Takashi Kosaki

• Doctor of Agriculture, Kyoto University, Japan
• Professor at Tokyo Metropolitan University, Tokyo, Japan

Soil erosion by wind is a major cause of nutrient loss in the Sahel. The amount of nitrogen lost from the field by the wind is up to three times higher than the amount absorbed by the crop. The fallow band system (FBS) was designed to capture the windblown sediments. In the system, 5-m-wide fallow strips (fallow bands) are made in a north-south dir...

Forest management practices such as clearcutting risk increasing the leaching loss of cations and soil acidification by increasing nitrification and reducing plant uptake. To evaluate the effect of two forest management practices, clearcutting and stem girdling, on soil acidification, we quantified proton budgets by measuring ion fluxes associated...

Aims The loss of soil organic matter (SOM) has widely been reported in the tropics after changing land use from shifting cultivation to continuous cropping. We tested whether continuous maize cultivation accelerates SOM loss compared to upland rice and forest fallow. Methods: Because litter sources include C4 plants (maize in maize fields and Imper...

AimsThe loss of soil organic matter (SOM) has widely been reported in the tropics after changing land use from shifting cultivation to continuous cropping. We tested whether continuous maize cultivation accelerates SOM loss compared to upland rice and forest fallow. Methods: Because litter sources include C4 plants (maize in maize fields and Impera...

Impacts of forest management practices on soil carbon (C) and nitrogen (N) dynamics remain under debate due to complex interactions between belowground biogeochemical processes. To optimize practices that minimize soil C and N losses, we investigated the effects of management practices on soil C and N fluxes, including the leaching of dissolved org...

Being critical to achieving Sustainable Development Goals (SDGs) of the United Nations, strengthening understanding of the properties and processes of soil at national and regional scales is imperative. The necessity to realize SDGs by 2030 also inspires a greater sense of responsibility and care for soils. Sustainable management of soil health is...

Deposition of Asian dust, i.e. mica-bearing aeolian particles, throughout geological times has contributed greatly to the increased ability of soil to specifically retain radiocesium (137Cs), particularly in soils derived from mica-deficient parent materials. Allophanic Andosols, volcanic mica-deficient soils, in Japan were hypothesized to contain...

Rapid litter turnover in tropical forests and during summer seasons might be due to increases in ligninolytic enzyme activities during warmer periods. We compared ligninolytic enzyme activity [lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac)] in the organic layers of forest soils across a global climate gradient. As expected,...

Aims Land-use change of tropical forests causes loss of soil organic matter and plant productivity. Effects of fallow or plantation vegetation on soil organic matter storage need to be clarified to optimize land-use that maximizes soil organic matter storage and plant productivity. Methods We compared 30-year changes in soil carbon stocks and litt...

Soil organic carbon (SOC) dynamics after slash-burn agriculture are poorly understood in African tropical forest, though recent studies have revealed C4 grass invasion as a forest understory influences SOC dynamics after deforestation. This study aimed to quantify the relative SOC contribution of C4 and C3 plants separately through the sequential f...

Radiocesium (RCs) is selectively adsorbed on interlayer sites of weathered micaceous minerals, which can reduce the mobility of RCs in soil. Therefore, soils developed from mica-deficient materials (e.g. serpentine soils) may have a higher risk of soil-to-plant transfer of RCs. Soils were collected from three serpentine soil profiles; Udepts in Oey...

In humid regions, soil acidification is a natural process accelerated by acidic deposition and intensive agriculture. Proton budget analysis has revealed that excess cation uptake by plants is the dominant proton source in most forest ecosystems. However, translocation of temporary acids (e.g., organic acids) and distribution of root biomass contri...

Many surface soils in Japan may experience more frequent and intense drying–rewetting (DRW) events due to future climate changes. Such DRW events negatively and positively affect microbial biomass carbon (MBC) through microbial stress and substrate supply mechanisms, respectively. To assess the MBC immediately after DRW and during the incubation wi...

