Potassium Fertilization in Soybean

Association of Crop Response with Edaphic and Topographic Properties

Abstract

Our objectives were to quantify the soybean crop response to potassium (K) fertilization under variations of soil K supply, and to study the association of this reponse with other soil and topographic properties. A strip fertilization experiment was evaluated during two years in soybean. In 2012 treatments were established with K rates (0, 60 and 240 kg K₂O ha^-1) without phosphorus (P) limitations, and a control treatment without fertilization. In 2013, plots were refertilized with P and the 60 kg K₂O ha^-1 rate in the corresponding treatments. A 30 x 22 m regular sampling grid was delineated. Determinations included nutrients in soil, organic matter, texture, soil penetration resistance, electrical conductivity, terrain attributes, foliar K concentration (R2-R3) and grain yield. Exchangeable K (ex. K) in treatments without K fertilization was 0.46 cmol kg^-1 in 2012, and 0.40 cmol kg^-1 in 2013. There were significant yield responses to K fertilization only in 2013, when the highest yield was in the 240 kg K2O ha^-1 treatment. In 2013, ex. K interacted with treatments, with significant relationship in no K fertilization treatments, and without relationship where K was added. No other additional properties were identified to complement the interpretation of the soil K test and to better understand crop response to fertilization.