施用有机肥煤矿复垦耕地有机碳的固持效率及组分变化

  [【目的】]  研究长期施用不同量有机肥下复垦耕地总有机碳 (SOC) 及其各组分的固碳效率变化，为煤矿区复垦土壤肥力快速提升提供理论依据。  [【方法】]  山西煤矿塌陷区复垦长期定位试验始于2008年，设置不施肥(CK)、施用化肥(F)、化肥配施低量有机肥(LMF)和化肥配施高量有机肥(HMF) 4个处理。2019年玉米收获前，采集0—20 cm土层土壤样品，采用物理?化学联合分组方法，测定土壤总有机碳(SOC)及各组分有机碳含量，分析碳投入与土壤总有机碳及各组分有机碳含量之间的关系。  [【结果】]  复垦11年后，与CK相比，F、LMF和HMF处理SOC含量分别显著增加了23.8%、39.6%和82.1% (P<0.05)，固碳速率分别达到 0.57、0.83和1.28 t/(hm2·a)。复垦土壤的固碳效率为20.9%，游离态颗粒有机碳组分的固碳效率最大(9.0%)，是土壤固碳的主要形式。与CK相比，F处理的土壤游离态颗粒有机碳、化学保护粘粒组有机碳和生物化学保护粘粒组有机碳储量分别提高37.1%、52.3%和93.5%，而LMF和HMF处理提高了土壤游离态粗颗粒有机碳组分、物理保护有机碳、化学保护粉粒组和粘粒组有机碳及生物化学保护粘粒组有机碳储量。与CK相比，HMF处理对上述各组分的提升幅度分别为66.1%、179.6%、59.7%、48.6%及63.0%；与LMF处理相比，HMF处理对各组分的提升幅度分别为19.6%、32.1%、28.5%、5.3%和7.3%。与CK和F处理相比， LMF和HMF处理显著提高了土壤物理保护有机碳在总有机碳中的分配比例。复垦土壤有机碳年均固定量均与年均碳投入量之间极显著正相关，复垦土壤各组分有机碳年均固定量与年均碳投入量之间极显著正相关(P<0.01)。  [【结论】]  复垦土壤有机碳年均固定量与碳投入量之间极显著正相关，在复垦11年后，复垦土壤仍有很大的固碳潜力，固存的有机碳主要以游离态颗粒有机碳为主。施用高量有机肥是快速恢复煤矿区复垦土壤有机碳含量的有效措施。

Soil organic carbon sequestration efficiency and fractions as affected by organic fertilization rate in reclaimed cultivated land

  [[Objectives]]   We studied the variation of carbon sequestration efficiency of reclaimed soil after long-term application of organic fertilizer rates, to provide a theoretical basis for rapid reclamation of soil fertility in the subsidence area of coal mines.  [[Methods]]  The reclamation experiment, started in 2008, was located in the subsidence area of Shanxi coal mines. The treatments included no fertilizer input control (CK), chemical fertilizer (F), and low-level manure with chemical fertilizer (LMF) and high-level manure with chemical fertilizer (HMF). Before the harvest of maize in 2019, soil samples (0?20 cm) were collected for the measurement of total organic carbon (SOC). The SOC was further fractioned using a physical-chemical fractionation method for the quantitative analysis of SOC stock in different fractions.   [[Results]]  After 11 years of reclamation, compared with CK, fertilization (F, LMF, and HMF) significantly increased the total SOC by 23.8%, 39.6%, and 82.1% (P<0.05), respectively. The sequestration rates of SOC under F, LMF and HMF treatments were 0.57, 0.83, and 1.28 t/(hm2·a), respectively. The carbon sequestration efficiency of the reclaimed soil was averagely 20.9%. Among the seven organic carbon fractions, the unprotected organic carbon fraction had the highest carbon sequestration efficiency of 9.0% and was the main form of soil carbon sequestration. Compared with CK, F treatment significantly increased the unprotected organic carbon fraction, the chemically protected fraction, and the biochemically protected clay fraction (37.1%, 52.3%, and 93.5%); LMF and HMF treatment significantly increased the content of unprotected coarse organic carbon fraction, physical protection fraction, chemical protection silt fraction and clay fraction, and biochemical protection clay fraction (66.1%, 179.6%, 59.7%, 48.6%, and 63.0%), and the increment effects of HMF on the above fractions were significantly higher than LMF (19.6%、32.1%、28.5%、5.3% and 7.3%). The annual average total carbon sequestration and that in each fraction were all positively and significantly correlated with the annual average organic carbon input (P<0.01).   [[Conclusions]]  The annual input rate of organic carbon significantly affects the carbon sequestration efficiency, after 11 years of conservative application of manure, the reclaimed soil still has huge carbon sequestration potential, and the highest carbon sequestration efficiency is in the unprotected organic carbon fraction. Therefore, high-level organic fertilizer input is an effective measure to quickly restore the organic carbon content in the reclamation of coal mining soil.