Properties of soil adjacent to cracks and in bulk soil were compared in furrow irrigated Vertisols sown to intensively tilled cotton (Gossypium hirsutumL.) followed by (fb.) minimum-tilled wheat (Triticum aestivumL.) in a 2-year rotation; minimum-tilled cotton fb. and minimum-tilled wheat in a 2-year rotation; and a perennial pasture in NW New South Wales, Australia. A backhoe pit was dug at right-angles to cracks, and a 50 mm thick layer of soil sampled from the exposed crack walls and from adjacent bulk soil in 0.3 m depth increments to a depth of 0.9 m. Soil properties evaluated were: aggregate stability (dispersion index), soil resilience to structural destruction (as geometric mean diameter of aggregates formed after puddling and drying of soil), electrical conductivity (EC1:5), exchange able cations, EC/exchangeable Na ratio, CEC, CaCO equivalent, pH, and organic C1:53. Intensive tillage resulted in soil adjacent to cracks having lower exchangeable Ca, iCEC, and CaCO3 ksequivalent, and higher organic C and plastic limit than bulk so l away from crack. More stable aggregates also occurred with intensive tillage. With minimum tillage, only plastic limit and organic C in the 0.6-0.9 m depth of soil adjacent to cracks were higher, and CaCO 3 in all depths lower compared with bulk soil. In the untilled pasture, EC1:5 in the 0.0-0.3 m depth and EC1:5/exchangeable Na ratio in the 0-0.6 m depth were lower in soil adjacent to cracks than in bulk soil. We suggest that the differences between soil adjacent to cracks and bulk soil under intensive tillage, and similarities between soil adjacent to cracks and bulk soil under pasture and minimum tillage were due to the presence of stable biopores in the latter group. Biopores can function as an alternative pathway to soil cracks for root growth, preferential flow, and associated nutrient leaching and cracks become the dominant pathway for preferential flow, nutrient leaching, and root growth, significant differences in physical and chemical properties can occur between soil adjacent to cracks and bulk soil.
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