Spectrum Analytic Inc
1087 Jamison Rd
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1087 Jamison Rd
Washington Court House, OH 43160
(800) 321-1562
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| library:articles:soil_test_p_and_k_buildup_and_drawdown 2013/07/15 09:56 | library:articles:soil_test_p_and_k_buildup_and_drawdown 2022/01/19 07:00 current | ||
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| - | If you have heard agronomists quote this 9:1 or 4.5:1 ratio many times you might think that this is all that you need to know... it isn't that simple. Research at the University of Kentucky reported in 2002 (Table 1) illustrates how soil test P buildup occurs. In this study, they looked at 16 different soils with initial soil test P levels ranging from 6 to 240 lb P/acre (3 to 120 ppm P/a) using Mehlich 3 (M3) extraction. They applied 6 different rates of phosphorus ranging from 38 to 228 lb P<sub>2</sub>O<sub>5</sub>/acre. Their results nicely fit a mathematical relationship used to develop the data in Table 1. These results clearly show that the initial soil P test is a major factor in determining how much P<sub>2</sub>O<sub>5</sub> is required to buildup the soil test P. | + | If you have heard agronomists quote this 9:1 or 18:1 ratio many times you might think that this is all that you need to know... it isn't that simple. Research at the University of Kentucky reported in 2002 (Table 1) illustrates how soil test P buildup occurs. In this study, they looked at 16 different soils with initial soil test P levels ranging from 6 to 240 lb P/acre (3 to 120 ppm P/a) using Mehlich 3 (M3) extraction. They applied 6 different rates of phosphorus ranging from 38 to 228 lb P<sub>2</sub>O<sub>5</sub>/acre. Their results nicely fit a mathematical relationship used to develop the data in Table 1. These results clearly show that the initial soil P test is a major factor in determining how much P<sub>2</sub>O<sub>5</sub> is required to buildup the soil test P. |
| ^ Table 1 |||| | ^ Table 1 |||| | ||
| ^ ^ Buildup Ratio ^ Initial Soil P (lb/a) ^ Buildup Ratio | | ^ ^ Buildup Ratio ^ Initial Soil P (lb/a) ^ Buildup Ratio | | ||
| Line 116: | Line 116: | ||
| | ::: | ppm | 40-60 | 34-55 | 31-50 | 27-47 | 25-44 | 22-42 | | | ::: | ppm | 40-60 | 34-55 | 31-50 | 27-47 | 25-44 | 22-42 | | ||
| | < 6.0 | lb./a | 140-210 | 120-180 | 109-169 | 95-153 | 89-148 | 83-144 | | | < 6.0 | lb./a | 140-210 | 120-180 | 109-169 | 95-153 | 89-148 | 83-144 | | ||
| - | | ::: | ppm | 70-105 | 110-140 | 55-134 | 47-126 | 45-74 | 41-172 | | + | | ::: | ppm | 70-105 | 60-90 | 55-85 | 47-77 | 45-74 | 41-72 | |
| | Note: Recommendations are based on the center of a given range. Mehlich-3 extraction |||||||| | | Note: Recommendations are based on the center of a given range. Mehlich-3 extraction |||||||| | ||