Changes in water content of two agricultural soils does not alter labile P and C pools |
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Authors: | Clayton R Butterly Ann M McNeill Jeff A Baldock Petra Marschner |
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Institution: | 1. Department of Agricultural Sciences, La Trobe University, Melbourne, VIC, 3086, Australia 2. School of Agriculture Food & Wine, The University of Adelaide, Waite Research Institute, Glen Osmond, SA, 5064, Australia 3. CSIRO Sustainable Agriculture Flagship, CSIRO Land & Water, Glen Osmond, SA, 5064, Australia
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Abstract: | Aims An incubation study was conducted to investigate how changes in soil water content affect labile phosphorus and carbon pools, mineralisation patterns and microbial community composition. Methods Two soils from different climatic histories were subjected to four long-term (15 weeks) soil water regimes (constant field capacity (m); 3 dry-rewet (DRW) cycles evenly spaced (intermittent, int); 3 DRW cycles with a shorter interval after a long dry period (false break, fb); constantly air-dry (d)) (incubation period 1). In the subsequent incubation period 2, a set of cores from each treatment were subjected to one DRW cycle (air-dry for 7 day; field capacity for 14 day) or maintained at field capacity. Results Long-term soil water regime altered soil respiration with the largest CO2 pulse occurring in soil with the longest dry period. However, changing the distribution of the 3 DRW events within incubation period 1 (int/fb) did not alter cumulative CO2. In addition, DRW during incubation period 2 did not affect cumulative CO2 in either treatment (m, int, fb, d) (except for Hamilton int). Our results show that carbon and phosphorus availability and the size and community composition of the microbial biomass were largely unaffected by fluctuating soil water content. Conclusions Changes in soil water content altered respiration, phosphatase activity and microbial C:P ratio and indicate physiological and/or functional changes in the microbial community. However, it appeared that these would have little impact on plant P availability. |
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