抄録
Inadequate management of nitrogen and water stress are the main factors underlying poor growth and yield in maize (Zea mays L.). To evaluate the effects of nitrogen and water stress on the growth and physiology of maize plants, two field experiments were conducted at the National Corn and Sorghum Research Center, Thailand, during 2010-2011 and 2012 under short pre-anthesis drought and prolonged flowering-stage drought, respectively. A split-plot design with factorial randomized complete block arrangement was used for the experiment, with two water regimes (well-watered and water-stressed) forming the main plots and two maize hybrids (Pioneer 30B80 and Suwan 4452) and three nitrogen levels (0, 160 [optimal] and 320 [supra-optimal] kg N ha−1) forming the subplots. We found that supra-optimal nitrogen (urea) temporarily changed the soil pH significantly. Optimal nitrogen and well-watered conditions enhanced the net assimilation rate at the vegetative stage (NARv), ovule number per primary ear (ONpe), leaf area duration in the reproductive period (LADr), specific leaf weight at anthesis (SLWa), current assimilate transfer to kernels (CATK), chlorophyll content at anthesis (Chla), nitrogen use efficiency, biomass yield, and kernel yield per plant (KYP). In contrast, supra-optimal and zero nitrogen and water stress had detrimental effects on these parameters, except Chla. Prolonged flowering-stage drought was found to be more detrimental than short pre-anthesis drought regarding plant performance. Greater root-to-shoot ratio, LADr, Chla, nitrogen use efficiency, NARv, and ONpe were recorded as traits of nitrogen and water-stress tolerance in Pioneer 30B80. The optimal nitrogen level improved drought resistance, especially under short pre-anthesis drought. The correlations between KYP and LADr, Chla, NARv, ONpe, and CATK were positive and highly significant, and NARv, ONpe, and CATK had significant and positive direct effects on KYP under both short pre-anthesis and prolonged flowering-stage drought.
