ABSTRACT

The objective of this study was to investigate the effect of nitrogen (N) application combined with cotton stalk or its biochar on soil organic carbon (SOC) fractions and enzyme activity. The field experiment was conducted over three cropping seasons with three organic C treatments and three N application rates. Three organic C treatments were set as no organic C amended (CK), cotton stalk (ST), cotton stalk biochar (BC). Three N applied at rates of 0, 300, and 450 kg N ha⁻¹ (N0, N300, and N450, respectively). Results showed that N fertilisation alone reduced dissolved organic C (DOC) and N450 reduced easily oxidisable organic C (EOC) in 2015–2016. Microbial biomass C (MBC) basal soil respiration (BSR), β-glucosidase activity (BG), and N-acetyl-glucosaminidase activity (NAG) activity in N450 were greater than in N0. On average, SOC was 13.4% −36.6% greater in ST and 23.7–59.2% greater in BC than that in CK. ST and BC increased soil organic C fractions, MBC and non-labile organic C (non-LOC) were greater in BC than in ST. BC decreased soil DOC/TOC, EOC/TOC ratios, increased soil non-LOC/TOC ratio and cotton yield, ST increased the ratios of labile C and enzymes activity in soil. Therefore, integrating 300 kg ha⁻¹ N fertilisation with biochar is an optimising management strategy to promote C sequestration and sustain the crop productivity in a drip-irrigated cotton field.

摘要

这项研究的目的是调查氮肥与棉秆或其生物炭的结合对土壤有机碳（SOC）组分和酶活性的影响。田间试验是在三个种植季节进行的，进行了三种有机碳处理和三种氮肥施用量。设置了三种有机碳处理方法，分别为未修正有机碳（CK），棉秆（ST），棉秆生物炭（BC）。以0、300和450 kg N ha ^-1的比例施用3 N（分别为N0，N300和N450）。结果表明，仅氮肥在2015–2016年间减少了溶解有机碳（DOC），而N450减少了易氧化的有机碳（EOC）。N450中的微生物生物量碳（MBC）基础土壤呼吸（BSR），β-葡萄糖苷酶活性（BG）和N-乙酰葡萄糖苷酶活性（NAG）活性均高于N0。与CK相比，ST的SOC平均高出13.4％-36.6％，而BC的SOC高出23.7-59.2％。ST和BC增加了土壤有机碳含量，BC中的MBC和非不稳定有机碳（非LOC）均大于ST。BC降低了土壤DOC / TOC，EOC / TOC的比例，增加了土壤非LOC / TOC的比例和棉花产量，ST增加了土壤中不稳定C和酶活性的比例。因此，积分300 kg ha ^-1 施用生物碳氮肥是优化管理策略，可促进滴灌棉田固碳和维持作物生产力。