Abstract
Two Inceptisols and an Entisol representing the West Imphal district of Manipur, India, were studied for lime requirement as influenced by the nature of soil acidity. The EB–H+ and EB–Al3+ acidities constituted 25.8 and 74.2 percent of exchangeable acidity while EB–H+, EB–Al3+, exchangeable and pH-dependent acidities comprised 2.7, 9.4, 12.1 and 87.9 percent of total potential acidity. The pH-dependent acidity made a major contribution towards the TPA (72.8 % to 97.7 %). Grand mean of lime requirement determined by the methods of Woodruff, New Woodruff, SMP, Mehlich and exchangeable Al as expressed in Mg CaCO3 ha-1 was in the order : SMP (19.7) > New Woodruff (13.4) > Mehlich (11.7) > Woodruff (8.8) > Exchangeable-Al (2.6). Correlation analysis among different forms of acidity and lime requirement methods with selected soil properties showed that pH in two media, namely water and 1 molL-1 KCl had a significant negative correlation with different lime requirement methods except exchangeable aluminium method with pHKCl. The pHW showed significant negative correlation with EB–Al3+ acidity and exchange acidity. Organic carbon showed significant correlation with pH-dependent acidity, TPA and Woodruff lime requirement method. The CEC had a significant correlation with different forms of acidity and lime requirement methods, except the New Woodruff method. Clay, extractable Fe and Al and non exchangeable Al showed significant correlation with different forms of acidity except pH-dependent and TPA and different lime requirement methods. Significant positive correlations existed between lime requirements and different forms of acidity of the soils except pH-dependent and TPA and New Woodruff and exchangeable Al lime requirement methods. Statistically, the Mehlich method did slightly better than the Woodruff, New Woodruff, SMP and exchangeable Al methods at estimating lime requirement and hence, the Mehlich procedure may be recommended for routine soil testing because of its speed and simplicity.
