Nutrient losses from rain‐fed bench terraced cultivation systems in high rainfall areas of the mid‐hills of Nepal

Between the elevations of 1000 and 2000 m in the mid‐hills of Nepal, over 12 million people subsist on land‐holdings of less than 0·5 ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain‐fed crop terraces) in the hill community of Landruk (bench terraces 0–5° slope, 3000–3500 mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run‐on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO₃‐N in leachate ranged from 17·3 to 99·7 kg ha⁻¹ yr⁻¹, but only 0·7 to 5·6 kg ha⁻¹ yr⁻¹ in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright © 2007 John Wiley & Sons, Ltd.     

Land use and soil conservation strategies for potentially highly erodible soils of central-eastern Nigeria

In areas susceptible to erosion, there is the need for a comprehensive soil conservation programme so as to be able to prevent catastrophic soil erosion problems. The absence of such a programme in central eastern Nigeria, that has a total land area of 20 000 km², necessitated the drawing up of a soil conservation strategy for the area. The aim was to provide information for better land-use planning and proper environmental and soil management. To achieve this, topographic, soil and landform maps of the area at the scale of 1:50 000 were used to delineate into slope land units, viz: 0–4 per cent, <4 per cent, drainage basins and headwaters. These slope units and estimated soil erosion hazard units using the revised universal soil loss equation (RUSLE) were employed to form a general purpose land classification based on the USDA land capability classification and FAO framework on land evaluation.The soil loss tolerance of the area falls between 1·16 and 1·30 Mg ha⁻¹ yr⁻¹, while the erosion hazard units are considered generally suitable for the various land utilization types, with a number of limitations the main ones being erosion and waterlogging. The soil conservation measures proposed involved the application of bioenvironmental processes in the area and appropriate watershed management. The techniques proposed are those based on low input technology, affordable by rural farmers. It is concluded that these soil conservation measures will be adequate for sustainable agricultural production in the area. Copyright © 1999 John Wiley & Sons, Ltd.     

EXCLOSURE LAND MANAGEMENT FOR RESTORATION OF THE SOILS IN DEGRADED COMMUNAL GRAZING LANDS IN NORTHERN ETHIOPIA

In the northern highlands of Ethiopia, establishment of exclosures to restore degraded communal grazing lands has been practiced for the past three decades. However, empirical data on the effectiveness of exclosures in restoring degraded soils are lacking. We investigated the influence of exclosure age on degree of restoration of degraded soil and identified easily measurable biophysical and management‐related factors that can be used to predict soil nutrient restoration. We selected replicated (n = 3) 5‐, 10‐, 15‐, and 20‐year‐old exclosures and paired each exclosure with samples from adjacent communal grazing lands. All exclosures showed higher total soil nitrogen (N), available phosphorus (P), and cation exchange capacity than the communal grazing lands. The differences varied between 2·4 (±0·61) and 6·9 (±1·85) Mg ha⁻¹ for the total N stock and from 17 (±3) to 39 (±7) kg ha⁻¹ for the available P stock. The differences in N and P increased with exclosure age. In exclosures, much of the variability in soil N (R² = 0·64) and P (R² = 0·71) stocks were explained by a combination of annual average precipitation, woody biomass, and exclosure age. Precipitation and vegetation canopy cover also explained much of the variability in soil N (R² = 0·74) and P (R² = 0·52) stocks in communal grazing lands. Converting degraded communal grazing lands into exclosures is a viable option to restore degraded soils. Our results also confirm that the possibility to predict the changes in soil nutrient content after exclosure establishment using regression models is based on field measurements. Copyright © 2011 John Wiley & Sons, Ltd.     

