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Fluid Journal : Fluid Journal 1993-1995
Charleston, the prolific hybrid yielded significantly less than the two single-ear hybrids. There were significant N fertility effects on yield in six of eight experiments. Population significantly affected yield in seven of the eight environments. Re- sponses to nitrogen and plant population were strongly influenced by environmental conditions, primarily soil available moisture. Nonsignificant responses to N and plant population occurred at sites experiencing severe drought (South Charleston in 1991 and Hoytville in 1993). Prolificacy (ears per plant) was influ- enced by hybrid, N rate, and plant popula- tion. Significant interactions for ears per plant between 1) nitrogen and population, 2) hybrid and population, and 3) population and hybrid were indicated at four of the eight sites. The prolific hybrid increased number of ears per plant with increasing N rate. Higher plant densities reduced the prolific hybrids' ears per plant. The other hybrids remained relatively constant at about one ear per plant, regardless of plant N or plant density. Prolificacy was most pronounced in the B72X hybrid at low plant population and high N rate (225 lbs/A). The highest level of barrenness (plants with no ears) occurred in the CM747AX hybrid at low N rate (75 lbs/A) and high plant population (32,000/A) under drought stress conditions. Lodging Stalk lodging was affected by hybrid in all eight experiments, and by plant popula- tion in six of the eight experiments. Signifi- cant effects of N on lodging occurred in four of the eight experiments. Although hybrid/N, N/population, and hybrid/ population interactions occurred at certain locations, no consistent trend was evident. Levels of stalk lodging were negligible to moderate for the two single-ear hybrids. Lodging was greatest for the prolific hybrid, especially at high plant density. In 1992. the prolific hybrid exhibited lodging levels as high as 40 to 50 percent at 32,000 plants per acre. Randomized testing The experiments were arranged in a randomized complete-block design with four replications. Treatments were arranged in split-split plots with hybrids as main plots, N fertility rates as subplots, and plant density as sub-subplots. Nitrogen applica- tions of UAN (28%) were split with 50 lbs/ A banded shortly after planting. Balance was applied by surface dribbling when plots reached the six-leaf stage. Field plots at Hoytville were established no-till on a poorly drained but tiled Hoytville silty clay. At South Charleston, fall moldboard plowed plots were located on somewhat poorly drained Crosby silt loam and on Kokomo silty clay loam soil types with tile improvement. Dr. Thomison is associate professor, and Drs. Johnson and Eckert are professors, Department of Agronomy, Ohio State University ! 75 150 225 205 195 185 175 165 155 145 135 125 N Rate - lbs/A Figure 3. Nitrogen fertility and plant population effects on corn yield using a Countrymark 747AX hybrid on a Kokomo silty clay loam, South Charleston, Ohio, 1993. Yield (bu/A) 16,000 plants/A 24,000 plants/A 32,000 plants/A Spring 1994
Fluid Journal 1996-1998