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Fluid Journal : Fluid Journal 2002-2004
2 Fluid Journal Winter 2003 34 bu/A and Banner County 2 bu/A. At the Box Butte and Kimball sites, yields were 50 and 20 bu/A, respectively. Methodology Sites. Field studies were conducted at four Nebraska Panhandle locations. Experimental Design was a randomized complete block with a factorial treatment arrangement and five replicate blocks per site. Treatments consisted of all combinations of five plant populations and five N fertilizer rates. Hybrid. Pioneer 3893 was no-till seeded into winter wheat or proso millet (Panicum miliceum L.) stubble at a rate of 41,000 seeds/A. Population. About three weeks after emergence, plants were thinned by hand to final stands of 7,000, 11,000, 15,000, 19,000, and 23,000 plants/A. N rates. N was broadcast after corn planting but before emergence at rates of 0, 30, 60, 90, and 120 lbs/A. Yields and population 1999. We observed linear increases in corn yield with increasing plant populations at the Banner, Cheyenne, and Box Butte county sites (Figure 2). Apparently, the three sites could have supported plant populations exceeding 23,000 plants/A to maximize yield. At the Kimball site, the lowest populations of 7,000 plants/A resulted in lower yields than the other population levels. Raising populations above 11,000 plants/A did not result in greater yields at that site. 2000. The relationships between plant population densities and yield were quite different from 1999. At the Banner and Kimball sites we observed a negative relationship between plant populations and corn yield (Figure 3). At the Box Butte and Cheyenne sites the relationship between plant populations and corn yield was a quadratic function. The plant population to maximize yield at Box Butte was 15,800 plants/A and at Cheyenne 11,800 plants/A. We did not observe an interaction between plant populations and nitrogen fertilization at any of the sites in either year. Developing a population recommendation based on the data collected in the two very different years has been difficult. However, using crop simulation modeling and nearly 50 years of historical climate data to supplement these data has provided a means for making a corn population recommendation for western Nebraska. Median corn yield was maximized at a plant population between 12,000 and 16,000 plants/A. As soil moisture prior to planting in the top 5 feet of soil increased from 6 to 9.5 inches, optimal population increased from 12,000 to 16,000 plants/A. Yields and nitrogen 1999. Favorable growing conditions and vigorous plant growth resulted in a response to applied fertilizer N at all 0 10 20 30 40 50 60 70 5000 10000 15000 20000 25000 Plant population (plants/acre) Grain yield (bu/acre) Banner Cheyenne Kimball Box Butte Figure 3. Effect of plant population on corn yield, 2000. 10 20 30 40 50 60 70 80 90 100 110 0 20 40 60 90 120 140 Nitrogen fertilization (lb N/acre) Grain yield (bu/acre) Banner Cheyenne Kimball Box Butte Figure 4. Effect of N fertilizer on corn yield, 1999.
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