Sub-surface colluviation: An example from West Sussex, UK

Reported here is an unusual type of colluvial deposit whose associated transport pathway involves a substantial subsurface component. The deposit represents the downslope transfer of nitrogenenriched agricultural soil into a seminatural woodland soil, creating significant localised eutrophication. The amount of material involved was c. 65 kg, and covered an area of c. 7.7 m². It appears that the deposition was rapid, and the outcome of a single transport event. The absence of more general observations prevent the calculation of an aerally-representative long-term rate of operation. The status of this process in the general modification of temperate hillslopes is still a matter for conjecture.     

Curtailment of muddy floods in the Sompting catchment, South Downs, West Sussex, southern England

Abstract. Muddy floods due to runoff are a widespread problem on the South Downs of southern England and are associated with increased growing of autumn-sown cereals over the last two decades. The 10.6 km² Sompting catchment has been monitored over the 12-year period 1990/91–2001/02. A housing estate at the lower end of the catchment that was frequently inundated by muddy floods in the late 1980s and early 1990s has not been flooded since the winter of 1993/94, even during the heavy rainfall events of October and November 2000. This is a result of the ameliorative measures put in place in the early 1990s, primarily the reversion of some winter cereal fields to permanent grassland (set-aside). Other land management changes helped, for example, some parts of the catchment were put down to short-term grass leys and small dams were constructed to impound runoff. Flooding of the housing estate occurred when more than 30% of the catchment was covered by eroded fields, which contributed runoff to the valley floors leading down to the housing estate. The length of continuous down-valley flow was greater in the early 1990s compared with later years. The introduction of grassland reduced the risk of flooding not only by reducing the area contributing to runoff, but also by stopping valley floor flows linking up. Such measures to alleviate runoff, erosion and flooding fit well with policies proposed in the recent report by the UK Policy Commission on the Future of Farming and Food.     

Management of difficult soils for intensive winter cereals in central England: a farm case study

Abstract. After satisfactory results during the mid-1970s, winter cereal yields and profitability were disappointing during 1979–81 on a Buckinghamshire farm with Ragdale series stagnogley soil. Poor soil physical conditions were diagnosed and then improved by soil loosening and mole drainage. Other inputs and management remained intensive but essentially constant. Three-year average winter wheat and barley yields rose from 5.6 and 4.9 t ha for 1979–81 to 7.4 and 6.8 t ha respectively for 1982–84. A large part of this increase could be attributed to improved soil management. The observations were made as a farm case study and not as a replicated field trial. They may nevertheless be of interest to others and of national relevance as similar soils occupy some 30% of the cereal area in England.     

The classification and mapping of potassium reserves in soils of England and Wales

Potassium was extracted from samples of 21 surface soils and nine subsoils using a calcium-saturated cation exchange resin and concentrated HCI under reflux. Most of the important arable soils of England and Wales were represented in the samples. The two methods permitted determination of the amounts and rates of release of exchangeable K, K fixed in the weathered periphery of vermiculitic and illitic minerals, and K in the unweathered core of mica minerals. Potassium reserves in the soils were classified as High, Medium or Low according to the rate of release of fixed K and the amount and rate of release of mica K. The K reserves of soils in England and Wales could be mapped by soil series using this method of classification. Such mapping would provide data on the extent and availability of reserves in both the short term (i.e. to a crop over a growing season) and long term.     

The effects of the 1976 drought on chalk grassland in Sussex,England

The exceptionally severe drought during the spring and summer of 1976 resulted in almost 40% bare ground compared with c. 5% in normal summers. The high rainfall of September caused considerable regrowth and decreased bare ground to almost its normal autumnal value. Many species had significantly lower covers in 1976 than in normal summers. Many of these and some others significantly increased their cover during the wet autumn. It is considered that unpredictable drought stress is an important factor of chalk grassland and causes large but temporary fluctuations in species abundance and floristic composition.     