Offsetting global CO2 emissions by restoration of degraded soils and intensification of world agriculture and forestry

Increase in atmospheric concentration of CO₂ from 285 parts per million by volume (ppmv) in 1850 to 370 ppm in 2000 is attributed to emissions of 270 ± 30 Pg carbon (C) from fossil fuel combustion and 136 ± 55 Pg C by land‐use change. Present levels of anthropogenic emissions involve 6·3 Pg C by fossil fuel emissions and 1·8 Pg C by land‐use change. Out of the historic loss of terrestrial C pool of 136 ± 55 Pg, 78 ± 12 Pg is due to depletion of soil organic carbon (SOC) pool comprising 26 ± 9 Pg due to accelerated soil erosion. A large proportion of the historic SOC lost can be resequestered by enhancing the SOC pool through converting to an appropriate land use and adopting recommended management practices (RMPs). The strategy is to return biomass to the soil in excess of the mineralization capacity through restoration of degraded/desertified soils and intensification of agricultural and forestry lands. Technological options for agricultural intensification include conservation tillage and residue mulching, integrated nutrient management, crop rotations involving cover crops, practices which enhance the efficiency of water, plant nutrients and energy use, improved pasture and tree species, controlled grazing, and judicious use of inptus. The potential of SOC sequestration is estimated at 1–2 Pg C yr⁻¹ for the world, 0·3–0·6 Pg C yr⁻¹ for Asia, 0·2–0·5 Pg C yr⁻¹ for Africa and 0·1–0·3 Pg C yr⁻¹ for North and Central America and South America, 0·1–0·3 Pg C yr⁻¹ for Europe and 0·1–0·2 Pg C yr⁻¹ for Oceania. Soil C sequestration is a win–win strategy; it enhances productivity, improves environment moderation capacity, and mitigates global warming. Copyright © 2003 John Wiley & Sons, Ltd.     

Assessment of soil erosion hazard in Kilie catchment,East Shoa,Ethiopia

This paper reports on a field study conducted in Kilie catchment, East Shoa Zone, Ethiopia to assess the rate of soil erosion by employing a soil loss prediction model (Universal Soil Loss Equation) integrated with in remote sensing and geographical information systems (RS/GIS), environment and gully measurement techniques. The final soil erosion risk map was produced after multiplication of the six factors involved in the USLE and RS/GIS. Gully measurement showed that the erosion rate is higher for the upland areas than the lowlands due to inappropriate soil and water conservation measures, free grazing by animals and conversion of hillside areas into farmlands. About 97·04 per cent of the study catchment falls within a range of 0–10 t ha⁻¹ yr⁻¹ sheet/rill erosion rate. We found that 2·17 per cent of the study area in the uplands has a soil erosion rate falling between 10 and 20 t ha⁻¹ yr⁻¹. About 0·8 per cent of the study area in the uplands is hit by severe sheet/rill erosion rate within the range of 20–60 t ha⁻¹ yr⁻¹. Gully erosion extent in the study area was evaluated through gully measurement and quantification methods. Gully density of 67 m ha⁻¹ was recorded in the catchment. The gully to plot area ratio was found to be 0·14 on average. Hence, in the upland areas, sustainable land management practices are required in order to reduce the rate of soil erosion. Copyright © 2011 John Wiley & Sons, Ltd.     

PROJECTED CHANGES IN SOIL ORGANIC CARBON STOCKS UPON ADOPTION OF RECOMMENDED SOIL AND WATER CONSERVATION PRACTICES IN THE UPPER TANA RIVER CATCHMENT,KENYA

