Commodity prices are soaring, and this has growers thinking in new ways. This is especially true for soybeans. In the past, many have used the philosophy that they will fertilize corn; soybeans will use what's left over. Today, that philosophy is not the best.
University of Minnesota faculty have conducted considerable research with soybean fertilization in past years. The following suggestions have evolved from that research:
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With conventional tillage, broadcast rather than band phosphate and/or potash.
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In no-till production systems, don't leave phosphate and/or potash on the soil surface. This usually means that a banded application is the only alternative in this tillage system.
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Apply fertilizer in the spring before planting. Reduced time of contact between soil and fertilizer reduces tie-up or fixation. If fixation is reduced, efficiency of use is increased.
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Don't place any fertilizer in direct contact with the seed at planting. A small amount of soil between seed and fertilizer will eliminate potential problems.
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Use the soil test as the guide. If the Bray test is greater than 10 ppm or the Olsen test is greater than 8 ppm, a yield increase from the use of phosphate fertilizer is doubtful. If the soil test for potassium is greater than 100 ppm, a response to potash fertilizer is doubtful.
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If the soil test shows a need for phosphate and/or potash, rates of 50 lbs. phosphate and 60 lbs. potash/acre are general guidelines for application.
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There has been some promotion of foliar application of fertilizer for soybeans. This application method has been researched and has not consistently improved yields.
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Don't rely on fertilizer carryover to do the job. If fertilization is needed,fertilize each crop each year.
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If iron chlorosis is a problem, take care of that first, then tackle the phosphate and potash needs.
Take a close look at fertilizing soybeans. Don't pass up an opportunity to improve farm profits.
Editor's Note: George Rehm is a nutrient management specialist and professor emeritus from the University of Minnesota.