The importance of inorganic carbon in soil carbon databases and stock estimates: a case study from England

Many national and regional databases of soil properties and associated estimates of soil carbon stock consider organic, but not inorganic carbon (IC). Any future change in soil carbon stock resulting from the formation of pedogenic carbonates will be difficult to set in context because historical measurements or estimates of IC concentration and stock may not be available. In their article describing a database of soil carbon for the United Kingdom published in this journal, Bradley et al. [Soil Use and Management (2005) vol. 21, 363–369] only consider data for organic carbon (OC), despite the occurrence of IC‐bearing calcareous soils across a substantial part of southern England. Robust techniques are required for establishing IC concentrations and stocks based on available data. We present linear regression models (R² between 0.8 and 0.88) to estimate IC in topsoil based on total Ca and Al concentrations for soils over two groups of primary, carbonate‐bearing parent materials across parts of southern and eastern England. By applying the regression models to geochemical survey data across the entire area (18 165 km²), we estimate IC concentrations on a regular 500‐m grid by ordinary kriging. Using bulk density data from across the region, we estimate the total IC stock of soil (0–30 cm depth) in this area to be 186 MtC. This represents 15.5 and 5.5% of the estimated total soil carbon stock (OC plus IC) across England and the UK, respectively, based on the data presented by Bradley et al. [Soil Use and Management (2005) vol. 21, 363–369]. Soil geochemical data could be useful for estimating primary IC stocks in other parts of the world.     

The historical ecology of lakenheat warren in suffolk,England: A case study

This is a case study of the former use and management of Lakenheath Warren, a grass-heathland of 930 ha in Suffolk, England. It is suggested that the incidence of sheep and rabbit grazing, phases of cultivation, and the use of the site for military training, may have had a significant effect on the origins and development of the present-day and animal communities, which have been the subject of detailed ecological investigations.     

基于时序NDVI数据的中国红壤丘陵区土地覆被分类研究

选择位于红壤丘陵区的中国最大淡水湖——鄱阳湖及其整个流域作为研究对象,应用2000年SPOT4-VEGETATION的时序NDVI数据,结合野外实地考察和研究区相关资料,探讨了一种以地表覆盖物的光谱响应及其季节性变化特征为主要依据、以色彩作为类别命名基础的土地覆被分类新方法,构建了一个包含6个一级类别和14个二级类别的土地覆被分类方案。在此基础上,利用PCI软件中ISODATA算法以及ArcMap的空间分析功能对研究区土地覆被进行了非监督分类和判定。结果显示基于时序NDVI数据的ISODATA法分类能够较好地刻画不同土地覆被类型之间的差异性,流域的现状覆被以常绿覆被(主要是针叶林)和作物以及作物-树-草混合覆被为构成主体,三者共占鄱阳湖流域面积的94.97%。     

Integration of biophysical and economic data using an expert system: results from a case study in northern Australia

Abstract. Biophysical and economic data from numerous sources are integrated using the ALES expert system. A systematic approach to data collection and evaluation procedure is presented. The collection of management data is emphasized if management and crop yield data are to be adequately correlated. Different land utilization types are evaluated for numerous land mapping units. The results show that direct comparison of land mapping units is possible both within and between different land utilization types. Use of the model enabled objective relationships to be developed between biophysical criteria, crop productivity and management, allowing economic measures of performance to be routinely determined for large databases. The study shows that land mapping units with the most favourable physical suitability class may not necessarily have the largest net return and that the best lands are determined not only by their ability to produce high yields but also their ability to achieve them at the least cost.     

草原土壤：分布、分类与演化

草原土壤系指草原、湿草原和森林草原植被下形成的富含有机质、盐基饱和度高的暗色土壤.世界上此类土壤面积约900万km2,我国约76万km2,是粮食生产的重要基地.本文比较了国际上草原土壤分类.不论俄罗斯或中国,均腐土开垦以后土壤有机质开始下降迅速,而后减缓,逐步达到与当地生物气候相适应的水平.所以至今仍保持一定厚度的黑土层.在均腐土资源的利用和保护上,一方面应保持其有机质平衡,另一方面更重要的是严防水土流失,以保证其生产能力.     

