长期施肥红壤性稻田和旱地土壤有机碳积累差异

  【目的】  提高土壤有机碳水平对提升农田生产力有重要意义。基于长期定位施肥试验,比较施肥影响下相同成土母质发育的红壤性稻田和旱地土壤的总有机碳 (TOC) 及其组分的积累差异,以深入理解红壤有机碳的固持及稳定机制。  【方法】  稻田和旱地长期施肥试验分别始于1981和1986年,包含CK (不施肥对照)、NPK (施氮磷钾化肥) 和NPKM (有机无机肥配施) 3个处理,在2017年晚稻和晚玉米收获后,采集两个试验上述处理的耕层 (0—20 cm) 土样,通过硫酸水解法分离土壤活性与惰性有机碳,测定并计算土壤中TOC及其组分的含量及储量,并利用Jenny模型拟合试验期间耕层土壤TOC含量的变化动态,估算土壤固碳潜力。  【结果】  与CK相比,长期施肥可提高稻田和旱地土壤各有机碳组分的含量,且NPKM处理的效果优于NPK处理。相比于稻田土壤,施肥对旱地土壤各有机碳组分含量的提升更加明显。NPK和NPKM处理下,旱地土壤活性有机碳组分Ⅰ、活性有机碳组分Ⅱ、惰性有机碳含量的增幅分别是稻田土壤的2.7、2.7、5.8倍和2.0、1.4和2.5倍。不论施肥与否,稻田土壤TOC的固存量和固存潜力均显著高于旱地土壤。施肥促进土壤固碳,在稻田和旱地土壤上,NPKM处理的TOC固存量分别是NPK处理的1.7和25.5倍,TOC固存潜力则分别是NPK处理的1.4和5.8倍。长期不同施肥均显著提高稻田和旱地土壤年均碳投入量,线性拟合方程表明,随碳投入量增加,土壤活性有机碳储量的累积对稻田、旱地土壤TOC储量累积的贡献率分别达64.7%、44.6%。不同处理间稻田与旱地土壤活性有机碳 (包括活性有机碳组分Ⅰ与活性有机碳组分Ⅱ) 含量的差异可解释其TOC含量差异的52.9%～60.0%。  【结论】  与施氮磷钾化肥相比,有机无机肥配施可更好的促进土壤固碳,且在旱地土壤上的促进作用比在稻田土壤上更为明显。与稻田土壤相比,旱地土壤各有机碳组分含量的变化对长期施肥的响应更敏感,且在施氮磷钾化肥条件下表现更为明显。红壤性稻田和旱地土壤TOC积累的主要贡献组分分别为活性有机碳和惰性有机碳。红壤植稻虽有利于有机碳固持,但红壤性稻田土壤的活性碳占比较高,可能易因不当管理而发生损失。     

有机物料循环对红壤稻田系统磷素营养的影响

采用动态采样结合室内分析方法,比较研究了中国科学院桃源农业生态实验站的长期田间定位试验中长期施与不施磷肥、有机物料循环再利用和在有机物料循环再利用的基础上配施磷肥等几种施肥模式对土壤Olsen-P含量、水稻不同生育期茎叶和子实磷含量、以及各生育期累积吸收和利用磷的影响。结果表明,长期不施磷肥土壤速效磷(Olsen-P)降低到小于5.mg/kg;施磷肥或有机物料循环再利用模式,土壤Olsen-P维持在5～10mg/kg之间的中等水平;在保持系统内有机物料循环再利用的基础上配施磷肥,土壤Olsen-P迅速提高,超过10.mg/kg。稻田系统内有机物料循环再利用可促进水稻对磷的吸收,增加水稻各生育期茎叶和子实的磷含量,提高各生育期水稻累积吸收磷量和磷的利用率。     

