摘要:

SUMMARYI have tried to show in this paper that there is a need for our expertise in areas outside agriculture, though in the immediate future employment is likely to remain largely through applications to agriculture. At the same time, in broadening our interests we must not neglect to develop our understanding of the properties of soils, their behaviour and the processes that occur in them, because it is fundamental knowledge which finds applications. A related requirement is for us to be aware of innovation in other sciences and technologies. We also have the difficult task of selling our subject to the public while maintaining our scientific integrity. I believe that our image will improve if we can do all this.As interests broaden and the range of applications increases, as I expect they will, there is a danger of a Society like ours becoming fragmented. If one part isolates itself it can become sterile because soil biology, chemistry, mineralogy, physics and pedology interact with each other. In this narrow sense we should all be holists at heart even though developments in science require us to specialize.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01267.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYExpert systems and numerical classification in general are reviewed and their relative ability to improve soil classification systems are discussed. The inductive and deductive elements of expert systems are seen as corresponding to the class establishment and class assignment phases of classification; computerized expert systems have so far been set up only for very simple assignments. To date, numerical classification has been useful in the analysis and organization of local low‐level soil data but has been largely untried at the higher global levels of soil classification because of a lack of suitable data and scientific commitment. It is concluded that numerical classification has a potentially useful part to play in establishing soil classes and generating rules for assignment in expert systems. The inference procedures and user interface of expert systems should allow more integration and realistic assignment of available data and increase the usefulness and predictability of soil information, especially if presented in a user‐friendly m

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01268.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYA Xeralf on feldspathic sandstone was sampled from a hillslope in the Mount Lofty Ranges in order to study its genesis and, in particular, the origin of the strong texture contrast. Micromorphological study demonstrated that the clay present in void argillans and papules in the B2 horizon accounted for only a small amount of the clay present. Elemental analysis of the whole soil (<2 mm) and sand, silt and clay fractions showed that there had been considerable weathering of both quartz and microcline, which were the dominant minerals present. Kaolinite is the dominant clay mineral weathering product. Illite appears to be forming from vermiculite in the A horizon. Using zircon as an internal standard, it was shown that elemental losses of SiO2and reductions in weight and volume were similar in A and B horizons. Losses of aluminium and potassium were greatest in the A horizon, least in the B3. There has been an absolute increase in the amount of iron. A possible source is iron from heavy mineral bands upslope. It was concluded from the similarity of the quartz particle‐size distributions of the A2, B2 and B3 horizons that the intensity of weathering of quartz was the same in A and B horizons. In the case of feldspar (mostly microcline), there is a greater proportion of feldspar in the fine sand and silt fractions of the A2 horizon than in the B horizon. Weathering of feldspar is greatest in the A horizon. The texture profile is principally a function of greater lateral loss of clay from the A horizons compared to the B horizon

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01269.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYThe development of soil‐water transport theory is essentially that of the application of classical physical theories that were originally derived for the perceived analogous transport of fluids, heat and electricity in continua. Much of soil‐water transport theory was developed by Buckingham at the turn of the century, but it took several decades for it to become well understood and established. An inability to solve partial differential equations with water‐dependent transport coefficients hampered a rigorous analysis and a proper interpretation of early experiments. The theory has been well proven in the laboratory, but application to the field has been less than successful because of hetereogeneity and macropores. More recent theories based on other principles have not yet received adequate testing. Future work should extend the established theory as well as develop and test new

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01270.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYThe parameter identification technique for the evaluation of the exponential unsaturated hydraulic conductivity function is described. The identification is performed using the indirect approach with an output error criterion for steady soil moisture flow through peat‐muck soil columns. The identification procedure uses the Levenberg‐Marquardt algorithm to the solution of the stated least‐square optimization problem. Examination of the evaluated parameters from laboratory experiments justifies the use of this simple identification method for the whole soil profile when the variation of the soil properties in the soil profile is not too large. For layered soil profiles with relatively large differences of soil properties between layers, the parameters of the exponential function must be evaluated separately for each