Large areas in the Upper Tana river catchment, Kenya, have been over‐exploited, resulting in soil erosion, nutrient depletion and loss of soil organic matter (SOM). This study focuses on sections of the catchment earmarked as being most promising for implementing Green Water Credits, an incentive mechanism to help farmers invest in land and soil management activities that affect all fresh water resources at source. Such management practices can also help restore SOM levels towards their natural level. Opportunities to increase soil organic carbon (SOC) stocks, for two broadly defined land use types (croplands and plantation crops, with moderate input levels), are calculated using a simple empirical model, using three scenarios for the proportion of suitable land that may be treated with these practices (low = 40 per cent, medium = 60 per cent, high = 80 per cent). For the medium scenario, corresponding to implementation on ~348 000 ha in the basin, the eco‐technologically possible SOC gains are estimated at 4·8 to 9·3 × 10⁶ tonnes (Mg) CO₂ over the next 20 years. Assuming a conservative price of US$10 per tonne CO₂‐equivalent on the carbon offset market, this would correspond to ~US$48–93 million over a 20‐year period of sustained green water management. This would imply a projected (potential) payment of some US$7–13 ha⁻¹ to farmers annually; this sum would be in addition to incentives that are being put in place for implementing green water management practices and also in addition to the benefits that farmers would realize from the impact on production of these practices themselves. Copyright © 2012 John Wiley & Sons, Ltd.     

Soil and Water Assessment Tool Soil Loss Simulation at the Sub‐Basin Scale in the Alt Penedès–Anoia Vineyard Region (Ne Spain) in the 2000s

This paper evaluates soil loss due to water erosion in an area of 32,362 ha with a predominant land use of vineyards (Alt Penedès–Anoia region, Catalonia, Spain). The Soil and Water Assessment Tool (SWAT) was used incorporating daily climatic data for the period 2000–2010 and also detailed soil and land use maps. Particular attention was given to the universal soil loss equation cover and management factor (C factor) of vineyards, with a minimum value of 0·15 being determined for this crop. The model was calibrated using daily flow data for the year 2010, which yielded satisfactory results. Even so, significant differences were obtained on days with high‐intensity rainfall events, when the model overestimated runoff and peak discharge. In these vineyards, the simulated average soil losses per sub‐basin ranged between 0·13 and 9·73 Mg ha⁻¹ y⁻¹, with maximum values of between 26·32 and 42·60 Mg ha⁻¹ y⁻¹ registered in fine‐loamy soils developed on unconsolidated Tertiary marls. Other findings were related to problems associated with SWAT calibration under Mediterranean conditions characterised by major climate variability and high‐intensity rainfall events. Copyright © 2013 John Wiley & Sons, Ltd.     

Soil organic carbon stock for reclaimed minesoils in northeastern Ohio

Reclamation of disturbed soils is done with the primary objective of restoring the land for agronomic or forestry land use. Reclamation followed by sustainable management can restore the depleted soil organic carbon (SOC) stock over time. This study was designed to assess SOC stocks of reclaimed and undisturbed minesoils under different cropping systems in Dover Township, Tuscarawas County, Ohio (40°32·33′ N and 81°33·86′ W). Prior to reclamation, the soil was classified as Bethesda Soil Series (loamy‐skeletal, mixed, acid, mesic Typic Udorthent). The reclaimed and unmined sites were located side by side and were under forage (fescue—Festuca arundinacea Schreb. and alfa grass—Stipa tenacissima L.), and corn (Zea mays L.)—soybean (Glycine max (L.) Merr.) rotation. All fields were chisel plowed annually except unmined forage, and fertilized only when planted to corn. The manure was mostly applied on unmined fields planted to corn, and reclaimed fields planted to forage and corn. The variability in soil properties (i.e., soil bulk density, pH and soil organic carbon stock) ranged from moderate to low across all land uses in both reclaimed and unmined fields for 0–10 and 10–20 cm depths. The soil nitrogen stock ranged from low to moderate for unmined fields and moderate to high in some reclaimed fields. Soil pH was always less than 6·7 in both reclaimed and unmined fields. The mean soil bulk density was consistently lower in unmined (1·27 mg m⁻³ and 1·22 mg m⁻³) than reclaimed fields (1·39 mg m⁻³ and 1·34 mg m⁻³) planted to forage and corn, respectively. The SOC and total nitrogen (TN) concentrations were higher for reclaimed forage (33·30 g kg⁻¹; 3·23 g kg⁻¹) and cornfields (21·22 g kg⁻¹; 3·66 g kg⁻¹) than unmined forage (17·47 g kg⁻¹; 1·98 g kg⁻¹) and cornfield (17·70 g kg⁻¹; 2·76 g kg⁻¹). The SOC stocks in unmined soils did not differ among forage, corn or soybean fields but did so in reclaimed soils for 0–10 cm depth. The SOC stock for reclaimed forage (39·6 mg ha⁻¹ for 0–10 cm and 28·6 mg ha⁻¹ for 10–20 cm depths) and cornfields (28·3 mg ha⁻¹; 32·2 mg ha⁻¹) were higher than that for the unmined forage (22·7 mg ha⁻¹; 17·6 mg ha⁻¹) and corn (21·5 mg ha⁻¹; 26·8 mg ha⁻¹) fields for both depths. These results showed that the manure application increased SOC stocks in soil. Overall this study showed that if the reclamation is done properly, there is a large potential for SOC sequestration in reclaimed soils. Copyright © 2005 John Wiley & Sons, Ltd.     

