Identification of Modern High-Yield Soybean Genotypes for Potassium-Use Efficiency in Sandy Soil of the Brazilian Cerrado

Soybean is the main leguminous crop in Brazil, mostly grown in tropical soils with low potassium (K) availability. Therefore, the identification of new genotypes with efficient K uptake and utilization in environments with low exchangeable K content is an economically viable alternative to maximize crop yield in Brazil. A study was conducted to investigate the response of 25 modern high-yield soybean genotypes for K-use efficiency in a sandy tropical soil of the Brazilian Cerrado. Treatments were distributed in a completely randomized design in a 2 × 25 factorial scheme: two levels of K fertilization [20 mg K dm⁻³ (low level) or 200 mg K dm⁻³ (high level)] and 25 soybean genotypes with three replicates. Plant morphological traits, leaf K, and crop production components were measured. Based on grain production data, K-use efficiency (KUE) and response efficiency (RE) to K fertilization were calculated. Leaf area, shoot dry matter, pod number per plant, 1000-grain weight, and grain yield were the crop characteristics most limited by low soil K availability. The soybean genotypes “TMG7061 IPRO”, “BMX Bônus IPRO”, “RK6719 IPRO”, and “RK8317 IPRO” were classified as efficient in the use of soil K and are the most suitable genotypes to be cultivated in agricultural soils with low K availability. The genotypes “98R35 IPRO”, “HO Maracaí IPRO”, “BMX Bônus IPRO”, and “RK7518 IPRO” were classified as responsive to K fertilization and are the most recommended genotypes for cultivation in agricultural areas with the application of high K fertilizer rates. The genotype “BMX Bônus IPRO” simultaneously combines characteristics of K-use efficiency and response to K fertilization and hence can be grown in both K-deficient and optimal soils.