Showing papers in "Soil Use and Management in 2016"

Soil acidification and the importance of liming agricultural soils with particular reference to the United Kingdom.

Abstract: Soil acidification is caused by a number of factors including acidic precipitation and the deposition from the atmosphere of acidifying gases or particles, such as sulphur dioxide, ammonia and nitric acid. The most important causes of soil acidification on agricultural land, however, are the application of ammonium-based fertilizers and urea, elemental S fertilizer and the growth of legumes. Acidification causes the loss of base cations, an increase in aluminium saturation and a decline in crop yields; severe acidification can cause nonreversible clay mineral dissolution and a reduction in cation exchange capacity, accompanied by structural deterioration. Soil acidity is ameliorated by applying lime or other acid-neutralizing materials. 'Liming' also reduces N2O emissions, but this is more than offset by CO 2 emissions from the lime as it neutralizes acidity. Because crop plants vary in their tolerance to acidity and plant nutrients have different optimal pH ranges, target soil pH values in the UK are set at 6.5 (5.8 in peaty soils) for cropped land and 6.0 (5.3 in peaty soils) for grassland. Agricultural lime products can be sold as 'EC Fertiliser Liming Materials' but, although vital for soil quality and agricultural production, liming tends to be strongly influenced by the economics of farming. Consequently, much less lime is being applied in the UK than required, and many arable and grassland soils are below optimum pH.

Ammonia emissions from urea, stabilized urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland

Abstract: Irish Department of Agriculture Food and Marine. Grant Numbers: RSF 13S430, 11S138.Teagasc Walsh Fellowship Programme

How do we cultivate in England? Tillage practices in crop production systems.

Abstract: Reducing tillage intensity offers the possibility of moving towards sustainable intensification objectives. Reduced tillage (RT) practices, where the plough is not used, can provide a number of environmental and financial benefits, particularly for soil erosion control. Based on 2010 harvest year data from the nationally stratified Farm Business Survey and drawing on a sub-sample of 249 English arable farmers, we estimate that approximately 32% of arable land was established under RT, with 46% of farms using some form of RT. Farms more likely to use some form of RT were larger, located in the East Midlands and South East of England and classified as ‘Cereals’ farms. Application of RT techniques was not determined by the age or education level of the farmer. Individual crops impacted the choice of land preparation, with wheat and oilseed rape being more frequently planted after RT than field beans and root crops, which were almost always planted after ploughing. This result suggests there can be limitations to the applicability of RT. Average tillage depth was only slightly shallower for RT practices than ploughing, suggesting that the predominant RT practices are quite demanding in their energy use. Policy makers seeking to increase sustainable RT uptake will need to address farm-level capital investment constraints and target policies on farms growing crops, such as wheat and oilseed rape, that are better suited to RT practices.

The elusive role of soil quality in nutrient cycling: a review

Abstract: Cycling of nutrients, including nitrogen and phosphorus, is one of the ecosystem services we expect agricultural soils to deliver. Nutrient cycling incorporates the reuse of agricultural, industrial and municipal organic residues that, misleadingly, are often referred to as ‘wastes’. The present review disentangles the processes underlying the cycling of nutrients to better understand which soil properties determine the performance of that function. Four processes are identified (i) the capacity to receive nutrients, (ii) the capacity to make and keep nutrients available to crops, (iii) the capacity to support the uptake of nutrients by crops and (iv) the capacity to support their successful removal in harvested crop. Soil properties matter but it is imperative that, as constituents of ‘soil quality’, they should be evaluated in the context of management options and climate and not as ends in their own right. The effect of a soil property may vary depending on the prevailing climatic and hydrologic conditions and on other soil properties. We recognize that individual soil properties may be enhancing one of the processes underlying the cycling of nutrients but simultaneously weakening others. Competing demands on soil properties are even more obvious when considering other soil functions such as primary production, purification and flow regulation of water, climate modification and habitat provision, as shown by examples. Consequently, evaluations of soil properties and management actions need to be site-specific, taking account of local aspects of their suitability and potential challenges

