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Fluid Journal : Fluid Journal 1996-1998
1 Fluid Journal Summer 1997 Summary: Although corn planting was delayed by wet weather and yields were not as good as anticipated, the results of this study show the positive effect of phosphate fertilization on corn yields. Biennial applications beginning every other year in 1994 at varying rates twice the annual rate produced a corn yield increase curve on no-till that was consistently lower than that for chisel plow By contrast, annual applications at lower rates produced matching yield increase curves between the two tillage systems. Corn yield increases resulting from biennial applications used at twice the annual rate were equivalent to annual applications. Phosphorus concentration in the ear leaf tissue was affected by the same factors that had a significant effect on grain yield. Soil samples collected from 0-6 inches showed that phosphate fertilization produced positive changes in soil test values for phosphorus. The sampling scheme used could identify the location of a band applied on an annual basis. The presence of a single band applied in the fall of 1994 (biennial application) was less obvious. Very little research has focused on the various management options that might be appropriate for the most efficient use of phosphate fertilizer in the total corn/ soybean rotation. In developing the appropriate phosphate management system, it is essential that annual and biennial applications be compared. A management system that would allow for the application of phosphate fertilizer to the rotation on a biennial basis without reducing crop yields would be preferred by many growers. This approach to phosphate management would save time and fuel because each acre would not need to be fertilized each year. Previously, residual effects of phosphate fertilization were Dr. G.W. Rehm Annual/Biennial Applications of P Compared in No-till and Chisel Plow Researcher finds variance between tillage systems in corn yield response to biennial applications. • • • • • • • • • 120 110 100 90 80 70 60 Yield - bu/A Chisel No-till 0 23 46 69 92 P O Applied Fall 1994 (Annual) 25 • • • • • • • • • • 130 120 110 100 90 80 70 60 Yield - bu/A Chisel No-till 0 46 92 138 184 P O Applied Fall 1994 (Biennial) 25 measured when phosphate was applied in the corn production year. Although many farmers are interested in no-till production systems, conventional tillage systems will continue to be used on large acreages in Minnesota and the northern Corn Belt. The no-till planting system presents a special challenge for management of phosphate fertilizer. Phosphorus is not mobile in soils and, if broadcast on the soil surface, will remain there in a no- till planting system. Therefore, banded applications of phosphate are the only practical alternative if soil test results show that phosphate fertilizer is needed for optimum no-till corn and soybean production. The impact of annual or biennial applications of phosphate in a band have not been evaluated in both no-till and fall chisel planting systems. Objectives of our study were several: • evaluate two contrasting tillage systems suitable for corn/soybean rotation, using up-to-date management practices for each tillage system and crop • develop a system for management of phosphate fertilizer so that phosphorus efficiency is maximized for both crops in the rotation • evaluate corn/soybean production in two tillage systems when planted in row spacings of either 7 or 30 inches; optimum rates of fertilizer and other appropriate inputs will be used • monitor the effect of rate and placement of phosphate fertilizer on soil test values for P in each tillage system. Yield effects Corn grain yields in both tillage systems increased as the rate of applied phosphate increased. When annual applications were used, the response for both tillage systems was essentially the Figure 1. Corn yield as affected by phosphate applied on an annual basis for two tillage systems. Rehm, University of Minnesota, 1996. Figure 2. Corn yield as affected by phosphate applied on a biennual basis for two tillage systems, Rehm, University of Minnesota, 1996. same (Figure 1). However, with biennial applications beginning in 1994, the yield curve was consistently lower in the no-till planting system (Figure 2). The yields shown in both figures were averaged over placement and row spacing treatments. Not incorporating phosphate broadcast in the no-till system may help explain the lower yields. In 1996, phosphate placement had no significant effect on grain yield. There
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