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Comparison Between Source of Potassium for Corn, Soybean, and Wheat Production

Start Date: 2017
Principal Investigator: Dan Kaiser
Organization: University of Minnesota, Department of Soil, Water, and Climate
Status: Completed

Background Info

The primary objective of this study is to determine if routine application of removal based rates of K as KCL can lead to a buildup of Cl in poorly drained soils in Minnesota. Two separate studies will be utilized for this work. The first study will be long-term potassium study established at three locations in 2009 which has focused on K applied as KCl. The second study will be a new long-term trial comparing sources of K applied in a two-year rotation.

Objectives

Determine if Cl will carry-over on poorly drained soils.

Compare KCl and K2SO4 for supplying K to soybean.

Evaluate critical soil test K levels utilizing long-term K trials.

Compare soil test potassium analysis on air dried versus field moist soils.

Evaluate the impacts of K fertilizer rate and timing on soybean quality.

Determine if Cl impacts corn, soybean, or hard red spring wheat yield and soybean grain quality.

Determine if time of K or Cl application within a 2-year crop rotation affects corn, soybean, or spring wheat response to K or Cl.

Key Findings

Application of K or Cl increased their respective nutrient concentration in plant leaf samples collected at reproductive growth stages. The impact of K2SO4 was similar compared to KCL for increasing leaf K concentration and a similar effect was found comparing CaCl2 versus KCl considering leaf CL concentration. Corn grain yield was not significantly impacted by CL, but was increased by K at one of the three locations. Soybean or wheat grain quality were not impacted greatly as most sites tested high in soil test K. Additional years of research are needed to the locations to determine how Cl builds up over time. Fall soil samples showed their clear increases in soil Cl at most locations except for Morris which was uncharacteristically wet towards the end of the growing season.

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