长期有机物循环利用对红壤稻田土壤供磷能力的影响

采用盆栽试验,研究了长期不同施肥处理定位试验土壤供磷能力的差异,并从土壤磷素平衡、全磷、有机磷、Olsen-P和MB-P的含量的变化等方面探索了导致供磷能力差异的原因。结果表明,长期施用磷肥能显著提高土壤的供磷能力,其中以有机物循环利用配合磷肥施用处理土壤的供磷量能力最高,植株平均吸磷量是长期不施磷肥处理的3.5倍,比长期施用磷肥处理平均高出59.8%。长期单施氮肥导致土壤供磷能力衰竭,植株总吸磷量比长期不施肥还低17.2%,单一有机物循环利用和配施N肥植株总吸磷量比长期不施肥分别高80.3%和40.2%。有机物循环利用能明显提高土壤微生物对磷素的固持量,土壤微生物对无机磷的利用可能是其向有效磷转化的关键途径。磷肥配合系统内有机物循环利用,是提高红壤稻田土壤供磷能力的有效施肥模式。     

南方红壤稻田与旱地土壤有机碳及其组分的特征差异

大量研究证明稻田土壤比旱地土壤更具固碳潜力,但至今对稻田土壤固碳机制的认识尚不甚清楚。本研究于2007年利用两个开垦年代相似,近20多年分别一直种植双季稻和双季玉米的长期定位试验,来比较不同种植模式下土壤有机碳及其组分的差异。结果表明,水田土壤总有机碳和总氮的浓度分别是旱地的2.2倍和2.5倍。与试验前相比,水稻种植显著提高了土壤有机碳的含量,增幅达到30.8%,而旱地的前后差异不显著。在所有团聚体粒径水平上,水田有机碳的浓度均显著高于旱地。其中53～250μm微团聚体相差最大,水田是旱地的近3倍。水田微团聚体保护碳（iPOM_m）在土壤中的浓度是旱地的4.2倍,微团聚体保护碳在总有机碳中的比重也显著高于旱地,达到25.5%,是旱地的2倍。水田和旱地iPOM_m组分碳的差异能够解释其总有机碳差异的42.8%。上述结果可以增强我们对稻田土壤固碳机制的了解,为稻田土壤碳管理提供理论依据。     

红壤典型区不同类型土壤有机碳组分构成及空间分异研究

以江西省东乡县为研究区,基于土壤有机碳三库(活性、缓性和惰性碳库)一级动力学理论,通过22个土壤样品的实验室呼吸培养实验,计算了各土壤亚类的碳组分含量及占总有机碳的比例,并借助全县229个采样点获得了东乡县的活性、缓性和惰性有机碳的空间分布图。分析结果表明,淹育、潴育、潜育型水稻土和红壤的活性碳含量分别为0.54、0.72、0.72和0.33 g/kg,分别占其总有机碳含量的2.78%、2.83%、2.91%和2.57%;缓性碳含量分别为7.57、9.79、12.34和4.72 g/kg,分别占总有机碳含量的41.09%、45.25%、46.24%和37.12%;惰性碳含量分别为10.36、11.22、13.49和7.67 g/kg,分别占总有机碳含量的60.31%、56.13%、51.92%和50.67%。在空间分布上,活性、缓性和惰性碳含量均呈现由东南向西北减少趋势。分析表明水稻土各亚类活性和缓性碳含量高于红壤,说明水稻土不仅是该地区固碳的主要类型,也是较大的潜在碳排放源。红壤的惰性碳尽管比例最高,但总有机碳含量较低,其土壤固碳能力有待进一步提高。     

