铵、钾同时存在时, 土壤对铵的优先吸附

The water stability of aggregates in various size classes separated from 18 samples of red soils under different managements, and the mechanisms responsible for the formation of water-stable soil aggregates were studied. The results showed that the water stability of soil aggregates declined with increasing size, especially for the low organic matter soils. Organic matter plays a key role in the formation of water-stable soil aggregates. The larger the soil aggregate size, the greater the impact of organic matter on the water stability of soil aggregates. Removal of organic matter markedly disintegrated the large water-stable aggregates (> 2.0 mm) and increased the small ones (< 0.25-0.5mm) to some extent, whereas removal of free iron(aluminium) oxides considerably destroyed aggregates of all sizes, especially the < 0.25-0.5 mm classes. The contents of organic matter in water-stable aggregates increased with aggregate sizes. It is concluded from this study that small water-stable aggregates (< 0.25-0.5 mm) were chiefly cemented by Fe and Al oxides whilst the large ones (> 2.0 mm) were mainly glued up by organic matter. Both free oxides and organic matter contribute to the formation and water stability of aggregates in red soils.     

Regionalization for rice yield estimation by remote sensing in Zhengjiang province

The role of organic matter in the formaiton and stability of soil aggregates in mulberry plantation in the Hang-Jia-Hu Plain,northern Zhejiang Province,was evaluated in this study,A positive correlation was found between water-stable aggregate contents and organic matter contents in the ulberry plantation soils,which supported the hypothesis that organic matter was the main eenting agent in formation of aggregates.A close correlation was also foud between statility ofaggregate ad organic matter contents.Regression analysis showed that total nitrogen content was also an idicator of water-stable aggregate content and stability.The aggregate size distribution indicated that the water-stable aggregats 1-0.25mm in diaeter with the decreast of aggregate sizes,and the aggregates 1-0.25mm in diameter had the maximum organic matter content.     

黑土开垦后水稳性团聚体与土壤养分的关系

Water-stable aggregates, which are an index for the evaluation of the structural properties of the soil, are affected by many factors. Zhaoguang Farm, Longzhen Farm, and Jiusan Farm were chosen as the representative study sites in the region of black soils, a typical soil resource in Northeast China. The variation in the content of 〉 0.25 mm water-stable aggregates and its relationship with the nutrients in black soil were investigated after different years of reclamation. The results showed that the 〉 0.25 mm water-stable aggregates were more in the surface than in the subsurface soil and they changed in the following order： Longzhen Farm 〉 Zhaoguang Farm 〉 Jiusan Farm. The water-stable aggregates decreased sharply at the initial stage of reclamation and then became stable gradually with time. They were significantly correlated with the contents of organic C, total N, total P, and CEC in black soil, with the correlation coefficients r being 0.76, 0.68, 0.61, and 0.81 （P 〈 0.01）, respectively; however, their relationships with available P, available K, and total K were unclear. These showed that organic matter was the cementation of soil water-stable aggregates. Increasing decompositions and decreasing inputs of organic matter after reclamation were responsible for the amount of reduction of the water-stable aggregates. Thus, to maintain good soil aggregate structure, attention should be paid to improvement of soil nutrient status, especially the supply of organic C and N.     

Aggregate Stability and Its Relationship with Some ChemicalProperties of Red Soils in Subtropical China

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and A1 oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates,especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm.In addition, aggregate stability was positively and often significantly correlated with Fed, Ald, Feo and clay content, but significantly and negatively correlated to SOC.     

