Landuse impacts on soil organic carbon fractions in different rainfall areas of a subtropical dryland

Landuse can alter soil organic carbon (SOC) fractions by affecting carbon inflows and outflows. This study evaluated changes in SOC fractions in response to different landuses under variable rainfalls. We compared cropland, grassland and forest soils in high rainfall (Islamabad ~1142 mm) and low rainfall (Chakwal ~667 mm) areas of Pothwar dryland, Pakistan. Forest soils in both rainfall areas had highest SOC (11.32 g kg^?1), particulate organic carbon (POC, 1.70 g kg^?1), mineral-associated organic carbon (MOC, 7.17 g kg^?1) and aggregate-associated organic carbon (AOC, 7.86 g kg^?1). However, in rangeland and cropland soils, these varied with rainfall. Under high rainfall, SOC and MOC were 12% and 17% higher in rangeland than in cropland while POC and AOC were equal. Under low rainfall, SOC and MOC were higher in rangeland than in cropland by 7.21 and 1.79 g kg^?1 at 0–15 cm and equal at 15–30 cm depth. POC and AOC were higher in rangeland than in cropland, in both depths. Averagely, SOC, POC, MOC and AOC were 26%, 68%, 76% and 30% higher in high rainfall than in low rainfall soils. Sensitivity of SOC fractions to landuses observed under different rainfalls could provide useful information for soil management in subtropical drylands.     

耕地土壤有机碳组分的季节变化

Carbon fractions in soils apparently vary not only in space, but also over time. A lack of knowledge on the seasonal variability of labile carbon fractions under arable land hampers the reliability and comparability of soil organic carbon(SOC) surveys from different studies. Therefore, we studied the seasonal variability of two SOC fractions, particulate organic matter(POM) and dissolved organic carbon(DOC), under maize cropping: POM was determined as the SOC content in particle-size fractions, and DOC was measured as the water-extractable SOC(WESOC) of air-dried soil. Ammonium, nitrate, and water-extractable nitrogen were measured as potential regulating factors of WESOC formation because carbon and nitrogen cycles in soils are strongly connected. There was a significant annual variation of WESOC(coefficient of variation(CV) = 30%). Temporal variations of SOC in particle-size fractions were smaller than those of WESOC. The stocks of SOC in particle-size fractions decreased with decreasing particle sizes, exhibiting a CV of 20%for the coarse sand-size fraction(250–2 000 μm), of 9% for the fine sand-size fraction(50–250 μm), and of 5% for the silt-size fraction(20–50 μm). The WESOC and SOC in particle-size fractions both peaked in March and reached the minimum in May/June and August, respectively. These results indicate the importance of the time of soil sampling during the course of a year, especially when investigating WESOC.     

长期不同施肥对塿土大团聚体中有机碳组分特征的影响

【目的】研究长期施肥对土大团聚体中有机碳组分特征的影响,揭示不同施肥方式下土壤有机碳的固持机制,为合理施肥提供理论依据。【方法】采集土35年长期肥料定位试验不同施肥处理0—10 cm和10—20 cm土样,分析其大团聚体中各组分有机碳含量的变化。试验处理为:不施肥(CK)、单施化肥(NP)、单施有机肥(M)和有机肥配施化肥(MNP)。【结果】与CK相比,长期NP处理对大团聚体中粗颗粒有机碳(cPOC)、细颗粒有机碳(fPOC)、大团聚体中微团聚体内颗粒有机碳(iPOC)以及矿质结合态有机碳(MOC)组分的有机碳(OC)含量均无显著影响;而M处理以及MNP处理可显著提高两土层cPOC和iPOC组分的OC含量以及0—10 cm土层MOC组分的OC含量,其中,cPOC含量增幅分别为174%~338%和215%~245%,iPOC含量增幅分别为127%~241%和106%~130%,MOC含量增幅达28.9%~34.6%。MNP处理显著提高了0—10 cm土层fPOC组分的OC含量,增幅达482.1%。累积碳投入量与大团聚体中各组分的OC含量呈显著线性相关,尤其是iPOC含量,表明长期施肥过程中土有机碳在大团聚体中固存的差异主要受物理保护的颗粒有机碳组分的影响。【结论】关中地区土长期施化肥对大团聚体中各组分OC含量没有显著影响,而长期单施有机肥能进一步增加大团聚体中各组分OC含量,有机肥配施化肥能显著增加团聚体中各组分OC含量,特别是大团聚体中微团聚体内颗粒有机碳组分的含量,进而增加土的有机碳固持。因此,有机肥配施化肥是提高土有机碳含量的有效措施。     

