Four soil profiles located near a copper smelter in Poland were investigated for the distribution and chemical fractions of Cu, Pb, and Zn and their mobility in relation to soil properties. Contamination with heavy metals was primarily restricted to surface horizons and the extent of contamination was 7‐ to 115‐fold for Cu, 30‐fold for Pb, and 6‐fold for Zn as compared with subsurface horizons. In the less‐contaminated fine‐textured soil, the metals were distributed in the order: residual >> Fe–Mn oxides occluded > organically complexed > exchangeable and specifically adsorbed, while the order for sandy soils was: residual > organically complexed > Fe–Mn oxides occluded > exchangeable and specifically adsorbed. The contaminated surface horizons of these profiles showed no consistent pattern of metal distribution. However, the common features of highly contaminated soils were very low percentage of residual fraction and the dominance of the NH4OAc extractable fraction. The sum of mobile metal fractions was generally <10% in subsurface horizons, while in the contaminated surface horizons these fractions made up 50% of the total metal contents. Soil properties contributed more to the relative distribution of the metal fractions in the studied profiles than did the distance and direction to the source of pollution. The amounts of metal extracted by 0.01 M CaCl2 accounted for only a small part of the same metals extracted by NH4OAc. The mobility indexes of metals correlated positively and significantly with the total content of metals and negatively with the clay content.

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Soil aggregation serves as storage and cycling of soil organic carbon (SOC) and total nitrogen (TN), which are essential for the functioning of terrestrial ecosystems. Thus, aggregate and particle associated SOC and TN in 0‐ to 10‐cm and 10‐ to 20‐cm layers were estimated for five land uses: rainfed cultivation (RF), agroforestry (AF), open pasture (OP), silvopasture (SP), and irrigation (IR) each with five replications within a watershed in Ethiopia. OP had the highest WSA > 2 mm (88·7%) and SOC associated with macroaggregates (20·0 g kg−1), which were significantly higher (P < 0·0001; P = 0·0017 for WSA and SOC, respectively) than that in other land uses in 0‐ to 10‐cm depth. SOC associated with both macroaggregates and microaggregates decreased with depth. Macroaggregates contained higher SOC than microaggregates in both layers under all land uses. AF had the highest SOC associated with microaggregates (2·6 g kg−1) followed by that in SP (2·3 g kg−1), indicating its potential to stabilize SOC more than other land uses. TN associated with macroaggregates followed a trend similar to that of SOC. OP had also significantly higher SOC (P = 0·0001) and TN (P = 0·0004) associated with sand particles than RF, AF, and IR. Sand‐associated SOC and TN were the highest in uncultivated systems. Moreover, the higher SOC concentrations associated with clay particles in soils under OP, SP, and AF showed that grass‐based and tree‐based systems are rich in stable SOC as clay‐associated SOC has higher residence time than that associated with sand or silt fractions. Copyright © 2013 John Wiley & Sons, Ltd.

Restoration of degraded soils is a development strategy to reduce desertification, soil erosion and environmental degradation, and alleviate chronic food shortages with great potential in sub-Saharan Africa (SSA). Further, it has the potential to provide terrestrial sinks of carbon (C) and reduce the rate of enrichment of atmospheric CO 2 . Soil organic carbon (SOC) contents decrease by 0 to 63 per cent following deforestation. There exists a high potential for increasing SOC through establishment of natural or improved fallow systems (agroforestry) with attainable rates of C sequestration in the range of 0Á1 to 5Á3 Mg C ha À1 yr À1. Biomass burning significantly reduces SOC in the upper few centimeters of soil, but has little impact below 10 to 20 cm depth. The timing of burning is also important, and periods with large amounts of biomass available generally have the largest losses of SOC. In cultivated areas, the addition of manure in combination with crop residues and notill show similar rates of attainable C sequestration (0 to 0Á36 Mg C ha À1 yr À1). Attainable rates of SOC sequestration on permanent cropland in SSA under improved cultivation systems (e.g. no-till) range from 0Á2 to 1Á5 Tg C yr À1 , while attainable rates under fallow systems are 0Á4 to 18Á5 Tg C yr À1 . Fallow systems generally have the highest potential for SOC sequestration in SSA with rates up to 28Á5 Tg C yr À1.

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The effect of soil management and land use change are of interest to the sustainable land management for improving the environment and advancing food security in developing countries. Both anthropogenic changes and natural processes affect agriculture primarily by altering soil quality. This paper reviews and synthesizes the available literatures related to the influence of soil management and land use changes on soil carbon (C) stock in Ethiopia. The review shows that topsoil C stock declines approximately 0-63%, 0-23%, and 17-83% upon land use conversion from forest to crop land, to open grazing, and to plantation, respectively. An increase of 1-3% in soil C stock was observed within 10 years of converting open grazed land to protected enclosures. However, there was a little change in soil C stock below 20 cm depth.There is a large potential of increasing SOC pool with adoption of land restorative measures. Total potential of soil C sequestration with the adoption of restoration measures ranges 0Á066-2Á2 Tg C y À1 on rain-fed cropland and 4Á2-10Á5 Tg C y À1 on rangeland. Given large area and diverse ecological conditions in Ethiopia, research data available in published literature are rather scanty. Therefore, researchable priorities identified in this review are important.

Soil influences human health in a variety of ways, with human health being linked to the health of the soil. Historically, emphasis has been placed on the negative impacts that soils have on human health, including exposures to toxins and pathogenic organisms or the problems created by growing crops in nutrient-deficient soils. However, there are a number of positive ways that soils enhance human health, from food production and nutrient supply to the supply of medications and enhancement of the immune system. It is increasingly recognized that the soil is an ecosystem with a myriad of interconnected parts, each influencing the other, and when all necessary parts are present and functioning (ie, the soil is healthy), human health also benefits. Despite the advances that have been made, there are still many areas that need additional investigation. We do not have a good understanding of how chemical mixtures in the environment influence human health, and chemical mixtures in soil are the rule, not the exception. We also have sparse information on how most chemicals react within the chemically and biologically active soil ecosystem, and what those reactions mean for human health. There is a need to better integrate soil ecology and agronomic crop production with human health, food/nutrition science, and genetics to enhance bacterial and fungal sequencing capabilities, metagenomics, and the subsequent analysis and interpretation. While considerable work has focused on soil microbiology, the macroorganisms have received much less attention regarding links to human health and need considerable attention. Finally, there is a pressing need to effectively communicate soil and human health connections to our broader society, as people cannot act on information they do not have. Multidisciplinary teams of researchers, including scientists, social scientists, and others, will be essential to move all these issues forward.