STRUCTURAL FEATURES OF AGGREGATES IN SOME EAST ANGLIAN SILT SOILS

Samples from field plots of silty soils in East Anglia, which were high and low in organic matter, were subjected to mild ultrasonic vibration. In soils high in organic matter particles in the 2–20 μm or 20–50 μMm size range contained most humified organic matter, whereas in soils low in organic matter, most was present in the clay sized fraction. Scanning electron micrographs of the ultrasonically separated particles showed that those from the high organic matter soils had more extensive surface coatings. Clean fragments were left after peroxide and calgon dispersion treatment.     

EFFECT OF ORGANIC CONSTITUENTS AND COMPLEXED METAL IONS ON AGGREGATE STABILITY OF SOME EAST ANGLIAN SOILS

Paired soils of high and low organic matter content from the East Anglian silts were used to determine the role of different organic constituents and complexed metal ions in relation to aggregate stability. Although leaching with periodate and borate caused some loss of stability for most of the soils, the changes were much less than those due to extraction of the soils with pyrophosphate or acetylacetone which were more effective in removing organic materials complexed with iron and aluminium. Amounts of iron and aluminium extracted were not well correlated with changes in stability. The results indicate that in these soils polysaccharides are less important to aggregate stability than organic matter bonded to the clay particles through association with aluminium or iron.     

THE ORGANIC MATTER CONTENT OF THE SAVANNA SOILS OF WEST AFRICA

Published and unpublished data on the amounts of organic matter and nitrogen in the surface soils of the West African savanna are reviewed. In general, amounts are small; the mean carbon content of soils from 605 well-drained sites was 0.68 per cent. Two important factors governing amounts of organic matter in well-drained soils appear to be the clay content and a moisture factor related to the length of the wet season and represented here by mean annual rainfall. Multiple linear regression on soil clay content and rainfall accounted for 46.5 per cent and 57.2 per cent, respectively, of the observed variability of soil carbon and nitrogen contents. These findings suggest that the low levels of organic matter in savanna soils arise from their predominantly sandy nature and from the relatively low rainfall. In poorly drained soils organic matter levels are higher but are less significantly related to clay content and rainfall. The influence of human interference and of parent material and altitude on organic matter is demonstrated in the context of geographically limited areas within the savanna for which more detailed information was available.     

土壤有机质含量对土壤水动力学参数的影响

通过测定并分析不同有机质含量的壤质土样的饱和导水率,水分特征曲线,水分扩散率及几个水分常数,阐明了土壤有机质含量与水动力学参数的关系,从动力学角度探讨了有机质影响水分运动的机理。     

THE EFFECT OF ORGANIC MATTER ON THE BULK AND TRUE DENSITIES OF SOME UNCULTIVATED PODZOLIC SOILS

Organic matter content was found to have a dominant effect on both the bulk and true densities of soil in the organic and eluvial horizons of the podzolic soils examined. The soils were stone-free, structureless, and of similar texture. The effects of organic matter on bulk density were described by the equation: A similar equation was devised for true density. Use of these equations indicated that, in the soils examined, total pore space could be predicted from organic matter content measured as per cent loss on ignition.     

晋中淡褐土中有机质对阳离子交换量的影响

本文借用多元回归和通径分析方法,讨论了晋中淡褐土耕层的颗粒组成、比表面、可变电荷和永久电荷量以及有机质含量及其与矿质部分的复合程度和结合形态等,对土壤交换容量的贡献和影响。通径分析表明土壤中有机质含量虽远比矿质颗粒为低,但仅就对CEC影响的重要性而言,有机质超过矿质颗粒,对于质地较轻的土壤尤为如此。     

卧龙自然保护区森林土壤有机质的研究

研究了四川卧龙自然保护区不同海拔高度的五种植被(常绿阔叶林、落叶阔叶林、针阔混交林、暗针叶林和高山草甸)下的土壤中有机质的含量、组成和性质。主要结果如下。1.各土壤虽然生物气候条件差异悬殊,但其腐殖质均属于富里酸型。2.落叶阔叶林、针阔混交林和暗针叶林下的粗腐殖质也属于富里酸型;红外和紫外光谱说明,它们和“成熟的”腐殖酸有明显的不同。3.土壤有机质含量与土壤物理性质和速效性养分含量有密切的关系。     

风化煤对土壤胶体特性的影响

低产土壤是阻碍新疆地区农业生产发展的重要因素之一。这些土壤大部分有机质含$低,并有不同程度地盐碱化,亚待改良。新弧地区拥有较多的风化煤、揭煤、泥炭等资源,其中一些煤呈酸性或强酸性,可溶性有机物含量也较高。近年来,该地区各地群众用这些煤制成的腐铁或将煤粉直接施用于一些低产土壤上,在水稻、玉米、小麦等各种作物上均获得了不同程度的增产效果,其中在板结土、沙性土、粘质土和盐碱土上效果比较显著。连续大t施用煤粉的土壤,群众反映,土壤的肥力也有所提高。     

SOME PHYSICAL AND CHEMICAL PROPERTIES OF SOILS IN THE BEQA'A PLAIN, LEBANON

Physical and chemical properties of red soils, white rendzina, light chestnut, dark chestnut, grey, black, and recent alluvial soils as mapped by Geze (1956) were compared statistically. No statistically significant differences were found between surface soil (0–15 cm) and upper subsoil (15–30 cm) in any properties. Red soils were significantly lower than the others in total N, CEC, and CaCO₃ content. Recent alluvial soils were high in montmorillonite probably derived from the white rendzinas. The rendzinas were significantly higher in available P and CaCO₃ than any other soil. Black and grey soils, previously classified as one category, should be separated as they were significantly different in most properties.     

