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High subsoil exchangeable sodium percentage (ESP) and salinity; and low exchangeable K concentrations are common constraints in Vertisols of the semi-arid sub-tropics of Eastern Australia. Recommendations for ameliorating sodicity include applying gypsum alone or in combination with deep tillage. Potassium deficiencies are usually managed by applying mineral fertilizers, although many farmers are interested in using animal manures as substitutes. The efficacy of manure in ameliorating sodicity in Vertisols has not been documented under field conditions in Australia. The objective of this study was to quantify changes to sodicity-related soil properties (dispersion, ESP, pH, EC(1:5)(1), drainage) and exchangeable K concentration in a Vertisol due to applying amendments such as gypsum, K fertilizer, and cattle manure in a region with an erratic rainfall distribution. Soil was sampled from an experiment in southern Queensland which had been established by a farmer to evaluate several recommended management practices for dryland Vertisols.

Cattle manure (16 t ha(-1)) improved potassium availability by 0.16 t ha(-1) and decreased ESP. Gypsum (9 t ha(-1)) and K fertilizer application also decreased ESP, and the latter increased exchangeable K, albeit to a lesser extent than manure. Decrease in ESP was not, however, sufficient to reduce dispersion and increase drainage. Gypsum application did not overcome the effects of sodicity, thus validating the current growers’ practice of not applying gypsum. Crop yields were unaffected by gypsum, manure, or mineral fertilizer application, suggesting that their application may not be economically rational in an environment where rainfall is erratic.