In 1998, the International Union of Soil Sciences (IUSS) officially adopted the world reference base for soil resources (WRB) as the Union's system for soil correlation. The structure, concepts, and definitions of the WRB are strongly influenced by the FAO-UNESCO legend of the soil map of the world (1-2). At the time of itsinception, the WRB proposed 30 "Soil Reference Groups" accommodating more than 200 ("second level") soil units. WRB (3-5) was endorsed by the IUSS in 1998 and provides an opportunity to create and refine a common and global language for soil classification. WRB aims to serve as a framework through which ongoing soil classification throughout the world can be harmonized. The ultimate objective is to reach international agreement on the major soil groups to be recognized at a global scale as well as on the criteria and methodology to be applied for defining and separating them. Such an agreement is needed to facilitate the exchange of information and experience, to provide a common scientific language, to strengthen the applications of soil science, and to enhance the communication with other disciplines and make the major soil names into household names

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World Reference Base for Soil Resources

The designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. All rights reserved. Reproduction and dissemination of material in this information product for educational or other non-commercial purposes are authorized without any prior written permission from the copyright holders provided the source is fully acknowledged. Reproduction of material in this information product for resale or other commercial purposes is prohibited without written permission of the copyright holders. Applications for such permission should be addressed to the Chief,

https://library.wur.nl/isric/fulltext/isricu_i24995_001.pdf

World Reference Base for Soil Resources 2006

World reference base for soil resources 2014International soil classification system for naming soils and creating legends for soil maps

Nitrogen is the most limiting nutrient for crop production in many of the world's agricultural areas and its efficient use is important for the economic sustainability of cropping systems Furthermore, the dynamic nature of N and its propensity for loss from soil‐plant systems creates a unique and challenging environment for its efficient management Crop response to applied N and use efficiency are important criteria for evaluating crop N requirements for maximum economic yield Recovery of N in crop plants is usually less than 50% worldwide Low recovery of N in annual crop is associated with its loss by volatilization, leaching, surface runoff, denitrification, and plant canopy Low recovery of N is not only responsible for higher cost of crop production, but also for environmental pollution Hence, improving N use efficiency (NUE) is desirable to improve crop yields, reducing cost of production, and maintaining environmental quality To improve N efficiency in agriculture, integrated N management strategies that take into consideration improved fertilizer along with soil and crop management practices are necessary Including livestock production with cropping offers one of the best opportunities to improve NUE Synchrony of N supply with crop demand is essential in order to ensure adequate quantity of uptake and utilization and optimum yield This paper discusses N dynamics in soil‐plant systems, and outlines management options for enhancing N use by annual crops

Enhancing nitrogen use efficiency in crop plants

Nitrate (NO3
−) leaching from agriculturalproduction systems is blamed for the rising concentrations ofNO3
− in ground- and surface-waters around the world.This paper reviews the evidence of NO3
− leachinglosses from various land use systems, including cut grassland, grazed pastures,arable cropping, mixed cropping with pasture leys, organic farming,horticultural systems, and forest ecosystems. Soil, climatic and managementfactors which affect NO3
− leaching are discussed.Nitrate leaching occurs when there is an accumulation ofNO3
− in the soil profile that coincides with or isfollowed by a period of high drainage. Therefore, excessive nitrogen (N)fertilizer or waste effluent application rates or N applications at the wrongtime (e.g. late autumn) of the year, ploughing pasture leys early in the autumn,or long periods of fallow ground, can all potentially lead to highNO3
− leaching losses. N returns in animal urine havea major impact on NO3
− leaching in grazed pastures.Of the land use systems considered in this paper, the potential for causingNO3
− leaching typically follow the order: forest< cut grassland < grazed pastures, arable cropping < ploughing ofpasture < market gardens. A range ofmanagement options to mitigate NO3
− leaching isdescribed, including reducing N application rates, synchronizing N supply toplant demand, use of cover crops, better timing of ploughing pasture leys,improved stock management, precision farming, and regulatory measures. This isfollowed by a discussion of future research needs to improve our ability topredict and mitigate NO3
− leaching.

