硼在梨树苗不同部位的分布及与其他元素分配的关系

以‘翠冠'梨树苗为试验材料,采用微波消解提取灰分结合等离子发射光谱仪测定法,研究硼(B)添加对梨不同部位B分布及对P、K、Ca、Mg、Fe、Zn、Mn和Cu 8种元素吸收分配的影响.结果表明:‘翠冠'梨不同器官B浓度大小为叶片>根系>茎,随营养液B浓度增加,‘翠冠'梨根、茎、叶B浓度呈增加的趋势,营养液B浓度越高根系B浓度增加幅度越大,不同处理间差异显著.高B处理明显影响‘翠冠'梨苗8种矿质元素在根、茎、叶中的分配.根中P、K、Mg、Zn、Mn和cu浓度随营养液B浓度增加而提高,Ca和Fe浓度随营养液B浓度增加而降低,而转运系数均随B浓度增加而增大;茎中P、Ca、Mg、Zn、Mn和Cu浓度随营养液B浓度增加而提高,K和Fe随营养液B浓度增加而降低,P和K转运系数随B浓度增加而增大,Fe无明显变化,其他元素的转运系数随营养液B浓度增加而降低;叶中P、K、Mn和Cu浓度随营养液B浓度增加而提高,Fe和Zn则相反,而Ca和Mg则先升高后降低,除Zn与Mn外,其他元素的转运系数随营养液B浓度增加而增大.     

不同水肥条件下AM真菌对丹参幼苗生长和营养成分的影响

利用盆栽接种试验,探讨不同水肥条件下AM真菌摩西球囊霉Glomus mosseae对丹参幼苗生长和微量元素的影响,为丹参水肥合理施用提供理论依据。结果表明,不同水肥条件下,接种AM真菌显著提高了根系侵染率和生物量。40%相对含水量、不同施P水平,接种株丹参酮含量升高,总黄酮、丹参素及地下部总酚酸含量降低,植株Zn及地上部Ca、K、Mn、Fe含量升高,而对植株Mg、Cu和地下部Ca、K、Mn、Fe无显著影响;接种效应随施P量不同而变化。70%相对含水量、不同施P水平,接种株药用成分含量显著升高,植株Ca、Mn和地上部K、Cu及地下部Fe和Zn含量升高,而对植株Mg、地下部K、Cu和地上部Fe和Zn含量无显著影响。不同水分和同一施P水平,接种株丹参酮含量升高,地上部Ca、K和地下部Zn含量升高,接种效应因土壤含水量不同而变化,其中以70%含水量时效果最好。说明AM真菌能促进宿主植物根系对水分和矿质元素的吸收与利用,提高水分和P肥利用率,降低水分和P胁迫对丹参的伤害程度,其中以70%相对含水量,施P量为0.16 gP/kg土时AM真菌对丹参的接种效果最佳。     

微波消解-FAAS法分析并比较旱芹(Apium graveolens L.)不同部位八种金属元素的含量

采用微波消解法处理旱芹根、茎、叶,并用火焰原子吸收法测定其中的Na、K、Ca、Mg、Fe、Mn、Zn、Cu 8种金属元素的含量。结果表明:旱芹中富含人体必需的Na、K、Mg、Fe、Ca等元素,各元素在不同部位含量有一定差异。Fe元素在旱芹根中含量为883.57μg.g-1,明显高于茎和叶;Ca、Zn和Mn元素在旱芹叶中的含量分别为11 103.74,214.04,88.07μg.g-1,明显高于茎和根;K、Na和Mg元素在旱芹茎中的含量高于根和叶中,Cu元素含量在各部位差异不大。方法的加标回收率为96.8%～105.8%,相对标准偏差(RSD)≤3.36%。     

砂培条件下施加钙、砷对蜈蚣草吸收砷、磷和钙的影响

在砂培条件下 ,研究施加钙、砷对蜈蚣草生长和砷、磷和钙的吸收及转运的影响。添加砷对蜈蚣草的生物量 (根、叶柄和羽叶的干物重 )虽未达到显著影响 (p<0 .0 5) ,但添加 0 .1 mmol/L砷时 ,表现出刺激生长效应。提高介质中钙浓度明显抑制蜈蚣草根系生长 ,钙浓度过高还会显著限制地上部生长。供应 0 .0 3mmol/L钙时 ,蜈蚣草羽片砷浓度为 42 1 8mg/kg,明显高于 2 .5和 5 mmol/L钙处理下相应的砷浓度。砷的转运系数 (羽片 /根 )随着介质中砷浓度的升高而增大 ,随着介质中钙浓度的升高而减少。这说明一定范围内提高介质中砷浓度促进砷向地上部运输 ,而钙却明显抑制砷向地上部转运。钙和砷浓度过高时 ,植株均会出现中毒症状。钙中毒表现为叶脉变褐和叶肉坏死 ;而砷中毒现象表现在叶尖和叶缘变褐。介质中砷限制蜈蚣草根部对磷的吸收 ,但对地上部磷浓度无显著影响。介质中添加砷 ,植物体内钙浓度升高 ,可能起缓解砷毒的作用。钙、砷对蜈蚣草羽片砷累积量和总累积量均有极显著的交互作用 ,钙是负交互效应 ,砷是正交互效应。添加 2 .5和 5.0 mmol/L钙时 ,相对于 0 .0 3 mmol/L钙处理分别减少地上部砷累积量 2 0 .8%和73.1 %。这表明在应用蜈蚣草进行植物修复时 ,介质中出现过高浓度的钙是不利于提高土壤修复效率     

珍稀濒危植物矮牡丹体内矿质元素的研究

采用原子吸收分光光度法测定了矮牡丹体内的10种矿质元素,即K、Mg、Mn、Fe、Ni、Zn、Cu、Cd、Cr、Pb。分析了矿质元素在矮牡丹体内的分布规律及矮牡丹对各种元素的富集能力。结果表明:在不同器官中的矿质元素含量有显著差异, K、Mg、Mn、Ni、Cd、Cr、Pb以叶中为高, Fe、Zn、Cu分别以根、茎、叶柄中含量最高;大多数元素在叶柄中含量最低。矮牡丹对K、Mg、Mn、Fe、Zn有较强的吸收富集能力,一般叶的富集系数较其它器官为高。元素间相关分析表明:Zn、Cd、Cr、Pb、Mn、Fe、Ni、Cu之间有显著的相关性, K、Mg之间的相关性显著。此外,土壤与植物体内元素含量表现出显著的相关性。     

红花对土壤矿质元素的吸收和积累

采用电感耦合等离子体原子发射光谱法(ICP-AES)检测红花不同部位和时期以及栽培土壤中K、Ca、Na、Mg、Fe、Cu、Zn、Mn、Cr、Cd、Pb、Ba、Ni和Al元素的含量。结果表明:红花各部位矿质元素含量差异明显。在红花各不同部位中K、Fe、Zn元素在幼苗中含量最高,Ca、Mg元素在成熟叶中含量最高,Cu元素在种子中含量最高;而K和Ca元素在种子中含量最低,Mg、Fe、Cu和Zn元素分别在花、茎、成熟叶和茎中含量最低。红花的幼苗和花对K元素吸收积累明显,幼苗和种子对Cu元素吸收积累明显,Ca元素在成熟叶中积累较多,相应元素含量远比土壤中相应的元素含量高。红花对土壤不同矿质元素的吸收利用差异较大,在长期栽培红花的土壤中应注意对吸收利用多的元素结合施肥进行补充。     

