Phenotypic correlations and path analysis of soybean production components in the brazilian cerrado of Piauí state

The objective of this work was to examine the phenotypic correlations and their consequences in direct and indirect effects through path analysis among agronomic traits and soybean grain yields subjected to varying doses and times of application of potassium (K) in the Piau Cerrado. The experiment was conducted in the field, in the County of Bom Jesus, Piau State in the 2011/2012 crop season. A randomized block, factorial [(54)+1] design was used. Five K rates (30, 60, 90, 120. and 150 kg ha -1 K 2 O) and control (without K fertilizer) were applied at 4 times: 100% at planting, 50% at planting and 50% at 30 days after sowing (DAS), 100% at 30 DAS, 50% at 20 DAS and 50% to 40DAS. We evaluated the height (PHF) and dry weight of plants at flowering (DWAPF) and harvesting (DWAPH), number of grains pod -1 (NGPP), number of pods plant -1 (NPPP), weight of a thousand seeds (WOTS), grain yield and grain harvest index (GHI). The treatments that received potassium fertilization differed significantly (p<0.05) from the control in yield and height at flowering. The variables WOTS and GHI had higher correlations (0.88** and 0.71**), these being positive and significant with soybean yield. NGPP showed greater direct effect and high correlation (-0.89**) however negative with grain yield. The largest positive direct effects and superior to the residual effect on productivity were obtained with the variables WOTS, DWAPH and GHI, indicating that indirect selection for these primary characters would be effective.