A review of visual soil evaluation techniques for soil structure

Abstract: Soil structure forms a key component of soil quality, and its assessment by semi-quantitative visual soil evaluation (VSE) techniques can help scientists, advisors and farmers make decisions regarding sampling and soil management. VSE techniques require inexpensive equipment and generate immediate results that correlate well with quantitative measurements of physical and biochemical properties, highlighting their potential utility. We reviewed published VSE techniques and found that soils of certain textures present problems and a lack of research into the influence of soil moisture content on VSE criteria. Generally, profile methods evaluate process interactions at specific locations within a field, exploring both intrinsic aspects and anthropogenic impacts. Spade methods focus on anthropogenic characteristics, providing rapid synopses of soil structure over wider areas. Despite a focus on structural form, some methods include criteria related to stability and resiliency. Further work is needed to improve existing methods regarding texture influences, on-farm sampling procedures and more holistic assessments of soil structure.

Using mental models to understand soil management

Abstract: Funded by: LEDDRA. Grant Number: 243857 and Scottish Government's RESAS. Grant Number: 2011‐16

Extent, frequency and rate of water erosion of arable land in Britain – benefits and challenges for modelling

Abstract: Soil erosion on arable land in lowland Britain has been the subject of field-based surveys, which have assessed the volumes or masses of soil transported in channels across farmers’ fields. These surveys provide a unique database on the extent, frequency and rates of soil loss by water. This study synthesizes the key findings from those surveys and underscores the implications for soil erosion modelling. Rill erosion occurs in a small number of fields (consistently <10%). Over ~5 yr, a considerable proportion of the farmed landscape will suffer from rill erosion, but mostly in fields that erode only once. Mean erosion rates for lowland arable landscapes are much less than mean erosion rates for individual eroded fields within that landscape. These observations pose important challenges for modelling. Rainfall and cropping vary from year to year so that risk of wash or rill erosion in the same field also varies. Due to the infrequent occurrence of rill erosion, loss rates of eroding fields cannot be spatially extrapolated across the landscape, except in the case of wash erosion which takes place a number of times in almost all fields every year. A consistent pattern of increasing wash erosion, in terms of spatial extent, is emerging in lowland Britain. Resulting losses of fine silt and clay-sized particles are small in amount and possibly insignificant in terms of loss of soil as a resource, but have significant implications for contaminant concentrations and pollution of water courses.

Effect of low-temperature biochar derived from pig manure and poultry litter on mobile and organic matter-bound forms of Cu, Cd, Pb and Zn in sandy soil

Abstract: Numerous studies conducted so far have shown that biochar has a significant effect on physical, chemical and biological properties of soils. Biochar can be used to alleviate the effects of soil contamination with organic and inorganic compounds, for instance, to reduce the mobility of heavy metals. The aim of the research was to evaluate the effect of pig manure and poultry litter, as well as biochars produced from these materials at a temperature of 300 °C on Cu, Cd, Pb and Zn contents in mobile and organic matter-bound forms in soil. The research was conducted under laboratory conditions. The materials were introduced into sandy acid soil in doses of 0.5, 1.0 and 2.0% w/w. The application of pig manure-derived biochar (BPM) and poultry litter-derived biochar (BPL), depending on the amount added, reduced the mobility of copper from 28 to 69%, from 77 to 100% in the case of cadmium, from 94 to 99% in the case of lead, and from 15 to 97% in the case of zinc. The 2% amendment of pig manure (PM) and poultry litter (PL) caused an increase in the content of Cu extracted with NH4NO3 in comparison with the control treatment. A similar situation was observed in the case of zinc after the application of 0.5 and 1% amendments of pig manure (PM). Cu, Cd, Pb and Zn contents extracted with 0.025 mol C10H22N4O8 were higher than contents of these elements extracted with 1 m NH4NO3, mainly due to different extraction force of the extractants. The obtained results indicate that, compared with the content determined in soil from the control treatment, 1 and 2% amendments of both unconverted and thermally converted materials to the soil had a greater effect on contents of Cu, Pb and Zn in the organic matter-bound fraction than the 0.5% amendment. The organic materials applied did not affect the content of cadmium in organic matter-bound fraction.

