The interaction of drought stress and heat stress as determinant of dry matter yield and nutritional composition of maize (Zea mays L) whole-plant for silage

The objective of this study was to understand how abiotic factors affected dry matter (DM) yield and nutritional composition of maize whole-plant for silage. We analyzed data from maize hybrids performance trials completed at two sites (ie, Southern Piedmont and Shenandoah Valley regions) during 2011 and 2012. Data from eight maize hybrids (110 to 117 days to maturity) were tested in both sites and years. Dry matter yield and nutritional composition were analyzed through mixed model analysis. Climate data were obtained from weather stations located in Blackstone and Elkton (Virginia, USA). Whole-plant DM yields varied significantly across site.years (P < 0.01), ranging from 4,556 to 15,092 kg ha^-1. Dry matter (DM; P < 0.01) and crude protein (CP; P < 0.01) concentrations differed among site.years. These high variations are attributed to the low DM concentration (25.3% DM) and to the high CP concentration (10.9% CP) observed for the Southern Piedmont region in 2012. Neutral detergent fiber (NDF; P < 0.01) and acid detergent fiber (ADF; P < 0.01) were significantly different between site.years. That NDF concentration in 2012 was substantially lower for the Shenandoah Valley region (43.0% NDF) than for the Southern Piedmont region (56.6% NDF) indicates that maize crops were affected differently despite summer drought. We concluded that heat stress had a major adverse effect on kernel development in the Southern Piedmont region, but not in the Shenandoah Valley region, and that heat stress exacerbated the effects of drought reducing substantially DM yields and increasing whole plant fiber concentration.