Comparison of several lime requirement methods for agricultural soils in Pennsylvania

Two new double‐buffer methods have been proposed recently by Yuan and McLean, et al. to more accurately predict the lime requirement (L.R.) in sandy, low buffer capacity soils and in low L.R. soils respectively. The L.R. of 20 typical acid agricultural soils in Pennsylvania were determined by a 6 month incubation with a series of CaCO3 concentrations. These incubation L.R. values were then compared with the two double buffer methods as well as the more established SMP, Woodruff, Adams‐Evans, BaCl2 triethanol amine (BaCl2‐TEA) and Ca(OH)2 titration methods to determine which of these methods most accurately predicted the true, (CaCO3‐incubation), L.R. of these soils. All methods were very well correlated with the incubation L.R. (r = 0.919 to 0.987) but only the SMP single buffer was reasonably accurate in predicting the incubation L.R. for both low and high L.R. soils. A modification in recomnendation was proposed to eliminate the slight SMP underestimation of L.R. for low L.R. soils. The two double buffer methods, BaCl2‐TEA and the Adams‐Evans method overestimated the L.R. for low L.R. soils and underestimated lime needs for high L.R. soils. The Woodruff and Ca(OH)2 titration methods both underestimated the L.R. of high (>10 meq CaC03/100g soil) L.R. soils by more than 50%.