The particle-size distribution in soils: Problems of the methods of study,interpretation of the results,and classification

The analysis of literature sources and a database on soil physical properties collected by the Department of Soil Physics and Amelioration of Soils of the Faculty of Soil Science of Moscow State University made it possible to compare three major constituents of the particle-size distribution analysis (PSDA): (a) the classification of soil separates with respect to their sizes and the classification of soil textures, (b) the procedures used to prepare soil samples for the PSDA, and (c) the specificity of the determination of the particle-size distribution by different methods. It was shown that there are good physical and statistical grounds for the conversion of data on the particle-size distribution from the Russian classification system into other systems. Much larger problems are related to the pretreatment of soil samples for the PSDA. The diversity of existing methods, classification schemes, and technical devices based on different physical principles (sedimentation and laser diffractometry) should be taken into account in the analysis and quantitative conversion of particle-size distribution data from a given classification system into another system. The Russian classification of soil textures and soil particle-size groups developed by N.A. Kachinskii has certain advantages and can be easily converted into other systems. In the choice of a particular system, it is important to take into account the goals of the study. Agreement between soil scientists concerning the major constituents of the PSDA has to be reached.     

Predicting regional emissions and near-field air concentrations of soil fumigants using modest numerical algorithms: a case study using 1,3-dichloropropene

Soil fumigants, used to control nematodes and crop disease, can volatilize from the soil application zone and into the atmosphere to create the potential for human inhalation exposure. An objective for this work is to illustrate the ability of simple numerical models to correctly predict pesticide volatilization rates from agricultural fields and to expand emission predictions to nearby air concentrations for use in the exposure component of a risk assessment. This work focuses on a numerical system using two U.S. EPA models (PRZM3 and ISCST3) to predict regional volatilization and nearby air concentrations for the soil fumigant 1,3-dichloropropene. New approaches deal with links to regional databases, seamless coupling of emission and dispersion models, incorporation of Monte Carlo sampling techniques to account for parametric uncertainty, and model input sensitivity analysis. Predicted volatility flux profiles of 1,3-dichloropropene (1,3-D) from soil for tarped and untarped fields were compared against field data and used as source terms for ISCST3. PRZM3 can successfully estimate correct order of magnitude regional soil volatilization losses of 1,3-D when representative regional input parameters are used (soil, weather, chemical, and management practices). Estimated 1,3-D emission losses and resulting air concentrations were investigated for five geographically diverse regions. Air concentrations (15-day averages) are compared with the current U.S. EPA's criteria for human exposure and risk assessment to determine appropriate setback distances from treated fields. Sensitive input parameters for volatility losses were functions of the region being simulated.     

Resurrection of Soil Surveys: a case study of the acid sulphate soils of The Gambia.

Abstract. Statistical techniques are used to test and re-interpret archival data from soil surveys of the tidal floodplain of the River Gambia. Key soil attributes include salinity, ripeness and the acid sulphate hazard. Soil taxonomic units derived by cluster analysis of all the validated data do not correspond with the intuitively-defined soil series of the original surveys. However they do correspond with practical soil mapping units, and distinguish areas of quite different geotechnical behaviour, kinds and degrees of salinity and acid sulphate hazard.     

The basaltic soils of SE Nigeria: properties, classification and constraints to productivity

Four basaltic profiles located in northern Cross River State of Nigeria are described and characterized. The soils are classified as Typic Tropohumult and show strong acidity, low effective CEC, low N and available P. Organic matter levels of the surface soils are high. All the soils are well drained in spite of high YO clay, which is apparently kaolinitic, with moderate to high A1 saturation. Higher agricultural productivity of these soils is restricted by low effective CEC and strong acidity. Measures to combat these problems are suggested.     

Fertility of tropical soils under different land use systems—a case study of soils in Tabasco,Mexico

Increasing deforestation in Mexico in the past 40 years has led to significant land use changes. It is important to establish land use systems that allow for the necessities of an increasing population and the conservation of soil fertility in the long term. In this study, we investigated the influence of different land use forms on soil fertility in Tabasco, SE Mexico. We chose two different commonly used pastures (Cynodon plectostachyus and Brachiaria decumbens) and a succession forest. We characterised soil fertility by physico-chemical parameters (texture, density, pH, P, Corg., Ntot., cation exchange capacity (CEC)) as well as by biological parameters, such as litter decomposition, microbial biomass and earthworm community. To estimate litter decomposition we used leaves of Gliricidia sepium, a common fodder tree in the region. The three land use systems had very similar soil chemical characteristics. All three can be characterised as acidic (pH between 4.1 and 5.3) with a high content of organic matter and total nitrogen. However, the three land use systems differed significantly with respect to their soil biological characteristics. Earthworm density as well as litter decomposition were significantly lower under B. decumbens than in the other soils. In all land use systems, the participation of macrofauna and mesofauna accelerated litter decomposition rate significantly as compared with decomposition with microfauna and microflora alone.We extracted two components of the pool of data by main component analysis. The acidity component explained mainly the microbial litter decomposition rate. The rate of litter decomposition – with participation of soil meso- and macrofauna – could be explained by the humus component. We assume that biological parameters were more suitable to characterise differences between the different land use systems. The use of C. plectostachyus and succession forest showed a positive effect on soil fertility.     

