Pclp purdue
To demonstrate, within Michigan's most common field crop systems, that higher levels of crop diversity significantly increase soil microbial activity.Ģ. These results, in part, would be due to higher levels of soil microbial activity caused by the crop diversity. Rotations were thought to result in reduced loss of nutrients to the environment. This project was designed to test the degree to which, in the central part of Michigan's field crop region, crop rotations, particularly those including cover crops, would be more profitable, would result in better soil quality and would use nitrogen more efficiently. Farmer response to these results in field days and in numerous training sessions has been excellent.
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No decrease in physical, biological or chemical quality was found with high crop diversity in any comparison, and increases were seen in soil carbon, water infiltration and nitrogen mineralization on some farms. Soil quality differences were difficult to measure uniformly across the wide variation in soil types of the farm studies. The nitrogen credit for corn was measured at 60-70 lbs/A following wheat with clover, but the 15-18% increase in corn yield following this combination was due apparently to a combination of nitrogen and other yield-influencing effects. Without loss of profit using rotations, leaching losses of nitrogen were reduced by 50 to 60% in the experiment station trials. Linear program analysis of the farm data using PLANETOR-derived values showed that phosphorus runoff could be held below 8 lbs/A per year and nitrate leaching below 40 lbs/A per year. In experiment station trials in the third year of rotation the 1994-95 averages were 174 bu/A with rotation and cover, and 159 bu/A without rotation or cover.
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Farmer corn yields increased from 115 to 134 bushels with rotation. Introducing wheat into the rotation, particularly when clover was used following wheat, gave the greatest increase in corn yield. The increase was similar for experiment station trials, with most of the advantage coming from increased corn yield and profitability in the rotation. The return over variable costs was $84 per acre for continuous corn and $103 per acre average for the multi-crop rotations, a 23% increase in farmers fields. This project provided concrete evidence from 18 paired comparison farms, from detailed trials on a single farm and from experiment station trials that corn, soybean, wheat and cover crop rotations were superior to continuous corn.