红壤侵蚀区植被恢复过程中土壤有机碳组分变化

为了解土壤有机碳组分在植被恢复过程中的变化规律,选取了红壤区本底条件基本一致的不同恢复年限马尾松林为研究对象,以未治理的侵蚀裸地(CK1)和恢复后的次生林(CK2)为对照,采用物理化学分组法,将土壤有机碳分为由溶解性有机碳(DOC)和颗粒有机碳(POM)组成的活性碳库、物理保护态的团聚体与粉粒和黏粒组合成的缓效性碳库以及化学结构稳定的惰性碳库。结果表明:在植被恢复过程中(0~30年)活性碳库储量及其分配比例在植被恢复7~10年显著提高(P0.05),并在植被恢复27~30年保持较稳定水平,缓效性碳库储量及其分配比例在27~30年呈显著变化(P0.05),而活性碳库分配比例有所降低,且POM、DOC与缓效性碳库均达显著相关(P0.01),说明活性碳库在恢复7~10年后逐渐向缓效性碳库转化;惰性碳库储量随恢复年限不断增加,但其分配比例保持较稳定水平。相关性分析显示,恢复年限、不同组分与不同碳库均达显著相关(P0.01),且缓效性碳库随植被恢复最敏感,说明在马尾松恢复过程中土壤有机碳以活性碳库积累逐渐转化为缓效性碳库积累为主,进而影响惰性碳库的积累,有利于土壤有机碳的长期保持。     

典型稻田红壤发生层团聚体稳定性及有机碳的含量变化

【目的】探究土壤团聚体组成及其稳定性对土壤有机碳(SOC)的储存与周转的影响机制。【方法】以江西鹰潭孙家典型红壤小流域内不同坡位稻田红壤发生层土壤为研究对象,分析了机械稳定性团聚体（MSA）、水稳定性团聚体（WSA）比例及其有机碳含量、团聚体破碎率（PAD）、平均重量直径（MWD）、几何平均重量直径（GMD）及分形维数（D）等指标的剖面变化差异,并借助于结构方程模型（SEM）探讨了各指标间的相关关系。【结果】不同坡位稻田红壤各发生层的MSA比例以10～5 mm所占比例最高（27.6%～87.6%）,而<0.25 mm所占比例最低（1.59%～15.3%）;以<0.25 mm WSA所占比例最高（3.06%～70.1%）,5～2 mm WSA所占比例最低（0.17%～20.4%）。稻田红壤发生层中团聚体碳（SOCa）均随着土壤发生层深度的增加先迅速降低后缓慢降低;其中,2～0.25 mm SOCa对SOC的贡献率（7.53%～76.7%）显著高于其它粒级团聚体。PAD、MWD、GMD及D均随发生层深度增加先降低后缓慢增加,但随坡位降低显著增加。SEM分析结果表明,土壤pH、游...     

红壤稻田土壤溶解有机碳含量动态及其生物降解特征

本通过田间采样分析和室内培育试验,研究了不同利用年限的3种红壤水田土壤中溶解有机C(DOC)的含量动态和生物降解特征。结果表明：土壤DOC的含量随土壤深度而降低,二具有显负相关性。0-30cm土壤DOC的含量及其占总C比例随土壤有机C含量的升高而增大。DOC的季节变化明显,主要与气候因素有关：降雨和灌水可显提高DOC的含量,是落干时含量的1．44-2．50倍。淋溶试验结果表明,从试验开始,淋滤液中DOC的浓度呈增加趋势,至2l天时达到最大,其后又趋下降。在49天的培养期内,DOC的分解速率为3l％-58％,其中低分子量组分能在数天内降解掉。不同土壤间DOC的分解速率有明显差异。     

侵蚀红壤区植被恢复对表层与深层土壤有机碳矿化的影响

试验研究了典型红壤侵蚀区不同植被恢复年限(0,11,31a)的表层(0—10cm)和深层(60—80cm)土壤有机碳矿化特征。结果表明:深层土壤有机碳84d累积矿化量或潜在矿化量显著低于表层土壤,植被恢复则显著增加了表层和深层土壤累积矿化量或潜在矿化量(P0.05),相关分析显示土壤有机碳累积矿化量或潜在矿化量与WSOC、MBC和SOC显著(P0.05)或极显著(P0.01)相关,表明碳矿化底物数量是决定土壤碳累积矿化量或潜在矿化量的主导因子;对照表层土壤的矿化速率常数(k)高于深层土壤的,植被恢复降低了表层土壤的k值(P0.05),对深层土壤的k值却没有显著影响;而深层土壤矿化率显著高于表层土壤,且植被恢复后均显著降低(P0.05),相关分析显示土壤有机碳矿化率与微生物代谢熵呈极显著的正相关(P0.01),表明微生物碳利用效率是影响土壤碳矿化率的重要因素,而深层土壤微生物碳利用效率显著低于表层土壤,但植被恢复可以改善侵蚀红壤的环境条件,提高土壤微生物的碳利用效率,从而增强土壤固碳能力。     

