Composition of microbial community in pig manure biochar‐amended soils and the linkage to the heavy metals accumulation in rice at harvest

Abstract

Abstract Manure biochar (MB) is recognized to be a beneficial material for absorbing heavy metals from soil and alleviating soil degradation. However, the effects of the addition of MB on the phospholipid fatty acid concentrations and their linkage to heavy metals accumulation in rice are poorly understood. A microcosm incubation experiment was conducted to study the effects of a swine MB amendment on (a) the composition of the soil microbial community in 2 soils (clay‐loam vs. silt‐loam) and (b) heavy metals accumulation in rice grains and straws. MB amendment increased microbial diversity, and bacteria had greater magnitude of increase than did fungi in 2 soils after 98 days of incubation. The G − rather than G + bacteria phospholipid fatty acid concentrations were significantly increased with MB amendment rates for both soils. The higher MB addition rate (1.5%) did not get more benefit for aerobic bacteria but significantly led to anaerobic bacteria proliferation as compared with the 0.5% MB treatment. The 1.5% MB addition suppressed grain and straw Pb, Cu, and As, while it increased grain and straw Cd and Zn from two soils. Significant soil type × MB rate interactions were observed in most microbial indicators (except F/B and G + ) and grain Pb, grain As, and straw Zn. Linkages of bacteria (mainly as G − and/or An), actinobacteria, fungi, and protozoa (in silt‐loam soil) to the MB rate and heavy metals in rice were identified.