Growth and yield of soybeans under wet soil culture and conventional furrow irrigation in south-eastern Australia

Summary

An experiment was conducted to determine the growth and yield responses of two soybean cultivars (Ridley and Sab40) grown on raised beds with continuous water applied in furrows (wet soil culture, WSC), and with conventional furrow irrigation applied at soil water deficits of 35 mm (F) and 70 mm (I). The early growth and leaf area development of both cultivars was reduced by both waterlogging (WSC) and water stress (1) effects compared to the frequently irrigated (F) treatment. Both cultivars acclimated to the WSC conditions and resumed active growth rates comparable to the F treatment. Excessive dry matter accumulation into leaves and stems of Ridley under WSC resulted in severe lodging and significantly reduced grain yield compared to Ridley under F irrigation. The physiological analysis presented showed that under WSC Ridley had a substantially lower light use efficiency compared the F irrigated crop during reproductive growth. It is hypothesised that lodging during this period reduced photosynthate supply as a result of detrimental changes in the pattern of leaf illumination throughout the canopy. The cultivar Sab40 did not lodge under WSC and grain yield was not significantly different from the F irrigated treatment.

Further studies on the response of lodging resistant cultivars and different sowing time by plant arrangements to WSC are required to fully assess this technique under commercial conditions. More importantly, studies on soybean production in relation to crop water use and deep drainage losses on a range of soil types are needed to demonstrate that irrigation water applied is used as efficiently as conventional methods.