Irrigation effects of cooling tower effluent on soil chemistry and alfalfa in the Rio Grande river basin

Development of alternative sources through wastewater reuse is important to meet water demands in arid regions. However, effects of wastewater irrigation on soil properties and crop performance must be evaluated before advocating its widespread use. Objectives of this study were to evaluate: (i) effects of prior evaporative disposal of saline‐sodic blowdown water (BW) on soil (fine‐loamy, mixed, and thermic Typic Calciorthods) properties in the disposal area, and (ii) effects of flood irrigation with three water qualities (control, BW 1X, and BW 2X) on soil salinity and alfalfa performance using a greenhouse soil column study (soil collected from same study area as objective (i)). Results indicated that although prior land disposal of BW had increased salinity and sodicity of soil, they were within the tolerance limits of the intended crop, alfalfa. Mass balance calculations indicated measured (15·6 Mg ha⁻¹) and calculated (13·2 Mg ha⁻¹) salt accumulation at the test site used for evaporative disposal were similar. Alfalfa grown using BW under greenhouse conditions produced prime quality hay and biomass yield similar to the control treatment (8·3 g column⁻¹ vs. 10·5 g column⁻¹ in control). Although 3·6 years equivalent of flood irrigation with BW 1X did not result in saline soil (BW 1X irrigated soils EC ranged from 2·2 to 3·5 dS m⁻¹), BW 2X irrigation resulted in saline soils. Sodicities of irrigated soils were greater in fine textured deep soils than coarse textured surface soils (e.g., SAR of 6·1 at 0–5 cm vs. 19·5 mmol^1/2 L^−1/2 at 30–60 cm in BW 1X), indicating the need for high solubility Ca amendments for long‐term irrigation with BW on fine texture soils within the soil profile. Copyright © 2010 John Wiley & Sons, Ltd.     

Carbon stocks in Ethiopian soils in relation to land use and soil management

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 0·066–2·2 Tg C y⁻¹ on rain‐fed cropland and 4·2–10·5 Tg C y⁻¹ 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. Copyright © 2008 John Wiley & Sons, Ltd.     

SOIL CO2 FLUX IN GRASSLAND,AFFORESTED LAND AND RECLAIMED COALMINE OVERBURDEN DUMPS: A CASE STUDY

The aim of this study was to measure the in situ soil CO₂ flux from grassland, afforested land and reclaimed coalmine overburden dumps by using the automated soil CO₂ flux system (LICOR‐8100® infrared gas analyzer, LICOR Inc., Lincoln, NE). The highest soil CO₂ flux was observed in natural grassland (11·16 µmol CO₂ m⁻²s⁻¹), whereas the flux was reduced by 38 and 59 per cent in mowed site and at 15‐cm depth, respectively. The flux from afforested area was found 5·70 µmol CO₂ m⁻²s⁻¹, which is 50 per cent lower than natural grassland. In the reclaimed coalmine overburden dumps, the average flux under tree plantation was found to be lowest in winter and summer (0·89–1·12 µmol CO₂ m⁻²s⁻¹) and highest during late monsoon (3–3·5 µmol CO₂ m⁻²s⁻¹). During late monsoon, the moisture content was found to be higher (6–7·5 per cent), which leads to higher microbial activity and decomposition. In the same area under grass cover, soil CO₂ flux was found to be higher (8·94 µmol CO₂ m⁻²s⁻¹) compared with tree plantation areas because of higher root respiration and microbial activity. The rate of CO₂ flux was found to be determined predominantly by soil moisture and soil temperature. Our study indicates that the forest ecosystem plays a crucial role in combating global warming than grassland; however, to reduce CO₂ flux from grassland, mowing is necessary. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of vertical hedge interval of vetiver grass on erosion on steep agricultural lands

