Field crop responses to lime in the mid-north region of South Australia

in the cropping regions of South Australia there is little information on whether acidity and acidification associated with high-input agriculture is affecting crop production and profitability. In much of the mid-north of South Australia, where thermic Calcic Palexeralf soils predominate, the levels of Al are low compared with other acid-soil types reported in comparable studies in Australia. In this study lime requirement curves have been used to predict the lime rate that achieves 80-90% maximum yield for different crop species on 3 sites on the red-brown earth soil type in the mid-north of South Australia. The results given demonstrate that the approach used for predicting lime responsiveness, with lime requirement calculated using the model of [Hochman, Z., Godyn, D.L., Scott, BJ., 1989. The integration of data on lime use by modelling. In: Robson, A.D. (Ed.). Soil Acidity and Plant Growth. Academic Press, Sydney, Australia, pp. 265-301], has provided good estimates of final pH changes. Yield response curves show that the largest yield gains mostly occurred in the second season of the experiment when lime at about 2.0 t/ha increased pH(Ca) to 5.5-6.0. With the lime treatments calculated, yield of wheat, barley and faba beans were increased by about 70%, and durum by 30% compared with the control. It would appear that liming to achieve a pH(Ca) of 5.2 has removed Al toxicity, and further liming to achieve pH(Ca) 5.5-6.0 may have improved other soil properties to realise further yield gains. With cropping in this region commonly using practices that include high fertiliser nitrogen input and retention of crop residues, acidification is likely to be an on-going issue with these red-brown earth soils. Thus it is appropriate that soil testing and, where required, liming at the rate of 1.5 t/ha is used by farmers to both improve cropping profitability and also offset acid input associated with the farming practice. (C) 2008 Elsevier B.V. All rights reserved.