Fertilizer value of phosphorus in different residues

Abstract: The phosphorus (P) fertilizer effect of a range of commonly available manure, waste treatment and by-product residues was tested in pot, field and incubation experiments. The effect of the residues on P offtake was compared with that of commercial mineral P (super phosphate) to calculate the mineral fertilizer equivalent (MFE). Possible relationships between MFE and P extractable from residues using different agents (ammonium lactate, citrate, water) were examined. Dry matter yield and P concentration were measured in ryegrass grown in pots amended with 14 different residues. The effect on the first cut (after 5 weeks) was significantly higher for residues with a low organic matter content, for example ash and biogas residues (MFE = 74–85%), than for many other products with higher organic matter content, for example meat meal (MFE = 44%), cattle slurry (MFE = 57%) and sewage sludge (MFE = 0–37%). However, the effect on two combined cuts (after 11 weeks) was more similar between residues (MFE = 40–60% for most residues). Ammonium lactate-extractable P (P-AL) in residues correlated better with MFE (r2 = 0.48) than water-extractable or citrate-extractable P. Grain yield and P concentration were measured in a field experiment with spring wheat fertilized with four different residues. Pelleted meat meal had a similar effect on yield and P offtake as mineral fertilizer P, whereas two different sewage sludge and chicken manure had approximately 50% of the mineral fertilizer effect. The effect of residues on soil P-AL (the Swedish measure of easily available soil P) in the incubation experiment showed no correlation with MFE from the pot experiments.

A review of ammonia emission measured using wind tunnels compared with micrometeorological techniques

Abstract: Ammonia (NH3) emission from livestock manure constitutes a loss of crop-available nitrogen (N) and poses a threat to the environment. Therefore, low NH3 emission slurry application technologies have been developed, the reduction efficiency of which has typically been estimated through measurements using wind tunnels or integrated horizontal flux (IHF) micrometeorological techniques. A recovery of 100% of released NH3 can be obtained if wind tunnels are designed to avoid pulses of wind into the tunnel through the canopy opening and leaks from the tunnels. The NH3 emission measured with wind tunnels adjusted to an air flow of 1 m/s deviated significantly (P < 0.05) from the emission measured using IHF methods, which are generally considered to give reliable emission estimates for ambient conditions. If wind tunnel air flow was adjusted to the ambient wind speed at height 0.25-0.30 m, then measured emissions were not significantly different from those measured using IHF methods. Wind tunnels influence the air flow pattern and cause turbulent convection in the air layers above the emitting surface, so the similarity in measured emissions for the two measuring techniques is perhaps surprising. This may be because the soil surface resistance to NH3 transport is often the most important rate-regulating variable, so that the absence of a laminar boundary air layer resistance as caused by wind tunnels is of minor importance. It is concluded that the wind tunnels are well suited to test the emission reduction efficiency of new technologies.

Sowing a winter catch crop can reduce nitrate leaching losses from winter-applied urine under simulated forage grazing: a lysimeter study

Abstract: Grazing of winter forage crops is a common management option used in the dairy industry of New Zealand, particularly in the South Island, where they are used to feed nonlactating, pregnant dairy cows prior to calving. However, there is concern that the large crop yields per hectare grazed, combined with a high stocking density of cows, lead to large amounts of urinary nitrogen (N) deposited on bare, wet soil that, in turn, could lead to large nitrate leaching losses. We report the results of a simulated winter forage grazing event using field lysimeters planted with a kale (Brassica oleracea L.) crop. The effect of sowing a ‘catch crop’ of oat (Avena sativa L.) following the simulated winter forage grazing on nitrate leaching losses from urine applied at different times throughout the winter was measured. A catch crop sown between 1 and 63 days after the urine deposition in early winter reduced N leaching losses from urine patches by ~34% on average (range: 19–49%) over the winter–spring period compared with no catch crop. Generally, the sooner the catch crop was sown following the crop harvest, the greater the uptake of N by the catch crop and the greater the reduction in nitrate leaching losses. The results indicate that sowing of a catch crop following winter crop grazing could be an effective management strategy to reduce nitrate leaching as well as increase the N-use efficiency of dairy winter forage grazing systems.