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01271.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYChanges in soil structure and macroporosity were investigated using large thin sections and image analysis of photographs taken from fluorescent resin impregnated soil blocks. In this way porosity measurements were combined with visual assessment of the distribution and type of soil pores and aggregates. Three sites were chosen on a clay soil at Cruden Bay, Aberdeenshire, and sampled throughout two growing seasons in order to characterize various stages of a 7‐year rotation.The seasonal pattern of structural change depended on the crop. During a dry period in April and May 1980, a system of cracks developed on the grass site but not on sites sown to spring barley. The changes in structure on the grass sites could mainly be attributed to changes in water content, and the resulting cycle of shrinking and swelling.After cultivation, structural changes resulting from settling were evident. Earthworm activity, especially after manure spreading, also had a pronounced effect on structure. Since many of these processes are cyclic in this environment, the resulting structural states showed a pattern of cyclic recurrenc

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01272.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYThe effects of direct drilling and ploughing on the structure and macroporosity of a clay soil at Compton Beauchamp, Oxfordshire, growing winter wheat, were studied using large thin sections (10 * 5 * 3.5 cm) and image analysis of photographs of fluorescent resin impregnated soil blocks.Composite coarse angular to subangular blocky and medium to fine granular aggregates were present in the top 3 cm of the direct drilled soil and in the top 10 cm of the ploughed soil. Settling of the soil and coalescing of these aggregates took place throughout the year under both treatments, but was most marked in the ploughed soil. In the subsoil (20 to 30 cm) most of the structural changes could be attributed to changes in the soil water content. Swelling in the winter led to the closure of the most macropores and shrinking in the spring and summer led initially to the development of vertical planar macropores and then to large cracks. Freezing and thawing in the winter created many very small subcuboidial aggregates at the soil surface which later coalesced as a result of raindrop impact.

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01273.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYThe effect of cattle manure and its humic fractions on the aggregate stability of a sandyloam soil has been studied. Cattle manure was extracted with 0.1mNaOH and the extract was dialysed to obtain a combined fulvic acid + humic acid fraction (FHA). Humic acid (HA) was precipitated from this extract, redissolved in 0.1mNaOH solution and dialysed. The manure and the organic fractions were added at two rates to a sandy–loam soil and the mixtures incubated for 2 and 17 weeks.Changes in the water‐stable aggregation of the soil were followed. In these tests, the effects on water stability of pre‐wetting with alcohol or benzene were also examined. Addition of manure, by itself, was rather ineffectual, but stability was significantly improved after two weeks of incubation by addition of the organic fractions. FHA was much more effective than HA, particularly in increasing stability after the benzene pretreatment. There were only slight changes in aggregation after 17 weeks as compared with 2

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01274.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARY136 samples were collected from soils under wet schlerophyll forest in southern Tasmania. The samples were from different depths and covered a wide range of bulk density and organic matter content. A simple linear relationship between specific volume (the reciprocal of bulk density) and low‐temperature ignition loss was established. Since the variance about the regression tended to be homogeneous with bulk density rather than specific volume, the relationship was fitted as a generalized linear model using bulk density as the dependent variable with an ‘inverse’ link and normal error assumption.For soils with loss‐on‐ignition at 375 ± 5°C (I) ranging from 1.8% to 87.9%, the bulk density, pbwas given by an equation of the forml/pb=α+βI, where α and β are constants related to the bulk densities of the mineral and organic matter of the soils studied.The existence of the simple linear relationship in the deterministic part of the model implies that these soils are made up of a mineral framework and organic matter, with neither of the two components penetrating the interstic

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01275.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

SUMMARYA model is developed which describes uptake of Ca, Mg, K, NO3, Cl, and SO4. The electrical neutrality of plant and soil are maintained through exchange of H or OH at the root‐soil interface, constant partial pressure of CO2and non‐exchangeable H reaction with the soil cation exchange complex.An important innovation in this model is the inclusion of electrical neutrality as a condition for plant, soil and soil solution. The uptake of cations is a function of both concentration of anions in solution and the suite of exchangeable cations. The model emphasizes an important role for CO2in soil chemistry and plant nutrition. Presently, the model is most useful for generating research hypotheses. Perhaps the most important hypothesis is that something about as complicated as the present model will be required to model multiple ion uptake and crop yie

ISSN:0022-4588    

DOI:10.1111/j.1365-2389.1989.tb01276.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY