About 10% of Indiana's corn and soybean acres were no-tilled in 1990, just 25 years ago. Based on 2013 numbers, which will be updated with 2015 fall transect information soon, no-till soybean acreage is about 55% of all soybean acres in Indiana, corn no-till acres are at about 20%, and combined, just under 40% of all acres are no-tilled. That does include strip-till and ridge-till operations. The key is minimal soil disturbance.
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The figures are kept by the Division of Soil Conservation within the Indiana Department of Agriculture. Transect data means conservation partners in each county actually traveled the county at random, recording the tillage found at random locations that were pre-determined before the drive began.
Usually a Natural Resources Conservation person, an Extension person and an ISDA person, plus someone from the local soil and water conservation district, participate in these transects. They have not been done every year in every county.
Numbers actually peaked in 2007 to 2008 at 25% for corn and 70% for soybeans. Barry Fisher of NRCS and others theorize why the numbers have dropped back. It appears that they are leveling out, especially for no-till corn.
One factor was marketing of vertical tillage tools, which leave residue but don't qualify as no-till per se, Fisher notes. Farmers in the period after 2007 enjoyed high crop prices and many had money to buy these tools.
Several stories appeared indicating tillage was the way to handle tough Bt corn residue, although at least one university report indicated that Bt stalks aren't tougher than conventional stalks – stalk strength has improved through genetics.
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More corn after corn acres when corn prices were high and wet springs when tillage was one way to control weeds that got out of hand may have also contributed to the decrease. Time will tell if the trend line levels out or goes back up for soybeans, and if it stays level for corn.