RAINDROP IMPACT STRESS AND THE BREAKDOWN OF SOIL CRUMBS

The stress produced by raindrop impact, calculated as the rate of change of momentum divided by area of contact, was found to be only partly satisfactory in studies of breakdown of paper tissue and soil crumbs. The calculated stresses for failure did not agree closely with values found by other methods, and varied systematically with raindrop size. The differences were related to the effect of duration of application of stress, and to the concentration of stress around the periphery of the drop.     

从容重计算土壤总孔隙度的初步探讨

土壤总孔隙度是土壤物理的重要特征之一,据此可以计算土壤通气孔隙度,而且对于确定灌溉与排水也有重要的参考价值;在农业实践中,土壤通气性与土壤水分、导热性及作物养分等好多方面都有关,所以对总孔隙度的了解就很重要。     

DIRECT MEASUREMENTS OF THE DISTRIBUTION OF OXYGEN IN SOIL AGGREGATES AND IN COLUMNS OF FINE SOIL CRUMBS

The micro electrode of Evans and Naylor was modified to permit measurements of oxygen concentration in soil and was used to determine the distribution of oxygen in (a) agar which contained yeast and glucose and served as a model of a respiring water-saturated soil; (b) saturated spherical soil aggregates; (c) partly saturated columns of fine soil crumbs. Measurements in (a) and (b) but not in (c) agreed closely with predictions by diffusion theory. The disagreement appeared to result from water being unevenly distributed in the columns.     

MOISTURE RELEASE CHARACTERISTICS AND POROSITY OF TWELVE SCOTTISH SOIL SERIES AND THEIR VARIABILITY

Moisture release characteristics were measured in triplicate at nine sites for each of twelve soil series. Water content was linearly related to log suction for loamy soils, but a strongly curved relationship was found for dominantly sandy or clayey soils. Some series were highly variable, due mainly to textural variations within series, but texturally uniform series were less variable. The largest significant differences between series were given by the drainable pore space of B horizons, a useful property for drainage design advice; for some series drainable pore space indicated a different permeability than might have been expected from natural profile morphology.     

土壤颗粒粒径分布质量分形维数和体积分形维数的对比

用激光衍射法(LD法)和吸管法实测了60个富铁土土样的颗粒粒径分布(PSD)数据,在此基础上分别计算了颗粒的质量分形维数Dm和体积分形维数Dv。结果发现:由于LD法"低估"了黏粒部分,因此Dv相对低于Dm;由于Dv和Dm之间呈现出了一定的正相关性(p<0.001),且Dv与其实测黏粒之间呈一定的正相关性,因此Dv在一定程度上也能够用于表征土壤的某些基本属性;LD法可以对粒径进行更多的分级,但不同的粒径分级会对Dv产生影响,对粒径的再细分会导致Dv略微降低。     

土壤颗粒的体积分形维数及其在土地利用中的应用

土壤具有自相似特征或尺度不变特征。许多研究表明,土壤质量(重量)分形维数是土壤内在属性之一。但是,在计算土壤质量分形维数的推导过程中需要做一些假设,而有些假设,如不同粒级的土壤颗粒具有相同的密度等假设,已受到一些学者的批评。此外,用传统的比重法测量土壤颗粒分布不仅工作量大,且操作结果更易受人为因素的影响。鉴此,本文提出了土壤体积分形维数的概念。通过对宜兴不同土地利用方式下178个土壤样品的体积分形维数的测定发现:土壤体积分形维数和土壤质量分形维数一样,都是土壤的固有属性;土壤颗粒体积分形维数与土壤颗粒体积百分含量具有显著的对数相关关系;对茶园、菜地和农田土壤剖面上土壤颗粒体积分形维数的变化分析表明,在茶园和菜地土壤剖面上,随着土壤剖面深度的增加,土壤粘粒体积百分含量增加,土壤颗粒体积分形维数也随之增加;在农田土壤剖面上,随着深度的增加,土壤粘粒体积百分含量和土壤体积分形维数也表现出基本保持一致的变化规律。此外,农业管理措施对土壤颗粒的组成会产生影响,使土壤粘粒体积百分含量发生变化,从而使土壤颗粒体积分形维数也随之变化,如菜地土壤体积分形维数随着种植年限的增加而出现下降趋势。     

面包糠辐照杀菌工艺研究

研究了面包糠辐照杀菌工艺。结果表明 ,剂量均匀性和堆码高度与产品转向有着密切关系 ,杀菌效果与剂量呈正相关 ,色泽与剂量呈负相关。面包糠粗蛋白质、粗脂肪、碳水化合物、微量元素和 1 7种氨基酸含量辐照前后无显著差异 ;提出了适宜杀菌剂量为 6～ 1 0kGy ,可将面包糠保质期延长至 1年。     

贵州土壤的发生特性及分布规律

贵州省在云贵高原的东部,大地构造是滇桂台向斜和鄂黔台向斜的一部分.境内地形地貌复杂,山峦起伏,丘陵盆地,高山峡谷和宽谷盆地交错分布,具有显著的高原岩溶地貌特征.高原面呈阶梯状上升,海拔高度由600米左右逐渐升高到2300米左右.成土母质类型在山区以残积物和坡积残积物为主.     

