Effect of Rice Stubble Burning on Soil Health - Link (February 2006)

Kirkby, C,A Fattore, A

2006

This RIRDC report present the findings of the investigation comparing the effects of stubble burning and stubble retention on a range of soil chemical and biological properties. The method  included comparing paired sites on eight properties, four pairs, with different histories and soil types in the Murrumbidgee Irrigation Area. The chemical properties included total soil carbon, nitrogen, phosphorus and sulphur (C, N, P and S). Soil biological properties included the size and activity of the microbial biomass, the microbial and metabolic quotients, the rate of cellulose decomposition and a range of information concerning the composition of the microbial population derived from fatty acid methyl ester (FAME) analysis. The findings included sites retaining stubble had significantly more C, N, P and S than the corresponding property that burnt stubble despite differences in other management strategies. It is considered that the biological properties of the stubble retained soils healthier than the corresponding stubble burnt soils. Whilst  two measurements used to indicate soil stress, the microbial quotient and a stress indicator derived from FAME analysis, indicate that the stubble retained soils were less stressed than the stubble burnt soils. The findings supported the view that for rice, or other summer crop stubble, to decompose at the fastest rate in the field it should be incorporated as soon as possible after harvest, before winter, and not during the sowing of the following summer crop, before summer. It is suggested that there needs to be a balance of available nutrients to optimise nutrient availability and potential carbon sequestration in stubble retained systems, especially in the early years after switching from a stubble burning regime.