Improving soil organic carbon pools through inclusion of summer mungbean in cereal-cereal cropping systems in Indo-Gangetic plain

Long-term effect of mungbean inclusion in lowland rice-wheat and upland maize-wheat systems on soil carbon (C) pools, particulate organic C (POC), and C-stabilization was envisaged in organic, inorganic and without nutrient management practices. In both lowland and upland systems, mungbean inclusion increased very-labile C (Cfrac₁) and labile C (Cfrac₂) in surface soil (0–0.2 m). Mungbean inclusion in cereal-cereal cropping systems improved POC, being higher in lowland (107.4%). Lowland rice-based system had higher passive C-pool (11.1 Mg C ha^?1) over upland maize-based system (6.6 Mg C ha^?1) indicating that rice ecology facilitates the stabilization of passive C-pool, which has longer persistence in soil. Organic nutrient management (farmyard manure + full crop residue + biofertilizers) increased Cfrac₁ and carbon management index (CMI) over inorganic treatment. In surface soil, higher CMI values were evident in mungbean included cropping systems in both lowland and upland conditions. Mungbean inclusion increased grain yield of cereal crops, and yield improvement followed the order of maize (23.7–31.3%) > rice (16.9–27.0%) > wheat (lowland 7.0–10.7%; upland 5.4–16.6%). Thus, the inclusion of summer mungbean in cereal-cereal cropping systems could be a long-term strategy to enrich soil organic C and to ensure sustainability of cereal-cereal cropping systems.     

Effect of long-term cropping systems on soil organic carbon pools and soil quality in western plain of hot arid India

Maintaining soil organic carbon (SOC) in arid ecosystem is important for soil productivity and restoration of deserted sandy soil in western plain of India. There is a need to understand how the cropping systems changes may alter SOC pools including total organic carbon (TOC), particulate organic C (POC), water soluble carbon (WSC), very labile C (VLC), labile C (LC), less labile C (LLC) and non-labile C (NLC) in arid climate. We selected seven major agricultural systems for this study viz., barren, fallow, barley–fallow, mustard–moth bean, chickpea–groundnut, wheat–green gram and wheat–pearl millet. Result revealed that conversion of sandy barren lands to agricultural systems significantly increased available nutrients and SOC pools. Among all studied cropping systems, the highest values of TOC (6.12 g kg^?1), POC (1.53 g kg^?1) and WSC (0.19 g kg^?1) were maintained in pearl millet–wheat system, while the lowest values of carbon pools observed in fallow and barren land. Strong relationships (P < 0.05) were exhibited between VLC and LC with available nutrients. The highest carbon management index (299) indicates that wheat–pearl millet system has greater soil quality for enhancing crop productivity, nutrient availability and carbon sequestration of arid soil.     

长期施肥下褐土易氧化有机碳及有机碳库的变化特征

本研究探讨了24年长期施肥对褐土土壤有机碳(TOC)、有机碳储量(TOCs)、净固碳效率(NCSE)和碳库管理指数(CPMI)的影响,为评价褐土土壤碳库变化与质量及科学施肥提供理论依据。研究以褐土肥力与肥料长期定位试验为平台,通过9个处理[A组:不施肥处理(N_0P_0、CK);B组:单施无机肥处理(N_1P_1、N_2P_2、N_3P_3和N_4P_4);C组:有机肥与无机肥配施处理(N_2P_1M_1、N_3P_2M_3和N_4P_2M_2);D组:单施高量有机肥处理(M_6)]测定土壤TOC与易氧化有机碳(ROOC)含量,并计算TOCs、NCSE及CPMI等相关指标。结果表明,在不同土层不同时期施用较高量有机肥配施无机肥及施用高量有机肥(N_3P_2M_3、N_4P_2M_2和M_6)均可提高TOC和ROOC含量,且随土层深度加深提升作用减弱。TOCs、NCSE与0~20 cm土层TOC含量在时间和空间上的变化规律基本一致。施用高量有机肥(C组、D组)可有效提高TOCs,A组、B组的TOCs均值分别比C组、D组低76.77%与17.36%。长期施肥处理可提高NCSE,尤其是施用有机肥处理可显著提高NCSE。NCSE为D组C组A组=B组;D组NCSE为1 152.27 kg·hm~(-2)·a~(-1),是C组的2.51倍,B组的16.20倍。与试验前相比,C组和D组的CPMI无显著变化,且C组与D组间差异不显著,但A组与B组比试验前降低16.38~40.02。与A组(CK)相比,B组中N1P1处理与C、D组处理显著影响CPMI,提高了23.30~45.67。在0~40 cm土层CPMI与ROOC含量呈显著正相关,CPMI可以很好地指示有机碳的变化。可见,施用高量有机肥或者较高量有机肥与无机肥配施可极显著提高褐土土壤TOCs、NCSE和CPMI,即施用高量有机肥或者较高量有机肥与无机肥配施(N_3P_2M_3和N_4P_2M_2)有利于褐土有机碳的固存,可减少无机肥的施用量,使土壤性质向良性方向发展,培肥土壤。     

