Lime Rate and Moisture Effects on Soil pH Change and Buffer Correlations to Observed Lime Requirements in Kansas.

Kansas state soil testing lab currently uses Shoemaker-McLean-Pratt (SMP) buffer to estimate lime requirements.  Hazardous waste produced by SMP adds unnecessary risk to commercial lab operations, as non-hazardous buffers exists.  A room temperature incubation study was performed to evaluate SMP, Sikora, and modified-Mehlich buffer pH values across a range of Kansas soils with incremental lime additions.  Three lime rates (0, 2240, and 4480 kg ha^-1) were added as a Ca(OH)₂ slurry to 50 g of Belvue loam and Smolan silty clay loam soils creating 10, 20, 30, and 40% gravimetric  moisture content, with three replications.  A similar un replicated study was performed on 25 soils using 10 g of soil, incubated for 56 days.  Additionally, five lime rates (0, 2240, 4480, 8960, and 17920 kg ha^-1) were added to 10 g of 45 soils. Soils were brought to 20% gravimetric moisture, allowed to dry, and brought back to 20% moisture on eight occasions.  Initial pH, Sikora, SMP, and modified Mehlich buffer values were taken for each soil. Buffer values were regressed to observed lime requirements to target pHs of 6.0, 6.4, and 6.8.