Effect of irrigation interval and plant population on growth, yield and water use of soybeans in a semi-arid environment

Abstract

The influence of irrigation interval and plant population on seed yield, yield components and water use of soybeans was examined. Plant populations of 12,20 and 28 plants m-2 were furrow irrigated at irrigation intervals of 70 mm and 140 mm of estimated evapotranspiration. Although 12 plants m-2 yielded significantly less than 28 plant m-2, plant population had little influence on plant performance or on water use. Any effect was small when compared with the effect of irrigation interval. Highly significant differences were recorded between the two irrigation intervals. Extending the irrigation interval to 140 mm reduced seed yield by 1286 kg ha-1 or 34 per cent. The drop in yield resulted principally from a substantial decrease in the number of pods per plant. There was little effect on protein and oil content of the seed. Crop water use at the 70 mm interval was 786 mm or 75 per cent of pan evaporation. Although the 140 mm interval reduced water use by 15 per cent, production of seed and protein was less efficient. Peak demand for soil moisture coincided with the end of flowering-early pod fill period.