Alfred E. Hartemink

Digital Soil Map of the World

Increased demand and advanced techniques could lead to more refined mapping and management of soils. Soils are increasingly recognized as major contributors to ecosystem services such as food production and climate regulation (1, 2), and demand for up-to-date and relevant soil information is soaring. But communicating such information among diverse audiences remains challenging because of inconsistent use of technical jargon, and outdated, imprecise methods. Also, spatial resolutions of soil maps for most parts of the world are too low to help with practical land management. While other earth sciences (e.g., climatology, geology) have become more quantitative and have taken advantage of the digital revolution, conventional soil mapping delineates space mostly according to qualitative criteria and renders maps using a series of polygons, which limits resolution. These maps do not adequately express the complexity of soils across a landscape in an easily understandable way.

Digital soil mapping with limited data

There has been considerable expansion in the use of digital soil mapping technologies and development of methodologies that improve digital soil mapping at all scales and levels of resolution. These developments have occurred in all parts of the world in the past few years and also in countries where it was previously absent. There is almost always a shortage of data in soil research and its applications and this may lead to unsupported statements, poor statistics, misrepresentations and ultimately bad resource management. In digital soil mapping, maximum use is made of sparse data and this book contains useful examples of how this can be done. This book focuses on digital soil mapping methodologies and applications for areas where data are limited, and has the following sections (i) introductory papers, (ii) dealing with limited spatial data infrastructures, (iii) methodology development, and (iv) examples of digital soil mapping in various parts of the globe (including USA, Brazil, UK, France, Czech Republic, Honduras, Kenya, Australia). The final chapter summarises priorities for digital soil mapping.

Nutrient stocks, nutrient cycling and soil changes in cocoa ecosystems - a review

It is generally assumed that agricultural systems with perennial crops are more sustainable than systems with annual crops. Soil erosion is negligible and perennial crops have more closed nutrient cycling. Moreover, inorganic fertilizers are used more commonly in cash crops such as perennial crops so that soil fertility decline and nutrient mining are less likely to occur. In the past decades, considerable research has been devoted to the quantification of nutrient stocks and nutrient cycling in agro-ecosystems. This article reviews the main stocks and flows of nutrients in cocoa ecosystems for several cocoa-growing regions in the tropics. Most of the nitrogen is found in the topsoils, and less than 10% of the total N stock is in the cocoa and shade trees. Nitrogen in the annual litter fall is about 20 to 45% of the total N in the vegetation and 2 to 3% of the total N in the soil. The accumulation of potassium is low in cocoa ecosystems, and in most systems the total amount in the biomass is equivalent to the available P content in the topsoil. Phosphorus in the annual litter fall is about 10 to 30% of the total P in the vegetation and 10 to 40% of the available P in the soil. Potassium is a major nutrient in mature cocoa. Stocks of exchangeable K in the topsoil vary from 100 to 550 kg ha −1 , and high K levels in the soil correspond to high K levels in the vegetation and litter. Partial nutrient balances were calculated that compares the losses, addition, and transfer of N, P, and K. The nutrient balance is negative in the absence of inorganic fertilizers, especially for K. Rainwash and litter fall are key components in the cycling of nutrients of cocoa ecosystems. The amount of nutrients transferred by rainwash is less than 8 kg ha −1 for N and P but varies from 38 to more than 100 kg ha −1 year −1 for K. Most soils under cocoa had a lower fertility when compared to primary forest, although soil chemical properties seem to settle at equilibrium levels. This review shows that large amounts of nutrients in cocoa ecosystems are transferred each year and that such nutrient cycling is essential for maintaining cocoa production.

