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Fluid Journal : Fluid Journal 1993-1995
2 Fluid Journal Spring 1994 (P2O5), 140 lbs/A of potash (K2O), and 35 lbs/A of S. Canola is extremely sensitive to seed placed nitrogen. For example. 1993 starter studies by Baileyand Grant on the Canadian Prairies showed that as little as 20 lbs/A of N placed directly on the seed at planting significantly reduced stand and yield on both sandy loam and silty clay loam soils. The opposite occurred when a year earlier the researchers banded N at 60 lbs/A and phosphate at 20 lbs/A just before seeding. Yields were optimized. At low to moderate rates, phosphate is most efficiently used when placed in a band with or close to the seed. Band phosphate placement with or near the seed promotes crop utilization early in the growing season. Seed-placed phosphate recommendations of 15-20 kg/ha (13-18 lbs/A) are common in the Canadian Prairies. Greater amounts may reduce stand and yield. However, phosphate placement 2.5 cm below and 2.5 cm beside (1 in. x 1 in.) the seed at 40 kg/ha (36 lbs/A) increased yield without significant stand reduction. Off- seed placement is recommended where high phosphate rates are needed. Other Canadian research also has shown that canola is very responsive to starter P, producing large yield increases on low P soils (Figure 1). Response varies, depending on soil type, soil moisture, and the amount of available soil P. Studies have also shown good responses from starter P on soils testing high in available P. Sorghum Alabama. Three-year studies rnn by Touchton, et. al., (1986-88) on the Coastal Plains of southeast Alabama resulted in inconsistent response by grain sorghum. At a high soil test P level, starter responses were +12, +2, and -7 bu/A across the three years. The starter was formulated from ammonium polyphosphate and UAN (18-15-0) and applied at a rate of 110 lbs/A. Placement was two inches to the side and below the seed. Kansas. Dramatic responses were achieved in three-year tests run by Lamond and Whitney (1984-86) on low P clay loam soils, using 30-inch row spacing. Bray P1 was 11 lbs/A. A 9-18- 9 starter (containing orthophosphate), or a 7-21-7 starter (containing polyphosphate) was placed with the seed. Both performed similarly, resulting in five- to ten-fold increases in early plant growth and a 29 bu/A average yield increase across three years (Figure 2). Nebraska. In 1988 research by Penas, et al., response of grain sorghum to starter was minimal across eight sites. Bray P1 varied from 8 to 96 ppm, with six of the eight sites between 17 and 42 ppm. Early growth increased at four of eight sites, but the maximum increase was only 20 percent. Grain yield was 90 80 70 60 50 Check NPK1 NPK2 NPK3 Average of 7-21-7 Extr. K = 420 lbs/A Yield (bu/A) Starter Rate - lbs/A NPK1 = N + Potash (4-6); Phosphate (6) NPK2 = N + Potash (8-12); Phosphate (12) NPK3 = N + Potash (12-18); Phosphate (18) Figure 2. Effect of starter rates on grain sorghum yield in Kansas, Lamond and Whitney, 1984-86 16 15 14 13 12 11 10 9 8 Check DAP TSP Liquid Liquid Ortho-P Poly-P Source Yield (tons/A) Figure 3. Effect of P source on marketable yield of potatoes in Florida, Locascio and Rhue, 1980-81
Fluid Journal 1996-1998