The forest–savanna transition zone is widely distributed on nutrient-poor Oxisols in Central Africa, and a population explosion has led to the rapid cultivation of these vegetation types in this zone. To reveal and compare the effects of short-term (3 years) cultivation on the soil nutrient status of the forest and savanna vegetation in this area,...

Low molecular weight organic acids (LMWOAs) are key pools regulating carbon (C) stabilization and destabilization in tropical forest soils. The variation in clay contents and mineralogy between sites or within a profile might regulate magnitude of LMWOA sorption and biodegradation in tropical soils poor in short-range-order (SRO) Al/Fe oxides. We a...

The forest–savanna transition zone, which contains nutrient-poor soils (Oxisols), is found throughout central Africa. To evaluate the effect of deforestation on soil phosphorus dynamics, which regulate the plant growth in this area, we quantified the relationship between phosphorus (P) and carbon (C) in different fractions and compared their relati...

There are contrasting results regarding the effect of repeated drying–rewetting (DRW) cycles on microbial biomass carbon (MBC), and two fundamentally different mechanisms have been postulated. The first is a microbial stress mechanism which will reduce MBC as stress-sensitive microbes die, and the second is a substrate supply mechanism which will i...

The fates of carbon (C) input to soils widely vary under different nutrient availability. In this study, both initial substrate-induced respiration (SIR) rates and substrate-induced growth responses to nitrogen (N) and/or phosphorus (P) additions were investigated together because the two approaches had been assessed separately in previous studies....

Soil fertility was measured in contrasting regions of sub-Saharan Africa, i.e., Tanzania, Rwanda, western D. R. Congo, Cameroon, Nigeria, Burkina Faso, Ivory Coast, and others, with special reference to geological and climatic conditions. The general properties of the soils in each region of equatorial Africa could be summarized as follows: when co...

Tropical sandy soils are highly susceptible to acidification as a consequence of intensive farming. We analyzed the dominant processes of acidification and neutralization in a sandy soil of cropland system in northeast Thailand. Proton budgets in the soil (Typic Ustipsamments) were quantified for a sugarcane field and a mango plantation by measurin...

Many surface soils, including those that have rarely experienced dry conditions, may experience more frequent and/or intense drying–rewetting (DRW) events in the future. Such DRW events are likely to induce large and sudden CO2 pulses derived from increased substrate availability owing to their release from non-biomass soil organic C (SOC) and micr...

Microbial nitrogen (N) immobilization following the addition of organic materials to soils regulates soil N availability, which affects plant growth and N leaching from soils. In this study, the potential for microbial N immobilization was evaluated by short-term incubation experiments following the addition of available carbon (C) under non-limiti...

Slow release of added phosphate in soils is of fundamental importance for plant nutrition and pollution in aqueous environments. The diffusion of phosphate in micropores and mesopores after desorption from the inside surface of pores is the most likely mechanism for the slow release. There are limited experimental data on the effects of micropores...

This book contains a collection of 14 case studies from around the globe that illustrate the impact of a range of land-use changes on the physical, chemical and biological characteristics of soils and provide a snapshot of the challenges faced in ensuring sustainable soil management in tropical and savannah environments. This book is not a comprehe...

The wet-dry cycles of soil primarily drive carbon (C) dynamics in dry croplands that mainly experience sporadic rainfall events. We evaluated the in situ short-term (hourly) dynamics of soil carbon dioxide (CO2) efflux and microbial biomass, to compare the significance of a single rainfall event with/without C substrate to reveal the effects of a s...

On the basis of field and laboratory measurements of the dynamics of soil organic matter (SOM) in Japan, Thailand, Indonesia, Kazakhstan, and Ukraine having different soil pH levels, we postulate that soil acidity plays an important role in the accumulation of SOM through two processes. Firstly, the amount of potentially mineralizable C (C 0) in th...