Nitrate leaching in temperate agroecosystems: sources, factors and mitigating strategies

Publisher Summary Volcanic ash soils have many unique physical properties that are attributable directly to the properties of the parent material, the noncrystalline materials formed by weathering, and the soil organic matter accumulated during soil formation. These properties include dark soil color, difficult clay dispersion, unique consistence, low bulk density, and high water holding capacity. Soil color is the most striking feature observed for volcanic ash soils, especially for their A horizons. Andisols typically display a large difference in texture when comparing field and laboratory determination methods. Noncrystalline materials play an important role as cementing agents and react with an excess amount of sodium hexametaphosphate. Furthermore, each of the inorganic colloids shows a different point of zero net charge, so that complete dispersion of mineral particles is virtually impossible. Andisols generally have low bulk densities that are attributable to the development of highly porous soil structure. Andisols usually show low degrees of stickiness, plasticity, and hardness that result from the abundance of noncrystalline materials and/or soil organic matter. These physical properties also provide an excellent environment for root growth. Andisols have well-developed soil structure resulting in high porosity with a range of pore sizes that retain a large amount of water with varying tensions.

Chapter 7 Physical Characteristics of Volcanic Ash Soils

We studied the forms, properties, and significance of active Al and Fe in the humus horizons of Andosols from northeastern Japan and formed a hypothesis to elucidate the surface weathering of volcanic ash.Our soil samples were divided into two groups: nonallophanic and allophanic. Nonallopha

Active aluminum and iron in the humus horizons of andosols from northeastern japan: their forms, properties, and significance in clay weathering

This paper reviews some of the benefits of polyolefin-coated fertilizers (POCFs) with accurate controlled release properties. They are helpful in developing innovative rice farming systems, such as no-till direct seeded rice with single basal fertilization and transplanting of rice seedlings with single basal fertilization. These new cultivation systems can increase fertilizer efficiency and reduce farming costs. The recovery of basal N can be increased from 22–23% with conventional broadcast application of ammonium sulfate or urea to 79% withco-situs application of polyolefin-coated urea. The no-till rice cultivation of transplanting of rice seedlings with single basal application of POCFs decreased the farming cost by 65% as compared to that of the conventional rice cultivation. Theco-situs application of POCFs containing NPK reduced nitrate leaching and nitrous oxide emissions from cultivated soils with heavy fertilization. Since POCFs have various nutrient composition and release types, a variety of application methods to agricultural and horticultural plants are being developed in Japan.

Use of polyolefin-coated fertilizers for increasing fertilizer efficiency and reducing nitrate leaching and nitrous oxide emissions

We studied various properties of nonallophanic Andosols in Japan. Our results showed that, despite many similarities between nonallophanic and allophanic Andosols, significant dissimilarities also exist between the two groups of soils. The nonallophanic Andosols used for our study formed from rhyolitic, dacitic, or andesitic volcanic ash in a humid temperature climate. They had distinctive morphological properties common to allophanic Andosols in Japan: (1) very dark, thick humus horizons, (2) granular structure in the humus horizons, (3) friable to very friable consistence, and (4) abrupt or clear smooth boundaries between humus and nonhumus horizons. The clay mineralogy of the nonallophanic Andosols was very different from that of the allophanic Andosols. In nonallophanic Andosols the clay fractions are mostly dominated by chloritized 2:1 minerals and the active Al (acid-oxalate-ex-tractable Al) consists largely or wholly of Al complexed with humus (pyrophosphate-extractable Al). The nonallophanic Andosols had mostly medium to fine textures and considerable high water retention at 15 bars. We noted that these soils have characteristically low bulk density, which is closely correlated with the organic carbon content. A remarkable accumulation of humus took place in the nonallophanic Andosols and was closely correlated with the formation of Al-humus complex. The high CEC of these soils was ascribed to the high humus content. We noted that nonallophanic Andosols are strongly acid to very strongly acid, reflecting the abundance of chloritized 2:1 minerals and the very low base saturation. Therefore, they had high Al saturation and large amounts of KCl-exchangeable Al, which is a major deterrent to plant growth in the soils. The average values of Al saturation and KC1-ex-changeable Al were 74.4% and 5.51 meq/ 100 g for humus horizon soils and 59.8% and 3.50 meq/100 g for nonhumus horizon soils, respectively. Almost all the nonallophanic Andosol samples had pH (NaF) >10 and phosphate retention > 85%. These values were significantly correlated with the acid-oxalate-extractable Al (Alo). Soils containing > 1% Alo have pH (NaF) > 9.4 and phosphate retention >85%. Therefore, we noted that Al complexed with humus has a significant amount of OH groups and is highly reactive. The analysis of pyro-phosphate-soluble components indicated that the humus associating with Al and Fe consists largely or wholly of humic acid with the highest degree of humification.

