003, the crop yield differences between no-till and full-width tillage systems - like chisel plowing - were smaller than normal," Vyn said. "This means that even though there was considerable stress for plants in the heavy rainfall periods that we had in early July and again around Labor Day, yields in no-till corn and no-till soybean trials did not fare any worse than normal. "So if the inclination of some farmers disappointed with their yields in 2003 is revenge tillage to loosen the soil, that's not going to pay off economically." Any tillage a farmer decides to do also could lower surface residue cover, which kept soil in place during the 2003 storms, Vyn said. In field trials conducted annually since 1975 at Purdue's Agronomy Center for Research and Education (ACRE) near West Lafayette, Ind., corn and soybeans are planted in plowed, chiseled, ridge- and no-till systems. Each tillage system is compared in both rotated and non-rotated plots. "Except for a corn yield gain of 20 bushels per acre for any tilled system - compared to no-till - when corn followed corn, all tillage effects on corn and soybean yield were insignificant in 2003," Vyn said. "No-till soybeans averaged near 50 bushels per acre following both corn and soybeans. None of the other three tillage systems did any better in final yields." A second group of field trials have been done each year since 1997 at Pinney-Purdue Agricultural Center near Wanatah, Ind. The trials compare fall chisel, fall disk and no-till systems in corn after corn and corn-soybean rotations. Crop yield responses at Pinney were similar to those at ACRE in 2003, Vyn said. No-till corn yielded 10 bushels fewer per acre than yields in tilled systems when corn followed corn. In corn following soybeans or soybeans following corn, none of the three tillage systems yielded significantly more than any other. Corn yields averaged 220 bushels per acre when following soybeans and 208 bushels per acre when following corn. Soybean yields averaged just 38-39 bushels per acre, regardless of the tillage system. "The rotation advantage for corn in 2003 was less than we typically observe," Vyn said. "With all the crop stress, the rotation advantage was only about 5 percent whenever we had a tillage system. Corn yields usually are about 8 percent better when corn is rotated with soybeans than when corn follows corn. "We normally observe a stronger rotation advantage in soybeans. That typically means about an 11 percent yield gain when soybeans followed corn rather than when soybeans followed soybeans." Planting corn in a field every other year reduces the threat soilborne diseases pose to soybean crops, Vyn said. By rotating crops, soilborne pathogens that can lead to Phytophthora, soybean cyst nematode and Sudden Death Syndrome are contained. Research indicates that spreading soybean crops out over an even longer rotation cycle is better, Vyn said. "There are a couple of studies in Indiana as well as Minnesota, which confirm that soybean yields can improve if soybeans are grown every third year rather than every second year," he said. The Indiana study, conducted at ACRE, found that soybean yields increased an additional 10 percent when winter wheat was added to the crop rotation. The Minnesota study examined soybean yield response after five years of corn, a single year of corn or after soybeans. Soybean yields came in 8 percent higher after five years of corn than after one year of corn. "That study also confirmed that the actual percentage of soybean yield response to rotation was higher in low-yielding years than in high-yielding years," Vyn said. "Thus, farmers with soybean yields consistently above 60 bushels per acre may benefit less from longer rotation cycles than those with yield averages of 40 bushels per acre." Vyn said soybean growers should seriously consider more than just the market price of soybeans or relative input costs compared to corn when making rotation decisions. The impact of rotation in a field can play a major role in net profits, he said. "I would encourage those who are currently in the one-year-corn/one-year-soybean sequence to think about having more time between successive soybean crops," he said. Writer: Steve Leer, (765) 494-8415, sleer@purdue.edu Source: Tony Vyn, (765) 496-3757, tvyn@purdue.edu Ag Communications: (765) 494-2722; Beth Forbes, bforbes@aes.purdue.edu Related Web sites:
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