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Soil spatial variability
Soil & Tillage Research, 9 (1987) 91--94 Elsevier SciencePublishers B.V., Amsterdam -- Printed in The Netherlands
91
Book Reviews SOIL SPATIALVARIABILITY Soil Spatial Variability. Proceedings of a workshop held in Las Vegas, U.S.A., 30 November--1 December, 1984. D.R. Nielsen and J. Bouma (Editors). Pudoc, Wageningen, 1985, 243 pp. Price, US$ 18.00, Dfl. 43.80, ISBN 90-220-0891-6.
This book, as its title reflects, is the compiled proceedings and discussions held during the first meeting of the working group on Spatial and Temporal Variability of Field Soils, sponsored by Commissions I (Soil Physics) and V (Soil Genesis, Classification and Cartography) of the International Society of Soil Science (ISSS) and the Soil Science Society of America (SSSA). The book consists of invited papers and the extended ensuing discussions, the objectives of which were: (a) to evaluate and explore new statistical concepts and methods to enhance our understanding of soil variability; (b) to improve soil survey and land use techniques for quantification of soil survey maps, as well as soil and hydrological management practices of field soils. The book represents current research efforts in using newly developed geostatistics techniques in the design, analyses and interpretation of field experimental results. Special reference is given to varying soil properties and their effect on accuracy of soil survey mapping, and to management of soil water storage, water solutes and drainage regimes as well as yield analysis. This book contains, besides the editors' foreword, 11 invited presentations, each followed by the discussion it promoted. The first paper, which gives an overview on applying geostatistical techniques to soil properties analysis and their effect on crop yields, serves as the introduction to this subject. The following two presentations present the basic theory underlying spatial variability: (a) Geostatistical methods by A. Gutjah; and (b) Time series in soil science: is there life after Krigi~g? by R.H. Shumway. The authors also discuss the basic equations, the underlying assumptions and methods of describing space and time variability of soil properties, constituents concentrations and crop yields. The following articles present methodology to analyze and interpret soil data: (a) Spatial variability of soil properties by G. Uehara, B.B. Trangmar and R.S. Yost; (b) Spatial variability of soil-water properties in irrigated softs by P.J. Wierenga; and (c) Measurement and interpretation of spatially variable leaching processes by R.J. Wagenet. Two articles deal with analysis of water cycling and drainage processes: (a) Stochastic models
92 of fluid flow in heterogeneous media by L. Smith; and (b) The analysis of water quality variations in a stream-aquifer system; nonpoint source by C.J. Duffy. Several articles show how to relate soil data variability to soil survey maps and documentation, as well as to land use: (a) Soil variability and soil survey by J. Bouma; (b) Transect sampling for reliable information on mapping units by J.J. de Gruiter and B.A. Marsman; and (c) Spatial variability: its documentation, accommodation and implication to soil survey by L.P. Widing. The geostatistical approach to spatial variability deals with parameters or processes which vary randomly. Yet, unlike the traditional Fisherian approach of complete randomness, assumptions are made that a certain degree of connectedness or association between values at some proximity can be detected; namely, there is some degree of structure in the assumed randomness. The theoretical presentations and the ensuing discussion bring about some interesting insights to the reader. Theoretically, when no structure exists or the structure variance cannot be detected in the studied data, one deals with data that should be analyzed by means of traditional statistics. Yet, when some structured variance is found, the question of how far one is allowed to " s t r e t c h " the structured randomization is not discussed, and thus remains to be investigated. In the meantime, one must depend on the m e t h o d by which the data were collected, together with the user's subjective decision. The procedures presented in the book do n o t discuss the applicability of this approach to predict the variability of properties of a given soil as based on an independent data set of another, similar soil, even though the theory substantiates a basis to formulate predictive models. The theory for prediction exists only when a direct, unique correlation exists between one measured property (which was analyzed according to the statistical procedure) and the property to be predicted. However, such direct, unique relationships are rather scarce. Another problem of geostatistical technique, namely that of the scale ratios for using the presented procedures such as the ratio between the studied lengths of transects, sampled areas or soil volumes, their respective characteristic area or representative elementary volume, and their relative dimension with respect to the area under investigation, is n o t discussed. These scale ratios are often left to the subjective determination, methods and instrumentation of the researcher. In other words, it is generally suggested that the size scale of an experiment area or tested volume should be several times larger than the characteristic scale in order to properly describe the problem one has to solve, but how large these ratios should be is left to the researcher's discretion. These proceedings and discussions reflect the current state of the art in applying geostatistical techniques to field work, and point the reader to where research efforts should be directed in the future. Generally speaking, the study of spatial variability is still developing.
