Evaluation of Field Dry-Down Rates in Early Maize

Field drying of maize (Zea mays L.) is a little-understood process that greatly influences production costs. This field research was conducted to evaluate ear drying rates of hybrids, to study the breeding potential of parental lines at different drying stages, and to interrelate plant and ear characteristics with rates and stages of drying. Yield, ear moisture, test weight, ears per plant, kernel depth, kernel rows per ear, ear length, and shelling ratio were measured at 11 environments for a late-maturing diallel set and nine environments for an early maturing diallel set of hybrids. Within each diallel set the individual hybrid moisture contents were regressed against an environmental index (El) to estimate each hybrid's relative rate of moisture loss (RML) and to predict its moisture content at Els of 500 and 200 g kg⁻¹. Phenotypic correlation coefficients (PR) and correlations among general combining ability (GCA) effects (GCAR) were computed for pairs of traits by using hybrid means or GCA effects over environments. Hybrids and inbred GCAs differed significantly for all eight traits in both diallel sets. Mean moisture contents of the 10 hybrids with the lowest predicted moisture at an El of 200 were 14.3 and 5.4 g kg⁻¹ lower than those of the 10 hybrids with the lowest predicted moisture at 500 El for the late and early sets, respectively. The RMLs were higher for the 10-hybrid groups differed in GCA effects for RMLs, but inbreds with large GCA effects for fast RML did not necessarily have large GCA effects for low moisture when averaged over all environments. The RMLs of hybrids in the late diallel set were negatively correlated with grain yield (r = −0.37*), and there was a significant positive correlation between RML and ear moisture (r = 0.35*). The RML was negatively correlated with kernel depth (r = −0.30*), kernel rows per ear (r = −0.34*), and shelling ratio (r = −0.47*) for the early diallel set, and with ear length (r = −0.42*) for the late diallel set. Test weight was negatively correlated with predicted moisture contents at both 200 (r = −0.71**) and 500 Els (r = −0.59**) for the early diallel but not for the late diallel set. Evaluation of hybrids at very high Els would not identify the same low moisture hybrids as evaluation at low Els; selection for both low moisture and fast RMLs might be more effective than considering either character alone. Contribution of North Dakota Agric. Exp. Stn., Journal article no. 1684.