The recent increase in the number of tourists has raised serious concerns about grassland degradation by tourism activities in Inner Mongolia. Thus, we evaluated the effects of tourism activities on the vegetation and soil in Hulunbuir grassland. We identified all the plant species, measured the number and height of plant and plant coverage rate, a...

Organic acids released by lichen play an important role in mineral weathering and podzolization in the Boreal–Tundra transition zone of Canada; however, importance of low-molecular-weight organic acids in the soil carbon (C) cycle in the black spruce–lichen forests remains unclear. We examined soil solution composition and mineralization kinetics o...

The soils in Saskatchewan in the Central Interior Plains of Canada vary from semi-arid to sub-humid climates and between parent materials deposited during deglaciation. The Brown and Black Chernozem soils are the zonal soils of the grassland in the semi-arid to sub-humid climates. However, formation of intra-zonal soils depends on parent materials,...

Cellulose decomposition experiments were conducted under field conditions to analyze the effects of climatic and soil properties on rates of organic matter decomposition in temperate and tropical forests. The mass loss rates of cellulose filter papers buried in the soil surface were measured to estimate the respiratory C fluxes caused by cellulose...

Modern soil science was introduced just after the reformation of Japan in 1867 by Max Fesca, Oskar Kellner and other German teachers together with their Japanese students, who were traced back to Justus von Liebig and thus started studying and teaching soils based on agrogeology and agricultural chemistry. After the German teachers left, the gradua...

Physiochemical and microbial properties of soils at the Environmental Horticulture and Forestry Farm of Chiba University（ hereafter referred to as Numata Farm）, investigated by the six universitiesʼ joint soil research event in September 2011, are reported in this paper. The comparisons between the current and previously reported data（2011 and 2002...

We investigated the activities of ligninolytic enzymes, lignin peroxidase (LiP), manganese peroxidase (MnP), and laccase (Lac), in forest floor layers collected from temperate and tropical regions in Japan, Thailand, and Indonesia. The effects of pH and Mn levels on the ligninolytic enzyme activities in the forest floor layers were analyzed. The ac...

In the humid tropics, conversion of forests into croplands has the potential to alter the flux of dissolved organic matter (DOM) and influence C balance and N availability in soil. Sites located on a clay-rich Ultisol in Thailand and a highly acidic and sandy Ultisol in Indonesia were used to quantitatively evaluate effects of land use change on fl...

The distribution coefficient of cesium (Cs) (Kd) was investigated for clays which were collected from upland forest soils developed from granites and Paleozoic shales in Japan. They were divided into three size fractions, coarse (2.0–1.0 µm), medium (1.0–0.2 µm), and fine-clay fractions (

Phosphorus deficiency is one of the largest constraints to crop production in tropical African soils owing to low native soil P and the high P fixation capacity of highly weathered soils. To achieve better soil P management, it is necessary to evaluate the effects of land management on soil P dynamics and P budget. We conducted a 4-year cultivation...

Leaching of dissolved organic matter (DOM) is an important process in the translocation and stabilization of organic carbon (C) and in influencing nitrogen (N) availability in forest soils. The roles of DOM in soil carbon and nitrogen cycles were evaluated by quantifying the fluxes of dissolved organic carbon (DOC) and nitrogen (DON) entering and l...

In Sub-Saharan Africa, conservation of available soil N during early crop growth, when N loss by leaching generally occurs, is important to improve crop productivity. In a dry tropical cropland in Tanzania, we assessed the potential role of soil microbes as a temporal N sink–source to conserve the available soil N until later crop growth, which gen...

a b s t r a c t Evaluation of carbon dynamics is of great concern worldwide in terms of climate change and soil fertility. However, the annual CO 2 flux and the effect of land management on the carbon budget are poorly understood in Sub-Saharan Africa, owing to the relative dearth of data for in situ CO 2 fluxes. Here, we evaluated seasonal variati...

Low molecular weight (LMW) organic compounds in soil solution are easily biodegradable and could fuel respiration by soil microorganisms. Our main aim was to study the mineralization kinetics of monosaccharides using C-radiolabelled glucose. Based on these data and the soil solution concentrations of monosaccharides, we evaluated the contribution o...

