Agronomic practices affect com (Zea TTUlJS L.) grain yield and may affect physical and chemical characteristics of com kernels. These characteristics affect feed, food, and industrial uses of corn grain. Four field experiments consisting of planting date and population combinations were conducted to determine the effect of these agronomic practices on grain yield, kernel N concentration, and kernel hardness. Kernel hardness was estimated by kernel weight, kernel density, and grinding resistance. A fixed ear hybrid, 873 x LH38, was used in all four experiments. Two of the four experiments also included LH119 x LH51, a flexible ear hybrid. Planting date affected yield in only one experiment. In this instance, delaying planting 4 wk decreased yield 55%. Yield reduction from planting delay was greater for 873 x LH38 than for LH119 x LH51. In two experiments, increasing population increased yield quadratrically; whereas, in the other two experiments the effect of population on yield was linear. No interaction between hybrid and population occurred. Delayed planting increased kernel N concentration in one experiment. In all four experiments, increasing population resulted in a linear decrease in kernel N concentration. Few effects from either planting date or population on kernel weight and density were found. Grinding resistance was increased by delayed planting in one experiment but was not affected by plant population in any of the four experiments. Inverse relationships between yield and important kernel physical and chemical characteristics were found. Emphasis on high yield may result in less desirable grain. End-users that require high grain quality may need to provide incentives to growers.

Corn (Zea mays L.) is a major source of nutrition for humans and animals. Chemical and physical properties of corn endosperm vary among hybrids, are influenced by genotype and environment, and may affect the crop's response to nitrogen (N) fertilization. The objective of the study was to measure the responses of grain yield and grain N, phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), manganese (Mn), iron (Fe), boron (B), zinc (Zn,) and copper (Cu) concentration of different endosperm types to N fertilization. The study was conducted at two Ohio locations in 1988, where six endosperm types and two N rates (34 and 200 kg N/ha) were combined in a split plot arrangement.Nitrogen rate (main plots) had little effect on yield at either location, and the soft endosperm hybrid was the only hybrid to respond to N fertilizer. Within fertilizer level, hybrids differed in grain yield with the waxy hybrid out yielding the normal endosperm hybrid, and the hard endosperm hybrid out yielding the soft one at the 200 kg N/ha rate. Application of N fertilizer increased the grain N concentration of all hybrids. Grain of the waxy hybrid contained an equal or greater N concentration than the normal hybrid. In contrast, no difference in N level was found between hard and soft endosperm hybrids at either fertilizer level. Climatic conditions and soil fertility differences might have been partly responsible for location effects. Genetic make-up could have been a factor in differing hybrid response 1.

No abstract

No abstract

No abstract