Vetiver grass is widely used to reduce soil erosion and has been applied in many areas of the world. However, studies of the effect of vertical hedge intervals on runoff, soil loss and outflow sediment size distribution under a steep slope area are rare. The vetiver grass system (VGS) with three vertical hedge intervals (0·75, 1·5 and 3 m) and no hedgerow were tested at three land slopes (30, 40 and 50 per cent) under three simulated rainfall intensities (60, 85 and 110 mm h⁻¹). It has been observed that vetiver grass (Vetiveria nemoralis) has great potential for reducing runoff and soil loss by about 38·7–68·6 and 56·2–87·9 per cent, respectively. The vetiver strips delayed incipient runoff and reduced peak runoff rate and steady erosion rate. The land slope affected soil loss but did not have a significant effect on runoff. A narrow vetiver hedge interval slightly reduced runoff and soil loss more than a wider one. The soil loss equation obtained in this study revealed that runoff has a higher effect on soil loss. The median sediment size that passed through the vetiver strip increased with rainfall intensity and was mostly dominated by very fine sand, silt and clay. Copyright © 2009 John Wiley & Sons, Ltd.     

Spatiotemporal Heterogeneity of Soil Available Nitrogen During Crop Growth Stages on Mollisol Slopes of Northeast China

Spatiotemporal heterogeneity of soil available nitrogen (AN) (sum of NO₃⁻–N and NH₄⁺–N) is the essential basis for soil management and highly correlates to crop yield. Both geostatistical and traditional analyses were used to describe the spatiotemporal distribution of AN in the 0–20‐cm soil depth on typical Mollisol slopes (S1 and S2) in Northeast China. The concentration of NO₃⁻–N dynamics at slope positions was typically opposite to NH₄⁺–N. The peak values of AN typically moved from the summit of the slope to the bottom from spring to autumn and were mainly influenced by the content of NO₃⁻–N (S1, 7·9–18·9 mg kg⁻¹; S2, 1·2–103·6 mg kg⁻¹), both of NO₃⁻–N (S1, 3·9–8·3 mg kg⁻¹; S2, 2·2–28·0 mg kg⁻¹) and NH₄⁺–N (S1, 21·4–30·5 mg kg⁻¹; S2, 2·1–23·3 mg kg⁻¹), and NH₄⁺–N (S1, 10·5–28·9 mg kg⁻¹; S2, 5·0–39·0 mg kg⁻¹) in the seedling stage, vegetative growth stage, and reproductive growth stage, respectively. The spatial autocorrelation of AN was strong and was mainly influenced by structural factors during crop growth stages. This was mainly determined by soil erosion–deposition (SED) and soil temperature–moisture (STM) in the seedling stage; this was also mainly influenced by SED, STM, crop type, and crop growth in the vegetative growth stage and by early STM and early SED in the reproductive growth stage. Generally, the content of AN, NO₃⁻–N, and NH₄⁺–N on the whole slope was mainly determined by the early SED and local fertilizer application, while their spatiotemporal heterogeneity, especially the evenness, was mainly changed by SED, STM, crop growth, and crop types on the slope scale. In order to increase more crop yields, additional N fertilizer application on both the summit and the bottom during the vegetative growth stage and conservation tillage systems or additional soil amendments on the back slopes was necessary. Copyright © 2016 John Wiley & Sons, Ltd.     

