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Two forms of biosolids, with and without lime, were applied to acid soils at 2 sites in central New South Wales. Wheat and triticale were then grown on these sites to determine the effect of biosolids on crop growth and yield. The forms of biosolids used were dewatered sewage sludge cake, and N-Viro Soil which is a lime amended sewage sludge. Dewatered sewage sludge cake was applied at rates of 0, 6, 12 and 24 dry Mg/ha, and N-Viro soil at 0, 1.5, 3.0 and 4.5 dry Mg/ha. Biosolids produced grain yield increases of over 50% at both sites, with the largest yield increases at the highest rate of dewatered sewage sludge. Continued cropping at 1 of the sites showed that significant yield increases were still obtained 3 years after the initial application. The addition of lime and N-Viro Soil raised soil pH, and produced small but long lasting yield increases. However, the main benefit of biosolids seems to have come from the nutrients they supplied rather than changes in soil pH. |
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