The interaction of drought stress and heat stress as determinant of dry matter yield and nutritional composition of corn whole-plant for silage

Abstract Text: The objective of this study was to better understand how abiotic stresses affected DM yield and nutritional composition of corn whole-plant destined for silage. We analyzed data from corn hybrids performance trials completed at two sites over the 2011 and 2012 growing seasons within the state of Virginia. The first site is referred as the Southern Piedmont region (Blackstone, VA). The second site is referred as Shenandoah Valley region (Lynnwood, VA). Data from eight corn hybrids (110 to 117 days to maturity) were tested in both sites and years. Dry matter yield and nutritional composition was analyzed through mixed model analysis, using hybrid as a fixed effect and site-year as a random effect (i.e., blocking factor). Climate data were obtained from weather stations located in Blackstone and Elkton, VA. Whole-plant DM yields did not differ between hybrids, but varied significantly across site-years. The extremely low DM yield observed for the Southern Piedmont region in 2012 (4,556 kg/ha) is partially attributed to severe drought conditions (227 mm). However, substantially higher DM yields (12,678 kg/ha) were observed in the Shenandoah Valley region with only slightly more precipitations (262 mm) during the same year. Neutral detergent fiber concentrations did not differ among hybrids, but was significantly different between site-years. That NDF concentration in 2012 was much lower for the Shenandoah Valley region (43.0% NDF) than for the Southern Piedmont region (56.6% NDF) indicates that corn crops were affected differently despite summer drought. For year 2012, the Southern Piedmont region had maximum daily temperatures above 35°C for an extended period right after corn silking, whereas maximum daily temperatures were 7.1±2.3°C milder in the Shenandoah Valley region for the same corn crop stage. 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, therefore, heat stress exacerbated the effects of drought reducing substantially DM yields and increasing whole plant fiber concentration. As an overall conclusion, low DM yields and poor quality of corn whole-plant for silage are beyond drought stress. Daily maximum temperatures should be considered when planning strategies to insure good quality forage supply and reduce risk in dairy farming systems. 

Keywords: corn, drought, heat, silking