Soil carbon as affected by cover crops under no-till under tropical climate

Abstract: In tropical, low-fertility soils, crop yields are dependent on soil carbon, and cropping systems under no-till can increase soil C stocks. Plant residues supplied by cover crops in no-till systems may improve aggregate stability and soil carbon, which may be further increased with the introduction of a legume in the cropping system. This research studied the effects of cover crops in rotation with soybean under no-till on soil carbon and nitrogen, in Botucatu, Brazil, for 3 yr. The cover crops were millet (Penninsetum americanum Leek), cober crop (Sorghum bicolor × Sorghum sudanense) and sunn hemp (Crotalaria juncea L.), grown in the spring. Fallow without cover crops was used as a control. Grain sorghum (Sorghum bicolor L. Moench) and soybean (Glycine max (L.) Merril) were grown in fall–winter and summer, respectively. Generally, cover crops increased soil carbon contents, but soil N was only increased by sunn hemp in the particulate organic C fraction. An increase in the labile carbon fraction in the topsoil layers was closely related to cover crop root development. Fallow in spring should not be recommended in degraded soils with lowcarbon stock. Labile-fractioned soil organic carbon and total carbon levels are more efficiently increased by grasses than by legumes in the short term, and grasses cropped in spring increase soil C/N ratio. Conversely, the introduction of a legume (sunn hemp) maintained a more stable C/N ratio, that is around 10, which would be more effective in increasing soil C in the long term.

Physical properties of peat soils under different land use options

Abstract: Pristine peat soils are characterized by large porosity, low density and large water and organic matter contents. Drainage and management practices change peat properties by oxidation, compaction and mineral matter additions. This study examined differences in physical properties (hydraulic conductivity, water retention curve, bulk density, porosity, von Post degree of decomposition) in soil profiles of two peatland forests, a cultivated peatland, a peat extraction area and two pristine mires originally within the same peatland area. Soil hydraulic conductivity of the drained sites (median hydraulic conductivities: 3.3 × 10−5 m/s, 2.9 × 10−8 m/s and 8.5 × 10−8 m/s for the forests, the cultivated site and the peat extraction area, respectively) was predicted better by land use option than by soil physical parameters. Detailed physical measurements were accompanied by monitoring of the water levels between drains. The model ‘DRAINMOD’ was used to assess the hydrology and the rapid fluctuations seen in groundwater depths. Hydraulic conductivity values needed to match the simulation of observed depth to groundwater data were an order of magnitude greater than those determined in field measurements, suggesting that macropore flow was an important pathway at the study sites. The rapid response of depth to groundwater during rainfall events indicated a small effective porosity and this was supported by the small measured values of drainable porosity. This study highlighted the potential role of land use and macropore flow in controlling water table fluctuation and related processes in peat soils.

Mineralization of organic nitrogen from farm manure applications

Abstract: This study aimed to quantify the amount of nitrogen (N) mineralized from the organic fraction of farm manures under field conditions. Nine different farm manures were stripped of their ammonium-N content prior to soil incorporation and establishment of ryegrass at two sites in England. Grass N uptake and nitrate-N leaching were measured for five consecutive seasons and compared with an untreated control, with the sum of N uptake + leaching (net of the control) used as an estimate of the amount of organic N mineralized from the applied manures. The amount mineralized was related to thermal time (cumulative day degrees above 5 °C – CDD), with two distinct phases – an initial phase up to 2300 CDD (c.18 months under UK climatic conditions) where mineralization proceeded at rates ranging between 0.005 and 0.027%mineralized/CDD and a slower phase at >2300 CDD, where rates were negligible at <0.001%mineralized/CDD. There was no difference between soil types, both being light-textured (<20% clay), but there were differences between manure types depending on the manure C: organic N ratios. For pig slurry and layer manure (C:organic N = 9–12:1), up to 70% of the organic N was mineralized, compared to 10–30% mineralization from the cattle slurry and straw-based farmyard manures-FYMs (C:organic N = 10–21:1).The relationships derived provide a useful tool for predicting both the amount and timing of manure N release, with important implications for both crop N uptake and leaching risk.

