Eco-physiological drivers influencing mungbean [Vigna radiata (L.) Wilczek] productivity in subtropical Australia

Mungbean crop yields are highly variable across seasons and the factors causing the yield variability in mungbean are poorly understood. In the current study, we investigated the effects of in-crop weather variability including water availability, solar radiation and temperature, on the canopy development, growth and yield of mungbean cultivar 'Jade'. The crop was grown in three sowing windows, with or without irrigation and three row spacing treatments, in two contrasting environments, Hermitage and Emerald in Queensland, during 2015-16 and 2016-17 summer seasons. Mungbean planted in sowing window 1 at Emerald experienced extreme temperatures ( > 35 degrees C to 40 degrees C) during flowering and pod set phase consequently yield was low ( < 1 t/ha) compared to > 2 t/ha at Hermitage, despite similar total dry matter productivity (about 5 t/ha). However, in sowing window 3 (February-early March) temperatures were more congenial (mean 27 degrees C) at Emerald for crop growth as evidenced by higher yields (up to 2 t/ha), similar to Hermitage site. The crops planted at 0.25 m row spacing treatment consistently intercepted more solar radiation and produced higher yields than 1 m row spacing in all treatments at both sites. Combined data from the two sites suggested that the radiation use efficiency for total dry matter was 0.5 g/MJ. However, the RUE for grain yield differed significantly between the two sites, with crops at Hermitage site recording 0.18 g/MJ compared to 0.12 g/MJ at Emerald. The cumulative radiation intercepted by the crop per unit thermal time between flowering and maturity phase was linearly associated with dry matter and yield of mungbean.