Seasonal Crop Evapotranspiration in Modern and Older Maize Hybrids.

It is well known that grain yield of modern maize (Zea mays L.) hybrids is greater than that of older ones under different abiotic stresses; however, there is little information on the physiological mechanisms contributing to a greater yield of the modern hybrids under water stress. The objective of this research was to determine whether seasonal crop evapotranspiration (ET) in modern maize hybrids was increased or equaled that of an older maize hybrid under different soil water availabilities. Field experiments were conducted at Balcarce, Argentina during two growing seasons. Two modern maize hybrids released in Argentina on 2000 (DK682RR and DK690MG) and one old maize hybrid released in 1980 (DK2F10) were evaluated under different water regimes that included (i) rain-fed during the whole growing season (season 1 and 2), (ii) irrigated from silking to physiological maturity (season 1) and (iii) irrigated during the whole season (season 1 and 2). Water stress was evident during both seasons and total rainfall and its distribution differed between seasons (i.e. season 1 was drier than season 2 during the whole growing season; drought during season 2 was evident during the vegetative period only). Seasonal crop evapotranspiration averaged through hybrids was greatest for the irrigated treatment during the whole season (443 mm for season 1 and 672 mm for season 2) and it was lowest for the rain-fed treatments (295 mm for season 1 and 452 mm for season 2; p<0.05). Seasonal crop evapotranspiration was similar between modern and old hybrids at each water regime (p>0.05).