Nutrient availability and corn growth in a poultry litter biochar‐amended loam soil in a greenhouse experiment

Abstract: Nutrient-rich biochar produced from animal wastes, such as poultry litter, may increase plant growth and nutrient uptake although the role of direct and indirect mechanisms, such as stimulation of the activity of mycorrhizal fungi and plant infection, remains unclear. The effects of poultry litter biochar in combination with fertilizer on mycorrhizal infection, soil nutrient availability and corn (Zea mays L.) growth were investigated by growing corn in a loam soil in a greenhouse with biochar (0, 5 and 10 Mg/ha) and nitrogen (N) and phosphorus (P) fertilizer (0, half and full rates). Biochar did not affect microbial biomass C or N, mycorrhizal infection, or alkaline phosphomonoesterase activities, but acid phosphomonoesterase activities, water-soluble P, Mehlich-3 Mg, plant height, aboveground and root biomass, and root diameter were greater with 10 Mg/ha than with no biochar. Root length, volume, root tips and surface area were greatest in the fully fertilized soil receiving 10 Mg/ha biochar compared to all other treatments. The 10 Mg/ha biochar application may have improved plant access to soil nutrients by promoting plant growth and root structural features, rather than by enhancing mycorrhizal infection rates.

Nitrogen release from differently aged Raphanus sativus L. nitrate catch crops during mineralization at autumn temperatures

Abstract: In temperate climates with surplus precipitation and low temperatures during autumn and winter, nitrate catch crops have become crucial in reducing nitrate leaching losses. Preferably, the N retained by the catch crop should remain in the soil and become available to the next main crop. Fodder radish (Raphanus sativus, L.) has emerged as a promising nitrate catch crop in cereal cropping, although the course of remineralization of residue N following termination of this frost-sensitive crucifer remains obscured. We incubated radish residues of different age (different planting and harvest dates) with a loamy sand soil; mineralization of residue N was determined after 1, 2, 4 and 7 months of incubation at 2 °C and 10 °C. Incubations with soil only and with residues of white mustard (Sinapis alba, L) and perennial ryegrass (Lolium perenne, L.) were included as references. Using linear regression, net N release was fitted to plant chemical characteristics (initial concentrations of N, fibre fractions, lignin and C/N ratio). Residue C/N ratio (ranging from 10 to 25) and N concentration (ranging from 17 to 40 mg N/g dry matter) showed superior fits to net N release at both temperatures (r2, 0.64–0.94) while fibre analyses provided inferior fits (r2, 0.12–0.64). This was true across planting date and plant age. Net N release after 7 months of incubation at 2 °C and 10 °C accounted for up to 40% and 50% of residue N, respectively. During most of the incubation period, nitrate dominated the mineral N pool at both temperatures. The N mineralization and nitrification potential at these low soil temperatures suggest that a considerable fraction of the N captured by nitrate catch crops may be remineralized, nitrified and thus available for plant uptake but also for loss by leaching and denitrification.

Production and management of cattle manure in the UK and implications for land application practice

Abstract: A review of livestock and manure management across the UK was undertaken as part of a wider study of important factors impacting on greenhouse and other gaseous emissions from agriculture. All major livestock sectors were covered by the review, but only data on cattle manure are reported in this study. Cattle manure comprises 67 Mt (80%) of the total 83 Mt of UK annual livestock manure production during the housing period. Overall, about 47% of total UK cattle manure production was estimated to be as undiluted slurry and 53% as solid, mainly straw-based farmyard manure (FYM). Survey data suggested important regional differences in cattle manure management across the UK; examples include the predominance of slurry in SW Scotland, N Ireland and to a lesser extent, in Wales, compared to the continued importance of straw-based FYM systems in England. Survey data on land application of manures from the British Survey of Fertiliser Practice (BSFP) generally showed the expected distribution of cattle manure application timings, dominated by crop sowing/establishment or growth patterns. However, in recent years, an apparent increase in land spreading in February–April, with less application in November–January is encouraging, the trend towards spring/early summer spreading of cattle slurry suggesting greater appreciation of its value as a nutrient source. BSFP returns on manure application techniques have also shown increasing uptake of shallow injection of cattle slurry, from <1% (2004) to 10% (2013) and for increasing rapid (<6 h) incorporation of FYM, from 3% (2007) to 14% (2013).