Soil quality assessment based on soil organic matter pools under long-term tillage systems and following tillage conversion in a semi-humid region

A field study was conducted to assess the long-term effects of no-tillage (NT) and conventional tillage (CT), and the short-term effects following tillage conversion from CT to NT (NT_n) and from NT to CT (CT_n) on soil quality (SQ) indicators in a semi-humid climate. First, plots of a long-term tillage experiment on a Luvic Phaeozem initiated in 1986 were split into two subplots in 2012, yielding four treatments: NT, CT, NT_n and CT_n. In 2015, composite soil samples were collected from each treatment and from a natural site (Ref) at depths 0–5, 5–10, 10–20 and 0–20 cm. Several indicators were determined: soil organic carbon (SOC) and nitrogen (SON); particulate organic C (POM-C) and N (POM-N); potential N mineralization (PMN) and soil respiration (R_s). Moreover, bulk density was determined in long-term tillage systems. Different ratios between indicators were calculated, with emphasis on its function in the agroecosystem, that is functional indicators. Significant differences in SOC, SON and PMN were found between CT and NT at most depths. In contrast, 3 years after tillage conversion, only a part of the SQ indicators studied were modified mainly at the 0–10 cm depth. The functional indicators showed differences between tillage systems in the long-term and after short-term tillage conversion depending on the depth; however, the PMN/SON ratio demonstrated differences at all depths. Under these conditions, this ratio-related to easily mineralizable N fraction proved to be a promising indicator for assessing SQ under contrasting tillage systems regardless of the sampling depth.     

Effects of organic wastes on labile organic carbon in semiarid soil under plastic mulched drip irrigation

ABSTRACT

The objective of this work was to evaluate the variation in labile organic carbon fractions after the application of organic wastes (OWs) in semiarid soil under plastic mulched drip irrigation. The two-year experiment involved six treatments: chicken manure (CM), sheep manure (SM), mushroom residue (MR), maize straw (MS), fodder grass (FG), and tree leaves (TL), with an unamended soil (no OWs) as control. In 2015 and 2016, treatment with OWs led to increased levels of soil organic carbon (SOC), dissolved organic carbon, microbial biomass carbon, easily oxidized organic carbon, as well as higher carbon management indexes and yields and lower oxidation stability coefficients. Higher SOC contents (p <0.01) were achieved in both years for TL and MS compared to the other OWs. In particular, the SOC content in 2016 was higher (p <0.05) for TL than MS. Compared to the other OWs, the easily oxidized organic carbon levels and carbon management indexes in both years were higher (p <0.01) for CM, SM, and MS, whereas the oxidation stability coefficients were lower (p <0.01). In conclusion, among the studied treatments, the application of MS was the most effective for improving soil fertility and enhancing soil carbon sequestration.     

不同保护性耕作措施对麦-豆轮作土壤有机碳库的影响

通过设置在甘肃省定西市李家堡镇的不同保护性耕作试验,对春小麦、豌豆两种轮作次序下的土壤总有机碳、活性有机碳、微生物量碳含量进行了测定,并计算了各处理土壤碳库管理指数.结果表明:经过5年的轮作后,与传统耕作相比,两种轮作次序下免耕秸秆覆盖和传统耕作结合秸秆还田处理均能不同程度地提高土壤总有机碳、活性有机碳、微生物量碳含量及土壤碳库管理指数,而免耕不覆盖处理除在0～5 cm提高了土壤有机碳库管理指数外,其他各层次均降低了土壤有机碳库管理指数,说明仅依靠免耕而不结合秸秆覆盖或还田对于土壤有机碳库的管理来讲是不可持续的.     