93 Future developments of this approach will further broaden our research scope and deepen our understanding of field phenomena, sources of variability (natural or man-made) imbedded in our observed field properties, characteristics or crop yields. Only careful, knowledgeable application of the theory will be instrumental in data interpretation, improving our understanding of natural processes, systems, and finally, enabling the developm e n t of proper physical models to describe them. This b o o k is educative in that respect, however, it does n o t serve as a good methods or theoretical text. AMOS HADAS Agricultural Research Organization Institute for Soils and Water The Volcani Center P.O. Box 6 Bet-Dagan 50-250 Israel
PADDY SOILS Physical C h e m i s t r y o f P a d d y Soils. Yu Tian-ren (Editor), Science Press,
Springer-Verlag, Heidelberg, Berlin, 1985, vi + 217 pp., 153 figs., 95 tables, price US$ 56.00, DM 150.00, ISBN: 3-540-13001-2. This b o o k presents a comprehensive treatment of the physico-chemical behavior of p a d d y soils based on fundamental research carried o u t between 1957 and 1983 in the People's Republic of China, especially in Nanjing at the Institute of Soil Science (Department of Soil Electrochemistry) belonging to the Academia Sinica. The information supplied is of great interest, and makes possible a direct and profitable access for foreign soil scientists to the original conception, m e t h o d o l o g y and experimental data of Chinese researchers, otherwise unavailable due to the barrier of language (only 5 papers quoted in this b o o k have previously been published in English or German). The b o o k is organised into 10 chapters, each of which has a large number of figures, tables and references (in total approx. 70 quotations). Few classical works (Ponnamperuma, 1972, 1978; Stolzy and Letey, 1964) were used for comparison; nevertheless, as research in China developed during years of effort, in parallel with that of other countries, the authors report a highly comprehensive coverage of all topics concerning the physical chemistry of p a d d y soils. The first 5 chapters, Oxidation--Reduction Potential; Reducing Substances; Oxygen; Iron and Manganese; and Sulfur, describe the oxido-reduction reactions. Data obtained b y original methods, in an original concept considering the oxido--reduction potential as "intensity factor" and reducible substances concentration as "capacity factor" are presented. The
91
Book Reviews SOIL SPATIALVARIABILITY Soil Spatial Variability. Proceedings of a workshop held in Las Vegas, U.S.A., 30 November--1 December, 1984. D.R. Nielsen and J. Bouma (Editors). Pudoc, Wageningen, 1985, 243 pp. Price, US$ 18.00, Dfl. 43.80, ISBN 90-220-0891-6.
This book, as its title reflects, is the compiled proceedings and discussions held during the first meeting of the working group on Spatial and Temporal Variability of Field Soils, sponsored by Commissions I (Soil Physics) and V (Soil Genesis, Classification and Cartography) of the International Society of Soil Science (ISSS) and the Soil Science Society of America (SSSA). The book consists of invited papers and the extended ensuing discussions, the objectives of which were: (a) to evaluate and explore new statistical concepts and methods to enhance our understanding of soil variability; (b) to improve soil survey and land use techniques for quantification of soil survey maps, as well as soil and hydrological management practices of field soils. The book represents current research efforts in using newly developed geostatistics techniques in the design, analyses and interpretation of field experimental results. Special reference is given to varying soil properties and their effect on accuracy of soil survey mapping, and to management of soil water storage, water solutes and drainage regimes as well as yield analysis. This book contains, besides the editors' foreword, 11 invited presentations, each followed by the discussion it promoted. The first paper, which gives an overview on applying geostatistical techniques to soil properties analysis and their effect on crop yields, serves as the introduction to this subject. The following two presentations present the basic theory underlying spatial variability: (a) Geostatistical methods by A. Gutjah; and (b) Time series in soil science: is there life after Krigi~g? by R.H. Shumway. The authors also discuss the basic equations, the underlying assumptions and methods of describing space and time variability of soil properties, constituents concentrations and crop yields. The following articles present methodology to analyze and interpret soil data: (a) Spatial variability of soil properties by G. Uehara, B.B. Trangmar and R.S. Yost; (b) Spatial variability of soil-water properties in irrigated softs by P.J. Wierenga; and (c) Measurement and interpretation of spatially variable leaching processes by R.J. Wagenet. Two articles deal with analysis of water cycling and drainage processes: (a) Stochastic models
