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

Abstract

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.

Keywords: Crop yield response function; Crop-soil interactions; Long-term experiment; Soil acidity.

Fig. 1

The effect of lime treatments on mean soil pH (a, b) over the course of the long-term liming experiment at Rothamsted and Woburn; four rates of lime were applied, the treatments were: control (⬤), low (○), medium (▾) and high (△). Rothamsted site: (a); Woburn site (b). * along the base of the x axis indicates a significant difference (P <  0.05) between the treatments; Along the top of (a) and (b) + marks the years in which lime was applied.

Fig. 2

The relationship between grain yield (t ha⁻¹) and soil pH for (a) spring oats in 1975 (⬤), 1977 (○), 1981 (▾), 1982 (△) and (b) spring beans in 1963 (⬤), 1964 (○), 1989 (▾) and 1990 (△) at Rothamsted; in (b) the regression curves represent significantly different fits for separate years for spring beans.

Fig. 3

Relationship between crop relative yield (RY) and pH only for spring oats (a), spring beans (1989 data only) (b), winter oilseed rape (c), potato (d), winter wheat (e) and spring lupins (f) at the Rothamsted (⬤) and Woburn (○) sites; regression fit for Rothamsted are given with solid lines and for Woburn with dashed lines. For actual crop yield (t ha⁻¹) refer to Table 6, Table 7.

Fig. 4

Relationship between crop relative yield (RY) and pH with the effect of phosphorus (⬤ +P, ○ -P) for spring barley (a, d), winter triticale (b, e) and winter wheat (c, f) at the Rothamsted (a, b, c) and Woburn (d, e, f) sites; regression fit for + P are given with solid lines, for -P with dashed lines and a single dotted line where there was no difference between + P and -P. For actual crop yield (t ha⁻¹) refer to Table 6, Table 7.

Fig. 5

The critical soil pH at 90% relative yield for selected crops at the Rothamsted and Woburn sites. Rothamsted = R, Woburn = W, Spring barley = SB, Winter wheat = WW, Winter triticale = WT and Linseed = Lin; where there is a significant P effect a separate symbol is given for each crop: +P (⬤), -P (○), for crops with no P effect (△).