Responses of Short‐Season Corn Hybrids to a Humid Subtropical Environment

Abstract

Corn (Zea mays L.) hybrids commonly grown in the lower Mississippi River valley often encounter heat and drought stress during reproductive growth, which impairs yield and increases preharvest mycotoxin contamination. Four short‐season hybrids developed for production at ≥ 40° N latitude and two hybrids adapted to the Midsouth USA were grown at Stoneville, MS (33°26′ N, 90°55′ W), in 2002 and 2003 using N fertility treatments of 112 kg N ha−1 preplant, 224 kg N ha−1 preplant, or 112 kg N ha−1 preplant + 112 kg N ha−1 side‐dress at growth stage V6 (six leaves). Growing degree units at 10°C base temperature required for growth stages R1 (silking) and R6 (physiological maturity) of the four short‐season hybrids were 50 and 100 units greater, respectively, than when grown in their adapted environments. Yields of two of the short‐season hybrids compared well with the adapted hybrids. Kernel weights and grain bulk density differed among hybrids but were not below levels subject to dockage. Aflatoxin and fumonisin levels were higher in 2002 than 2003. Three of the short‐season hybrids did have aflatoxin levels in 2002 at least three times greater than the other three hybrids. Plots receiving 224 kg N ha−1 preplant yielded more than the other N fertility treatments. Kernel weights were 10 mg greater for the higher N fertility treatments. Nitrogen fertility had no effect on mycotoxins. Short‐season hybrids need to be individually evaluated for production potential in the lower Mississippi River valley.