Effects of Furrow Irrigation on Corn in the Humid Sub-tropical Mississippi Delta

Abstract

Corn (Zea mays L.) production in the Mississippi Delta has nearly doubled since 1990 but is more susceptible to aflatoxin and fumonisin contamination when grown under drought. Four corn hybrids -- two Bt and two non-Bt -- were grown at Stoneville, MS under irrigated and non-irrigated treatments in 1999, 2000, and 2001. Furrow irrigation was applied at a rate of 1 inch per application during growth stages R1, R3, and R5 in 1999, R1 in 2000, and R1 and R3 in 2001. Irrigation increased grain yields in 2 out of 3 years. More irrigation treatments in 2000 and 2001 would have likely benefited yields. Yields in 2000 were lower than comparable treatments in 1999 and 2001 due to less weight per kernel indicating drought stress occurred during later reproductive growth (R4 to black-layer). Kernel weights were generally higher in both irrigated and non-irrigated treatments in 2001 than they were in 1999 or 2000. This compensated for having fewer kernels per ear, which likely resulted from drought stress at growth stage V12 in 2001. Differences in test weights were observed among years but not irrigation treatments. The Bt hybrids did not differ from the non-Bt hybrids in yield or mycotoxin levels. Aflatoxin and fumonisin contamination did not differ among years or irrigation treatments. Levels were below maximum acceptable concentrations for both mycotoxins. The hybrid N79-L3 had significantly lower fumonisin levels than the other hybrids.