Effects of fallow management and cropping history on aggregate breakdown under rainfall wetting for a range of Queensland soils
1994
Loch, R.J. (Queensland Dept. of Primary Industries, Toowoomba (Australia). Natural Resource Management Unit)
For 8 sites where fallow management treatments significantly reduced the proportion of particles smaller than 0.125 mm (P125) under high energy rainfall (HER) wetting, those reductions were generally small, and likely to increase steady infiltration rates of high energy rain into bare soil by only 2-6 mm per h. In contrast, steady infiltration rates could be increased by 15-42 mm per h if those same soil surfaces were completely covered by stubble so that they received low energy rain. At least under Queensland conditions, retention of crop residues to protect soils from drop impact is therefore likely to be of much greater importance in improving water storage during fallows than any improvement in soil aggregation under 'improved' fallow management practices. Effects of fallow management and cropping history on P125 under HER varied across the sites. Wetting by immersion showed responses to treatments that, for some soils, differed greatly from those obtained using HER. Neither low energy rainfall nor wetting under tension appeared useful, as the former gave occasional inconsistent results, the latter caused little aggregate breakdown for most soils.
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