Yield responses of arable crops to liming – An evaluation of relationships between yields and soil pH from a long-term liming experiment

The management of optimal soil pH is fundamental to sustainable crop production. Understanding the lime requirement for arable crops has developed gradually over the last several decades. The aim of this study was to examine the yield-pH relationship for a range of arable crops to understand their response to liming, based on the Long-Term Liming experiments established in 1962 at Rothamsted Research, UK. The main treatments of four different rates of lime and, therefore, four distinctly different soil pH levels were maintained for 35 years at two sites (Rothamsted and Woburn). The pH ranged from 4.4 to 8.0. The lime response was tested on the following crops: spring barley, spring oats, spring beans, spring lupins, winter lupins, potatoes, linseed, winter oilseed rape, winter triticale and winter wheat. Relative yield (RY) was used for non-linear regression analysis to detect site, year and phosphorus (P) fertiliser effects on the relationship with pH. Liming had a highly significant positive effect on soil pH, but overall there was no consistent increase or decrease in soil extractable P (Olsen) or exchangeable K. There were significant site effects detected for RY for most crops which reflect differences in the two soil types. Spring oats and potatoes had very weak responses to lime within the pH range tested. For spring barley, winter triticale, winter wheat and winter oilseed rape significant effects of P fertiliser on the yield-pH relationship were found, although the nature of effects differed between crops and sites. Findings from the Long-Term Liming experiment are invaluable in improving the fundamental understanding on the yield-pH relationship for important arable crops and this has significant implications on selecting crops for rotations. The pH at 90% RY was calculated for selected crops and the beneficial effect of fertiliser P was detected in significantly reducing the critical pH value.