Response of water deficit regime and soil amelioration on evapotranspiration loss and water use efficiency of maize (Zea mays l.) in subtropical northeastern Himalayas.

Rainfed maize production in the hilly ecosystem of Northeastern Himalayas often suffers from moisture and soil acidity induced abiotic stresses. The present study measured evapotranspiration loss (ET) of maize crop under controlled condition (pot experiment) of water deficit (W-25 % and W-50 % of field capacity soil moistures) and well watered (W = 100 % of field capacity (FC)) regimes in strong acid soils (pH = 4.3) of the Northeastern Himalayan Region of India. The response of soil ameliorants (lime) and phosphorus (P) nutrition under differential water regimes on ET losses and water use efficiency was also studied. The measured seasonal ET loss varied from 124.3 to 270.9 mm across treatment combinations. Imposition of water deficit stress resulted in significant (p < 0.05) reduction (by 33-50 %) of seasonal ET losses but was at the cost of delay in tasseling to silking, 47-65 % reduction in dry matter accumulation (DMA), 12-22 days shortening of grain formation period, and complete kernel abortion. Liming @ 4 t ha significantly (p < 0.05) increased ET losses and DMA across water regimes but the magnitude of increase was higher in severely water deficit (W) regime. Unlike lime, P nutrition improved DMA only in well-watered regimes (W) while seasonal ET loss was unaffected. Vegetative stage (tillering to tasseling) contributed the maximum ET losses while weekly crop ET loss was estimated highest during 11th-14th week after sowing (coincided with blistering stage) and then declined. Water use efficiency estimated from dry matter produced per unit ET losses and irrigation water used varied from 4.33 to 9.43 g dry matter kg water and 4.21 to 8.56 g dry matter kg, respectively. Among the input factors (water, P, and lime), water regime most strongly influenced the ET loss, growth duration, grain formation, and water use efficiency of maize.