Potential of mine land reclamation for soil organic carbon sequestration in Ohio

Soils are an effective sink for carbon storage and immobilization through biomass productivity and enhancement of soil organic carbon (SOC) pool. The SOC sink capacity depends on land use and management. Degraded lands lose large amounts of C through SOC decomposition, erosion, and leaching. Thus, restoration of disturbed and degraded mine lands can lead to increase in biomass productivity, improved soil quality and SOC enhancement and sequestration. Reclamation of mined lands is an aggrading process and offers significant potential to sequester C. A chronosequence study consisting of 0‐, 5‐, 10‐, 15‐, 20‐ and 25‐year‐old reclaimed mine soils in Ohio was initiated to assess the rate of C sequestration by pasture and forest establishment. Undisturbed pasture and forest were used as controls. The SOC pool of reclaimed pasture sites increased from 15·3 Mg ha⁻¹ to 44·4 Mg ha⁻¹ for 0–15 cm depth and from 10·8 Mg ha⁻¹ to 18·3 Mg ha⁻¹ for 15–30 cm depth over the period of 25 years. The SOC pool of reclaimed forest sites increased from 12·7 Mg ha⁻¹ to 45·3 Mg ha⁻¹ for 0–15 cm depth and from 9·1 Mg ha⁻¹ to 13·6 Mg ha⁻¹ for 15–30 cm depth over the same time period. The SOC pool of the pasture site stabilized earlier than that of the forest site which had not yet attained equilibrium. The SOC sequestered in 0–30 cm depth over 25 years was 36·7 Mg ha⁻¹ for pasture and 37·1 Mg ha⁻¹ for forest. Copyright © 2000 John Wiley & Sons, Ltd.     

Organic Farming Affects C and N in Soils Under Olive Groves in Mediterranean Areas

Under semiarid climatic conditions, intensive tillage increases soil organic matter losses, reduces soil quality, and contributes to climate change due to increased CO₂ emissions. There is a need for an agricultural management increasing soil organic matter. This paper presents the organic carbon (OC) and nitrogen (N) stocks, C:N ratio and stratification ratios (SRs) of these properties for olive groves soils under long‐term organic farming (OF), and conventional tillage (CT) in Los Pedroches valley, southern Spain. The results show that OF increased C and N stocks. The soil organic carbon (SOC) stock was 73·6 Mg ha⁻¹ in OF and 54·4 Mg ha⁻¹ in CT; and the total nitrogen (TN) stock was 7·1 Mg ha⁻¹ and 5·8 Mg ha⁻¹ for OF and CT, respectively. In the surface horizon (A: 0–16·9 cm in OF and Ap: 0–21·8 cm in CT) and Bw horizon (16·9–49·6 cm in OF and 21·8–56 cm in CT), SOC and TN concentrations and C:N ratios were higher in OF than in CT. Soil properties stratification in depth, expressed as a ratio, indicates the soil quality under different soil management systems. The SR of SOC ranged from 2·2 to 3·1 in OF and from 2·1 to 2·2 in CT. However, only SR2 (defined by Ap‐A/C) showed significant differences between CT and OF. The SR of TN showed similar trends to that of the SR of SOC. Organic farming contributes to a better soil quality and to increased carbon sequestration. Copyright © 2013 John Wiley & Sons, Ltd.     

