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Fluid Journal : Winter 2015
15 The Fluid Journal Winter 2015 nutrient management systems in Virginia: • All of the required P and K was broadcast prior to planting • 100 lbs of ammonium polyphosphate solution (10-34-0) per acre was Table 1: Mehlich I extractable phosphorus and potassium at 0-3, 3-6, 6-9, 9-12 inch depths at TAREC and Lewiston Depth inches TAREC Lewiston P K P K ppm 0-3 49 (H+)¶ 99 (H-) 30 (H) 126 (H) 3-6 31 (H) 86 (M+) 18 (H-) 59 (M) 6-9 20 (H-) 73 (M) 13 (M) 37 (L+) 6-12 19 (H-) 68 (M) 7 (M-) 33 (L+) ¶ Indicates the soil test level based on Virginia's soil test calibration Table 2. Treatment List for 2013 Locations Tr t Placement Description 1 Unfertilized Control No P or K Fertilization 2 Broadcast Agronomic Control P + K Broadcast -- Soil test recommendation‡ 3 Starter Agronomic Control 100 lbs /acre† of 10-34-0 in 2X2 band + Remaining P+K broadcast 4 2X2 Band 50%P + 50%K¶ 5 2X2 Band 100%P + 100%K 6 2X2 Band 150%P + 150%K 7 Deep Placement 50%P + 50%K 8 Deep Placement 100%P + 100%K 9 Deep Placement 150%P + 150%K † 100 lbs/acre of 10-34-0 is the recommended rate for cotton placed in a 2X2 band at planting in by North Carolina State University Cooperative Extension. ‡ Recommended nutrient application rates applied based on Mehlich 1 extractable phosphorus and potassium and Virginia Cooperative Extension Recommendations ¶ Percentages represent the proportion of recommended nutrient application rates applied based on Mehlich 1 extractable phosphorus and potassium and Virginia Cooperative Extension Recommendations. Figure 1: Picture of the strip-tillage fertilizer systems and shank to place fluid phosphorus and potassium fertilizers at 6, 9, and 12 inches below the soil surface during strip tillage. applied in a 2 x 2 band at planting with the K broadcast prior to planting (Table 2). Treatments 4 through 9 evaluated the response to P and K fluid fertilizer applied ina2x2bandatplantinganddeep placement during strip-tillage at 50, 100, and 150 percent of the recommended rate based on soil tests. Treatment application Deep placement treatments were applied with a two strip-tillage implement three days prior to planting at TAREC and 14 days prior to planting at Lewiston. Fertilizer placement with strip-tillage was accomplished with an apparatus depicted in Figure 1. To dispense fluid fertilizer at 6, 9, and 12 inches below the soil surface, holes drilled 90o to the direction of travel allowed the fluid fertilizer to exit each down-spout and maximize contact with the soil at the targeted depths. The 2 x 2 banded fertilizer was applied at planting, using a double disk opener mounted on the toolbar of a two-row Monosem planter. The application rate for the fluid P and K sources was controlled by a carbon dioxide pressurized system and the application rates were controlled using inline orifices (Figure 1). The broadcast P and K were applied on the same day as the strip tillage cultivation and deep placement of P and K for both locations. Diammonium phosphate (DAP, 18-46-0) and muriate of potash (0-0-60) were used as the P and K sources for the broadcast agronomic control treatment. The liquid phosphate source applied was ammonium polyphosphate (10-34-0) (APP) and the fluid potassium source was potassium thiosulfate (0-0-25-17S). The potassium thiosulfate supplied 40.8 lbs. S/acre when applied at the 150 percent rate, which is greater than the recommended agronomic S rates in cotton. Ammonium thiosulphate (12-0- 026S) (ATS) was used to balance the S rate among treatments. In the treatments where a combination of placement techniques was implemented, the added S was applied using deep placement to prevent any potential injury to cotton seedlings. Preplant N was balanced at the same level as the broadcast agronomic control, plus additional N from ATS. The preplant N rate for the P and K fertilized treatments was 35 pounds N per acre. The N was balanced using the fluid urea-ammonium nitrate (UAN 30-0-0). The total N application rate was set at 115 lbs N/acre, with the remaining 80 lbs N being applied in a sidedress application using a 24-0-03S at TAREC and UAN30 at Lewiston, applied at match- head square. At TAREC, the unfertilized control treatment received no sidedress