YIELD TRAITS OF SOYBEAN CULTIVATED UNDER BRACHIARIA AND MILLET STRAW AND POTASSIUM DOSES

Resumo

There are many doubts about which straw-supplying species should be cultivated in a no-tillage system and which potassium doses are adequate for the Cerrado soils. Therefore, the current study aimed to evaluate the agronomic traits (plant height, first pod insertion height, and stem diameter); yield traits (number of pods per plant, number of grains per pod, and 100-grain weight), grain yield (kg ha^-1) and potassium content in the leaves, in the production of soybean cultivated in different straws and potassium doses in two crop seasons under Cerrado conditions in the region of Ceres, Goiás, Brazil. Two types of straw (Brachiaria and millet) and four potassium doses were evaluated. A randomized complete block design arranged in a 2x2x4 factorial scheme with four repetitions was used. Two crop seasons (2011/2012 and 2012/2013), two types of straw (Millet and Brachiaria), and four potassium doses (0, 30, 60, and 90 kg ha^-1 of K₂O using KCl as source) were evaluated. Phosphate fertilization was performed using 400 kg ha^-1 of simple superphosphate, and the cultivar used was P98Y12. The largest plant height values were obtained by applying 90 kg ha^-1 of K₂O. The Brachiaria straw promoted a grain yield increase associated with the potassium doses increment. The highest grain yield was 4,353.90 kg ha^-1, achieved by applying 65 kg ha^-1 of K₂O using millet straw. The highest grain yield reached was at the rate of 90 kg ha^-1 of K₂O, resulting in 5,208 kg ha^-1. The greatest K accumulation in the leaf is provided by Brachiaria straw.