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How predictable is nitrogen from manure for corn production?


December 5, 2008
By University of Minnesota Extension

NEWS HIGHLIGHT

How predictable is nitrogen from manure for corn production?
How much nitrogen is the corn crop getting from fall-applied
manure? That question was tested in on-farm trials conducted by the
University of Minnesota in cooperation with thirteen farm operators.

How much nitrogen is the corn crop getting from fall-applied manure? That question was tested in on-farm trials conducted by the University of Minnesota in cooperation with thirteen farm operators.

It turns out that with liquid swine or dairy manure the question is easier to answer if the manure was injected than if it was broadcast and later incorporated. Nitrogen availability as measured by corn yield response to manure rate was much closer to published university predictions (University of Minnesota Extension Bulletin 03553, “Manure Management in Minnesota”) for injected than for broadcast-incorporated manure on an individual field basis.

Research scientist Michael Russelle indicated that the greater variability for broadcast-incorporated manure was likely due to ammonia losses from manure that were higher or lower than average due to weather conditions (rainfall, temperature, and wind speed) after application and before incorporation. The conclusion is that direct injection by knives or sweeps is recommended to get the best and most predictable value from manure nitrogen.

Results from the field trials are described in a new Extension publication, “Nitrogen Availability from Liquid Swine and Dairy Manure: Results of On-Farm Trials in Minnesota,” available in print and online. The publication includes methods, results and conclusions from the trials regarding nitrogen availability, as well as three stand-alone single-page fact sheets that:

  • summarize the results from the yield trials,
  • compare small-plot vs large strip-plot results, and
  • present results of the use of chlorophyll meters in determining needs for additional nitrogen when manure was the primary nitrogen source.


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