Abstract

The nature of carbon input to soil, its transformation to soil organic matter (SOM), and the degree of protection from decomposition are important for long-term persistence of SOM. The effect of exogenous addition of organic matter on SOM build-up is well known; however, changes in quality vis-à-vis composition of added organic matter have been less investigated. It is necessary to ascertain the form under which C accumulates and how the composition of added organic matter influences the stabilization of soil organic C (SOC). Changes in composition of SOM were studied by fractionating the soil into coarse (cPOC; >250 µm) and fine particulate organic C (fPOC; 53–250 µm) and mineral-associated organic C (MinOC; <53 µm) and measuring the acid non-hydrolyzable C (NHC) as well as mineralizable C following repeated applications of farmyard manure (FYM), rice straw compost (RSC) and vermicompost (VC) in a rice (Oryza sativa L.)–wheat (Triticum aestivum L.) system field experiment. Addition of organic amendments for 10 years significantly increased SOC stocks and the increase was greatest with RSC (12.2 t ha⁻¹) followed by FYM (9.1 t ha⁻¹), and lowest with VC (8.5 t ha⁻¹), compared with solitary application of NPK. The C accumulation in separated pools was influenced by the chemical composition of the organic source. Compost applications accumulated C preferentially in the MinOC pool, whereas the FYM accumulated a greater proportion of C as POC, particularly as fPOC. The differences were attributed to the lower C/N ratio and higher lignin content of RSC than FYM. The RSC application increased NHC stocks to a significantly greater extent than FYM and VC, indicating recalcitrance of the accumulated C. This was substantiated by the significantly lower C mineralization potential of RSC-amended soils compared to the FYM- and VC-amended soils. The results showed that addition of compost, besides leading to C build-up, improved C stabilization by imparting recalcitrance to SOC.

摘要

碳输入土壤的性质，其向土壤有机质的转化以及对分解的防护程度对于SOM的长期持久性很重要。外源添加有机物对SOM积累的影响是众所周知的。但是，关于添加有机物的质量相对于组成的变化的研究较少。必须确定碳的累积形式以及添加的有机物的组成如何影响土壤有机碳（SOC）的稳定性。通过将土壤分为粗颗粒（cPOC；> 250 µm）和细颗粒有机碳（fPOC； 53–250 µm）和与矿物相关的有机碳（MinOC； <水稻-小麦（Triticum aestivum L.）系统田间试验。添加有机修正剂10年显着增加了SOC储备，RSC（12.2 t ha ^-1）其次是FYM（9.1 t ha ^-1），增幅最大，而VC（8.5 t ha ^-1）最低。），与单独施用NPK相比。分离池中的碳积累受到有机源化学成分的影响。堆肥应用优先在MinOC池中积累C，而FYM则以POC（尤其是fPOC）的形式积累C。差异归因于RSC的C / N比较低，而FYM的木质素含量较高。RSC施用增加了NHC的存量，远高于FYM和VC，表明对累积的C产生了顽固的抵抗力。这可以通过RSC改良的土壤与FYM和VC改良的土壤相比明显更低的C矿化潜力来证明。结果表明，堆肥的添加除了导致碳积累以外，还通过赋予SOC顽抗性来改善C的稳定性。