The nitrogen content of agricultural soils collected from throughout Japan was characterized according to the form and availability, and with reference to land use and soil types. In total, 147 plow layer soil samples were collected - 80 from paddy fields and 67 from upland fields to include various soil types. Soil N was separated into four fracti...

In the previous field-scale wind erosion studies in the Sahel, mass flux profiles, mass transport rates, and soil mass balance in the cultivated field and fallow land were estimated without measuring the mass flux at 0- to 0.05-m height where most soil particles are expected to move. We first addressed these deficiencies using a 3-yr field study in...

Cesium (Cs)-selective sites in smectite were multiplied by means of potassium (K) saturation and wet-dry repetition treatment, which may reduce ^<137>Cs transfer from soil to plants. Japanese soils with different clay mineralogies, smectitic paddy soils and allophanic cropland soils, were treated; then the solid-liquid distribution coefficients (Kd...

Wind erosion is a major contributor to desertification in the Sahel. Although three effective countermeasures for wind erosion (i.e. ridging, mulching with post-harvest crop residue, and windbreaks) have been proposed, they are not practical for Sahelian farmers. Therefore, we designed a new land management practice, termed the “Fallow Band System,...

Leaching of dissolved organic carbon (DOC) from the organic (0) horizon plays an important role in soil C cycles and formation of soil organic matter. The magnitude of DOC fluxes in throughfall and soil solutions was quantified in three tropical secondary forests affected by the former selective logging in East Kalimantan, Indonesia. The sites were...

In the Sahel, determining the effects of wind erosion on soil fertility and soil carbon balance is crucial for achieving sustainable agriculture and for carbon sequestration, respectively. We designed the Aeolian Materials Sampler (AMS) to measure the surface flux of soil nitrogen and carbon, which limit crop production as well as water in the Sahe...

Soil acidification is one of major pedogenetic processes under tropical forests, however, proton sources and weathering reactions vary from soil to soil. The dominant soil-acidifying processes, along with their spatial heterogeneity, under tropical forests were analyzed for five Indonesian soils formed, from different parent materials (serpentine a...

The wetting–drying cycles of soil primarily drive carbon (C) and nitrogen (N) dynamics in tropical monsoon climates. We evaluated the in situ short-term C and N dynamics and the effect of soil texture during a wetting–drying cycle in relation to hourly microbial dynamics. Two croplands of differing soil textures (clay [THc] and sand [THs]) in Thail...

Short-term dynamics of soil respiration rates over time measured at hourly intervals during less than 12 h after microbial substrates were added to soils can be classified into first-order, zero-order and growth-associated types. To simulate the zero-order type respiration rates, a model using Michaelis-Menten kinetics is proposed, because this kin...

Low molecular weight (LMW) organic compounds in soil solution could be important substrates for heterotrophic soil respiration. The importance of LMW organic compound mineralization in heterotrophic soil respiration needs to be confirmed for different types of soils. The concentrations of LMW organic compounds in soil solution and mineralization ki...

Soil microbes are considered to be an important N pool in dry tropical croplands, which are nutrient poor. To evaluate the N contribution of soil microbes to plant growth in a dry tropical cropland, we conducted a maize cultivation experiment in Tanzania using different land management treatments (no input, plant residue application, fertilizer app...

Soil microbes are an essential component of most terrestrial ecosystems; as decomposers they are responsible for regulating nutrient dynamics, and they also serve as a highly labile nutrient pool. Here, we evaluated seasonal variations in microbial biomass carbon (MBC) and nitrogen (MBN) as well as microbial activity (as qCO2) for 16 months with re...

To examine the effect of NPK application on the growth, yield and nutrient uptake by sugarcane (Saccharum officinarum L.) and to elucidate the limiting factors of cultivation on sandy soils in the tropics, a field experiment was carried out in 2005 on a sandy soil in Khon Kaen, Northeast Thailand. Six treatments were applied: NPK (300 kg ha⁻¹ each)...