超富集植物蜈蚣草中砷化学形态的EXAFS研究

采用同步辐射扩展X射线吸收精细结构(SREXAFS)技术研究了超富集植物蜈蚣草(PterisvittataL.)中As的化学形态及其在转运过程中的变化。结果表明,蜈蚣草中的As主要以As(Ⅲ)与O配位的形态存在。As(V)被植物吸收后,很快转化为As(Ⅲ),其转化过程主要发生在根部。As(Ⅲ)向地上部转运的过程中价态基本不变。在植物的根部和部分叶柄中存在少量与As-GSH相似的As-S结合方式,但是在As含量最高的羽叶中基本上未发现这种结合方式。与需要提取和分离过程的化学方法相比,采用EXAFS方法研究植物中的砷形态不需经过预分离或化学预处理就可以直接测定植物样品中元素的化学形态,因此可以避免样品预处理过程对As形态的干扰,并获得可靠的砷化学形态方面的信息。     

超富集植物蜈蚣草中砷化学形态的EXAFS研究

采用同步辐射扩展X射线吸收精细结构(SR EXAFS)技术研究了超富集植物蜈蚣草(Pteris vittata L.)中As的化学形态及其在转运过程中的变化.结果表明,蜈蚣草中的As主要以As(Ⅲ)与O配位的形态存在.As(Ⅴ)被植物吸收后,很快转化为As(Ⅲ),其转化过程主要发生在根部.As(Ⅲ)向地上部转运的过程中价态基本不变.在植物的根部和部分叶柄中存在少量与As-GSH相似的As-S结合方式,但是在As含量最高的羽叶中基本上未发现这种结合方式.与需要提取和分离过程的化学方法相比,采用EXAFS方法研究植物中的砷形态不需经过预分离或化学预处理就可以直接测定植物样品中元素的化学形态,因此可以避免样品预处理过程对As形态的干扰,并获得可靠的砷化学形态方面的信息.     

镉胁迫对秋华柳根系活力及其Ca、Mg、Mn、Zn、Fe积累的影响

以秋华柳为试验材料,采用水培试验方式,设置CK(0 mg·L^-1 Cd²⁺)、T₁(2 mg·L^-1 Cd²⁺)、T₂(10 mg·L^-1Cd²⁺)、T₃(20 mg·L^-1Cd²⁺)、T₄(50 mg·L^-1Cd²⁺)5种镉处理浓度,通过对秋华柳根系活力,叶、韧皮部、木质部和根部的镉含量,以及Ca、Mg、Mn、Zn、Fe 5种常规金属元素含量的测定,研究了不同浓度镉胁迫下秋华柳根系活力及Ca、Mg、Mn、Zn、Fe 等金属元素含量的变化.结果表明:1)秋华柳根系活力随着镉处理浓度的增加而逐渐下降,当镉浓度≥10 mg·L^-1时,根系活力与对照相比显著下降.2)随着镉处理浓度的增加,秋华柳叶中Fe的积累受到显著抑制;韧皮部Mg、Mn、Fe的积累受到显著抑制;木质部Ca、Mg、Mn、Zn、Fe 等5种常规金属元素的积累无显著性差异;根部5种常规金属元素的吸收和积累受到显著抑制,表现出镉对其他金属元素积累的拮抗作用.其中,50 mg·L^-1的镉胁迫下,根部Zn的积累量降幅最大,受Cd的抑制最明显.3)各处理组Fe的转移系数与对照相比均无显著性差异;Ca、Mg、Mn、Zn的转移系数均高于对照,且在一定的镉处理水平上差异显著.4)镉胁迫下,秋华柳根部镉的积累量与Ca的积累量呈显著负相关,与其他4种常规金属元素的积累量呈极显著负相关,说明根部常规金属元素的变化可作为秋华柳受镉毒害程度的指示之一.     

