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Fluid Journal : Fluid Journal 1999-2001
2 Fluid Journal Spring 1997 temperatures were below normal (Table I). An early frost also was recorded in mid-September of 1993 that affected yields of some treatments. Seasonal rainfall in 1994 and 1995 was below the long-term averages. Below normal temperatures in September of 1995 also may have affected grain fill and yield. Yields up North Central Kansas. Applied P treatments on a producer's field near our North Central Kansas Experiment Field significantly improved grain yields over those of no-P check plots in all three years of the experiment (Figure 1). Orthogonal contrasts were used to compare rate and placement effects. When averaged over three years, applied P compared to no P improved grain yields by 40 bu/A. Surface broadcasting P2O5 at 40 lbs/A increased yields by 9 bu/A when compared to the 20 lbs/A rate of P2O5. On the low soil testing P soil, however, banding P proved to be more effective than broadcasting. Comparison of all band treatments showed that 20 lbs/A of P2O5 was just as effective as 40 lbs/A. Previous studies report P placed in a soil volume intermediate between a small fraction with a row-placed band and a large fraction broadcast, gave higher P recovery and greater yields than either banding or broadcasting. However, on this Can sandy loam soil a single band beside the row was just as effective as bands placed on either side of the row. Broadcasting half of the P and placing half as a single starter band was as effective as a single starter band. Knifing P in the center of the row middle was not as effective as placing P in a band beside the row. Nitrogen and P applied in either a 1:1 or 3:1 ratio produced the greatest 3-year average yields. The 1:1 N:P2O5 (40 lbs/ A of N and 40 lbs/A of P2O5) ratio applied as a single band starter increased yields by 16 bu/A over the single band that provided only 10 lbs/A of N. Higher N starter treatments resulted in consistently greater grain yields. The 140 130 120 110 100 90 80 70 60 PO @20lbs/A PO @40lbs/A 25 25 Yield - bu/A Check B S2x2 D2x2 Knife 1:1 3:1 N:PO N:PO 25 25 B = Broadcast; S = Single; D = Dual 140 130 120 110 100 90 80 70 60 PO @20lbs/A PO @40lbs/A 25 25 Yield - bu/A Check B S2x2 D2x2 Knife 1:1 3:1 N:PO N:PO 25 25 B = Broadcast; S = Single; D = Dual Figure 2. Effects of P application method and rate on grain sorghum yield, N rates of 40 lbs/A (1:1) and 120 lbs/A (3:1), Gordon, et al., KSU, Scandia, 1993. Figure 1. Effects of NP application method and rate on grain sorghum yield, all N rates at 10 lbs/A, except 40 lbs/A (1:1) and 120 lbs/A (3:1), Gordon, et al., KSU, Scandia, 1993.
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