145-2 Correction of Potassium Deficiency In Soybean Production In Kansas.

See more from this Division: S08 Nutrient Management & Soil & Plant Analysis
See more from this Session: S4/S8 Graduate Student Oral Competition-Managing Nutrients for Optimum Crop Production
Monday, October 17, 2011: 8:20 AM
Henry Gonzalez Convention Center, Room 209
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Jason D. Matz, Kansas State University, Manhattan, KS and David Mengel, Department of Agronomy, Kansas State University, Manhattan, KS
Over the last decade low soil test K levels and K deficiency, especially in soybeans, has become a major concern in the claypan soils of southeast Kansas.  The use of more intense crop rotations (corn/wheat/double crop soybeans) and increased production of high K extracting crops such as soybeans has increased K removal.  The traditional use of nutrient sufficiency based fertilizer recommendations has also resulted in K application rates substantially below crop removal.  In addition, farmers and crop consultants who maintain good soil test records are reporting substantial variation in soil test K from year to year in the same soil sampling areas.  This project was initiated in 2009 to determine the extent of the K soil test variation seen between years and during the crop year, and if this variability was impacting K availability as indicated by leaf K content and crop yield.  Monthly soil tests during the past three crop years at multiple locations have shown the ammonium acetate exchangeable K levels to change as much as 50% during the growing season.  The changes seem to follow soil moisture and precipitation trends.  As soils dry, soil tests drop and rewetting increases K levels.  K content of the leaf tissue tends to follow soil test K levels.  However, no impact on corn or soybean yield, or response to spring applied K has been observed, if the spring soil test K level was initially above the current critical level of 130 mg kg-1
See more from this Division: S08 Nutrient Management & Soil & Plant Analysis
See more from this Session: S4/S8 Graduate Student Oral Competition-Managing Nutrients for Optimum Crop Production