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Fluid Journal : Fluid Journal 1996-1998
2 Fluid Journal Summer 1997 was no significant interaction between tillage system and fertilizer placement. There was also no significant interaction between placement and rate. The yield effects of placement on corn, row spacing used for 1995 soybean production, frequency of application, and tillage system are shown in Figure 3. These yields were typical of corn yields throughout west-central Minnesota. When averaged over all other factors, fall chisel system yields were 109 bu/A while the no-till system produced an average yield of 98 bu/A. This yield difference, however, was not statistically significant. P concentration Ear leaf samples were collected at silking to monitor treatment effect on corn uptake of P. In 1996, when averaged over all other factors, P concentration in corn planted in the chisel plow system was .202 percent. When tile no-till planting system was used, P concentration was . 191 percent. This was not a statistically significant difference. Phosphate placement had no significant effect on ear leaf P 120 110 100 90 80 70 60 50 Control - No-till Broadcast - No-till Broadcast - Chisel Band - No-Till Band - Chisel Band - No-till Band - Chisel Control - Chisel Broadcast - No-till Broadcast - Chisel 730 730 730 730 730 730 730 730 730730 Row Spacing - Inches Annual Bienniel Bu/A Figure 3. Corn grain yield as affected by tillage system, placement of phosphate, row spacing for previous soybean crop, and frequency of phosphate application, Rehm, University of Minnesota, 1996. concentration. When averaged over other factors studied, P concentration was . 194 percent when the phosphate was applied in a band and .200 percent when phosphate was broadcast. Ear leaf P concentration increased with applied phosphate rate. There was no significant interaction between rate applied and frequency of application (annual, biennial). There also was no significant interaction between tillage system and applied phosphate rate. The effects of the various treatments on ear leaf P concentration were similar to the effects of these treatments on grain yield. Soil test values Soil samples (0 to 6 inches) were collected from selected treatments in the fall of 1996 to measure changes in soil test P values. Samples were analyzed by both the Bray and Kurtz #1, and the sodium bicarbonate (Olsen test) procedures. Because of high pH values (range 7.5 to 8.0), soil test values measured by the Bray and Kurtz procedure were low and did not provide a good measure of the effect of treatment on soil test values. The bicarbonate extractions provided a better indication of changes. In general, soil test values were increased by phosphate fertilization. Considering the broadcast application, two annual applications of either 23 or 46 lbs/A of P2O5 produced extractable P levels higher than a single application of either 46 or 92 lbs/A of P2O5, respectively. For treatments where phosphate fertilizer was applied in a band, samples were collected from directly beneath the row. Corn was planted over the band in the no-till planting system. For the fall chisel system, this subsurface band could have been disturbed by the chisel operation. The sampling scheme used was successful in detecting the presence of the band in both tillage systems. The chisel operation apparently did not disturb the band. Presence of the band was not obvious when phosphate was applied biennially. Methodology Site. This study was conducted at the West-Central Experiment Station at Morris, Minnesota.
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