Soil Property Changes After Conversion from FOrest to Pasture in Mount Sacinka,Artvin, Turkey

Turkey's forests have been continuously facing conversion into both agriculture and pasturelands, causing not only degradation and fragmentation of forested lands but also negative changes in soil properties that have not been thoroughly investigated. In order to determine possible changes in some physical and hydrophysical soil parameters along with the dispersion ratio between natural coppice forests and the neighbouring forest‐to‐grassland converted areas, a foothill of Mount Sacinka in Artvin was chosen as a research area. Besides land use, possible effects of elevation change on soil properties due to the mountainous and moderately steep landscape of the region were also taken into consideration. The soil samples were analysed for soil texture, permeability, field capacity, bulk density, organic matter, pH and dispersion ratio. The results indicated that whereas permeability (43·05 mm h⁻¹ in forest and 18·82 mm h⁻¹ in pasture), field capacity (43·45% in forest and 38·08% in pasture) and organic matter (6·36% in forest and 5·34% in pasture) values turned out to be higher in forest soils, bulk density (0·91 g cm⁻³ in forest and 1·06 g cm⁻³ in pasture) and pH (5·89 in forest and 6·55 in pasture) values were low in grassland soils, meaning that conversion has negative effects on soil properties. Additionally, the mean dispersion ratios of 27·55% and 33·58% for forest and pastureland soils, respectively, indicated soil erosion problems in both land uses. In addition, as for elevation effect, forest soils especially showed better characteristics at higher elevations with high permeability, field capacity and organic matter and low pH and dispersion ratio. Copyright © 2015 John Wiley & Sons, Ltd.     

Chemical and microbial properties in contaminated soils around a magnesite mine in northeast China

We measured soil chemical and microbial properties at a depth of 0–20 cm among mine tailings, abandoned mined land, contaminated cropland, and uncontaminated cropland around a magnesite mine near Haicheng City, Liaoning Province, China. The objective was to clarify the impact of Mg on the soils. We found that soluble Mg²⁺ concentration and pH were significantly higher in contaminated soils (266–345 mg kg⁻¹ and 9·9–10·3, respectively) than in uncontaminated soils (140 mg kg⁻¹ and 7·1, respectively). Soil nutrients (total N, total P, mineral N, available P and soluble Ca) and microbial biomass C and N decreased as pH and soluble Mg²⁺ concentration increased. In addition, an increase of microbial metabolic quotient and a decrease of N mineralization rate were found in contaminated soils. Soluble Mg²⁺/Ca²⁺ ratios in contaminated soils were 3·5–8·9‐times higher than in uncontaminated soils. Our results indicate that soil contamination in such magnesite mine regions is characterized by high pH, Mg²⁺ concentration and soluble Mg²⁺/Ca²⁺ ratio, and low microbial activity and N and P availability. Future soil amelioration in the magnesite regions should consider applying acid ameliorants to neutralize high pH and applying calcareous ameliorants to increase Ca²⁺ concentration. Copyright © 2011 John Wiley & Sons, Ltd.     

Effectiveness OF Mulching Under Miraba in Controlling Soil Erosion,Fertility Restoration and Crop Yield in the Usambara Mountains,Tanzania

Soil erosion is a major threat to food security in rural areas of Africa. Field experiments were conducted from 2011 to 2014 in Majulai and Migambo villages with contrasting climatic conditions in Usambara Mountains, Tanzania. The aim was to investigate the effectiveness of mulching in reducing soil erosion and restoring soil fertility for productivity of maize (Zea mays) and beans (Phaseolus vulgaris) under miraba, a unique indigenous soil conservation measure in the area. Soil loss was significantly higher (p < 0·05) under miraba sole than under miraba with mulching, for example, 35 versus 20 and 13 versus 8 Mg ha⁻¹ y⁻¹ for Majulai and Migambo villages, respectively, in 2012. Soil fertility status was significantly higher (p < 0·05) under miraba with Tughutu mulching than under miraba sole, for example, 0·35 versus 0·25% total N, 37 versus 22 mg kg⁻¹ P and 0·6 versus 0·2 cmol(+) kg⁻¹ K for the Majulai village; and 0·46 versus 0·38 total N, 17·2 versus 10·2 mg kg⁻¹ P and 0·50 versus 0·2 cmol(+) kg⁻¹ K for the Migambo village. Maize and bean yields (Mg ha⁻¹) were significantly higher (p < 0·05) under miraba with Tughutu mulching than under miraba sole, 2·0 versus 1·3 for maize and 0·9 versus 0·8 for beans in Majulai; and 3·8 versus 2·6 for maize and 1·0 versus 0·8 for beans in the Migambo village in 2012. This implies that Tughutu mulching is more effective in improving crop yield than Tithonia, although both could potentially protect the arable land from degradation caused by water erosion under miraba. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of Land Management on Different Forms of Soil Carbon in Olive Groves in Mediterranean Areas

