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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Fall 95 Leaf N, P (%) 3.5 3.0 2.5 2.0 1.5 1.0 .05 0.0 No Fertilizer Surface Broadcast Surface Banded Coulter -Nozzle Backswept Knife-Deep Application Method N, 1986 N, 1987 P, 1986 P, 1987 Figure 3. NP uptake response to surface vs. subsuface applications on sorghum, Chichester and Morrison, USDA-ARS, Temple, TX, 1986-87. evaluation of various applicator tools. Applications were with solution-type fertilizers because they are most commonly used by farmers in central Texas. We selected both backswept applicator knives and a coulter-nozzle applicator that minimized residue and soil disturbance. Vertical distribution was unknown for fertilizer applied with the coulter-nozzle applicator in a narrow soil slot. Objective of this research was to test the effectiveness of new shallow sub-surface applicators (as well as existing tools) against surface applicators. Resulting nutrient uptake and yield were measured to determine the effectiveness of each placement system. Rainfall possible factor Agronomic responses to six fertilizer applicator treatments were not significantly different within each year. For grain yield, the only differences were between the control and those receiving N and P (Figures 1 and 2). Similarly, plant uptake of N and P showed little or no differences in response to fertilizer application method (Figure 3). One exception was increased uptake of N in 1986 from deeper placement with the backswept knife (Figure 3). Another was lower P uptake with the coulter-nozzle treatment than for the three other application treatments in 1987 (Figure 3). A third was lower N uptake in surface applications when compared to five subsurface placements in 1989. When grain yield data were analyzed in terms of N-use efficiency, there were no differences within each year. similar to the above discussion of yield. Lack of differences in plant response among treatments in this study may reflect the adequacy of rainfall that is usual during the early spring season when these tests were run. Other workers have shown that differences in surface and subsurface placement, especially N. may he compensated under conditions where surface-applied fertilizer moved into the soil with infiltrating rainfall and/or where plant roots were not water stressed in shallow soil layers. Had the trials been carried out under moisture stress conditions, greater differences in yield response might have been observed. The resulting 68 percent increase in soil slot width (made by thickening coulter blade from 0.153 to 0.257 inch) suggests there may have been a trend for the N to be distributed deeper in the wider slot. Criteria Placement system. Our choice of subsurface application over simpler surface application is based on previous studies, as cited earlier in this text, not on the results of this three-year study. Implements. The backswept knife, thin Yetter knife, and Vee wheel did not produce plant responses different from those to coulter-nozzle applications at the same depth. What tipped us toward the coulter-nozzle were: 1) preferential reduced soil and residue disturbance, and 2) least sensitivity to high soil moisture adhesion. Methodology Crop. Grain sorghum was grown in rotation with winter wheat and corn. Fertilizer treatments were made into wheat stubble after nine months of chemical fallow. Plots. No-till plots were configured in 61-inch-wide-raised beds between permanent-controlled traffic lanes on 80-inch spacings. Treatments. Fertilizer treatments included 1) control, 2) surface broad-cast, 3) surface band, 4) coulter- nozzle, 5) backswept knife, 6) Yetter knife, and 7) Vee-wheel. Fertilizers. Solution-type fertilizers were mixes of 32% VAN solution and APP (10-34-0) solution. Application rates were 135 and 26 lbs/A of N and P2O5, respectively in 1986 and 1987, and 70 and 28 lbs/A of N and P2O5, respectively in 1989. Dr. Chichester is a retired soil scientist/ chemist and Dr. Morrison is an agricultural engineer at the USDA Agricultural Research Service in Temple, Texas.
Fluid Journal 1996-1998