不同封育年限草地土壤有机质组分及其碳库管理指数

土壤有机质对草地封育的生态效应具有重要指示作用,本文结合野外调查和室内分析,研究了半干旱区不同封育年限草地土壤有机质组分及其碳库管理指数变化,以分析土壤有机质对草地封育的响应特征,从而为该区土壤质量的改善和植被建设的生态效应评价提供依据。研究结果表明,土壤有机质及不同活性有机质含量均随土层加深而降低,且在各土层基本表现出封育18年、封育23年封育13年未封育封育3年的趋势。除封育3年土壤的3种活性有机质碳库管理指数在090cm土壤剖面均低于100外,封育13年草地060cm土层、封育18和23年草地090cm土层的3种活性有机质碳库管理指数均高于100,表明随年限的延长,封育对土壤有机质的改善深度也在加深。土壤3种活性有机质与有机质及多数土壤性质呈极显著正相关,能更为灵敏和直观地表征土壤管理的长期效应和土壤质量变化。     

Impact of cultivation on soil organic carbon and carbon sequestration potential in semiarid regions of China

Dynamic changes in soil organic carbon (SOC) have become a popular topic in global research on organic carbon as part of the increasing attention being paid to food security and reducing greenhouse gas emissions. In this paper, the semiarid regions of China were selected as a research focus, and SOC data from 1980 to 2015 were analysed using IBM SPSS Statistics 20.0 software. SOC in farmland varied according to cultivated land type, mulching material type and planting method in the studied regions. The SOC content is 10.3–10.8 g kg⁻¹ in supplementally irrigated land and flat dry land, 7.1–8.7 g kg⁻¹ in terraced dry land and river beach land, and 6.2–6.4 g kg⁻¹ in sloping dry land. The SOC content increased to 16.1–17.4 g kg⁻¹ when crop stalks were used as mulch. The increase was only 11.5–13.5 g kg⁻¹ in soils mulched with film or sandstone. The SOC value in wheat, maize and potatoes sown on single or double ridges was 2.4%–3.2%, 35.7%–36.4% and 4.4%–4.8%, respectively, which are higher than the values for wheat, maize and potatoes sown using the flat planting method. The SOC sequestering potential also varied according to the previously noted factors and was improved from 224.1% to 383.8% depending on cultivated land type, from 96.5% to 182.3% depending on mulching material type and from 96.1% to 191.3% depending on planting method. The SOC sequestering potential can be improved by 453.2%–757.4% with the integration of the optimal cultivated land type, mulching material type and planting method. Thus, there is substantial soil carbon sequestration potential in China's semiarid regions.     

Effects of long-term fertiliser regime on soil organic carbon and its labile fractions under double cropping rice system of southern China

ABSTRACT

This study was designed to explore changes in soil bulk density, soil organic carbon content, soil organic carbon stock and soil labile organic carbon fractions under 34 years fertilizer regime in the double-cropping rice system of southern China. The experiment including five fertilizer treatments: chemical fertilizer alone (MF), rice straw residue and chemical fertilizer (RF), 30% organic manure and 70% chemical fertilizer (LOM), 60% organic manure and 40% chemical fertilizer (HOM), and without fertilizer input as control (CK). The results showed that soil bulk density in the 0-20 cm soil layer with long-term fertilizer treatments were significantly decreased compared to CK treatment. The soil organic carbon content and stock with RF, LOM and HOM treatments were significantly higher than that of MF and CK treatments. These results confirmed by the soil carbon management index which were significantly increased with RF, LOM and HOM treatments. As a result, combined application of organic manure with chemical fertilizer is a benefit nutrient management for improving soil organic carbon content and stock, soil carbon management index in paddy field of southern China.     