加拿大一枝黄花对土壤营养元素吸收与转运特征

选择临海沿江镇加拿大一枝黄花重度入侵区域,分别收集植物与土壤样品,研究加拿大一枝黄花对土壤中7种营养元素的吸收、转运特征。研究结果表明：7种营养元素在植物组织中的平均含量排序为：Zn〉K〉Ca〉N〉Mg〉P〉Mn。而且不同器官对同一种元素的积累存在显著差异,总体规律表现为叶和花蕾积累元素最多,其次是枝条和根状茎,根和茎则积累最少。地上器官对各元素的转移能力表现出明显差异,但各器官均对氮素有较强的转运能力,转运因子均明显高于1。地下器官（根和根状茎）对氮素有较高的富集能力,富集因子同样明显高于1。7种元素在加拿大一枝黄花不同器官的吸收转运存在着一定的促进或者拮抗作用。在花蕾、枝条和根中,磷吸收分别与Mg、Mn和Zn吸收呈现显著负相关;在花蕾中,氮的吸收和Mn的吸收呈现显著正相关;在不同器官里,K、Ca、Mg、Zn和Mn吸收之间多呈现正相关。     

刈割对蜈蚣草的砷吸收和植物修复效率的影响

以野生苗移栽的蜈蚣草为试材 ,通过盆栽试验研究了收获次数对蜈蚣草生长、砷吸收和植物修复效率的影响。结果表明 :在 3次收获中 ,随着收获次数的增加 ,不同砷浓度处理之间蜈蚣草生物量的差异逐步缩小 ;不加砷的对照处理中 ,每次收获后的砷吸收速率下降趋势 ,而在 3个加砷处理中 ,第 2次收获和第 3次收获的蜈蚣草的吸砷速率为 6 3～ 75 μg/ (plant· d)、4 4～ 5 5μg/ (plant· d) ,均显著高于第 1次收获时的吸收速率。表明多次收获并没有降低砷的积累速度。由此可见 ,通过适当增加蜈蚣草的收获次数是提高砷修复效率的一种策略     

海南稻田土壤硒与重金属的含量、分布及其安全性

采集了海南省18个市(县)代表性的稻田土壤耕作层(0—20cm)样品280个,研究了硒(Se)和5种有毒重金属元素(Hg、Cd、Cr、Pb和As)的含量、分布及其相关关系,并对Se和重金属的安全性进行评价,可为合理区划清洁且富Se稻田提供理论依据。结果表明:海南稻田土壤中Hg、Cd、Cr、Pb和As平均含量均低于国家土壤环境质量一级标准值和全国土壤背景值,以绿色食品产地环境技术条件限量标准为标准,用单项污染指数法和内梅罗综合污染指数法评价海南稻田土壤重金属的污染状况,结果都是清洁的。但以海南省土壤背景值做参比值,Hakanson潜在生态危害指数达到211.54,属于强生态危害,从潜在生态危害系数来看,Hg(102.61)和Cd(98.89)达到强生态危害,分别比海南省土壤背景值增加1.56和2.3倍,今后应注意控制Hg和Cd污染源。稻田土壤Se含量从痕量到1.532mg/kg之间,平均值为0.211mg/kg,占47.5%的稻田土壤Se含量处于中等及以上水平(>0.175mg/kg)。Se含量高的稻田土壤主要集中在东北部的海口及其周边的澄迈、定安、文昌和琼海,还有东南部的万宁和保亭。由于重金属平均含量还比较低,可暂时忽略重金属污染,故可在上述Se含量高的稻田土壤上种植富Se水稻。稻田土壤Se含量与Hg、Cd和As含量呈极显著或显著正相关,因此今后应加强研究稻田土壤Se与Hg、Cd和As的有效性及其相互作用,以便生产出绿色的富Se优质大米。     

Effects of Groundwater Irrigation and Petroleum Exploiting on Soil Arsenic Levels

