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Liming improved soil microbial growth, but trash blanket placement increased labile C and N availability in a sugarcane soil of subtropical Australia
Liming has been widely used to decrease soil acidity, but its effects on soil nitrogen (N) availability and microbial processes in sugarcane fields are largely unknown. Adjacent sugarcane soils of 26 months after liming (26ML), 14 months after liming (14ML) and no lime amendment (CK) in Bundaberg, Australia, were selected to investigate the effect of liming on soil N bioavailability and microbial activity in a long term subtropical sugarcane cropping system. Liming in both 14ML and 26ML treatments significantly increased soil pH (by 1.2-1.4 units) and exchangeable Ca2+ (> 2 folds) compared with the CK treatment. The lower concentrations of hot water extractable organic C and total N and NH4+-N in the 14ML treatment compared with the CK and 26ML treatments, can be attributed to the absence of trash blanket placement in the former. Enhanced microbial immobilization due to improved soil pH Liming (14ML and 26ML treatments) led to increased soil microbial biomass C and N, particularly at the presence of the trash blanket (26 ML treatment), but decreased soil respiration and qCO2, indicating the acidic stress conditions were alleviated in the liming treatments. Soil pH is shown to be the main factor governing soil enzyme activities, with an overall decrease in all enzyme activities in response to liming. Overall, liming and trash blanket practices improved sugarcane soil fertility. Further study is warranted to investigate the shifts in soil microbial community composition and the diversity and abundance of N-associated functional genes in response to liming in sugarcane fields.
SR17116 Accepted 13 September 2017
© CSIRO 2017