Growth and Physiological Responses to Supra-Optimal Nitrogen and Pre-Anthesis Drought Stress in Maize

Abstract

Water and nitrogen (N) are major limiting factors in the production of maize (Zea mays L.) in the tropics and subtropics. A field experiment was conducted during the dry season in 2010–11 at the National Corn and Sorghum Research Center, Thailand to determine the sole and interactive effects of N, water and variety on the growth, physiology and grain yield of maize. Two water regimes (wellwatered and water-stressed) formed the main plots and two hybrids (Pioneer 30B80 and Suwan 4452) and three N levels (0 kg.ha-1, 160 kg.ha-1 (optimal) and 320 kg.ha-1 (supra-optimal) were subplots with three replications using a split plot design and a factorial randomized complete block arrangement. Zero and supra-optimal N, and water-stress significantly reduced the green leaf area (37.86, 6.76 and 17.64%, respectively, at silking), root dry matter (RDM) (62.48, 15.66 and 48.83%, respectively), grain number (20.43, 11.96 and 16.76%, respectively) and grain yield (GY) (31.64, 14.07 and 19.20%, respectively) but not leaf rolling when compared to the control. The leaf relative water content (RWC) decreased (12.87%) significantly only with water-stress. The two hybrids responded differently to N with regard to leaf area—Suwan 4452 was more sensitive to zero N and Pioneer 30B80 was more sensitive to supraoptimal N. Suwan 4452 was lower in RDM (53.92%), grain number (12.90%), and GY (9.66%) than Pioneer 30B80, with the latter performing better under single or combined stress. Higher RDM levels in the surface soil during vegetative growth, the amount of kept green leaves and more grain and a higher RWC were exhibited as drought and N stress tolerance indicators.