92 of fluid flow in heterogeneous media by L. Smith; and (b) The analysis of water quality variations in a stream-aquifer system; nonpoint source by C.J. Duffy. Several articles show how to relate soil data variability to soil survey maps and documentation, as well as to land use: (a) Soil variability and soil survey by J. Bouma; (b) Transect sampling for reliable information on mapping units by J.J. de Gruiter and B.A. Marsman; and (c) Spatial variability: its documentation, accommodation and implication to soil survey by L.P. Widing. The geostatistical approach to spatial variability deals with parameters or processes which vary randomly. Yet, unlike the traditional Fisherian approach of complete randomness, assumptions are made that a certain degree of connectedness or association between values at some proximity can be detected; namely, there is some degree of structure in the assumed randomness. The theoretical presentations and the ensuing discussion bring about some interesting insights to the reader. Theoretically, when no structure exists or the structure variance cannot be detected in the studied data, one deals with data that should be analyzed by means of traditional statistics. Yet, when some structured variance is found, the question of how far one is allowed to " s t r e t c h " the structured randomization is not discussed, and thus remains to be investigated. In the meantime, one must depend on the m e t h o d by which the data were collected, together with the user's subjective decision. The procedures presented in the book do n o t discuss the applicability of this approach to predict the variability of properties of a given soil as based on an independent data set of another, similar soil, even though the theory substantiates a basis to formulate predictive models. The theory for prediction exists only when a direct, unique correlation exists between one measured property (which was analyzed according to the statistical procedure) and the property to be predicted. However, such direct, unique relationships are rather scarce. Another problem of geostatistical technique, namely that of the scale ratios for using the presented procedures such as the ratio between the studied lengths of transects, sampled areas or soil volumes, their respective characteristic area or representative elementary volume, and their relative dimension with respect to the area under investigation, is n o t discussed. These scale ratios are often left to the subjective determination, methods and instrumentation of the researcher. In other words, it is generally suggested that the size scale of an experiment area or tested volume should be several times larger than the characteristic scale in order to properly describe the problem one has to solve, but how large these ratios should be is left to the researcher's discretion. These proceedings and discussions reflect the current state of the art in applying geostatistical techniques to field work, and point the reader to where research efforts should be directed in the future. Generally speaking, the study of spatial variability is still developing.
93 Future developments of this approach will further broaden our research scope and deepen our understanding of field phenomena, sources of variability (natural or man-made) imbedded in our observed field properties, characteristics or crop yields. Only careful, knowledgeable application of the theory will be instrumental in data interpretation, improving our understanding of natural processes, systems, and finally, enabling the developm e n t of proper physical models to describe them. This b o o k is educative in that respect, however, it does n o t serve as a good methods or theoretical text. AMOS HADAS Agricultural Research Organization Institute for Soils and Water The Volcani Center P.O. Box 6 Bet-Dagan 50-250 Israel
PADDY SOILS Physical C h e m i s t r y o f P a d d y Soils. Yu Tian-ren (Editor), Science Press,
Springer-Verlag, Heidelberg, Berlin, 1985, vi + 217 pp., 153 figs., 95 tables, price US$ 56.00, DM 150.00, ISBN: 3-540-13001-2. This b o o k presents a comprehensive treatment of the physico-chemical behavior of p a d d y soils based on fundamental research carried o u t between 1957 and 1983 in the People's Republic of China, especially in Nanjing at the Institute of Soil Science (Department of Soil Electrochemistry) belonging to the Academia Sinica. The information supplied is of great interest, and makes possible a direct and profitable access for foreign soil scientists to the original conception, m e t h o d o l o g y and experimental data of Chinese researchers, otherwise unavailable due to the barrier of language (only 5 papers quoted in this b o o k have previously been published in English or German). The b o o k is organised into 10 chapters, each of which has a large number of figures, tables and references (in total approx. 70 quotations). Few classical works (Ponnamperuma, 1972, 1978; Stolzy and Letey, 1964) were used for comparison; nevertheless, as research in China developed during years of effort, in parallel with that of other countries, the authors report a highly comprehensive coverage of all topics concerning the physical chemistry of p a d d y soils. The first 5 chapters, Oxidation--Reduction Potential; Reducing Substances; Oxygen; Iron and Manganese; and Sulfur, describe the oxido-reduction reactions. Data obtained b y original methods, in an original concept considering the oxido--reduction potential as "intensity factor" and reducible substances concentration as "capacity factor" are presented. The