In order to evaluate the combined effects of drip irrigation and petroleum extraction activities on As contamination and distribution in local soils, a total of 141 soil and 30 groundwater (GW) samples from field sites drip-irrigated with GW in Kuitun, Xinjiang, China were collected and analyzed arsenic (As) levels. Soil As levels ranged from 6.74 to 23.10 mg·kg^?1. For the field irrigated with As-loaded GW for 0.5-10 years, As levels in soils increased by 0.50-9.10 mg·kg^?1 as compared with the control soils. As levels in all top-layer (0-10 cm in thickness) irrigated soils A (0-5 cm away from dripper) were found to be higher than those in top-layer irrigated soils B (5-10 cm away from dripper). It was estimated that As in agricultural soils increased by approximately 11～3789 g·yr^?1·ha^?1 under drip irrigating, most of which in top-layer soils covering the plant roots. The widely used drip irrigation system in Kuitun enhanced the ecological and human-health threats of As via affecting its spread into soils. Furthermore, the petroleum exploiting activity further promoted As levels in local soils. Within a distance of 10～1000 m away from petroleum exploiting sites, the soil As level decreases significantly with the distance.     

Topsoil organic carbon storage of China and its loss by cultivation

Topsoil is very sensitive to human disturbance under the changing climate. Estimates of topsoil soil organic carbon (SOC) pool may be crucial for understanding soil C dynamics under human land uses and soil potential of mitigating the increasing atmospheric CO₂ by soil C sequestration. China is a country with long history of cultivation. In this paper, we present an estimate of topsoil SOC pool and cultivation-induced pool reduction of China soils based upon the data of all the soil types identified in the 2nd national soil survey conducted during 1979–1982. The area of cultivated soils of China amounted to 138 × 10⁶ ha while the uncultivated soils occupied 740 × 10⁶ ha in 1980. Topsoil SOC density ranged from 0.77 to 1489 t Cha⁻¹ in uncultivated soils and 3.52 to 591 t Cha⁻¹ in cultivated soils with the average being 50 ± 47 t Cha⁻¹ and 35 ± 32 t Cha⁻¹, respectively. Geographically, the maximum mean topsoil SOC density was found in northeastern China, being of 70 ± 104 t Cha⁻¹ for uncultivated soils and of 57 ± 54 t Cha⁻¹ for cultivated soils, respectively. The lowest topsoil SOC density for uncultivated soils was found in East China, being of 38 ± 33 t Cha⁻¹ and that for cultivated soils in North China, being of 30 ± 30 t Cha⁻¹. There is still uncertainty in estimating the total topsoil SOC of uncultivated soils because a large portion of them was not surveyed during the 2nd Soil Survey. However, an estimate of total SOC for cultivated soils amounted to 5.1 Pg. On average, cultivation of China’s soils had induced a decrease of SOC density of 15 t Cha⁻¹ giving rise to an overall pool reduction at 2 Pg. This is significantly smaller than the total SOC pool decline of 7 Pg due to cultivation of natural soils in China reported by Wu et al. (Glob. Change Biol. 2003, 9: 305–315), who made a pool estimation of whole soil profile assuming 1 m depth for all soils. As the mean topsoil SOC density of China was lower than the world average value given by Batjes (J. Soil Sci. 1996, 47: 151–163), China may be considered as a country with low SOC density and may have great potential for C sequestration under well defined management. However, the dynamics of topsoil C storage in China agricultural soils since 1980’s and the effects of modern agricultural developments on C dynamics need further study for elucidating the role of China agriculture in global climatic change.     

成土母质和种植制度对土壤pH和交换性铝的影响

研究了我国南方 3种不同成土母质发育的酸性自然土壤的 p H与交换性铝含量状况和种植不同作物后它们的变化。研究结果表明 ,自然土壤的 p H平均值大小顺序为雷州半岛地区玄武岩发育砖红壤≤粤中花岗岩发育赤红壤 <粤北石灰岩发育红壤 ,土壤交换性铝含量的平均值的大小顺序为粤北石灰岩发育红壤 <雷州半岛地区玄武岩发育砖红壤 <粤中花岗岩发育赤红壤。种植茶树将使这 3种土壤的 p H显著降低 ,交换性铝的含量则将不同程度升高 ,最为明显的是种茶后石灰岩发育的茶园土的 p H在这 3种土壤中变为最低 ,交换性铝数量的增加幅度最大。种植水稻将提高土壤的 p H和交换性铝的含量。轮作花生后土壤的 p H也将上升 ,但受施用石灰的影响土壤交换性铝的含量将降低     