有机物料碳和土壤有机碳对水稻土甲烷排放的影响

基于30年水稻土长期施肥定位试验,在保证原有定位试验正常开展的前提下,将部分化肥处理变更为有机肥处理(或反之),通过观测一年水稻轮作周期内不同处理甲烷(CH_4)排放通量季节性变化,探讨不同肥力水稻土中外源有机碳及土壤有机碳含量对田间CH_4排放的影响。结果表明:施化肥处理和有机肥处理,水稻土全年CH_4累积排放量范围分别为1.73~4.72和35.09~86.60 g·m~(-2)。有机肥处理改施化肥后,田间土壤CH_4的排放量显著降低;化肥处理改施有机肥或有机肥处理增施有机肥后,田间土壤CH_4的排放量显著提高。外源有机碳的输入量是田间土壤CH_4年排放量的决定性因素,外源有机碳输入量(x)与水稻土CH_4年累积排放量(y)之间满足直线方程:y=0.087 7 x+3.265 7(R~2=0.965 9,n=21)。土壤有机碳同样也是影响稻田CH_4排放的因素,在不同有机碳水平的水稻土上施用等量相同化肥或有机肥,土壤有机碳含量高的水稻土都更有利于CH_4的产生。单施化肥稻田土壤CH_4排放的最主要碳源是土壤有机碳,有机碳含量(x)和水稻土CH_4年累积排放量(y)之间的指数方程:y=0.162 4 e~(0.162 2 x)(R~2=0.940 6,n=9)。有机肥可促进土壤有机碳分解释放CH_4,土壤有机碳含量相同的条件下,高量有机肥比常量有机肥的土壤有机碳分解比率高0.65%,等量相同有机肥但土壤有机碳含量不同的条件下,土壤有机碳分解比率无显著差异;同样,土壤有机碳也可促进有机物料碳分解释放CH_4,在常量有机肥或高量有机肥处理中,土壤有机碳含量高者比低者的有机物料碳分解比率分别多出3.57%和2.34%。     

耕作措施对双季稻田土壤碳及有机碳储量的影响

针对不同耕作措施对双季稻田的固碳效应和固碳潜力问题,选择湖南省宁乡县的双季稻区试验点进行了有机碳、活性有机碳以及耕层有机碳储量的研究,以期为制定适合于稻田条件下的合理耕作方式提供理论依据。结果表明,耕作措施和秸秆还田对有机碳（SOC）和活性有机碳（AOC）含量均产生不同程度的影响。免耕处理下,有机碳和活性有机碳含量皆随土壤深度的增加而减少,土壤0～5cm的SOC和AOC的含量最高,且与其他层次达到显著性差异水平（P＆lt;0.05）,具有明显的表层富集现象。与免耕相比,旋耕和翻耕则更利于5～10cm和10～20cm土层的有机碳和活性有机碳的积累。比较秸秆还田对SOC和AOC的影响表明,秸秆还田有效地提高了0～10cm有机碳含量,但对10～20cm并未产生显著影响,秸秆的输入并未增加土壤活性有机碳的含量。采用等质量方法计算了耕层土壤有机碳储量,结果显示旋耕秸秆还田使有机碳储量明显增加,而免耕只增加了土壤0～5cm和5～10cm土层有机碳储量,10～20cm有机碳储量有所降低,但耕作措施对有机碳储量的长效作用还有待于进一步研究。     

