Submitted to: Crop Management at www.cropmanagement.org
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/21/2003
Publication Date: 6/1/2004
Citation: Bruns, H.A., Meredith Jr, W.R., Abbas, H.K. 2004. Effects of irrigation on corn in the humid sub-tropical Mississippi Delta. Crop Management at www.crop management.org. 10.1094/CM-2003-1222-02-RS. Interpretive Summary: Information on the effects of irrigation on yield, yield components, and mycotoxins with currently grown hybrids in the Mississippi Delta and comparisons of Bt and non-Bt hybrids is limited. Four corn hybrids, two Bt and two non-Bt, were grown in furrow irrigated and non-irrigated plots at Stoneville, MS in 1999, 2000, and 2001. Data on grain yield, kernel weights, kernel numbers, test weights, aflatoxin, and fumonisin levels were collected. Irrigation increased grain yields in 1999 and 2001. Compensation between kernel weights and kernels per ear were noted between years and irrigation treatments. No differences in yields or test weights were observed between the Bt and non-Bt hybrids. Aflatoxin and fumonisin levels were observed to be below the maximum allowable standards set by the US-FDA. These data show that irrigation improves corn grain yields with no differences being observed between Bt and non-Bt hybrids. Drought stress does not have to be visible to have an adverse affect on yield by affecting kernels per ear and kernel weight. These results are valuable to corn growers in the Mississippi Delta because they show the importance of applying sufficient irrigation to maximize yields. More severe drought stress than was experienced by plots in this study is necessary before mycotoxins are a problem.
Technical 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 growth stages R2, R3, and R4 in 1999, R2 in 2000, and R2 and R4 in 2001. Irrigation tended to increase grain yields and more applications in 2000 and 2001 would have likely benefited yields more. Yields in 2000 were lower than comparable treatments in 1999 and 2001 due to less weight kernel-1 indicating drought stress occurred during later reproductive growth (R4-R6). Kernel weights were higher in three hybrids for both irrigated and non-irrigated treatments in 2001 than in 1999 or 2000. This compensated some for having fewer kernels ear-1, which likely resulted from drought stress at growth stage V12. Irrigation at V12 may be necessary to prevent such yield reductions. Differences in test weight were observed among years but not irrigation treatments. The Bt hybrids did not differ from the non-Bt hybrids in yield or grain quality. Aflatoxin and fumonisin contamination was not a factor among years or irrigation treatments. Levels were below maximum acceptable concentrations for both mycotoxins. The hybrid N79-L3 was significantly lower in fumonisin levels than the other hybrids.