安徽农田表层土壤中有机氯农药的分布及其组成

以安徽省寿县等19个地区的农田表层土壤(0～20 cm)为对象,采用超声波提取,气相色谱法/电子捕获检测器(GC/ECD)检测,分析了α-六六六、β-六六六、γ-六六六、δ-六六六、op′-DDE、pp′-DDD、α-硫丹和百菌清等8种有机氯农药(OCPs)在农田表层土壤中的分布及组成特征.结果表明： 19个取样点中8种有机氯农药残留的总含量范围为ND～23.75 μg·kg^-1,其中PP′-DDD、γ-HCH为主要污染物,平均质量浓度分别为13.83和13.49 μg·kg^-1.与1990年的调查结果相比,六六六平均值含量呈明显下降趋势;与国内外土壤相比,安徽省农田表层土壤中的六六六(HCHs)处于中等偏高的水平.安徽省农田表层土壤中OCPs、HCHs和pp′-DDD平均浓度分别为48.58、28.64和13.83 μg·kg^-1,均未超过《土壤环境质量标准》(GB 15618-1995)的一级土壤质量标准(<50 μg·kg^-1),污染较轻.     

新疆焉耆盆地辣椒地土壤重金属污染及生态风险预警

从新疆加工辣椒主产地(焉耆盆地)采集105个辣椒地典型土壤样品,测定其中As、Cd、Cr、Cu、Mn、Ni、Pb和Zn等8种重金属元素的含量。采用污染负荷指数(Pollution load index,PLI)、潜在生态风险指数(Potential ecological risk index,RI)和生态风险预警指数(Ecological risk warning index,I_(ER))对辣椒地土壤重金属污染及生态风险进行评价。结果表明:(1)焉耆盆地辣椒地土壤Cd、Cr、Ni、Pb和Zn含量的平均值分别超出新疆灌耕土背景值的1.65、1.40、1.32、3.21、6.42倍。辣椒地土壤Pb和Zn呈现重度污染,Cd、Cr和Ni轻度污染,As、Mn和Cu无污染。(2)土壤PLI平均值为1.40,呈现轻度污染。各重金属元素单项生态风险指数从大到小依次为:Cd、Ni、As、Cu、Pb、Cr、Zn。土壤RI平均值为18.40,属于轻微生态风险态势,IER平均值为-4.78,属于无警态势;博湖县辣椒地污染水平、潜在生态风险程度与生态风险预警等级最高,焉耆县污染水平、潜在生态风险程度与生态风险预警等级最低。(3)辣椒地土壤As、Cd、Pb与Zn主要受到人类活动的影响,Cr、Cu、Mn和Ni主要受到土壤地球化学作用的控制。Cd是焉耆盆地辣椒地生态风险等级最高的重金属元素,研究区农业生产过程中要防范Cd的污染风险。     

Red mud (RM)-Induced enhancement of iron plaque formation reduces arsenic and metal accumulation in two wetland plant species

Human activities have resulted in arsenic (As) and heavy metals accumulation in paddy soils in China. Phytoremediation has been suggested as an effective and low-cost method to clean up contaminated soils. A combined soil-sand pot experiment was conducted to investigate the influence of red mud (RM) supply on iron plaque formation and As and heavy metal accumulation in two wetland plant species (Cyperus alternifolius Rottb., Echinodorus amazonicus Rataj), using As and heavy metals polluted paddy soil combined with three rates of RM application (0, 2%, 5%). The results showed that RM supply significantly decreased As and heavy metals accumulation in shoots of the two plants due to the decrease of As and heavy metal availability and the enhancement of the formation of iron plaque on the root surface and in the rhizosphere. Both wetland plants supplied with RM tended to have more Fe plaque, higher As and heavy metals on roots and in their rhizospheres, and were more tolerant of As and heavy metal toxicity. The results suggest that RM-induced enhancement of the formation of iron plaque on the root surface and in the rhizosphere of wetland plants may be significant for remediation of soils contaminated with As and heavy metals.     

