
%0 Journal Article
%A Naidu, R 
%A Mcclure, S 
%A Mckenzie, NJ 
%A Fitzpatrick, RW 
%T Soil solution composition and aggregate stability changes caused by long-term farming at four contrasting sites in South Australia
%J Soil Research
%D 1996/08/01
%V 34
%N 4
%P 511-527
%K organic matter, Gapon coefficient, chemical composition, sodicity, microscopy.
%R https://doi.org/10.1071/SR9960511
%U https://www.publish.csiro.au/paper/SR9960511 
%X The effect of long-term farming on the cation exchange capacity (CEC), organic carbon content, soil solution composition, and aggregate stability was investigated using contrasting soils from 4 sites in the Mid North of South Australia. Undisturbed and farmed profiles were characterised at each site. Farming led to a 10&ndash;50% decrease, approximately, in organic matter and CEC in the surface horizon. Scanning electron microscopic study of the surface and selected subsurface soils revealed poor aggregation, compaction, reduced porosity, and a decrease in aggregate particle size in the farmed surface soils. Intra-aggregate binding in the undisturbed soils appeared to be largely due to fungal hypha, with the roots largely contributing to inter-aggregate binding of soil particles. Electrical conductivity (EC) of soil solutions was generally 2&ndash;3 times higher in the undisturbed soils than farmed soils, suggesting increased leaching of ions associated with loss of tree cover. This was also supported by a decrease in the concentrations of mobile ions such as Cl&#45;and Na&#43; in the farmed soils. The concentrations of Na&#43; and K&#43; decreased with farming leading to a decrease in the Gapon selectivity constant for Na&ndash;Ca and K&ndash;Ca exchange. The changes in soil solution composition together with the decline in organic matter concentrations resulted in increased sensitivity of soils to dispersion. 
