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Direct effects of stubble burning on soil hydraulic and physical properties in a direct drill tillage system

1997; Elsevier BV; Volume: 42; Issue: 3 Linguagem: Inglês

10.1016/s0167-1987(96)01101-4

1879-3444

F. P. Valzano, Richard Greene, Brian Murphy,

Landslides and related hazards

Stubble burning is widely practiced in cropping systems and is often utilised as a means of reducing stubble loads on the soil surface. However, the short-term effects of these burning regimes on soil surface properties are largely unknown. Therefore, a study was carried out at Cowra, N.S.W., Australia, to investigate the direct effects of stubble burning on the hydraulic and physical properties of a hardsetting red-brown earth soil. Five paired 1 m2 plots were set up in a paddock that had been direct drilled for 15 years. Stubble in one plot of each pair was burnt by a low intensity fire (2.8 Mg ha−1 fuel load), while that in the other plot remained unburnt. Two days later the soil hydraulic properties of the burnt and adjacent unburnt plots were measured using disc permeameters at a supply potential of −10 mm. The volumetric moisture content and bulk density of the 0–40 mm layer were also measured using undisturbed cores. Disturbed soil samples were taken from the 0–20, 20–50 and 50–100 mm depths from both treatments for laboratory determinations of water repellency, organic carbon, clay dispersion and aggregate stability. There was a significant (P < 0.05) decrease of approximately 50% in sorptivity, final infiltration rate and hydraulic conductivity in the burnt plots relative to the adjacent unburnt plots. However, fire had no significant effect on volumetric moisture content or bulk density in the 0–40 mm layer. No water repellency was recorded before or after fire. Clay dispersion and aggregate stability tests found no significant differences between burnt and unburnt plots. These findings indicate that low intensity fires used for removing stubble can have an immediate, direct effect on soil hydraulic properties. However, the mechanisms causing these effects are as yet uncertain.