Effects of forage type and gibberellic acid on nitrate leaching losses

Abstract: Nitrogen (N) leaching from soil into water is a significant concern for intensively grazed forage-based systems because it can cause a decline in water quality and is a risk to human health. Urine patches from grazing animals are the main source of this N. The objective of this study was to quantify the effect that forage type and gibberellic acid (GA) application had on N leaching and herbage N uptake from urine patches on perennial ryegrass–white clover (RGWC), Italian ryegrass and lucerne. A lysimeter study was conducted over 17 months to measure herbage growth, N uptake and N loss to water beneath each of the three forage types with the following treatments: control, urine (700 kg N/ha) and urine with GA (8 g GA active ingredient/ha). Compared with RGWC (205 kg N/ha), N leaching losses were 35.3% lower from Italian ryegrass (133 kg N/ha) and 98.5% higher from lucerne (407 kg N/ha). These differences in leaching loss are likely to be due to winter plant growth and N uptake. During the winter months, Italian ryegrass had higher N uptake, whereas lucerne had lower N uptake, compared with RGWC. The application of GA had no effect on N leaching losses, DM yield or N uptake of forage treated with 700 kg N/ha urine.

Farmer knowledge, perception and management of soils in the Las Vegas agricultural district, Madrid, Spain

Abstract: A sample group of 119 farmers from a semi-arid district of Madrid was interviewed to determine the knowledge of individuals about soil conservation and management. Farmers commonly identify physical factors in the landscape that are visually recognizable and those chemical factors that clearly affect productivity. Often, factors, such as salinity or pH that require laboratory analysis, are less readily identified. Farmer knowledge of soils is influenced by their main source of income, gender, education and age. Although there is a high degree of correspondence between scientific and traditional knowledge of soil, some gaps have been identified, notably those related to erosion. Key steps identified for promoting the adoption of sustainable soil management practices to farmers were as follows: involvement of public institutions, the need for increased agricultural prices and an improvement in training and public awareness. Farmers were aware of their own limitations and demanded capacity building, technical and policy support.

Production of the forage halophyte Atriplex amnicola in metal-contaminated soils

Abstract: Clean-up of contaminated soils is a costly and slow process that requires long periods of time to be effective. Therefore, direct use of contaminated sites with appropriate management is often likely to be a more efficient use of such land. Consequently, the production of safe animal forages from contaminated soils was the aim of this research. Field studies were conducted to evaluate the growth and elemental composition of river saltbush (Atriplex amnicola) grown on a metal-contaminated soil. The soil was amended with compost at rates of 0, 15 and 30 t/ha to assess its role on plant growth and metal uptake. Compost application significantly (P < 0.05) increased biomass yield, crude protein (CP) and ash content of river saltbush; in contrast, it decreased the Zn and Pb concentrations in shoot tissues. When 30 t/ha of compost was added, the Pb concentrations in the stems and leaves decreased by 32 and 38%, respectively. Despite the large total and extractable content of metals in the studied soil, shoot concentrations of these metals in A. amnicola were always maintained below potentially toxic levels. The biomass material of A. amnicola had a high nutritive value compared to conventional forage crops and could safely be used as animal forage. This work demonstrates that an Atriplex spp, A. amnicola, has significant potential for use as a safe forage crop in the sustainable on-site management of contaminated soils

Ammonia emissions from cattle dung, urine and urine with dicyandiamide in a temperate grassland

Abstract: This research was financially supported by the Department of Agriculture, Food and the Marine (Grant numbers RSF13S430 and 11S138)

Enhancing pedotransfer functions with environmental data for estimating bulk density and effective cation exchange capacity in a data‐sparse situation

