MULTIPLE DISCRIMINANT ANALYSIS IN SOIL SURVEY

Multiple discriminant analysis can be used to distinguish to best advantage several multivariate, more or less polythetic, classes of soil. The method allows profiles to be allocated consistently and most appropriately to existing groups for which representatives have already been chosen. The method is described in geometric terms and is applied to the allocation of profiles in both well known and little known areas, South Central England and Sabah. For the areas in England good separation between soil classes was demonstrated; in Sabah the classes of the reconnaissance survey were less distinct. Representative profiles were chosen for all existing classes and the remainder of the profiles allocated using discriminant functions. In all cases a better classification resulted in that there was less dispersion within classes and hence better separation between them. Provided conformant data can be collected in routine survey the method promises to allow a good working combination of man and machine: the soil surveyor to decide the classes desired, and the computer to handle large quantities of data and make routine allocation.     

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.     

THE RATE OF SOIL SURVEY IN BRITAIN

Typical rates of soil survey (area, length of boundary and number of observations per day or hour) are presented for routine surveys on 1:25,000 and 1:10,560 base maps by the Soil Surveys of Scotland, and of England and Wales, in five areas. The distance a soil surveyor walks between observations sites each day is highly correlated with (Area surveyed x No. of observation sites).     

土壤阳离子交换量在上海城市土壤质量评价中的应用

上海城市园林土壤的阳离子交换量(CEC)多集中在10~20cmol/kg,与土壤的理化性质:有机质、pH、黏粒含量、体积质量、通气孔隙度都存在极好的相关关系,能够综合反映土壤的肥力水平、保肥能力和缓冲能力。在城市绿地土壤的综合评价中应加入CEC这一评价指标。上海土壤CEC的控制标准可定在≥14cmol/kg。     

THE RELATION BETWEEN COST AND UTILITY IN SOIL SURVEY

This paper discusses how to compare the utility of soil maps. For three contrasting areas, in Southern England, it compares the utilities of a number of single-property and general purpose (series) soil maps, produced by free and grid survey, at map scales from 1 :20,000–1:70,000. The‘purity’of series mapping units increases with survey effort. Where the soil boundaries had fairly clear external expression free survey was superior to grid survey. On average the purity of maps by grid survey was higher than for maps by free survey at comparable survey effort. The uniformity of soil properties within mapping units was measured by relative variance (RV)= within-unit variance/total variance, (1–RV) indicates the increased precision achieved by the soil map. It increased with survey effort. For series maps by free or grid survey (1–RV) depended on how closely soil properties were associated with profile classes, and on the extent to which soil boundaries could be mapped on their external expression. Free survey was preferred at scales between 1: 100,000 and 1:30,000, when the soil boundaries could be mapped on their external expression, (1–RV) for the profile classes on which the mapping units are defined puts a ceiling to the utility of series maps (grid or free) which is already nearly achieved at map scales near 1:25,000. Except for properties very poorly associated with profile classes, single property maps do not have great advantage over series maps at medium map scales, but they attain higher values of (1–RV) at scales greater than 1: 25,000.     

RECONNAISSANCE FOR SOIL SURVEY

The total length of soil boundary on a map can be measured by counting the number of intercepts between boundaries and a randomly distributed array of sampling lines. It is thus also possible to estimate the length of the same boundaries before survey by means of a similar array of field traverses. The per cent sampling error of estimates of boundary density (boundary per unit area), is approximately the reciprocal of the square root of the number of intercepts.     

全国第二次土壤普查与土壤肥料科学的发展

建国40年，中国开展了两次全国土壤普查。本文简要回顾了第一次全国土壤普查，着重综述全国第二次土壤普查在发展土壤肥料科学方面的成就。全国第二次土壤普查是《1979-1985年全国科学技术发展规划纲要（草案）》重点科技研究项目内容这一，在科技顾问组的指导下，采用新的大比例尺地形图和遥感、测试、微型电子计算机等调查制图和化验手段，取得丰硕的科研成果。对于发展中国土壤分类科学、充实了土壤基层分类的基本单元，建立土壤测试网络、改进土壤分析方法以及普查成果在制订农业区划、科学施肥、土壤改良、基地建设等方面广泛应用，为发展农林牧业生产服务。并对土壤普查中建立的土壤肥力监测网作了论述。本文从一个侧面反映了中国土壤肥料学科的发展。     

全国土壤普查科研项目成果简介

１９７９年起，执行“六五”重点研项目全国土壤调查制图时，受到中央重视，国务院发专文要求开展全国土壤普查。该项目由基层（乡）做起，逐级汇总成县，地，省级土壤报告与图件。各省分别完成省土壤专著与系列分省图件，全国已汇总成：＜＜中国土壤与土壤资源＞＞专著与六本分大区《中国土种志》及１：１００万全国土壤图与１：４００万土壤系列图。并对全国土壤资源按质与量（面积数）分别论述其合理开发利用。     

红壤地区杉木人工林土壤肥力质量性状的演变

通过在江西省红壤地区主要林区的铜鼓县和德兴县选择不同林龄（1～28年）的杉木人工林样地采用随机网格法对土壤分层取样，并对土壤样品进行分析后的研究结果表明，从造林阶段到5～8年的幼林期，包括林地凋落物层、土层厚度、有机质、全N、CEC、BS、pH和速效N、P、K在内的林地主要土壤质量性状大幅度退化。随着树龄的增大，林地土壤质量性状开始缓慢恢复。但是，即使杉木人工林进入了主伐期，土壤质量性状的恢复程度仍选低于其初始水平。     

