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Fluid Journal : Fluid Journal 1999-2001
3 Fluid Journal Spring 1997 1:1 and 3:1 N:P2O5 ratio starters were equally effective. Scandia, Kansas. Broadcasting P on a producer's field near Scandia, Kansas, improved yield of grain sorghum compared to no-P check plot, but was not as effective as banding (Figure 2). Single degree of freedom contrasts (P>0.04) show that 40 lbs/A of P2O5 was superior to 20 lbs/A on a soil testing low in P. Broadcast plus starter treatment produced yields that were equal to those achieved with a banded starter of 40 lbs/A of P2O5. Greatest yields resulted from banding starters in ratios of 1:1 or 3:1. Uptake When averaged over three years, broad-casting 20 lbs/A P2O5 increased P uptake by 32 percent compared to the no-P check. However, banded starter was more effective than broadcasting. Greatest P uptake occurred when banded starter was applied in a 1:1 or 3:1 N:P2O5 ratio. Previous research has shown that when P is banded, N also is needed in the band for stimulation of P uptake. Banded starters that supplied 10 lbs/A of N were not as effective as treatments that supplied 40 lbs/A of N. N uptake at the V8 stage of growth also was maximized in banded starters, with N and P applied in either a 1:1 or 3:1 ratio. Surface broadcasting P increased leaf P above critical levels, and those at 40 lbs/A of P2O5 were statistically equal to those with banded starters that supplied 10lbs/AofNwith20or40lbs/Aof P2O5 . Leaf P concentration was maximized by banded starter applied either at a 1:1 or 3:1 N:P2O5 ratio. The three-year average leaf N concentration was greatest when N and P were placed in a starter band in a 1:1 or 3:1 N:P2O5 ratio. Methodology Soil was a Can sandy loam with a pH of 6.9, organic matter content of 1.5 percent, and Bray-1 P in the low soil test category. Tillage. The experimental area had been in ridge-tillage corn for three years prior to establishment of this study. Design. Experimental design was a randomized complete block replicated four times. Plots consisted of four rows, 30 feet long and 30 inches apart. Population. Dekalb 40Y was planted each year at 90,000 seeds/A. Planting dates were in the latter part of May in all years. Irrigation. In 1994 and 1995, plots were irrigated twice, once at boot stage and again 10-14 days later. A total of 3 inches of water was applied at each irrigation. Since rainfall in July of 1993 was much above average, plots were irrigated only once in mid-August. All irrigation water was applied in-furrow. Dr. Gordon is professor at the North Central Kansas Experimental Fields, KSU, and Dr. Whitney is professor of Extension Agronomy, KSU.
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