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Northern Illinois Agriculture

University of Illinois Extension
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Have the P and K crop removal numbers been adjusted in Illinois?

As the number of harvested acres increase, management decisions including fertilization for the 2014 crop are at hand. Those who attended recent Corn & Soybean Classics or the Northern Illinois Crop Management Conference may remember Dr. Fabian Fernandez sharing preliminary data that suggested the current  "book" values for P and K grain concentrations, used to calculate removal, used in Illinois are high. Dr. Fernandez, now at the University of Minnesota, produced data from Illinois grain samples (taken mostly in 2009) showing average P and K concentrations in corn grain of only 0.27 and 0.19 lb per bushel, compared to the book values (from the Illinois Agronomy Handbook) of 0.43 lb P and 0.27 lb K per bushel. Soybean values were closer to book values, at 0.69 (new) compared to 0.83 (old) lb P and 1.17 (new) compared to 1.30 (old) lb K per bushel. Other states also have some data showing lower values than the ones commonly used.

University of Illinois Professor and Agronomist Emerson Nafziger is suggesting that growers who are considering decreasing their P and K application rates based on the lower crop removal rates may consider "splitting the difference" until more data is in. Emerson's Illinois Bulletin article which also addresses dry fertilizer placement, lime and gypsum can be accessed here

Activities at the NIARC today included the harvest of several of our remaining soybean trials, including the White mold trials and the second planting date of our soybean maturity study planted on June 14th.

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