Surface hydraulic properties of a red earth under continuous cropping with different management practices [wheat-lupin rotation]
1993
Chan, K.Y. (New South Wales Agriculture, Rydalmere (Australia). Biological and Chemical Research Inst.) | Heenan, D.P. (New South Wales Agriculture, Wagga Wagga (Australia). Agricultural Research Inst.)
Differences in surface soil hydraulic properties after 10 years of different tillage (direct drilled (DD) versus conventional tillage (CT)) and (stubble retained (SR) versus stubble burnt (SB)) were measured in a lupin-wheat rotation on a red earth at Wagga Wagga, New South Wales. Sorptivity and hydraulic conductivity measurements using a disk permeameter under negative matric potential (-40 mm) was complicated by water repellence found under SR as compared to SB treatments. Despite similar bulk density, hydraulic conductivity under ponded infiltration of SR-DD was 4.1 times that of SB-CT. Differences in hydraulic conductivity between -40 mm and under ponded conditions suggest the presence of significantly more transmitting macropores greater than 1.5 mm in diameter under direct drilling. Dye infiltration results indicated that tillage significantly reduced the number of transmitting macropores (greater than 1 mm) even though the total number of macropores remained similar amongst the different treatments. 65 percent of the macropores were transmitting under SR-DD compared to 1 percent under SB-CT. A significant correlation was found between transmitting macropores and the earthworm population. Tillage but not stubble burning significantly reduced earthworm population.
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