Predictors of Lime Needs for pH and Aluminum Management of New York Agricultural Soils
2009
Dietzel, Kevin A. | Ketterings, Quirine M. | Rao, Renuka
Periodic lime addition is recommended for naturally acidic agricultural soils, as soil pH affects nutrient availability and the toxicity of elements such as Al. Currently, lime requirements (LRs) for New York soils are derived from the actual and target pH, and exchange acidity (EA) determined by BaCl₂–triethanolamine (TEA) titration, a time-consuming and toxic-waste-generating procedure. Our objectives were to: (i) calibrate and evaluate four buffer pH methods and EA as predictors of LRs; and (ii) determine the impact of CaCO₃ addition on Morgan-extractable Al (MEA). Forty-three soils, ranging in EA from 4.1 to 18.6 cmolc kg⁻¹, were collected from New York agricultural areas. Eighteen soils were incubated at 21°C for 12 wk with CaCO₃ added at six rates. The EA-based method was highly correlated with incubation LR (r ² > 0.96, RMSE < 0.62) across the 18 soils. A comparison of LRs derived by EA and buffer pH applied to all 43 soils showed the highest correlation and lowest RMSE for the modified Mehlich (MM) and Mehlich buffers (r ² = 0.91, RMSE = 0.88–0.89). The MM buffer has the advantage of not generating toxic waste. These buffers were followed by the Shoemaker–McLean–Pratt (r ² = 0.90, RMSE = 0.96) and Sikora (r ² = 0.87, RMSE = 1.09) buffers. Final MEA levels could be accurately predicted when initial MEA, CaCO₃ application rate, and soil organic matter (OM) content were known. The MM buffer is an acceptable replacement of the EA-based method for predicting LRs, and initial MEA and OM level are necessary to determine the amount of CaCO₃ needed for a specific target MEA.
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