Effect of Irrigation Amounts on Quantitative and Qualitative Characteristics of Soybeans (Glycine max L) Variety Hobbit

In order to evaluate the effect of irrigation amounts on soybean yield and quality, an expriment was conducted as randomized complete block design with three replications in Kermanshah, during summer of 2015. Irrigation treatments were in eight levels including T1=100%, T2=120%, T3= 80%, and T4=60% of crop water requirement in all growth periods, and T5= 80% and T6=60% in vegetative stage, and for T7= 80% and T8=60% water requirement was applied at flowering stage. During other stages of plant growth in T5, T6, T7, and T8, plants received 100% of water requirement. In this study, some geometric and gravity properties of seeds including length, width, area, perimeter, length to width ratio, circulatory coifficent, distance from the center of gravity to the junction of length and width, and leaf area index by using SmartGrain model and yield components, the number of pods, seed weight, dry weight, and plant height were measured and evaluated. The results showed that irrigation significantly affected all traits, except for the distance between the center of the intersection of width and length grain and circulatory coifficent. So, the most sensetive stage to water stress wass flowering, followed by the 60% water requirement treatment in the whole growth period. The highest water use efficiency for grain and oil yield was obtained in 120% treatment, followed by the 80% treatments in vegetative growth stage. In general, the results showed that, if deficit irrigation is to be carried out on soybean, it is better to have 20% irrigation deficit (80% water requirement) at the vegetative stage.