中国亚热带红壤团聚体稳定性与土壤化学性质的关系

The stability of aggregates in the surface soil is crucial to soil erosion and runoff generation. Thus, to understand the stability and the breakdown mechanisms of soil aggregates as well as the relationship between aggregate stability and selected soil chemical properties, such as different forms of Fe and Al oxides, organic matter, CEC and clay content, the aggregates of slightly and severely eroded red soils derived from Quaternary red clay in subtropical China were analyzed using the routine wet sieving and the Le Bissonnais methods. The results indicated that the aggregates of the severely eroded soils were more stable than those of the slightly eroded soils. Different aggregate breakdown mechanisms resulted in different particle size distribution. The slaking from entrapped air in aggregates severely destroyed the soil aggregates, especially in the slightly eroded soils. Meanwhile, mechanical breakdown and microcracking had little effect on the aggregates compared to slaking. The fragments resulting from slaking were mainly microaggregates that increased in size with increasing clay content. The main fragment size of the slightly eroded soils was 1.0-0.2 mm, while for the severely eroded soils it was 5.0-2.0 mm and 1.0-0.5 mm. Overall, more than 20% of the fragments were smaller than 0.2 mm. In addition, aggregate stability was positively and often significantly correlated with Fe_d, Al_d, Fe_o and clay content, but significantly and negatively correlated to SOC.     

城郊结合区蔬菜种植地土壤性质特征

Human activity and urbanization result in urban-rural environmental gradients.Undersanding effect of the gradients on soil properties is necessary for management of the soils around urban areas.In this study,soil quality of some vegetable fields was characterized along an urban-rural gradient in shaoxing County,Zhejiang Province.Fifteen soilphysical and chemical properties were evaluated by using principal component analysis.Results showed that there was a great variation in the soil quality along the gradient.From rural to urban zones,soil organic matter,water-stable aggregates,cation exchangeable capacity(CEC),total N and P,and available K increased,whereas soil pH value decreased.In addition,Pb,Cu,Ni,Co,Zn and Cr in the soils tended to be accumulated toward the urban zone.Sequential chemical extraction showed that mobility of all the heavy metals in the soils tended toincrease from the rural to the urban zones.The variation of soil properties accounted for by the first principal component was significantly explained bythe difference in application rates of municipal wastes.     

利用方式和土壤肥力对土壤团聚体和养分的影响

The size distribution of water-stable aggregates and the variability of organic C, N and P contents over aggregate size fractions were studied for orchard, upland, paddy, and grassland soils with high, medium, and low fertility levels. The results showed that > 5 mm aggregates in the cultivated upland and paddy soils were 44.0% and 32.0%, respectively, less than those in the un-tilled orchard soil. Organic C and soil N in different size aggregate fractions in orchard soil with high fertility were significantly higher than those of other land uses. However, the contents of soil P in different size aggregates were significantly greater in the paddy soil as compared to the other land uses. Soil organic C, N and P contents were higher in larger aggregates than those in smaller ones. The amount of water-stable aggregates was positively correlated to their contribution to soil organic C, N and P. For orchard and grassland soils, the > 5 mm aggregates made the greatest contribution to soil nutrients, while for upland soil, the 0.25-0.053 mm aggregates contributed the most to soil nutrients. Therefore, the land use with minimum disturbance was beneficial for the formation of a better soil structure. The dominant soil aggregates in different land use types determined the distribution of soil nutrients. Utilization efficiency of soil P could be improved by converting other land uses to the paddy soil.     

阳离子表面活性剂改性水稻土对甲磺隆和苄嘧磺隆的吸附

The distribution of light fraction carbon （LF-C） in the various size classes of aggregates and its relationship to water- stable aggregates as well as the influence of cultivation on the organic components in virgin and cultivated black soils were studied by wet sieving and density separation methods. The total organic carbon （TOC） and LF-C were significantly higher （P≤ 0.05） in the virgin soils than in the cultivated soils. The LF-C in aggregates of different size classes varied from 0.9 to 2.5 g kg^-1 in the cultivated soils and from 2.5 to 7.1 g kg^-1 in the virgin soils, whereas the ratio of LF-C to TOC varied from 1.9% to 7.3% and from 5.0% to 12.2%, respectively. After being incubated under constant temperature and controlled humidity for three months, the contribution of LF-C to TOC sharply decreased to an amount （1.7%4.5%） close to the level in soils that had been cultivated for 20 to 25 years （1.3%-8.8%）. As a result, the larger water-stable macro-aggregates （especially 〉 1 mm） decreased sharply, indicating that the LF-C pool in virgin soils declined quickly after cultivation, which reduced the water stability of soil aggregates.     