Abstract: Soil bulk density (BD) and effective cation exchange capacity (ECEC) are among the most important soil properties required for crop growth and environmental management. This study aimed to explore the combination of soil and environmental data in developing pedotransfer functions (PTFs) for BD and ECEC. Multiple linear regression (MLR) and random forest model (RFM) were employed in developing PTFs using three different data sets: soil data (PTF‐1), environmental data (PTF‐2) and the combination of soil and environmental data (PTF‐3). In developing the PTFs, three depth increments were also considered: all depth, topsoil ( 0.40 m). Results showed that PTF‐3 (R²; 0.29–0.69) outperformed both PTF‐1 (R²; 0.11–0.18) and PTF‐2 (R²; 0.22–0.59) in BD estimation. However, for ECEC estimation, PTF‐3 (R²; 0.61–0.86) performed comparably as PTF‐1 (R²; 0.58–0.76) with both PTFs out‐performing PTF‐2 (R²; 0.30–0.71). Also, grouping of data into different soil depth increments improves the estimation of BD with PTFs (especially PTF‐2 and PTF‐3) performing better at subsoils than topsoils. Generally, the most important predictors of BD are sand, silt, elevation, rainfall, temperature for estimation at topsoil while EVI, elevation, temperature and clay are the most important BD predictors in the subsoil. Also, clay, sand, pH, rainfall and SOC are the most important predictors of ECEC in the topsoil while pH, sand, clay, temperature and rainfall are the most important predictors of ECEC in the subsoil. Findings are important for overcoming the challenges of building national soil databases for large‐scale modelling in most data‐sparse countries, especially in the sub‐Saharan Africa (SSA).

Spatial distribution and risk assessment of heavy metals in the farmland along mineral product transportation routes in Zhejiang, China

Abstract: Various metal pollutants transported from certain sources may considerably contaminate the soil environment. It was reported that transportation related metal pollution was closely associated with the distance, the freight volume and traffic emissions. However, the effect of topography on the heavy metal distribution in the soils along transportation routes has received little attention. In the present investigation, arable soils along two selected transportation routes for mineral products were studied to characterize the topographic impacts on their level of metal pollution. Soil samples were collected within a 5-m radius following ‘S’ sampling procedure using spatial autocorrelation analysis. The descriptive statistics showed that most of the heavy metal (Pb, Zn, Cu and Cd) concentrations exceeded the background value of Zhejiang Province and contents of most metals in Area B, within a plain, were generally higher than in Area A, a valley within a hilly region. LISA maps showed that all heavy metals did not have similar spatial autocorrelation in Area B. The spatial distribution maps in Area A showed that distribution of most of the contaminants Zn, Cu, Cd and Pb had a similar spatial structure and were located along a transportation route. In Area A within valley topography, metal concentrations in soils were found generally to decrease with increasing distance from the road. However, this was not valid for Area B on the plain, where the metals concentrated in the soils could be derived from multiple sources, particularly emissions from nearby local industry.

Determining the longer term decline in plant-available soil phosphorus from short-term measured values

Abstract: Once phosphorus (P) applications stop, it is important to know how long it will take for plant-available P in soil to decline to a particular level for soils with a history of intensive management. The rate of decline in the absence of applied P can be expressed as a half-life, that is the time in years for it to halve relative to the lowest level measured in the soil. This knowledge is essential when planning long-term policies for managing the P status of soils. It is important to farmers who wish to optimize applications of P fertilizers and make better use of accumulated P residues to ensure that plant-available P does not fall below the critical level for the soil and crop because of the risk of losing yield and the inefficient use of other inputs, especially N fertilizer. Lower levels of plant-available P are also desirable for environmental and ecological reasons. Allowing plant-available P to decline to the critical level from unnecessarily high concentrations will reduce the risk from P on eroded soil causing adverse effects of eutrophication in surface water. Low levels of plant-available P are usually considered necessary for establishing species-rich grassland. A method for determining the longer term decline in plant-available soil P from short-term measured values is presented.

A method-centric ‘User Manual’ for the mitigation of diffuse water pollution from agriculture

Abstract: We describe the development of a manual of methods for mitigating diffuse water pollution from agriculture and its important influence on policy and practice in England and Wales. The objective of the ‘User Manual’ was to provide policy makers and those implementing policies with information about the cost, effectiveness and applicability of potential methods in a form that would be readily understood by non-specialists. The ‘User Manual’ was based on earlier reports synthesizing available research data and, where data were unavailable, used expert elicitation. The outcome generated 44 potential methods (under the broad categories of land use, soil management, livestock management, fertilizer management, manure management and farm infrastructure) and described the simultaneous impact of applying each method on losses of nitrate, phosphorus and faecal indicator organisms relative to baseline losses. Estimates of cost and effectiveness were presented at the whole-farm level for seven model farm types. Methods differed widely in their cost-effectiveness and applicability to the different model farms. Advantages and limitations of the approach are discussed and subsequent developments of the original ‘User Manual’ are described, together with the opinions of catchment officers who have used the ‘User Manual’ to implement mitigation methods on farms.