SOIL CLASSIFICATION IN THE SOIL SURVEY OF ENGLAND AND WALES

The development of soil classification as a basis for soil mapping in England and Wales is briefly reviewed, and a system for future use is described. The things classified are soil profiles, and classes are defined by relatively permanent characteristics that can be observed or measured in the field, or inferred within limits from field examination by comparison with analysed samples. Profile classes are defined at four categorical levels by progressive division, and are termed major groups, groups, subgroups, and soil series respectively. Classes in the three higher categories are defined partly by the composition of the soil material and partly by the presence or absence of particular diagnostic horizons, or evidence of recent alluvial origin, within specified depths. Soil series are distinguished by other characteristics, chiefly lithologic, not differentiating in higher categories. Most of the soil groups, regarded as the principal category above the soil series, are closely paralleled in other European systems, in the U.S.D.A. system (7th Approximation with subsequent amendments), or in both. Compared with the system used hitherto, the main innovations are the use of specific soil properties to define classes at all categorical levels, and the separation at group level of classes based primarily on inherited lithologic characteristics. The soil-profile classification provides a uniform basis for identifying soil map units, considered as classes of delineated soil bodies. When a map unit is identified by the name of a profile class, it is implied that most of the soil in each delineation conforms to that class, and that unconforming inclusions belong to one or more closely related classes or occupy an insignificant proportionate area. Map units identified by land attributes not differentiating in the profile classification are termed phases.     

国外评价土壤侵蚀与土壤生产力关系的模式

土壤侵蚀减少了植物可利用的有效水分,损失了土壤的营养物质,破坏了土壤肥力结构,影响农业耕作制度,从而严重地降低了土壤生产力。土壤侵蚀与土壤生产力关系的模式(EPIC),系统地定量地表达了土壤侵蚀与土壤生产力的相互关系。这个模式包括水文、气象、水蚀和风蚀、氮磷元素、土壤温度、作物生长状况、耕作与作物残茬的处理方法、经济因子和土壤排灌与施肥等9个因子,共36个方程。为了保护和提高土壤生产力,我国需要发展这项研究工作,制定具有中国特色的土壤侵蚀与土壤生产力关系的模式。     

土壤磷酸盐位的理论与应用

要正确判断土壤中有效养料的供应状况,需要有三方面的指标。第一,供应的强度;第二,养料的数量;第三,补给的速率。所谓供应强度即是指土壤中所存在养料的能量水平。     

RELATIONSHIPS BETWEEN SOIL VOLUME USED BY ROOTS AND NUTRIENT ACCESSIBILITY

Increasing the volume of soil available to plants growing in pots increased yields of oats, ryegrass, kale, and tomatoes and decreased the intensity of rooting; it increased the supply of N more than that of P, as P uptake was correlated with root intensity and N uptake was not. Responses to P fertilizer were greater in the larger volumes of soil, but responses to applied N were less than in small volumes. Isoquants showed that, when soil volume is restricted, it is more important to apply a mobile nutrient (nitrate) than an immobile nutrient (phosphate), although the value of either nutrient in compensating for inadequate soil volume depends on the supply of the other.     

瓦碱的碱度与板结

“瓦碱”是一种碱化的浅色草甸土,零星分布于我国黄淮海平原的盐碱土地区。瓦碱的土表板平,呈灰白色,没有盐霜或很少盐霜。早春干旱时,土表易于板结,抑制幼苗生长,常引起缺苗现象,土壤板结严重时,甚至全部死亡,形成光板地。瓦碱上难以出苗,卽使出苗,苗也弱,分蘖少,但是出苗以后植株的生长此在附近盐土上好得多,因此羣众说:“瓦碱发老苗,不发小苗”。黄淮海平原内瓦碱的情况已有报导^[1-6],但少有详细的理化研究。本文拟就瓦碱苗弱和不出苗的原因及其改良原则进行初步研究。     

土壤水分状况对物质移动及作物生长的影响

水分状况不仅影响水稻土的发生性质,也影响水稻土生态系统的生产力.当稻田灌水量满足蒸发,蒸腾和渗漏需要时,水稻可获高产;如水分过多,反不利于水稻生长.太湖与华南等大面积种植双季稻地区,多因地势低平,土质粘重,土壤排水不良,引起了次生潜育作用,出现青泥层,致使三麦常受渍害,水稻迟发.从而削弱了水稻土生态系统功能的发挥.     

黄土高原水土流失与土壤退化的研究

本文研究了黄河干支流悬移质泥沙(采自1983年)和流失地土壤的颗粒组成与养分含量以及它们之间的相互关系。结果表明,黄河下拧河床淤积的泥沙以0.05—0.25毫米的颗粒为主,大于0.25亳米的颗粒组成低于1%,它们与流失地耕层土壤、黄土沉积物及风积砂的颗粒组成类同。皇甫川与窟野河的泥沙中可见到产自基岩剥蚀物的大于0.25毫米的粗颗粒,但在黄河干流中基本未见。为进一步查明黄河下游河床粗颗粒泥沙的来源,应划分大于0.25毫米粒径的粗颗粒。黄河大部分支流泥沙中的有效养分接近耕层的低限或平均水平,其中速效碘为耕层含量的2倍以上。加速坡耕地水土流失的治理,对防止土壤养分流失和减少入黄泥沙,具有重要的实际意义。