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Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil

KAMBLE, Pramod N., BÅÅTH, Erland
Pedosphere 2018 v.28 no.2 pp. 255-260
ammonium nitrate, bacterial growth, carbon, fungal communities, fungal growth, glucose, nitrogen, nutrients, soil amendments, soil bacteria, soil fungi, soil pH, starch, straw
Microbial growth in soil is mostly limited by lack of carbon (C). However, adding fresh, C-rich litter can induce nitrogen (N) limitation. We studied the effect of alleviating C and N limitation in high-pH (> 8) soils, soils expected to favor bacterial over fungal growth. Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks. Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH4NO3) and measuring microbial growth and respiration after 4 d. In non-amended, C-limited soils, adding C but not N increased both microbial respiration and bacterial growth. In N-limited, substrate-amended soils, adding C increased respiration, whereas adding N increased both microbial respiration and growth. Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N, whereas with starch, only bacterial growth responded to alleviating N limitation. Compared to earlier results using a low-pH soil, the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation. Furthermore, we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil, suggesting no drastic changes in C use efficiency.