定位施用菌渣对稻田土壤团聚体中碳氮含量的影响

研究定位施用菌渣对稻田土壤团聚体中碳、氮含量的影响,对菌渣的合理利用和农业的可持续发展具有一定的意义,同时可为揭示施用菌渣对稻田土壤肥力形成及演变的影响提供理论依据。本研究通过采集不同菌渣用量处理土壤,分析了稻田施用菌渣下土壤总有机碳和全氮及各粒级团聚体中碳、氮含量的变化,得出了各级团聚体对土壤有机碳和全氮的贡献率。结果表明:施用菌渣各处理土壤总有机碳含量较对照提高4.07%~15.71%(P0.05),其中,中量和高量菌渣处理土壤总有机碳含量分别为13.27 g/kg和12.81 g/kg。施用菌渣各处理土壤全氮含量较对照提高1.75%~8.61%(P0.05),其中,中量和高量菌渣处理土壤全氮含量分别为1.47 g/kg和1.43 g/kg。总体而言,各处理中1.0 mm的各级土壤团聚体中碳、氮含量显著高于其他粒径团聚体,碳、氮主要分布在较大粒级团聚体上。不同处理各粒级团聚体分离的碳、氮回收率分别为77.05%~87.36%、77.66%~89.68%,说明获得的各粒级团聚体有机碳和全氮含量分布的结果是相对可靠的。由此,菌渣的施用提高了稻田土壤水稳性大团聚体中碳、氮的含量,其是改善土壤团粒结构,提高稻田土壤生产力的有效措施。     

Use of organic carbon and loss-on-ignition to estimate soil organic matter in different soil types and horizons

Summary Loss-on-ignition (LOI) and the organic C content have been used to estimate soil organic matter. Organic matter is often estimated from organic C by applying a factor of 1.724. Several authors have examined the relationship between LOI, used as an estimate of organic matter, and C by simple linear regressions. In the present study, this approach was examined in relation to two sets of data. LOI overestimates organic matter in soils with significant proportions of clay minerals because of bound water, and correcting for bound water gives some LOI: C ratios of less than 1. It is concluded that differences in the nature of the organic matter in different soils and horizons make the simple regression approach unsuitable. More attention needs to be paid to studies of the nature of the organic matter.     

长期施肥红壤稻田有机碳演变规律及影响因素

利用1981年起设置的水稻土长期施肥定位试验,分析了CK(不施肥)、N(单施氮肥)、NPK(氮磷钾配施)、NPK2(2倍氮磷钾配施)和NPKM(有机无机肥配施)等施肥措施下土壤有机碳的演变规律及其与作物产量和土壤养分(全氮、碱解氮、全磷、速效磷、全钾和速效钾)的相关性.结果表明:试验30年后,各个处理的土壤有机碳含量均有上升,其中CK、N、NPK、NPK2和NPKM的土壤有机碳在试验30年分别比试验前增加18.95％、17.72％、23.36％、16.92％和32.68％.与CK处理相比,NPK、NPK2和NPKM处理的土壤有机碳平均提高了4.09％、4.03％和25.68％.土壤有机碳含量与水稻产量呈显著相关(P＜0.001),相关系数r为0.410,这说明土壤有机碳含量的增加可以促进水稻增产.土壤有机碳与土壤养分中的碱解氮、速效磷和全磷含量均表现出极显著相关(P＜0.001),相关系数r分别为0.452、0.559和0.487,但是与钾含量相关不显著.这表明:有机无机肥配施可以持续快速提高红壤性水稻土的有机碳含量,同时在有机无机肥配施过程中应适当增施钾肥,从而促进土壤肥力平衡和维持作物高产稳产,实现农业可持续性.     