长期施肥对中国亚热带水稻土土壤稳定性和机械属性的影响

Wet stability, penetration resistance （PR）, and tensile strength （TS） of paddy soils under a fertilization experiment for 22 years were determined to elucidate the function of soil organic matter in paddy soil stabilization. The treatments included no fertilization （CK）, normal chemical fertilization （NPK）, double the NPK application rates （2NPK）, and NPK mixed with organic manure （NPK＋OM）. Compared with CK, Fertilization increased soil organic carbon （SOC） and soil porosity. The results of soil aggregate fragmentation degree （SAFD） showed that fast wetting by water was the key fragmentation mechanism. Among the treatments, the NPK＋OM treatment had the largest size of water-stable aggregates and greatest normal mean weight diameter （NMWD） （P ≤ 0.05）, but the lowest PR and TS in both cultivated horizon （Ap） and plow pan. The CK and 2NPK treatments were measured with PR 〉 2.0 MPa and friability index 〈 0.20, respectively, in the Ap horizon, suggesting that the soils was mechanically unfavourable to root growth and tillage. In the plow pan, the fertilization treatments had greater TS and PR than in CK. TS and PR of the tested soil aggregates were negatively correlated to SOC content and soil porosity. This study suggested that chemical fertilization could cause deterioration of mechanical properties while application of organic manure could improve soil stability and mechanical properties.     

喀麦隆南部地区酸性土壤上增加P的施入后土壤质量和玉米生长的关系

A large array of soil properties influences plant growth response to phosphorus （P） fertilizer input in acid soils. We carried out a pot experiment using three contrasted acid soils from southern Cameroon with the following main objectives： i） to assess the main soil causal factors of different maize （Zea mays L.） growth response to applied P and ii） to statistically model soil quality variation across soil types as well as their relationships to dry matter production. The soils used are classified as Typic Kandiudox （TKO）, Rhodic Kandiudult （RKU）, and Typic Kandiudult （TKU）. Analysis of variance, regression, and principal component analyses were used for data analysis and interpretation. Shoot dry matter yield （DMY） was significantly affected by soil type and P rate with no significant interaction. Predicted maximum attainable DMY was lowest in the TKO （26.2 g pot^-1） as compared to 35.6 and 36.7 g pot^-1 for the RKU and TKU, respectively. Properties that positively influenced DMY were the levels of inorganic NaHCO3-extractable P, individual basic cations （Ca, Mg, and K）, and pH. Their effects contrasted with those of exchangeable Al and C/N ratio, which significantly depressed DMY. Principal component analysis yielded similar results, identifying 4 orthogonal components, which accounted for 84.7% of the total system variance （TSV）. Principal component 1 was identified as soil nutrient deficiency explaining 35.9% of TSV. This soil quality varied significantly among the studied soils, emerging as the only soil quality which significantly （P 〈 0.05） correlated with maize growth. The 2nd, 3rd, and 4th components were identified as soil organic matter contents, texture, and HCl-extractable P, respectively.     

黄土丘陵区植被恢复中土壤团聚体演变及其与土壤性质的关系

在野外调查与室内分析的基础上,对黄土丘陵区典型草原带植被自然恢复过程中土壤水稳性团聚体及其主要影响因子的演变规律进行了研究,并用通径分析法对二者的相互关系进行了定量分析。结果表明:随着植被演替,土壤中大粒级水稳性团聚体含量逐步增加,>5mm粒级团聚体在土壤团粒结构中占主导地位,含量占50%~80%。其次是5~2mm含量,占到10%~15%左右。不同群落之间>5mm团聚体含量在2m深土层加权平均值比较结果为:大羽茅群落>长芒草群落>铁杆蒿群落>百里香群落>香茅草群落,其中大羽茅群落是香茅草群落>5mm团聚体含量的近5倍,长芒草群落也是香茅草群落的近4倍左右。主要影响因子对团聚体直接作用系数的大小为:物理性粘粒>有机质>全氮>全铁>阳离子交换量>全量铝>游离铁>全磷>pH值>粘粒>碳酸钙。物理性粘粒、有机质和全氮是影响水稳性团聚体含量的主要因子。     