Field measurements of soil respiration were carried out under various bioclimatic conditions in Eurasia. The data were simultaneously analyzed to identify factors that control the in situ soil respiration and its temperature and moisture dependence, together with the laboratory incubation data to support the analysis of field data. We obtained the...

It is widely recognized that the efficiency of substrate C use in acid and/or disturbed soils by soil microorganisms is relatively low based on the observation that metabolic quotients (qCO2) are usually high in these soils. In the present study, threshold concentrations of glucose, at which the ratio of respiration to assimilation by soil microorg...

Leaching of dissolved organic carbon (DOC) from the organic horizon is an important process involved in translocation and stabilization of organic matter in forest soils. Despite there being many studies on the DOC fluxes in temperate forest soils, very little information is available in tropical forest soils. The roles of DOC leaching in soil orga...

Humus forms may vary in different forest stands, but the local influence of trees upon soil microbial and faunal activities is still imperfectly known. Optical methods could help to discern processes of litter transformation and formation of organo-mineral assemblages, allowing a better diagnostic of tree influences upon humus-soil development. The...

Soil microbial biomass C, the metabolic quotient ([qCO2] respiration rate to biomass ratio) and growth characteristics, such as lag period and specific respiration increment after the addition of glucose to the soil, were determined for 19 surface soils varying widely in pH and land use under different climatic conditions in Asia. The soil samples...

To understand the dynamics of soil organic matter in humid regions in Asia, several soil and meteorological properties were tested to estimate the amounts of potentially mineralizable organic carbon (PMC) and nitrogen (PMN) as well as recalcitrant organic carbon (ROC) and nitrogen (RON). Eighty-nine surface soil samples were collected in Thailand,...

Continuous cultivation has the potential to accelerate soil acidification. The influence of cultivation on soil acidification was evaluated by calculating proton budget in a soil–vegetation system including solute leaching, vegetation uptake and organic matter decomposition in cropland and adjacent forest in Thailand and Indonesia. In the forests,...

Wind can erode fertile topsoil and reduce soil fertility. Evaluating the effect of wind erosion on soil fertility is crucial to achieve sustainable agriculture in areas suffering from desertification caused by wind erosion. To estimate soil loss and associated soil nutrient loss by wind erosion, flux of coarse organic matter (COM) (defined here as...

Geophagy is defined as the practice of eating soil and is observed worldwide. In Tanzania, edible soil sticks called pemba are consumed mainly by pregnant women, but the physiological function of eating pemba has not yet been elucidated. The objectives of the present study were to evaluate the physicochemical properties of edible soil sticks compar...

The transformation of hydroxy-interlayered vermiculite (HIV) to vermiculite in humid temperate soils may involve the gradual alteration of illitic minerals. However, it is difficult to detect such minor and progressive changes using conventional methods. We measured the amount of the frayed edge site (i.e. the weathering front of illitic minerals)...

SummaryA frayed edge site can be a significant indicator of alterations in illitic minerals in soils evolving under different climates, because illitic minerals are known to enlarge the frayed edge site through vermiculitization. We investigated the relative abundance of this site in soil clays (<2 μm) using Radiocaesium Interception Potential (RIP...

Luvisols and Cambisols are two types of sub-boreal soils, which are known as continental and humid-ocean types of soils in deciduous forests respectively. Morphological features of soil, which are frequently used as the main argument in solum diagnostics, are subjective and do not give final decision that continental Cambisols are a specific type o...

It is essential to determine the relationship between soil chemical and mineralogical properties and soil response to acid load to understand the acid-neutralizing capacity and cation behavior of different ecosystems. For 46 soil samples from a subsurface horizon in humid Asia, that is, Japan, Thailand and Indonesia, exchangeable cations, total bas...

