Effects of gypsum and stubble retention on the chemical and physical properties of a sodic grey Vertosol in western Victoria

Abstract

The effects of gypsum (0 and 10 t/ha) and stubble management [retained (SR) or burnt (SB)] on a range of soil chemical, physical, and micromorphological properties were investigated on a grey Vertosol soil near Natimuk, Victoria, Australia. After 2.5 years and 3 winter crops, gypsum, and to a lesser extent the stubble treatments, resulted in significant changes to the composition of the exchangeable and soluble cations, and to soil physical properties. When gypsum was combined with SR, the beneficial effects of this ameliorant on soil properties were present in both the A and B horizons of the soil. When combined with SB, the gypsum treatments were only effective in the A horizon. Organic carbon levels in the A and B horizons were not significantly affected by the gypsum or stubble treatments. However, micromorphological evidence indicated that in the A horizon, biological activity was greater in SR plots than SB plots. Soil dispersion, penetrometer resistance, and bulk density were reduced in plots treated with gypsum compared with plots without gypsum. A stubble management effect was also present, showing lower dispersion scores, penetrometer resistance values, and bulk densities in SR plots than SB plots. The available water holding capacity of the soil from Natimuk was significantly (P < 0.05) higher in the gypsum-treated plots than in plots without gypsum. This effect was limited to the A horizon of the SB plots, but was apparent for the A and B horizons of the plots treated with SR. The use of gypsum in combination with SR (and break crops) may improve soil physical and chemical properties at a greater depth than the use of gypsum with SB alone.