Responses of Soybean Genotypes to Different Levels of Irrigation

To find out the responses of soybean genotypes in terms of different levels of irrigation with the aim of evaluating the growth, yield, and its optimum levels of irrigation, an experiment was conducted at the Field of Crop Botany Department, Bangladesh Agricultural University, Mymensingh during the period from November 2000 to February 2001. Five levels of irrigation viz. $\textrm{I}_0$: no irrigation, $\textrm{I}_1$: one time irrigation at 20 days after sowing (DAS), $\textrm{I}_2$:two times irrigation at 20 and 40 DAS, $\textrm{I}_3$: three times irrigation at 20, 40, and 60 DAS, and $\textrm{I}_4$: four times irrigation at 20, 40, 60, and 80 DAS and three genotypes of soybean viz. BS-3, BS-16, and BS-60 were used in this experiment. The crop was grown in a split plot design having three replications. The plant height, leaf area index, crop growth rate, shoot dry weight, branches $\textrm{plantI}_{-1}$, filled pods $\textrm{plantI}_{-1}$, seeds $\textrm{plantI}_{-1}$, seed yield, and harvest index were influenced significantly by irrigation and these were found to be highest at three times irrigation except branches $\textrm{plantI}_{-1}$. The chlorophyll content increased but empty pods $\textrm{plantI}_{-1}$ decreased with increase in irrigation levels. Genotypes of soybean varied significantly in terms of growth attributes at various growth stages except shoot dry weight at 90 DAS. The genotype BS-3 performed better compared to other genotypes and gave maximum seed yield.