Soils in humid Asia exhibit relatively incipient mineralogical characteristics because of the dominant steep slopes, crust movement and volcanic activity compared with many tropical soils on stable plains. In the present study, the relationship between the mineralogical and chemical properties of these soils was investigated with special reference...

A regional evaluation of the soil organic carbon (SOC) dynamics for the chernozem zone in northern Kazakhstan is now vitally important for agricultural and environmental policy making. The objectives of the present study were: (1) to predict spatial and temporal variability in C input as crop residues using multi-temporal MODIS satellite images, (2...

Radiocesium interception potential (RIP), a quantitative index of a frayed edge site of micaceous minerals, was investigated on test clay minerals (illite, kaolinite, montmorillonite and vermiculite) and soil clays formed under different pedogenetic conditions in the Kinki district of Japan and in northern Thailand to elucidate the effect of pedoge...

Agricultural production in southern Kazakhstan has experienced significant economic difficulty since the 1980s, accelerating agronomic problems including the salinization of irrigated fields. A thorough understanding of the up-to-date situation of soil salinization and its effects on cropping systems is necessary in order to establish sustainable a...

The contribution of different proton sources to pedogenetic soil acidification was evaluated for three Japanese forest soils, i.e. ando soil, podzolic soil and brown forest soil in relation to the respective soil forming processes. Soil acidification rate and net proton generation were quantified based on the theory of proton budget for the respect...

To understand the dynamics of soil organic matter (SOM) in the Eurasian steppe, several soil and meteorological properties were tested in order to estimate the amounts of potentially mineralizable organic carbon (PMC) and nitrogen (PMN). Total 41 surface soil samples were collected in Ukraine and Kazakhstan from cropland, forest, grassland, and des...

The ratio of respiration to assimilation of glucose in soil microorganisms is reported to increase as the concentrations of added glucose increase. To explain this, a conceptual model has already been proposed in which the glucose acquired by soil microbes is incorporated into either storage compounds or storage compounds together with structural c...

To elucidate factors contributing to plant growth in a mangrove plantation, the height of mangrove trees (Rhizophora apiculata BL.) was measured in addition to relative ground level and soil properties in an abandoned shrimp pond in Thailand. Tree height was measured at 1,853 points in the 25 ha experimental site. Soil was sampled from 74 points an...

Diagnosis of soil is essential for rational soil management in agricultural fields. Estimation of soil properties based on soil sampling is inevitable, because sampling is limited to a portion of soil both in space and time. The objectives of this research were to estimate spatial and temporal variation of soil properties, and to propose a rational...

To optimize regional crop rotation systems to mitigate soil organic carbon (SOC) depletion, monitoring the spatial and temporal variation of the SOC budget is of major importance. This study evaluated the influence of crop rotation and topography on the spatial and temporal variation of the SOC budget under cereal cropping in northern Kazakhstan us...

To analyze the potential risk of secondary soil salinization along with the development of irrigation agriculture, an extensive soil survey was conducted with special reference to the salt concentration in deeper layers of soils in different regions of Central Asia (Kazakhstan and Uzbekistan). In total, 41 soil profiles from different scales of dis...

This study aimed to improve the accuracy of spatial prediction for soil organic matter, potential mineralizable carbon (PMC) and soil organic carbon (SOC), using secondary information, namely topographic and vegetation information, in northern Kazakhstan. Secondary information included elevation (ELEV), mean curvature (MEANC), compound topographic...

The practice of monoculture land use without regard for local environmental conditions can accelerate organic matter decomposition. In the agriculturally and environmentally important soils of northern Kazakhstan, which primarily support cereal cultivation, economic rewards might encourage such monoculture practices. The purpose of this study was t...

Soil salinization is a serious problem in the arid and semi-arid regions of Central Asia. To address the problems, we analyzed the dynamics and distribution patterns of salts in both rice-based and cotton-based cropping fields in selected farms of southern Kazakhstan and Uzbekistan with special emphasis on the dynamics of gypsum, which had a lower...