长期施肥对土壤有机碳和无机碳的影响

利用18年长期定位试验,研究了在不同施肥条件下,土壤有机碳和无机碳在0~50 cm土层分布特征。结果表明,施肥对土壤有机碳的影响随着土层深度的增加而下降,0~7.5 cm土层的土壤有机碳比7.5~15 cm、15~30 cm、30~50 cm分别增加了4.6%、22.0%、63.1%,而无机碳含量随着土层深度的增加而增加,与有机碳的变化规律正好相反。不同种类的肥料对土壤有机碳的影响也不相同,化肥、有机肥长期配合施用和长期施用有机肥可以在0~30 cm土层增加土壤有机碳含量,降低土壤中的无机碳含量,而长期单施化肥对土壤的有机碳和无机碳含量无明显差异。     

长期施肥下灰漠土有机碳组分含量及其演变特征

采用湿筛和重液悬浮的物理分组方法分析了18年不同施肥模式下灰漠土有机碳组分含量差异及其演变特征。结果表明:与不施肥相比,长期有机无机肥配施(NPKM和1.5 NPKM)增加各有机碳组分的效果最显著,且粗和细自由颗粒有机碳、物理保护有机碳、矿物结合有机碳增加速率最高,平均分别达到0.12、0.06、0.08及0.17g/(kg.a);秸秆还田使粗和细自由颗粒有机碳分别以0.05和0.03 g/(kg.a)的速率增加,而撂荒和施化肥维持着各有机碳组分的含量。不同有机碳组分间存在显著的相关性,其中以粗自由颗粒有机碳含量增幅最高,不同施肥模式下平均增幅是其它有机碳组分的2.18~.0倍;以矿物结合有机碳所占比例最高,达到56.9%7~7.8%,说明粗自由颗粒有机碳对施肥较敏感,而矿物结合有机碳是灰漠土固存有机碳的主要形式。综上分析,长期有机无机肥配施是提高灰漠土有机碳组分含量和培肥土壤的有效模式。     

长期不同施肥下我国4种典型土壤活性有机碳及碳库管理指数的变化特征

研究长期不同施肥处理对3种旱作土壤(黑土、潮土和红壤)及1种水田土壤(水稻土)活性有机碳含量(LOC)及碳库管理指数(CMI)的影响,为优化施肥管理措施提供科学依据。结果表明:水田土壤总有机碳含量(TOC)和LOC含量高于旱作土壤。单施化肥(NPK),旱作3种土壤TOC、LOC较不施肥对照(CK)显著增加,而水田较CK无显著差异。化肥配施秸秆处理(NPKS),旱作和水田土壤TOC、LOC、活性有机碳占总有机碳的比例(LOC/TOC)及CMI均显著增加,潮土TOC和LOC含量增加最多,增加比例分别为37.6%和66.9%。化肥配施有机肥处理(NPKM),旱作和水田土壤的TOC、LOC、LOC/TOC及CMI均显著增加,其中黑土增加比例最大,分别为90.3%、140.9%、5.1%及277%。旱作和水田土壤的活性有机碳及碳库管理指数均对施肥响应敏感,具有相对一致的响应特征,即长期有机无机肥配施能显著提高土壤活性有机碳含量及碳库管理指数,且效果优于化肥配施秸秆和单施化肥处理。     

Changes in soil organic carbon fractions and bacterial community composition under different tillage and organic fertiliser application in a maize−wheat rotation system

ABSTRACT

The objective of this study was to assess the impact of different tillage and organic fertiliser regimes on soil carbon fractions and bacterial community composition within a maize–wheat cropping system. We conducted a six-year experiment on the Huang-Huai-Hai Plain of China. Six treatments were established: deep tillage (DT), shallow tillage (ST), no-tillage (NT), deep tillage with organic fertiliser (DTF), shallow tillage with organic fertiliser (STF), and no-tillage with organic fertiliser (NTF). Results indicated that during the winter wheat growing season, the highest contents of soil organic carbon (SOC) and easily-oxidised organic carbon (EOC) were in the STF treatment. During the summer maizegrowing season, the DTF treatment had the highest SOC and EOC contents. Compared with the other treatments, the NTF treatment had higher Chao1 and Shannon indices for bacteria; however, the relative abundance of Proteobacteria is highest in all treatments. A redundancy analysis (RDA) revealed that bacterial community composition was correlated with variation of the SOC, DOC, EOC, and microbial biomass carbon (MBC). Our results showed that combining the two components of the SOC fractions and bacterial community composition, STF practice in a maize–wheat rotation was a sustainable approach to optimising soil structure and improving soil quality.     