Properties of nonallophanic andosols from Japan

We conducted chemical and clay mineralogical studies on Ando soils, Brown forest soils, and Podzolic soils that had been formed mainly from felsic Towada-a (1000 B.P.) and Chuseri (4000 B.P.) ashes under different climates and vegetation. Organic carbon accumulated remarkably in the humus horizons of all the soils and contributed to the high CEC of the soils. Soil acidity was observed to be in the order of Ando soils < Brown forest soils < Podzolic soils, reflecting the differences in base saturation and clay mineralogy of these soils, and to have a tendency to decrease with depth within the same profiles. Diagnostic properties of soil samples, such as pH(NaF), phosphate absorption, pyrophosphate-soluble Fe(Fep)/dithionite-citrate-soluble Fe(Fed), pyrophosphate-soluble Al(Alp)/dithionite-citrate-soluble Al(Ald), Fep + Alp/percent clay, Fep + Alp/Fed + Ald, etc., were studied in detail. None of these chemical criteria, however, could distinguish satisfactorily among Ando soils, Brown forest soils, and Podzolic soils formed from Towada ashes. It was noted that both Fep/Fed and Alp/Ald ratios increase with decrease in the soil pH(H2O). Notable differences in clay mineralogy were observed between soil groups. Ando soils had mostly clay fractions dominated by amorphous materials consisting mainly of allophane and imogolite. Nonexpansible chloritized 2:1 mineral, which was major among the crystalline clay minerals, was present in relatively large amounts only in the surface horizons. Brown forest soils showed a diversity in clay mineralogy within the same soil profiles. The clay fractions of the surface soils showed an abundance of chloritized 2:1 mineral with high expansibility and an absence of allophane and imogolite. The subsoils showed major amorphous and paracrystalline materials with minor 2:1 layer silicates. The clay fractions of the Podzolic soils, except those of IIB horizon soils, were characterized by the abundance of chloritized 2:1 mineral varying widely in expansibility and by the absence of allophane and imogolite. The IIB horizons from Chuseri ash had clay fractions dominated by amorphous materials consisting mainly of free iron and alumina. Laminar opaline silica was found in almost all the humus horizons and was relatively abundant in the modern humus horizons of Brown forest soils. We concluded that formation of allophane and imogolite, as well as chloritization of 2:1 layer silicates, is related primarily to soil acidity. Allophane and imogolite formed only in the soils having pH(H2O) >4.9, irrespective of differences in soil groups and soil horizons. The 2:1 layer silicates were considered to have formed largely by alteration of volcanic glass. Chloritization of 2:1 layer silicates was observed to proceed with formation of allophane and imogolite. The formation of laminar opaline silica in the surface soil was considered to be suppressed not only in the Ando soils containing large amounts of allophane and imogolite, but also in the Podzolic soils, which are subject to strong leaching.

Sadao Shoji

Papers

Chapter 7 Physical Characteristics of Volcanic Ash Soils

Active aluminum and iron in the humus horizons of andosols from northeastern japan: their forms, properties, and significance in clay weathering

Use of polyolefin-coated fertilizers for increasing fertilizer efficiency and reducing nitrate leaching and nitrous oxide emissions

Properties of nonallophanic andosols from Japan

Chemistry and clay mineralogy of ando soils, brown forest soils, and podzolic soils formed from recent towada ashes, northeastern japan