Maize kernel moisture, carbon and nitrogen concentrations from silking to physiological maturity

Grain characteristics prior to physiological maturity are important for sil age harvest and for grain harvest when grain fill has been prematurely term inated by factors such as hail or early frost. The objective of this study was to investigate changes in grain moisture, C and N concentrations associ ated with the progression of milk line from silking to physiological maturi ty for hybrids with maturity ratings between 76 and 95 Minnesota relative m aturity days. A field experiment with a total of 15 hybrids was carried out on a well-drained sandy loam soil at Ottawa, Canada, from 1995 to 1997, in clusive. A large number of uniform plants with the same phenology were mark ed in each plot near tasseling, and ears were sampled from these plants at weekly intervals from R1 to final harvest. It was noted that 50% milk line was associated with a range of kernel moisture concentrations: in 1995, a r elatively warm year, kernel moisture was 389 g kg(-1) when 50% milk line oc curred; in 1996, a relatively cool year, kernel moisture was over 420 g kg( -1) at 50% milk line. During the course of grain fill, C concentrations rem ained relatively constant whereas N concentrations were dramatically reduce d from as high as 50 g kg(-1) to approximately 15 g kg(-1). Maximum dry mat ter accumulation was reached at 325 g kg(-1) moisture. In general, later-ma turing hybrids appeared to have longer duration from silking to 50% milk li ne; however, they took less time to reach physiological maturity (faster gr ain fill and dry down). Although benchmarks of 50% milk line and 0% milk li ne are commonly used for silage and grain production, there is a range of g rain moisture-milk line relationships among genotypes and under different e nvironmental conditions during grain fill.