Clay addition to lime-amended biosolids overcomes water repellence and provides nitrogen supply in an acid sandy soil
2014
Shanmugam, Sanjutha | Abbott, L. K. | Murphy, Daniel V.
The addition of clay to lime-amended biosolids has been proposed as a soil amendment (LaBC®) for remediating acidic-sandy soil. We investigated whether the presence of clay in LaBC® altered soil microbial processes over a 30-week period. Aerobic-incubation and CO₂ respiration assays were used to monitor water repellence and chemical and microbiological properties of amended soil. Dry LaBC® was applied at equivalent wet weight of 50, 100 and 150 t ha⁻¹. In addition, dry components of LaBC® (lime, clay, lime + clay (LAC) and lime + biosolids (LAB)) were applied separately at rates equivalent to their fractions within LaBC®. Inclusion of clay in LaBC® was effective in eliminating water repellence at all application rates. Inclusion of clay in LaBC® decreased nitrogen (N) release from the biosolids (by 58 %), even at 50 t ha⁻¹, but only during the first 2 weeks of incubation. LaBC® consistently decreased soil microbial respiration compared with LAB alone when applied at 150 t ha⁻¹ thereby protecting organic matter decomposition. There was no significant N release with lime and clay amendment alone or in combination (LAC) in the absence of the biosolids. There may be a complex interaction between clay, lime and organic matter, but each may have had a role in altering N release from biosolids at different times during the 30-week incubation. Addition of clay to LAB increased its effectiveness in remediating this water-repellent, acidic-sandy soil and prolonged the N release from the biosolids following soil amendment.
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