Carbon and nitrogen in operationally defined soil organic matter pools

Humic substances [humic acid (HA), fulvic acid (FA), and insoluble humin], particulate organic matter (POM), and glomalin comprise the majority (ca 75%) of operationally defined extractable soil organic matter (SOM). The purpose of this work was to compare amounts of carbon (C) and nitrogen (N) in HA, FA, POM, and glomalin pools in six undisturbed soils. POM, glomalin, HA, and FA in POM, and glomalin, HA, and FA in POM-free soil were extracted in the following sequence: (1) POM fraction separation from the soil, (2) glomalin extraction from the POM fraction and POM-free soil, and (3) co-extraction of HA and FA from the POM fraction and POM-free soil. Only trace amounts of HA and FA were present in the POM fraction, while POM-associated glomalin (POM-glomalin) and POM alone contributed 2 and 12%, respectively, of the total C in the soil. Mean combined weights for chemically extracted pools from POM and from POM-free soil were 9.92 g glomalin, 1.12 g HA, and 0.88 g FA kg⁻¹ soil. Total protein and C, N, and H concentrations showed that glomalin and HA were, for the most part, separate pools, although protein was detected in HA extracts. Even though percentage carbon was higher in HA than in glomalin, glomalin was a larger (almost nine times) operationally defined pool of soil organic C. Glomalin was also the largest pool of soil N of all the pools isolated, but all pools combined only contained 31% of the total N in the soil.     

Relationship between soil neutral sugar composition and the amount of labile soil organic matter in Andisol treated with bark compost or leaf litter

 The effect of short-term bark compost (Ba) and leaf litter (Li) applications on the labile soil organic matter (SOM) status was investigated. The SOM status studied in this paper includes soil microbial biomass, soil available N, hot water extractable C (HwC) and N (HwN) and soil neutral sugar-C composition. The soil microbial biomass C (MBC) and N (MBN), soil available N, HwC and HwN increased upon application of Ba and Li. No quantitative relationship was observed between application of organic material and MBC, MBN or soil available N. A positive linear correlation was observed between MBN and HwC but not between MBN and soil available N. Among the various soil neutral sugar C, xylose C (Xyl) content in Ba plots showed a remarkable increase but mannose C (Man) did not differ among Fer (fertilizer), Ba or Li plots. Soil neutral sugar C had a positive linear correlation with soil available N, MBN and HwC. The proportion of MBN : TN is positively correlated with the Xyl/Man ratio. The increase in the proportion of MBN in SOM seems to occur with the increase of SOM derived from plant debris. Received: 20 October 1997     

Biological, chemical and thermal indices of soil organic matter stability in four grassland soils

The various ecosystem functions of soil organic matter (SOM) depend on both its quantity and stability. Numerous fractionation techniques have been developed to characterize SOM stability, and thermal analysis techniques have shown promising results to describe the complete continuum of SOM in whole soil samples. However, the potential link between SOM thermal stability and biological or chemical stability has not yet been adequately explored. The objective of this study was to compare conventional chemical and biological methods used to characterize SOM stability with results obtained by thermal analysis techniques. Surface soil samples were collected from four North American grassland sites along a continental mean annual temperature gradient, each with a native and cultivated land use. Soil organic C concentrations ranged from 6.8 to 33 g C kg⁻¹ soil. Soils were incubated for 588 days at 35 °C, and C mineralization rates were determined periodically throughout the incubation by measuring CO₂ concentration using an infrared gas analyzer (IRGA) to calculate biological indices of SOM stability. Hot-water extractable organic C (HWEOC) contents were determined before and after incubation as chemical indices. Finally, samples from before and after incubation were analyzed by simultaneous thermal analysis (i.e., thermogravimetry (TG) and differential scanning calorimetry (DSC)) to determine thermal indices of SOM stability. Long-term incubation resulted in the mineralization of up to 33% of initial soil C. The number of days required to respire 5% of initial soil organic carbon (SOC), ranged from 27 to 115 days, and is proposed as a standardized biological index of SOM stability. The number of days was greater for cultivated soils compared to soils under native vegetation, and generally decreased with increasing site mean annual temperature. HWEOC (as % of initial SOC) did not show consistent responses to land use, but was significantly lower after long-term incubation. Energy density (J mg⁻¹ OM) was greater for soils under native vegetation compared to cultivated soils, and long-term incubation also decreased energy density. The temperatures at which half of the mass loss or energy release occurred typically showed larger responses to land use change than to incubation. Strong correlations demonstrated a link between the thermal and biogeochemical stability of SOM, but the interpretation of the thermal behavior of SOM in bulk soil samples remains equivocal because of the role the mineral component and organo-mineral interactions.     