有机肥对土壤磷吸附一解吸的直接影响

本文采用自行设计的一种扣除来自有机肥中磷的方法,对有机肥影响土壤磷吸附与解吸的直接作用进行了研究。结果表明,猪粪和牛粪均能明显降低两种水稻土对磷的吸附,增加磷解吸;而纤维素只有在土壤磷水平较高时才起作用。上述作用在红壤性水稻土中优于青紫泥;在同一土壤上,对磷水平高的土壤的作用明显大于磷水平低的土壤。在有机肥对土壤磷吸附解吸的直接影响中,其中的可溶性有机机物起主要作用。     

有机肥对土壤磷吸附一解吸的直接影响

本文采用自行设计的一种扣除来自有机肥中磷的方法,对有机肥影响土壤磷吸附与解吸的直接作用进行了研究。结果表明,猪粪和牛粪均能明显降低两种水稻土对磷的吸附,增加磷解吸;而纤维素只有在土壤磷水平较高时才起作用。上述作用在红壤性水稻土中优于青紫泥;在同一土壤上,对磷水平高的土壤的作用明显大于磷水平低的土壤。在有机肥对土壤磷吸附—解吸的直接影响中,其中的可溶性有机机物起主要作用。     

几种水稻土不同粒级中的有机质含量和组成

土壤有机质绝大部分与土壤矿质部分结合在一起。有机质与矿质部分结合是形成土壤良好结构的必要条件,同时也是有机质本身生物学稳定性较高的一个重要原因。研究土壤中不同粒径和比重的有机-无机复合体中有机质含量和组成,将有助于更好地了解有机质在土壤发生和土壤肥力中的作用。一些研究者通过这种途径已对一些自然植被下的土壤和早地土壤进行了研究,但对水稻土这方面的研究还未见有报道。本工作的目的在于研究不同种类和不同肥力水平的水稻土各粒级中有机质的含量和组成。     

交通对干草原土壤物理性质影响的试验研究

通过野外模拟实验，测定不同车速条件下草原交通便道相对起尘量，同时测定交通工具对草原土体结构的破坏，研究交通工具对干草原土壤物理性质的影响。研究结果表明，随着车速的增加，道路相对起尘量逐渐增加，且相对起尘量与车速之间呈现二次函数关系；在车轮的碾压作用下，土壤结构遭到破坏并形成直径在0．063～1．0mm之间的颗粒，随着碾压次数的增加，破碎颗粒的直径基本上都集中在0．125—0．18mm之间，且破碎土体总量也呈现增加趋势；车轮的碾压会导致土壤表面抗压强度增加，同时也使得土壤容重呈现增加趋势。     

百花山山地土壤中有机质的垂直分布规律

本文测定了北京百花山山地典型土壤剖面各发生层的有机质含量、腐殖酸组分、可见光谱,利用相关分析方法计算了有机质与海拔高度之间的相关系数。结果表明:有机质与海拔高度的相关系数为0.94,,呈显著相关水平;各剖面土壤腐殖质分析结果表明,该山地土壤的HA/FA值、E4/E6值随着海拔高度的升高而呈现上升趋势。     

THE ACCUMULATION OF SOIL ORGANIC MATTER AND ITS CARBON ISOTOPE CONTENT IN A CHRONOSEQUENCE OF SOILS DEVELOPED ON AEOLIAN SAND IN NEW ZEALAND

Soil organic matter was extracted by a mixture of O.IM Na₄P₂O: O.IM NaOH from a chronosequence of weakly weathered soils developed on aeolian sand, and fractionated into humin (non-extractable), humic acid, and fulvic acid. The mass of total organic carbon in the profiles, the ¹⁴C content and the ¹³C/12C ratios were also determined. The weight of total carbon increased rapidly at first and then gradually without attaining a steady state. This trend was also shown by the humin and fulvic acid fractions, but the humic acid fraction appeared to have reached a maximum after about 3000 years. The order of total weights of the organic fractions was humin > fulvic acid > humic acid. The evidence suggests that the proportions of the humic fractions formed by decomposition are related to soil differences but not to vegetation. The greater part of the plant material found in the soils appears in the humin and fulvic acid fractions.     

无机盐和有机质对毛管水上升高度的影响

在干旱、半干旱地区,地下水位和矿化程度过高,是土壤盐渍化的根本原因.地下水的盐分组成与含量,以及分散在水中的一定量的有机物质,对毛管水的上升无疑会产生影响.但是影响的程度如何?作用机制是什么?都是值得研究的问题.     

黄淮海平原盐渍土有机质消长规律的研究

7年微区试验表明，在黄淮海季风区内陆盐渍土一年两熟种植制度下，农田土壤有机质平衡含量约为1.50％。在相同的气候，土壤基础肥力，土壤质地条件下，采取不同措施，土壤有机质积累速率不同，到达土壤有机质平衡含量的时间不同。施用碳氮比大，木质素含量高的有机肥，土壤有机质积累快;施用同种有机肥，土壤有机质在达到平衡含量前，有机质的积累量与施肥量呈直线相关。为满足黄淮海平原农田稳产高产和盐渍上抑盐对土壤有机质含量的要求，采用秸秆直接还田，秸秆过腹还田或棉田种植冬牧草，发展畜牧业，增加优质粪肥施用量是提高盐渍土土壤有机质有效措施。