Digital soil mapping: bridging research, environmental application, and operation

Digital Soil Mapping is the creation and the population of a geographically referenced soil database. It is generated at a given resolution by using field and laboratory observation methods coupled with environmental data through quantitative relationships. Digital soil mapping is advancing on different fronts at different rates all across the world. This book presents the state-of-the art and explores strategies for bridging research, production, and environmental application of digital soil mapping.It includes examples from North America, South America, Europe, Asia, and Australia. The chapters address the following topics: - exploring new environmental covariates and sampling schemes - using integrated sensors to infer soil properties or status - innovative inference systems predicting soil classes, properties, and estimating their uncertainties - using digital soil mapping and techniques for soil assessment and environmental application - evaluating and using legacy soil data - protocol and capacity building for making digital soil mapping operational around the globe.

GlobalSoilMap: Toward a Fine-Resolution Global Grid of Soil Properties

Abstract Soil scientists are being challenged to provide assessments of soil condition from local through to global scales. A particular issue is the need for estimates of the stores and fluxes in soils of water, carbon, nutrients, and solutes. This review outlines progress in the development and testing of GlobalSoilMap —a digital soil map that aims to provide a fine-resolution global grid of soil functional properties with estimates of their associated uncertainties. A range of methods can be used to generate the fine-resolution spatial estimates depending on the availability of existing soil surveys, environmental data, and point observations. The system has an explicit geometry for estimating point and block estimates of soil properties continuously down the soil profile. This geometry is necessary to ensure mass balance when stores and fluxes are computed. It also overcomes some limitations with existing systems for characterizing soil variation with depth. GlobalSoilMap has been designed to enable delivery of soil data via Web services. This review provides an overview of the systems technical specifications including the minimum data set. Examples from contrasting countries and environments are then presented to demonstrate the robustness of the technical specifications. GlobalSoilMap provides the means for supplying soil information in a format and resolution compatible with other fundamental data sets from remote sensing, terrain analysis, and other systems for mapping, monitoring, and forecasting biophysical processes. The initial research phase of the core project is nearing completion and attention is now shifting toward establishing the institutional and governance arrangements necessary to complete a full global coverage and maintaining the operational version of the GlobalSoilMap . This will be a grand and rewarding challenge for the soil science profession in the coming years.

Assessing Soil Fertility Decline in the Tropics Using Soil Chemical Data

Soil fertility decline is perceived to be widespread in the upland soils of the tropics, particularly in sub‐Saharan Africa. Most studies have used nutrient balances to assess the degree and extent of nutrient depletion; these have created awareness but suffer methodological problems as several of the nutrient flows and stocks are not measured. This chapter focuses on the assessment of soil fertility decline using soil chemical data (pH, organic C, total N, available P, cation exchange capacity (CEC), and exchangeable cations) that are routinely collected in soil surveys or for the assessment of fertilizer recommendations. Soil fertility decline can be assessed using a set of properties from different periods at the same site or from different land‐use systems with the same soils. The former is easier to interpret; the latter can be rapidly collected but differences may be due to inherent differences and not have resulted from soil management. This study provides an analytical framework for the assessment of soil fertility decline and shows pitfalls and how they should be handled. Boundary conditions are presented that could be used in future studies on soil fertility management and crop productivity in the tropics.

Soil fertility decline in the tropics: with case studies on plantations.

Human population and soil degradation plantation agriculture soil fertility decline - theoretical considerations annual crops perennial crop plantations forest plantations sugar cane plantations case 1 - sugar cane plantation, Papua New Guinea case 2, sisal plantations, Tanzania. (Part contents.)

Soil chemical and physical properties as indicators of sustainable land management under sugar cane in Papua New Guinea

