Liming guidelines for soils under wheat cropping in the eastern Free State, South Africa

Soil acidity hampers the sustainability of wheat production in the eastern Free State, South Africa. Specific guidelines for liming are needed by farmers and advisors to ameliorate this condition. In this study, soils from four representative wheat producing farms were used for incubation and field studies to generate data for the development of liming guidelines. The clay content of the soils ranged between 8 and 33%, with pH (KCl) values below 4.5 and percentage acid saturation (%AS) above 8. These parameters are regarded as thresholds for wheat cultivation. Liming of the topsoil (0–200 mm) at different rates increased pH (KCl) linearly and decreased %AS exponentially. Either the resulting pH (KCl) or %AS values can be used in the development of liming guidelines. Using these values, an equation was established that is suitable for the estimation of lime requirement of soil: y 8.320× 1 + 0.0459× 2 − 1.0370, R 2 = 0.86 where y is the lime requirement (tonnes ha−1), x 1 = ΔpH (KCl) and x 2 = clay content (%). This equation was also used to compile a look-up table from which the soils’ lime requirement can be derived. Farmers and advisors can improve liming strategies for wheat production by applying this information.