Foliar applications of phosphorus, calcium, boron and potassium and their impacts on the seed yield and physiological and nutritional qualities of soybean

Using seeds of high physiological quality is important the establishment of a crop. Practices for quality seed production include sowing in the offseason and applying foliar macro and micronutrients to supplement fertilizers applied to the soil. The aim of this research was to evaluate the soybean yield and the physiological quality and nutritional content of seeds.  Foliar fertilizer (24% P, 8% Ca, 4% K and 2.5% B) was applied at 0.50, 1.0, 1.5, 2.0 and 2.5 kg ha-1 at the R3 soybean stage in a completely randomized design with six replications. The experiment was carried out at two sites. The following traits were evaluated at the R6 stage: the final stand, plant height, height of the first pod insertion, number of branches and number of pods per plant. After the soybeans were harvested, the thousand grain mass and yield were evaluated. The contents of nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, zinc, iron, copper and boron were evaluated. Furthermore, the germination, first germination count, accelerated aging, modified cold, electric conductivity and emergency speed index were measured. The data were analyzed by means of joint analysis. When the foliar fertilizer rates were significant, the polynomial regression models were adjusted. The number of pods per plant and yield increased at site 1 (Rancho Alegre d 'Oeste). Application of the foliar fertilizer only influenced the emergency speed index at site 2 (Mariluz) with regard to the physiological quality of the seeds. The P content was positively affected at both sites; the K, S, Zn and B contents were only positively affected at site 2.