The sustainability of land management was assessed for a sugar cane plantation using soil y1. 3.2 g kg . A significant decline in available P was found in Fluvisols 40 to 32 mg kg and y1. Vertisols 37 to 25 mg kg . Significant changes in soil chemical properties were mostly confined to the topsoil and differences between Fluvisols and Vertisols were relatively small. Changes in soil physical properties were assessed by measuring bulk density and infiltration under sugar cane and adjoining natural grassland areas. Bulk density and water intake were similar under natural grassland and within the sugar cane rows. The interrow had a significantly higher bulk density due to wheel traffic, which caused very low water intake. Bulk densities at which infiltration rates were severely reduced were slightly higher in Fluvisols than in Vertisols but for both Major Soil Groupings an increase of only 0.2 Mg m y3 was critical. Changes in soil chemical and physical properties indicated that land management is not sustaining the resource base for sugar cane cultivation in the long-term. Threshold values in soil chemical properties were not reached and they were in 1996 still favourable for sugar cane cultivation. The soil compaction, however, directly affect the sugar cane as it seriously reduce rooting. It is concluded that routine

Digital mapping of soil organic carbon contents and stocks in Denmark.

Estimation of carbon contents and stocks are important for carbon sequestration, greenhouse gas emissions and national carbon balance inventories. For Denmark, we modeled the vertical distribution of soil organic carbon (SOC) and bulk density, and mapped its spatial distribution at five standard soil depth intervals (0−5, 5−15, 15−30, 30−60 and 60−100 cm) using 18 environmental variables as predictors. SOC distribution was influenced by precipitation, land use, soil type, wetland, elevation, wetness index, and multi-resolution index of valley bottom flatness. The highest average SOC content of 20 g kg−1 was reported for 0−5 cm soil, whereas there was on average 2.2 g SOC kg−1 at 60−100 cm depth. For SOC and bulk density prediction precision decreased with soil depth, and a standard error of 2.8 g kg−1 was found at 60−100 cm soil depth. Average SOC stock for 0−30 cm was 72 t ha−1 and in the top 1 m there was 120 t SOC ha−1. In total, the soils stored approximately 570 Tg C within the top 1 m. The soils under agriculture had the highest amount of carbon (444 Tg) followed by forest and semi-natural vegetation that contributed 11% of the total SOC stock. More than 60% of the total SOC stock was present in Podzols and Luvisols. Compared to previous estimates, our approach is more reliable as we adopted a robust quantification technique and mapped the spatial distribution of SOC stock and prediction uncertainty. The estimation was validated using common statistical indices and the data and high-resolution maps could be used for future soil carbon assessment and inventories.

Leaf litter decomposition of Piper aduncum, Gliricidia sepium and Imperata cylindrica in the humid lowlands of Papua New Guinea.

No information is available on the decomposition and nutrient release pattern of Piper aduncum and Imperata cylindrica despite their importance in shifting cultivation systems of Papua New Guinea and other tropical regions. We conducted a litter bag study (24 weeks) on a Typic Eutropepts in the humid lowlands to assess the rate of decomposition of Piper aduncum, Imperata cylindrica and Gliricidia sepium leaves under sweet potato (Ipomoea batatas). Decomposition rates of piper leaf litter were fastest followed closely by gliricidia, and both lost 50% of the leaf biomass within 10 weeks. Imperata leaf litter decomposed much slower and half-life values exceeded the period of observation. The decomposition patterns were best explained by the lignin plus polyphenol over N ratio which was lowest for piper (4.3) and highest for imperata (24.7). Gliricidia leaf litter released 79 kg N ha−1, whereas 18 kg N ha−1 was immobilised in the imperata litter. The mineralization of P was similar for the three species, but piper litter released large amounts of K. The decomposition and nutrient release patterns had significant effects on the soil. The soil contained significantly more water in the previous imperata plots at 13 weeks due to the relative slow decomposition of the leaves. Soil N levels were significantly reduced in the previous imperata plots due to immobilisation of N. Levels of exchangeable K were significantly increased in the previous piper plots due to the large addition of K. It can be concluded that piper leaf litter is a significant and easily decomposable source of K which is an important nutrient for sweet potato. Gliricidia leaf litter contained much N, whereas imperata leaf litter releases relatively little nutrients and keeps the soil more moist. Gliricidia fallow is more attractive than an imperata fallow for it improves the soil fertility and produces fuelwood as additional saleable products.