Phosphorus and potassium fertilization for yield and quality of soybean seeds

The objective of this work was to evaluate the effects of phosphorus and potassium fertilization on the yield and quality of soybean seeds. Experiments were carried out in two growing seasons, in a randomized complete block design, in a 5x3 factorial arrangement with five levels of phosphorus (0, 40, 80, 120, and 160 kg ha(-1) P2O5 as triple superphosphate), three of potassium (0, 50, and 100 kg ha(-1) K2O as potassium chloride), and four replicates. The following were evaluated: yield, number of seeds per plant, number of pods per plant, weight of a thousand seeds, germination, vigor (accelerated ageing, electrical conductivity, and potassium leaching), and P and K contents in leaf and seed. Yield, weight of a thousand seeds, and pod and seed yield per plant increased linearly with P fertilization. The increase in yield was 17.6% in the first year and 39.7% in the second. However, P levels did not affect seed germination and vigor. Potassium fertilization do not influence yield or K concentration in the seeds, but may improve germination, without interfering in vigor.