Soil pH and Lime Management for Corn and Soybean

Abstract

Little field research evaluated buffer pH methods to estimate lime requirement (LR) such as Sikora and Mehlich that include no hazardous chemicals. This study assessed how Shoemaker-McLean-Pratt (SMP), Sikora, and Mehlich buffers, titratable acidity (TA), and soil properties relate to soil pH change due to liming under on-farm conditions. Experiments were established in 2.54to 6.42-ha areas of 14 Iowa fields. Replicated treatments were a control and 6.72 Mg ha -1 of effective calcium carbonate equivalent. Soil samples (19 48 per site, 15-cm depth) were collected before and 6to 12-months after liming. Soil pH was 4.60 to 8.05 across all samples. Mean SMP, Sikora, and Mehlich buffer pH values across all samples differed (P < 0.05) and were 6.44, 6.38, and 5.78, respectively. Soil pH, organic matter (OM), and clay explained a higher proportion of soil pH change variation due to liming (23, 9, and 6%) than any buffer method or TA (1 to 3%). Sikora and SMP were highly correlated (r 2 0.92), did not differ for most soil series, and current SMP calibrations for LR could be used for Sikora. Sikora needs a different calibration for five soils and Mehlich for all soils, however, because values were lower than for SMP. Soil pH and OM together with SMP, Sikora, or Mehlich explained 28, 37, and 45% of the field pH change variation. Therefore, use of pH and OM together with Sikora or Mehlich buffers would provide the best prediction of LR under conditions like those in this study.