上海典型新建绿地的土壤质量评价

本文对上海近年来新建的典型绿地─延中、凯桥、华山、黄兴和公路浦东龙东大道、远东大道沿线的景观绿地进行了土壤现状调查。结果表明:上海典型新建绿地的土壤主要为碱性和强碱性;EC 值基本达标;有机质含量达标率在 60%以上,但含量偏低;土壤容重偏高,通气性差;阳离子代换量总体偏低。使用山泥、泥炭客土的土壤质量较好,可以满足城市绿化造景的需要。建议园林植物要 “适土适栽”、“适地适树”,要充分利用生活垃圾、污泥堆肥等有机质含量高的城市废弃物来改良土壤,对现有的城市绿化土壤质量评价指标需要进一步完善,建议增加 CEC、土壤排水能力等土壤质量评价指标。     

南京市郊区蔬菜地土壤环境质量评价

在南京市郊区选择了3片蔬菜地分布相对集中的区域,按照国家无公害蔬菜产地环境要求进行了土壤环境质量评价。评价结果显示,调查区域约40%的蔬菜地土壤符合国家无公害蔬菜产地土壤环境要求,约30%的土壤在警戒线附近,30%的土壤遭受了不同程度的污染,不符合国家无公害蔬菜产地土壤环境要求。对土壤污染的贡献率主要为Cd污染,部分地区的Hg污染也较重。     

福建省的土壤侵蚀及其防治对策

引起土壤侵蚀的原因是多方面的,自然因素只是潜在因子,而人类自觉或不自觉地对自然的过渡干扰或破坏则是造成土壤侵蚀的主要原因。严重的土壤侵蚀是福建经济发展的最大障碍。防治土壤侵蚀的根本措施是:制订能调动群众治山造林种草积极性的“惠民政策”;以小流域为单元、全面规划、因地制宜、综合治理;发展多种农村能源;合理利用土地资源;加强科学研究,提高综合治理水平。     

土壤微生物生物量作为红壤质量生物指标的探讨

本文测定了中国科学院红壤生态实验站内林地,不同施肥制度的红壤旱地和受有机农药污染地的土壤微生物生物量,探讨了土壤微物量作为红壤生态系统土壤质早让放和可行性。     

投影寻踪等级评价模型在土壤质量变化综合评价中的应用

土壤质量动态变化研究是以土壤质量评价为基础，通过土壤质量指数的时空变化来反映。因评价实体、目标、指标体系的不同，评价模式（方法）也存在差异。由于涉及多个评价指标，所以属于高维数据处理问题。针对传统评价方法存在指标权重确定没有统一的理论和计算方法的不足，本文提出用基于实码加速遗传算法（Real coding based accelerating genetic algorithm，简称RAGA）的投影寻踪等级评价（Projection pursuit grade evaluation，简称PPE）模型。通过RAGA优化PPE模型中的投影方向参数，完成高维数据向低维空间的转换，即将每个样本的多个评价指标综合成一个综合指标，用倒S曲线建立投影寻踪土壤质量综合评价模型，从而实现对土壤样本的评价。     

热带地区农场尺度土壤质量现状的系统评价

以我国热带地区海南儋州的农场为典型样区 ,按网格方法系统调查和采集了不同利用条件下的土壤剖面和表层样品。提出了一个系统的评价方法 ,将土壤质量划分为水分有效性、养分有效性和根系适应性这三个功能 ,确定了十项符合热带地区特点的土壤质量指标 ,建立各项功能和各项指标的权重。综合参考国内外研究结果 ,结合热带地区实际状况 ,建立标准评分方程 (SSF)对各项指标进行标准化。研究根据海南儋州样区土壤质量分析数据 ,在GIS支持下 ,采用系统评价模型对样区的土壤质量进行综合评价 ,并对农场尺度土壤质量的变异进行了分析。结果表明 ,系统评价模型可以在对土壤功能进行评价的基础上综合评价土壤质量 ,在GIS支持下可以方便有效的直观反映土壤质量的状况。研究区域土壤具有较好的水分供应性能 ,能够提供根系生长的适宜环境 ,存在的主要问题在于养分供应和保持能力较弱 ,但是在合理的管理措施下 ,土壤养分能够较快增加 ,土壤质量可以改善     

苏南某市农田土壤环境质量评价及其分级

以苏南工业化与城市化水平较高的某市为试验区,在对该市农田土壤环境质量和污染状况进行较为系统的调研之后,对试区农田土壤的环境质量按照国家有关标准进行综合评价并分类。结果表明:单因子污染指数最小的是六六六,其次为Pb和Cr,均无超标样点;少数传统菜地和大棚菜地土壤中DDT的污染指数接近或超过1,表明其中DDT残留量已超标,单因子污染指数最为严重的是Cd。就综合污染指数而言,除水稻土均值为0.57,低于0.7,属安全外,其他3类土壤的综合污染指数均值在0.72~0.95之间,处于警戒值。试区内约有20%以上土壤综合污染指数超过1,表明土壤受到轻度污染,这是需要引起关注的。     

CALCULATING THE ECONOMIC BENEFITS OF SOIL SURVEY

A farmer (or other users of land) achieves greatest net return by using each soil for the crop and management which gives maximum return. A soil map indicates the boundaries between soils requiring different management for optimum returns. The benefits from a soil survey increase with the ‘purity’ of the soil units as mapped. The cost of soil survey increases sharply with the ‘purity’ to be achieved. So it is necessary to recognize the stage beyond which the costs of yet more detailed soil survey are unlikely to exceed the benefits to be expected from mapping units of greater ‘purity’. This paper reports a simple algorithm for calculating the probable benefits from further soil survey to produce a map of higher ‘purity’ than so far achieved.