Long-Term variability in Evapotranspiration and water productivity of Kharif maize in central and sub-mountainous Punjab

Abstract

Effect of climatic variations on crop evapotranspiration (ETc), yield and water productivity of irrigated maize was evaluated to explore options for sustainable use of natural resources under changing climatic conditions in Punjab. Long-term changes in ETc of kharif maize was computed through CROPWAT 8.0 model and Papadakis method for a period of 1970–2018 for Ludhiana in the central plain and 1984–2018 for ballowal Saunkhari in the sub-mountainous agro-climatic region of Punjab. The maize crop at Ludhiana had average ETc of 532.9 mm and ballowal Saunkhari 489.2 mm by CROPWAT model; whereas it was 519.5 mm at Ludhiana and 535.2 mm at ballowal Saunkhari by Papadakis method during the kharif maize growing period. Long term analysis of variability in maize yield during the period 1970–2018 indicated that it increased @ 63.7 kg/ha/year at Ludhiana and 90.6 kg/ha/year at ballowal Saunkhri. At Ludhiana, ETc of maize decreased @ 1.1 mm/year for CROPWAT model and @ 2.3 mm/year for Papadakis method; whereas water productivity increased @ 0.13 kg/ha/mm/year with CROPWAT model and @ 0.15 kg/ha/mm/year with Papadakis method. At ballowal Saunkhri, the ETc of maize decreased @ 2.5 mm/year by CROPWAT model and increased @ 1.5 mm/year by Papadakis method; whereas water productivity increased over years @ 0.21 kg/ha/mm/year with CROPWAT model and @ 0.16 kg/ha/mm/year with Papadakis method. The increase in water productivity of maize could be attributed mainly to increase in yield over years. Multiple regression models explained 61 to 99 per cent variation in ETc of kharif maize at Ludhiana and 78 to 97 per cent at ballowal Saunkhari due to variable weather conditions at these two sites. These models have the potential to assess the impact of climate change on ETc of kharif maize in these two agroecologies of Punjab.