Effects of Bora on growth and grain yield of soybean cultivar SJ.5

Effects of Bora on growth and grain yield of soybean cultivar SJ.5, were studied at the National Corn and Sorghum Research Center, Pakchong District, Nakhon Ratchasima Province, during August 1995-May 1996. A split plot in randomized complete block design was used with four replications. Growth stages (V7 R1 and R3) were main plots and application of water (W) and Bora at the rate of 0, 20 and 40 cc/20 litre of water (B0, B20 and B40) were sub-plots. For the last two sub-plot treatments Bora 40 was applied for 3 consective times at 7-day interval. The results showed that in the dry season B40 increased grain yield and pod number/plant of soybean. The increment of grain yield was significantly greater than B20, W and B0, respectively (481 vs 411, 408 and 369 kg/rai, respectively). Growth stages had no effect on the rate of Bora applied. However, application of Bora at R1 and R3 tended to increase grain yield and pod number/plant greater than at V7. In the late rainy season, grain yield was not affected by time (growth stages) of Bora application. Additionally, application of Bora at R3 increased pod number per plant greater than R1 and V7. For both seasons no statistical different was observed for seed number/plant and 100 seed weight either due to main plot or sub plot treatments. Nevertheless, the analysis revealed a positive correlation between grain yield and pod number/plant in both seasons. It indicated that the increase in grain yield of soybean applied with Bora was due to the increase in pod number/plant. Bora, either mainplot or sub-plot treatments, did not have pronounced effect on growth parameters (days to flowering, days to maturity, plant height, node number/plant, dry matter accumulation and LAI) of soybean under the condition of this study. Nevertheless, the tendency was that application of Bora tended to increase growth, dry matter accumulation and LAI. Seed growth rate (SGR) and effective seed filling period (EFP) were not effected by all the treatments in the dry season. Importantly, SGR had significantly negative correlation and EFP had positive, but not significant, correlation to grain yield.