Spatial and temporal variability of physical properties of Aquands under different land uses in southern Chile

Abstract: The aquands found in southern Chile are derived from volcanic ash and contain high levels of organic matter. Due to the presence of an impermeable stratum, they have shallow soil profiles, which induce waterlogging for several months each year. These fragile soils, locally known as 'Nadi', cover an area of 475 000 hectares and have undergone intensive land use changes, which have affected the soil physical properties. These are still not well understood but are relevant for the design of efficient drainage systems. The aim of this research was to analyse the impact of the land use change in Nadi soils on the spatial and temporal variability of their soil physical properties. For the land use change from secondary native forest (sNF) to naturalized grassland (NG), the effective soil depth was measured at defined points. Time-and space-dependent changes of water-table depth and penetration resistance were recorded. Volumetric water content and soil temperature were measured with sensors installed at three depths and the water retention curve and air permeability at these depths were also determined. The changes in land use over time have induced a reduction in soil depth. Soils under NG showed a smaller soil water storage capacity, air capacity and permeability compared with soils under sNF, as well as waterlogging during winter and greater mechanical strength and soil profile temperatures during summer. Therefore, the land use change affected the spatial and temporal variability of soil physical functions across the field.

Pedotransfer functions to assess adsorbed phosphate using iron oxide content and magnetic susceptibility in an Oxisol

Abstract: Adsorbed phosphate in soils can be chemically extracted; however, this process is both time-consuming and not cost-effective if large numbers of samples have to be analysed. Indirect assessment of adsorbed phosphate by pedotransfer functions (PTFs) can help optimize fertilizer strategies. This study aimed to evaluate the spatial variability of adsorbed phosphate (Pads), iron oxides and magnetic susceptibility (MS) in oxisols and to calibrate PTFs to predict Pads. A total of 308 soil samples were collected from Hapludox and Eutrudox soils formed from sandstone in Brazil. The contents of clay (196–607 g/kg), iron oxides (40–165 g/kg), MS (1.2–29 × 10−6 m3/kg) and Pads (327–842 mg/kg) were in the range of typical values for these highly weathered soils. This study showed that the attributes studied were spatially dependent. Geomorphic surfaces enabled understanding of spatial variability and helped to develop a more efficient sampling scheme to calibrate PTFs. Moreover, the adsorbed phosphate in these oxisols could be predicted by a PTF using iron oxides and MS as predictors. The MS attribute enabled the most accurate prediction (concordance coefficient = 0.95, root-mean-square error = 46 mg/kg and relative improvement in root-mean-square error = −4.12) of spatial variability through PTF compared to other predictors.

Effects of ridge-furrow and plastic mulching planting patterns on microflora and potato tuber yield in continuous cropping soil

Abstract: Planting patterns have distinctive effects on the soil micro-ecological environment and soil quality. To explore the effects of film mulch ridge-furrow (FMRF) cropping on soil microbial properties and potato yield, a study was conducted in 2013 and 2014 in a continuously cropped field under nonfilm-mulched flat plot (CK), half-mulched flat plot (T1), fully mulched ridge cropping (T2), fully mulched furrow cropping (T3), half-mulched ridge cropping (T4) and half-mulched furrow cropping (T5) planting patterns. Our results indicate that T3 increased the average bacteria/fungi (B/F) ratio by 253% compared to CK. On average, half-mulched ridge cropping increased the bacteria population and aerobic Azotobacter by 9 and 19%, respectively, compared with CK. On average, T3 had the greatest inhibitory effect on fungi populations. Half-mulched furrow cropping had the most anaerobic Azotobacter and nitrifying bacteria. The study showed that FMRF increased soil bacteria, especially Azotobacter but reduced fungi and actinomycetes. Treatment T2 gave the greatest potato yield, followed by T4, whereas the greatest biomass yield was recorded in T4. Full-mulch furrow cropping methods produced the greatest nutrient use efficiency. The findings of this study enhance our understanding of soil microbe and plant responses to plastic mulch and planting patterns under semi-arid conditions.