This study analyses soil organic carbon (SOC) and hot‐water extractable carbon, both measures of soil quality, under different land management—(i) conventional tillage (CT); (ii) CT plus the addition of oil mill waste alperujo (A); (iii) CT plus the addition of oil mill waste olive leaves (L); (iv) no tillage with chipped pruned branches (NT₁); and (v) no tillage with chipped pruned branches and weeds (NT₂)—in a typical Mediterranean agricultural area: the olive groves of Andalusia, southern Spain. SOC values in CT, A, NT₁ and NT₂ decreased with depth, but in NT₂, the surface horizon (0–5 cm) had higher values than the other treatments, 47% more than the average values in the other three soils. In L, SOC also decreased with depth, although there was an increase of 88·5% from the first (0–10 cm) to the second horizon (10–16 cm). Total SOC stock values were very similar under A (101·9 Mg ha⁻¹), CT (101·7 Mg ha⁻¹), NT₁ (105·8 Mg ha⁻¹) and NT₂ (111·3 Mg ha⁻¹, if we consider the same depth of the others). However, SOC under L was significantly higher (p < 0·05) at 250·2 Mg ha⁻¹. Hot‐water extractable carbon decreased with depth in A, CT and NT₁. NT₂ and L followed the same pattern as the other management types but with a higher value in the surface horizon (2·3 and 4·9 mg g⁻¹, respectively). Overall, our results indicate that application of oil mill waste olive leaves under CT (L) is a good management practice to improve SOC and reduce waste. Copyright © 2014 John Wiley & Sons, Ltd.     

Using farmer knowledge to combat low productive spots in rice fields of a Sahelian irrigation scheme

In the oldest sections of Burkina Faso's largest irrigation scheme in the Sourou Valley (13° 10′ N, 03° 30′W) rice (Oryza sativa L.) yields dropped from about 5 to 6 t ha⁻¹ in the early 1990s, shortly after establishment of the scheme, to 2 to 4 t ha⁻¹ from 1995 onwards. Farmers blamed this yield decline on the appearance of 2 to 20 m diameter low productive spots. According to farmers and field measurements, the low productive spots decreased yields by 25–50 per cent. The low productive spots are caused by Zn deficiency. Low Zn availability is related to the very low DTPA‐extractable Zn content of the soil (0·08–0·46 mg kg⁻¹), the alkaline‐calcareous character of the soil, the non‐application of Zn fertilizers, and a relatively large P fertilizer dose (21 kg P ha⁻¹). Farmers were correct in relating the calcareous nature of the soil to the presence of the low productive spots. They were instrumental in identifying application of decomposed organic resources (e.g. rice straw at 5 t ha⁻¹) as a short‐term solution that increases yields by 1·5 to 2·0 t ha⁻¹. Application of Zn fertilizer (10 kg Zn ha⁻¹) in 29 farmer fields in the 2001 dry season eradicated the low productive spots and increased yields from 3·4 to 6·0 t ha⁻¹. Although application of Zn fertilizer is strongly recommended, it is not yet available in Burkina Faso. Based on a comparison of fertilizer prices on the world market and the local market, we expect that the use of Zn fertilizers will be highly profitable (cost/value ratio ≫ 2). Despite the relatively recent introduction of irrigated rice cropping, most farmers showed a good understanding of cropping constraints and possible solutions. Both farmers and researchers mutually benefited from each other's knowledge and observations. Copyright © 2004 John Wiley & Sons, Ltd.