Effect of organic matter on changes in soil zinc fractions found in wetland soils

Abstract

Zinc fractions occurring in five wetland soils as a function of organic matter application and soil redox potential were studied under laboratory conditions. The results indicate that a large portion of native or added Zn is bound to the soil mineral component. Exchangeable and organic complexed Zn and Zn bound to amorphous and crystalline sesquioxides were found to be in dynamic equilibrium. Exchangeable and complexed Zn were positively correlated with both native and/or added organic matter, while Zn bound to the amorphous and crystalline sesquioxides were negatively correlated with added organic matter. As soil redox potential decreased, the amount of exchangeable and organic complexed Zn decreased, while Zn bound to the amorphous and crystalline sesquioxides increased. Zinc fractions examined varied, depending upon soil cation exchange capacity, clay and organic carbon content.     

吉林西部盐碱地区稻田土壤有机碳矿化特征

以吉林西部盐碱地区(前郭灌区)土壤为研究对象,选取不同盐碱程度的4块水田(P1、P2、P3和P4),采用野外实地调研采样与室内模拟试验相结合的方法,分别在培养期的第1,4,7,10,14,21,28,35,70天测定土壤CO_2气体的排放通量,结合土壤基本理化性质,分析盐碱稻田矿化模拟培养过程中CO_2通量的动态变化,研究土壤盐碱化程度对有机碳矿化过程的影响。结果表明:P1、P2、P3为弱碱化土,P4为强碱化土;各样地土壤有机碳(SOC)含量差异显著,并存在表层富集现象,与碱化度(ESP)呈显著负相关关系(r=-0.945);SOC矿化量累积过程与培养时间符合一级动力学模型C_t=C_0(1-e^-kt),各样地土壤在矿化培养初期CO_2释放量较大,释放强度降低较快,矿化速率随时间延长呈缓慢平稳下降,在培养期结束时降至最低。SOC矿化过程受多种因子共同作用,ESP是该过程的主要影响因子。土壤的盐碱化抑制了土壤碳循环的速度,相对于碳源过程而言,对碳汇的影响更大。伴随SOC含量增加,SOC矿化反应强度和矿化反应的完全程度加强,矿化反应累积量增加,反之,随ESP程度增加而减弱。     

长期有机肥替代化肥对水稻土有机碳稳定性的影响

针对不同有机肥替代化肥比例下红壤性水稻土有机碳稳定性不明确的科学问题,以第四纪红色黏土发育的水稻土的长期定位试验为研究对象,选取不施肥处理（CK）、化肥处理（100F0M）、化肥处理中30%、50%及70%的氮量被有机肥替代（70F30M、50F50M、30F70M）5个处理,明确长期不同有机肥替代化肥比例对水稻土活性/惰性碳组分含量及有机碳化学结构稳定性的影响。结果表明：不同有机肥替代化肥比例均提高了水稻土有机碳、活性碳、惰性碳的含量,活性碳含量表现为70F30M、30F70M>CK、50F50M,惰性碳含量表现为30F70M>70F30M、50F50M>100F0M>CK。随着有机肥替代比例的增加,惰性碳比例从69.67%逐渐增加至77.26%。不同有机肥替代比例下土壤有机碳的化学结构种类相同,相对含量百分比表现出相同的趋势：芳香碳（33.28%～37.79%）、烷基碳（27.81%～31.19%）最高,烷氧碳（16.19%～20.10%）、羰基碳（10.35%～12.07%）居中,羧基碳（2.52%～5.75%）最低。同时随着有机肥替代化肥比例的增加,芳香...