Abstract

Open field burning of rice straw besides causing environmental pollution and human health problems results in loss of organic carbon and essential nutrients. Urgent solution is required for management of rice straw in an eco-friendly and sustainable manner. The aim of the present study was to examine the efficiency of direct return of rice straw into the soil versus biochar generated from rice straw, and compare it with wood derived biochar in influencing soil biological processes and potential to accumulate soil organic C (SOC). We studied the effect of pyrogenic conversion of rice straw and wood chips to biochar on changes in chemical composition of feedstock by Fourier Transform Infrared (FTIR) spectroscopy and C and N mineralization kinetics, microbial metabolism, carbon use efficiency (CUE) and soil enzyme activities in a series of laboratory incubation experiments conducted at 25 °C temperature and field capacity moisture. Pyrogenic conversion of feedstock to biochar resulted in increase in C (39.6% to 69.2%) and N (0.4% to 1.65%) contents and lowering of C/N (99 to 28.4) and H/C (1.94 to 0.60) ratios. Charring resulted in decrease in aliphatic and increase in aromatic components. Decomposition of organic substrates was governed by aromaticity and C/N ratio; in 127 days, only 12% of rice straw biochar embodied C was mineralized as against 76% from rice straw. The addition of biochars resulted in soil N priming (120 ± 24 mg N kg⁻¹) whereas straw application resulted in net N immobilization (−13 mg N kg⁻¹). Compared to unpyrogenic straw, the rice straw biochar led to greater microbial growth, lower metabolic quotient, higher CUE (3.3 times) and decreased microbial respiration, with potential to promote SOC accumulation. It was concluded that addition of rice residue generated biochar into soil is more beneficial for soil biological processes and SOC stabilization to stymie climate change than direct return of plant residue into the soil. The results are significant for devising eco-friendly rice residue management practices in the Indo-Gangetic plains.

摘要

露天焚烧稻草除了造成环境污染和人类健康问题外，还会导致有机碳和必需营养素的流失。以生态友好和可持续的方式管理稻草需要紧急解决方案。本研究的目的是检查稻草直接返回土壤与稻草产生的生物炭的效率，并将其与木材衍生的生物炭在影响土壤生物过程和积累土壤有机碳 (SOC) 的潜力方面进行比较。我们通过傅里叶变换红外 (FTIR) 光谱和 C 和 N 矿化动力学、微生物代谢、在 25 °C 温度和田间持水量下进行的一系列实验室孵化实验中的碳利用效率 (CUE) 和土壤酶活性。原料热法转化为生物炭导致 C（39.6% 至 69.2%）和 N（0.4% 至 1.65%）含量增加，C/N（99 至 28.4）和 H/C（1.94 至 0.60）比率降低。炭化导致脂肪族成分减少而芳香族成分增加。有机底物的分解受芳香性和C/N比的控制；在 127 天里，只有 12% 的稻草生物炭含有 C 矿化，而来自稻草的 76% 被矿化。生物炭的添加导致土壤 N 引发（120 ± 24 mg N kg 4% 至 1.65%) 的含量和降低 C/N（99 至 28.4）和 H/C（1.94 至 0.60）比。炭化导致脂肪族成分减少而芳香族成分增加。有机底物的分解受芳香性和C/N比的控制；在 127 天里，只有 12% 的稻草生物炭含有 C 矿化，而来自稻草的 76% 被矿化。生物炭的添加导致土壤 N 引发（120 ± 24 mg N kg 4% 至 1.65%) 的含量和降低 C/N（99 至 28.4）和 H/C（1.94 至 0.60）比。炭化导致脂肪族成分减少而芳香族成分增加。有机底物的分解受芳香性和C/N比的控制；在 127 天里，只有 12% 的稻草生物炭含有 C 矿化，而来自稻草的 76% 被矿化。生物炭的添加导致土壤 N 引发（120 ± 24 mg N kg^-1 ) 而秸秆施用导致净氮固定 (-13 mg N kg ^-1 )。与未热源秸秆相比，稻草生物炭导致微生物生长更大、代谢商更低、CUE 更高（3.3 倍）和微生物呼吸减少，具有促进 SOC 积累的潜力。得出的结论是，将水稻残留产生的生物炭添加到土壤中比将植物残留物直接返回土壤更有利于土壤生物过程和 SOC 稳定以阻止气候变化。该结果对于在印度恒河平原设计生态友好型稻米残留管理实践具有重要意义。