宁南山区植被自然恢复中土壤团聚体特征及其与土壤性质关系

在野外调查与室内分析的基础上，对黄土丘陵区典型草原带植被自然恢复过程中土壤水稳性团聚体及其主要影响因子的演变规律进行了研究，并用典范相关分析法对二者的相互关系进行了定量分析。结果表明：随着植被演替，土壤中大粒级水稳性团聚体含量逐步增加，〉5mm粒级团聚体在土壤团粒结构中占主导地位，含量占50％～80％。其次是5～2mm含量，占到10％～15％左右。土壤全氮与有机质含量对〉5mm与1～0．5mm两个粒级团聚体影响较大。全量铝、全量铁、物理性粘粒对2～1mm与0．5～0．25mm两个粒级团聚体影响较大。全铝、全铁、全氮、有机质是影响土壤团聚体的主要因子群，其次为粘粒、物理性粘粒。主要作用因子可划分为综合物理因子（物理性粘粒，粘粒）、综合化学因子（全氮，有机质）、综合矿质因子（铁、铝氧化物）。     

稻田植茶后土壤团聚体水稳性变化特征及影响因素分析

采用野外调查与室内分析相结合的方法,研究名山地区稻田植茶后土壤团聚体水稳性变化特征及其影响因素。结果表明:稻田及植茶后的土壤水稳性团聚体含量在各粒径及土层间表现不同,稻田、茶园5年和10年土壤水稳性团聚体含量总体上随着粒径的减小呈先降低后上升的趋势,茶园15年水稳性团聚体含量则随着粒径的减小逐渐增加。从不同土层来看,在0—20,20—40cm土层中,随着稻田植茶年限的增加,土壤团聚体含量以2mm粒径团聚体为主转变为以0.25mm粒径团聚体为主,而在40—60cm土层中,总体上0.25mm粒径团聚体占据着主要地位;在0—20cm和20—40cm土层,稻田植茶后土壤团聚体水稳性逐年下降,由大到小依次为水稻田茶园5年茶园10年茶园15年,而在40—60cm土层,土壤团聚体水稳性由大到小依次为茶园5年茶园10年水稻田茶园15年,不同土层中团聚体的水稳性与0.25mm粒径团聚体含量呈正相关关系。稻田及稻田植茶后的土壤团聚体水稳性受土壤的理化性质影响,其中受0.25mm粒径团聚体含量、土壤容重、总孔隙度的影响较显著。就所测养分而言,稻田土壤团聚体的水稳性影响因素为有机质和游离氧化铁,茶园5年的影响因素为有机质和阳离子交换量(CEC),茶园10年的影响因素为有机质、CEC和有效磷含量,而茶园15年的影响因素主要是CEC含量。     

几种侵蚀红壤中有机质和团聚体的关系

以3种侵蚀红壤（轻度、中度、严重）为供试材料,利用干湿筛法获得其不同粒径的水稳性团聚体（〉4 mm,2～4 mm,1～2 mm,0.5～1 mm,0.25～0.5 mm）,分析团聚体中有机质的分布。结果显示,随着侵蚀程度的增强,〉0.25mm水稳性团聚体的含量逐渐下降,而团聚体的分散度却依次升高;无论何种侵蚀程度,湿筛后团聚体的组成均以小粒径团聚体（〈0.25 mm）占优势。轻度和中度侵蚀的红壤,其有机质含量随着团聚体粒径的增大而增大,严重侵蚀的则相反;侵蚀红壤有机质含量和〉0.25 mm水稳定性团聚体呈显著正相关,3种侵蚀红壤团聚体对土壤有机质的贡献为轻度侵蚀〉中度侵蚀〉严重侵蚀。     

