Effect of potassium fertilization in sandy soil on the content of essential nutrients in soybean leaves

Among the plant nutrients, potassium (K) plays a fundamental role in plant physiology and the soil-plant dynamics of various nutrients. Careful rate recommendations for K are needed to ensure that the balance between cationic nutrients and micronutrients is maintained, especially in sandy soils. The current research aimed to evaluate the absorption dynamic of several nutrients by soybean (Glycine max. Merrill.) growing in sandy soil under the application of five rates of K (0, 25, 50, 75, and 100 kg ha⁻¹) via potassium chloride (KCl) with five replications. The concentrations of K⁺ in the diagnostic leaves of the soybean plants presented quadratic behavior with the increase in K rate and reached a maximum of 17.74 mg kg⁻¹ at a rate of approximately 81 kg ha⁻¹ K, which was found through a regression test. The leaf concentrations of calcium (Ca²⁺) and magnesium (Mg²⁺) decreased linearly with increasing K rate. By contrast, the leaf concentrations of the micronutrients; boron (B) and iron (Fe²⁺) decreased with increasing K rate. Soybean productivity was not influenced by the application of K. Principal component analysis (PCA) showed a clear influence of increasing K rates on the leaf nutritional parameters of soybean plants. The results confirm that the high application of K in sandy soils can disrupt the balance of nutrient uptake by soybean plants.