长期施肥对棕壤有机碳组分的影响

对起始于1979年的棕壤长期肥料定位试验田2005年的耕层土壤不同有机碳组分进行了测定与分析,以探讨长期施肥影响土壤有机碳的过程及机理。结果显示:长期单施化肥降低了土壤的游离态颗粒有机碳（FPOM-C）含量,但进一步稳定了矿物结合态有机碳(MOM-C),最终提高了土壤总有机碳(TOC)含量;长期施用有机肥和有机肥配施化肥使土壤的FPOM-C、闭蓄态颗粒有机碳(OPOC)、MOM-C以及含量均显著提高,且增加效果好于单施化肥。从各组分有机碳所占比例或相对比值来看,长期施用有机肥和有机肥配施化肥提高了POM-C/TOC比例而降低了MOM-C/TOC比例,使FPOM-C/OPOM-C比值显著增大。表明土壤有机碳结构分组的应用有助于揭示长期施肥影响土壤有机碳的机理。     

不同利用方式对棕壤有机碳垂直分布的影响

采用野外采样和室内分析的方法研究了林地、园地、耕地3种利用方式对典型棕壤总有机碳(TOC)、颗粒有机碳(POC)及重组有机碳(HFOC)在0～20 cm、20～40 cm、40～60 cm 3层次中垂直分布的影响。结果表明,与林地相比,园地和耕地各层次的TOC含量和储量均显著下降;其分布份额和分布比则为园地中、下层略向上层转移,耕地则明显向中、下层转移。3种利用方式下POC的相对数量均随土层加深而递减,林地开垦为园地和耕地后,POC的相对数量仅在园地上、中层显著降低,分别减少6.67和1.70个百分点,而耕地则各层次均显著降低,其相对数量分别减少13.65、5.43和3.03个百分点;HFOC的相对数量随干预强度和土层深度增加而增大,耕地和园地比林地分别高出:上层5.77和4.00个百分点、中层10.44和6.40个百分点、下层7.35和3.92个百分点,且差异均显著。因此,将林地棕壤开垦为园地或耕地后应注重有机物料的投入,以减缓因开垦对有机碳所造成的损失和不尽合理的分布状况。     

不同轮作制度下土壤中不稳定有机碳组分的变化

Taking Kenli County in the Yellow River Delta, China, as the study area and using digital satellite remote sensing techniques, cultivated land use changes and their corresponding driving forces were explored in this study. An interactive interpretation and a manual modification procedure were carried out to acquire cultivated land information. An overlay method based on classification results and a visual change detection method which was supported by land use maps were employed to detect the cultivated land changes. Based on the changes that were revealed and a spatial analysis between cultivated land use and related natural and socio-economic factors, the driving forces for cultivated land use changes in the study area were determined. The results showed a decrease in cultivated land in Kenli County of 5321.8 ha from 1987 to 1998, i.e., an average annual decrement of 483.8 ha, which occurred mainly in the central paddy field region and the northeast dry land region. Adverse human activities, soil salinization and water deficiencies were the driving forces that caused these cultivated land use changes.     

长期施肥下红壤有机碳及其颗粒组分对不同施肥模式的响应

采集不同施肥24年的红壤,采用物理分组的方法,观测了长期不同施肥下红壤有机碳及其组分变化,并结合历史资料分析了不同施肥模式对红壤有机碳及其颗粒组分的影响。结果表明,化肥配施有机肥（NPKM）处理下红壤总有机碳含量（10.33 g/kg）,砂粒（2000～53 m）、细粉粒（5～2 m）和粘粒（2 m）组分中的有机碳含量显著高于其他处理。与不施肥（CK）相比,施用化肥（NPK、2NPK）和有机肥（NPKM、M）显著地提高了红壤有机碳在砂粒和粘粒中的分配比例,而降低了其在粗粉粒和细粉粒的分配比例。施化肥（NPK、2NPK）、单施有机肥（M）、化肥配施有机肥（NPKM）处理,土壤有机碳的平均固定速率分别为0.05 t/(hm2?a)、0.18 t/(hm2?a)、0.26 t/(hm2?a)。相关分析表明,不同施肥模式下红壤有机碳的固定量与碳投入量之间存在着极显著的线性相关关系（R2=0.909, P0.01）,土壤的固碳效率为8.1%;随着碳投入的增加,粗粉粒和细粉粒有机碳储量逐渐下降,而砂粒和粘粒中碳储量逐渐增加,并且粘粒增加速率要远远高于砂粒。以上结果说明,红壤中有机碳还没有达到饱和,还具有一定的固碳潜力,增加的有机碳主要固持在粘粒中,粘粒是红壤有机碳的主要固持组分。