Environmental Monitoring of Heavy Metal Status and Human Health Risk Assessment in the Agricultural Soils of the Jinxi River Area,China

Soil contamination with heavy metals is one of the main environmental concerns in China, mainly owing to rapid industrialization and mining activities in certain areas. The current study aimed at monitoring the levels of heavy metals in soils of the industrial areas along the Jinxi River and surrounding Lake Qingshan. In addition, a health risk assessment for humans in contact with these soils was also conducted. The results revealed that the soils of the studied areas were contaminated with Cr, Cu, As, Se, Cd, Pb, and Zn and that the industrial activities were the main source of soil contamination therein. Furthermore, soils of the sites adjacent to Lin’an city exhibited higher levels of heavy metals than the upstream and Lake Qingshan sites. Most of the studied heavy metals tended to concentrate in the fine soil fractions (PM100, PM10, and PM2.5). Calculation of the hazard index (HI) revealed that humans, especially children, have potential health risks. Moreover, As was found to contribute to more magnitude of cancer risks. Thus, we concluded that the unmanaged development negatively affects the Chinese environment and human health. Furthermore, fine fractions of soil particles should be considered for risk assessment.     

Storage and sequestration potential of topsoil organic carbon in China's paddy soils

Carbon (C) storage and sequestration in agricultural soils is considered to be an important issue in the study of terrestrial C cycling and global climatic change. The baseline C stock and the C sequestration potential are among the criteria for a region or a state to adopt strategies or policies in response to commitment to the Kyoto Protocol. Paddy soils represent a large portion of global cropland. However, little information on the potential of C sequestration and storage is available for such soils. In this paper, an estimation of the topsoil soil organic carbon (SOC) pool and the sequestration potential of paddy soils in China was made by using the data from the 2nd State Soil Survey carried out during 1979–1982 and from the nationwide arable soil monitoring system established since then. Results showed that the SOC density ranged from 12 to 226 t C ha^?1 with an area‐weighted mean density of 44 t C ha^?1, which is comparable to that of the US grasslands and is higher than that of the cultivated dryland soils in China and the US. The estimated total topsoil SOC pool is 1.3 Pg, with 0.85 Pg from the upper plow layer and 0.45 Pg from the plowpan layer. This pool size is ～2% of China's total storage in the top 1 m of the soil profiles and ～4% of the total topsoil pool, while the area percentage of paddy soil is 3.4% of the total land. The C pool in paddy soils was found predominantly in southeast China geographically and in the subgroups of Fe‐accumulating and Fe‐leaching paddy soils pedogenetically. In comparison with dryland cultivation, irrigation‐based rice cultivation in China has induced significant enrichment of SOC storage (0.3 Pg) in paddy soils. The induced total C sequestration equals half of China's total annual CO₂ emission in the 1990s. Estimates using different SOC sequestration scenarios show that the paddy soils of China have an easily attainable SOC sequestration potential of 0.7 Pg under present conditions and may ultimately sequester 3.0 Pg. Soil monitoring data showed that the current C sequestration rate is 12 Tg yr^?1. The total C sequestration potential and the current sequestration rate of the paddy soils are over 30%, while the area of the paddy soils is 26% that of China's total croplands. Therefore, practicing sustainable agriculture is urgently needed for enhancing SOC storage to realize the ultimate SOC sequestration of rice‐based agriculture of China, as the current C sequestration rate is significantly lower than the potential rate.