Glucose, xylan and cellulose differ in nitrate assimilation and remineralization in nitrate-rich plastic-greenhouse soils

Excessive nitrate accumulation in soils poses severe threats to soils and environment, which can be alleviated by microbial assimilation. However, it lacks information regarding how different organic carbon sources affect microbial nitrate assimilation and remineralization in nitrate-rich plastic-greenhouse soils with high moisture. Soil microcosm experiments using amino sugar probes were conducted to investigate the effects of the main components of natural carbon sources i.e. glucose, xylan, cellulose, xylose and lignin on soil nitrate turnover from and to necromass nitrogen (N) under 90 % water holding capacity. Key results revealed: 1) Glucose, xylan, and xylose rapidly enhanced nitrate assimilation, decreasing soil nitrate by 629, 774, and 680 mg N kg −1 , respectively, within 4 days, while cellulose required 16 days to deplete 385 mg N kg −1 . Cellulose induced slower assimilation yet minimized remineralization between Days 16–96; 2) Xylan increased denitrification gene abundances ( narG and nirS ) and coincided with an apparent total N loss of 159 mg N kg −1 inferred from N balance, 2.6 times higher than glucose (61 mg N kg −1 ), likely associated with greater soil aggregation; 3) Microbial necromass N increased by 226 %, 186 %, and 38 % with glucose, xylan, and cellulose in Day 4 respectively, with fungi contributing 1.97–2.83 times more than bacteria while cellulose increased bacterial more than fungal necromass N compared to glucose. In conclusion, xylan can additively promote soil aggregation and N loss besides as an energy source for nitrate assimilation compared to glucose and cellulose. Cellulose-rich carbon inputs can be an alternative for nitrate immobilization. • Two soil microcosm experiments used amino-sugar-based probing technique. • Glucose and xylan promoted nitrate assimilation and remineralization over cellulose. • Xylan enhanced denitrification via soil aggregation more than glucose or xylose. • Cellulose provided slow but stable nitrate immobilization with lower remineralization.