Interaction cultivar environment in soybean for protein yield with different fertilization and sowing dates

This study aimed at evaluating the interaction cultivar × environments for the oil and protein yield of the grains, in soybeans grown under different levels of potassium fertilization, in two sowing times, in the state of Tocantins. In the agricultural year of 2013/14, were performed twelve soybean cultivars competition trials in Palmas/TO. In each season, each test represented a distinct environment and consisted of a level of potassium fertilization (0, 40, 80, 120, 160, or 200 Kg K2O ha-1). The experimental design used in each test was a randomized block with 10 cultivars and three replications. Analyzes of stability and adaptability, stratification and environmental dissimilarity were performed. Potassium levels and sowing times resulted in differential performance of soybean cultivars. The BRS 333RR cultivar was presented as potentially promising for oil yield and BRS 9090RR for protein. The evaluation tests of soybean cultivars can be performed using low levels of potassium fertilization, providing reduced costs and less contamination of the water table.