长期不同施肥对黄泥土水稳性团聚体颗粒态有机碳的影响

研究了长期不同施肥处理(化肥与秸秆配施、化肥与猪粪配施、单施化肥和不施肥)下太湖地区黄泥土耕层水稳性团聚体颗粒态有机碳含量的变化。结果表明,供试土壤水稳性团聚体组成以>2mm和2~0.25mm粒径为主,施肥下>2mm水稳性团聚体显著增加,并伴随2~0.25mm水稳性团聚体明显减少。颗粒态有机碳主要存在于>2mm水稳性大团聚体中,并随着水稳性团聚体粒径的减小而明显减少。>2mm水稳性大团聚体中的POC对施肥的响应较为敏感,以化肥与秸秆配施下该粒径水稳性团聚体中POC的积累效果最为明显。而化肥与猪粪配施则显著增加了2~0.25mm和0.25~0.053mm水稳性团聚体中的POC含量。土壤不同层次水稳性团聚体中POC的来源不同,在0~5 cm表层可能主要来源于作物根茬生物量,而在5~15 cm土层则可能跟施入的外源有机物有关。     

土地利用方式对红壤团聚体稳定性的影响

以湖南、湖北和江西3省第四纪红土母质发育的土壤为材料,应用干、湿筛法比较不同利用方式下土壤的团聚体粒级分布、平均重量直径(MWD)以及团聚体破坏率(PAD)的差异,分析在不同利用方式下土壤团聚体的分布特征以及稳定性与土壤有机碳的联系。结果表明:不同利用方式下干筛团聚体均以>5mm粒级为主,其次为<0.25mm粒级,而湿筛团聚体则以<0.25mm粒级为主。各不同利用方式土壤团聚体干、湿筛MWD值变化趋势大体一致,并且与有机质含量均呈显著正相关关系。各不同利用方式下PAD有显著差异,表现为旱地>果园>水田>茶园>林地,并且PAD与土壤有机质含量和湿筛获得的MWD值呈极显著负相关。不同有机质含量可显著影响不同利用方式下水稳性团聚体粒级分布。>5mm,1～0.5mm,0.5～0.25mm,>0.25mm粒级水稳性团聚体的含量比例均与有机质含量之间有极显著的相关关系,而5～2mm和2～1mm粒级水稳性团聚体则与有机质含量相关性并不显著。不同土地利用方式对土壤有机质含量有极大的影响,有机质含量高低表现为水田>林地>茶园>旱地>果园。     

稻草易地还土对丘陵红壤团聚体碳氮分布的影响

利用新垦坡地、熟化旱地两个定位试验的典型处理(不施肥、化肥、稻草 NP),研究稻草易地还土对丘陵红壤水稳定性大团聚体(>0.25 mm)内碳、氮分布的影响。结果表明,稻草易地还土提高了土壤大团聚体含量;团聚体粒径越大,有机碳和全氮的含量越高;与对照相比,稻草易地还土提高大团聚体内的有机碳含量10.1%~78.5%、全氮含量9.4%~63.6%(p<0.05),同时也显著提高二者在较大粒径(1~2 mm,2~5 mm)团聚体内的分配比例;与化肥处理相比,稻草易地还土提高>0.5 mm各粒级大团聚体内的有机碳含量6.5%~46.1%,也提高了0.5~1 mm,1~2 mm,2~5 mm团聚体内的全氮含量8.7%~16.1%(p<0.05)。水稳定性大团聚体对土壤碳、氮具有强富集和物理保护作用;稻草易地还土提高水稳定性大团聚体内碳、氮的含量和分配比例,是改良丘陵红壤结构、提高并协调土壤肥力的有效保育措施。     

盱眙火山岩丘陵区不同林地土壤抗蚀性评价

以盱眙火山岩丘陵区5种不同的人工林（杨树林、杨梅林、朴树林、墨西哥柏林、桃树林）为研究对象,通过对土壤水稳性团聚体特征、有机质含量等指标的测定与分析,研究了人工林对土壤可蚀性的影响。对林地土壤的抗蚀性指标进行主成分分析和相关性分析将10个抗蚀指标降到了4个:> 0.5 mm水稳性团聚体含量、 > 0.25 mm水稳性团聚体含量、团聚体稳定性指数、有机质含量。并运用回归分析建立了不同林分下土壤抗蚀性综合评价模型Y=0.073X₄+1.066X₅+9.261X₉+0.554X₁₀-64.939。结果表明杨树林地土壤的抗蚀性在5种林分中是最好的。