Character analysis and numerical classification in a wheat collection from Sicily

Summary A study was undertaken using 48 characters observed in plants, spikes and seeds in order to determine the amount of information of different characters and their taxonomic importance in tetraploid wheat samples from Sicily. A classification of the material was also attempted using similarity indices.The most important characters appear: leaf pubescence, glume colour and length, and seed colour. Using all characters, similarity indices among samples were computed and a classification was worked out. This classification, which is very similar to those proposed by various scientists, produces hierarchical groups, showing different levels of merging, and offers very interesting hypotheses on the evolution of the Siciliandurum wheats.

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Merkmalsanalyse und numerische Klassifikation an einer Weizen-Kollektion aus Sizilien

Zusammenfassung Untersucht wurden 48 Pflanzen-, Ähren- und Kornmerkmale an Proben tetraploider Weizen aus Sizilien, um den Informationsgehalt unterschiedlicher Merkmale und ihren taxonomischen Wert zu erfassen. Anhand von Ähnlichkeitsindices wurde auch eine Klassifikation des Materials vorgenommen.Als bedeutsamste Merkmale erscheinen: Blattpubeszenz, Spelzenfarbe und-länge und Kornfarbe. Auf der Grundlage aller Merkmale wurden Ähnlichkeitsindices zwischen den Proben errechnet und eine Klassifikation ausgearbeitet. Diese ist den Klassifikationen anderer Wissenschaftler sehr ähnlich, ergibt hierarchische Gruppen mit unterschiedlichem Ähnlichkeitsniveau und ermöglicht die Aufstellung einer interessanten Hypothese zur Evolution der sizilianischendurum- Weizen.

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Compaction by wheels: a numerical model for agricultural soils

A simple, numerical model was developed to predict changes in soil dry bulk density resulting from the passage of wheels. The model uses Söhne's solutions to estimate stress increases, and empirical isotropic stress-strain data to predict soil volume changes. Predicted and measured increases in bulk density, resulting from the passage of various agricultural vehicles, compared favourably at most depths but the model underestimated the compaction of loose soil in close proximity to underlying dense layers. The model may also be used to compare the compaction caused by various types and arrangements of wheels and to assess the contribution made by a particular input variable. Examples of such uses are given.     

The estimation of losses of potassium and magnesium from chalky soils in southern England: laboratory studies

Abstract. Ten chalk topsoils (0-25 cm) were repacked into columns in the laboratory. After leaching similar to one year's throughflow in the field, loss of K was equivalent to between 9 and 74kg K/ha. This represented between 3 and 30% of the initial exchangeable K with which loss was poorly correlated. Loss was dependant on the soil solution concentration and was inversely proportional to potassium buffer power.
The loss of magnesium in the same columns was between 10 and 22 kg Mg/ha (6-21% of the initial exchangeable Mg). Magnesium loss was poorly correlated with exchangeable Mg.
When KCl fertilizer was incorporated into the soils, the increase in leaching of potassium was 1–35% of the K addition. Application to the top of the column resulted in less leaching than when the K was incorporated. Leaching of magnesium was increased by up to 5 kg Mg/ha.
Potassium leaching may be delayed by the underlying A/C horizon but pure chalk, with an extremely low buffer power for K, has little ability to retain K. Extremely calcareous topsoils were the most leaky although in practice it is the organic chalk soils on which it is most difficult to attain adequate K levels. On all chalk soils, maintenance of a high K level with K fertilizer is likely to cause unnecessary long-term leaching losses. Annual, rather than biennial, fertilizer applications are to be preferred.