The influence of N load and harvest intensity on the risk of P limitation in Swedish forest soils

Field burning of crop residue is a common post-harvest practice to dispose of these agricultural by-products and for land clearing. Burned crop residues may effectively adsorb pesticides and thus influence their bioavailability in agricultural soils. The adsorption of clomazone by a soil amended with a burned rice straw (BRS) was measured. The availability of clomazone to barnyardgrass in the soil in the absence and presence of BRS was tested. The BRS was 1000-20,000 times more effective than soil in sorbing clomazone. The sorption of clomazone by soil increased with increasing BRS amount in the soil. In a bioassay, the injury of barnyardgrass 9 days after planting decreased with increasing BRS amount in soil indicating the effect of BRS on clomazone availability. Residual analyses showed higher concentrations of clomazone in soils receiving higher rates of the herbicide than in soils with lower application rates suggesting the adsorptive role of BRS. At typical application rate of clomazone (0.3 microg g(-1)), BRS amounts of 0.02 wt.% and higher caused an appreciable reduction to a complete loss in clomazone availability. Calculations suggest that field burning of rice straw may result in sufficiently high amounts (>0.02 wt.%) of BRS, and hence contribute to often experienced loss of pesticide availability in agricultural soils. Our results may be extended to field situations where other crop residues and vegetation are burned. Alternative management of crop residues may improve the bioavailability of pesticides in agricultural soils.     

The impact of climate change on aquatic risk from agricultural pesticides in the US

We investigate how climate change may affect the acute and chronic toxicity risk to aquatic species from agricultural pesticides in 32 States of the US. We combine climate change projections from the Canadian and Hadley climate model, statistically estimated relationships between pesticide applications and climate and weather variables, and the environmental risk indicator REXTOX developed by the OECD. On average, we find that climate change is likely to increase the toxicity risk to aquatic species by 47% because of increased applications of agricultural pesticides. Daphnia and fish are more affected than algae. Across eight broad crop groups, pesticides used on pome and stone fruits and on fruiting vegetables contribute the most to aquatic risk. Within the 32 US States examined, more than 90% of the pesticide pollution impacts induced by climate change on the aquatic environment are caused by only 13 States near to the coast.     

Testing the validity of a Cd soil quality standard in representative Mediterranean agricultural soils under an accumulator crop

The validity of a quality standard for cadmium (Cd) in representative agricultural Mediterranean soils under an accumulator crop (Lactuca sativa L.) is evaluated in this work considering both its effect on the crop growth (biomass production) and the metal accumulation in the edible part of the plant. Four soils with different properties relevant to regulate the behaviour of heavy metals were selected from the Valencian Region, a representative area of the European Mediterranean Region. For all soils, the effective concentration of added Cd causing 50% inhibition (EC₅₀) on the biomass production was much higher than the minimum legal concentration used to declare soils as contaminated by cadmium, i.e. 100 times the baseline value for Cd, in Spain (Spanish Royal Decree 9/2005). As expected, Cd toxicity in the crop was higher in the soils having less carbonate content. On the other hand, for all soils, from the second dose on, which represents 10-times the baseline value for Cd, the metal content in crops exceeded the maximum level established for leaf crops by the European legislation (Regulation EC no. 466/2001). Soil salinity and coarse textures make the accumulation of Cd in the edible part of the plant easier. Therefore, the legal baseline soil cadmium content established by the Spanish legislation seems not valid neither from the point of view of the effect on the crop growth nor from the point of view of the metal accumulation in the edible part of the plant. In order to realistically declare contaminated soils by heavy metals, soil quality standards should be proposed taking into account the soil properties. Further research in other agricultural areas of the region would improve the basis for proposing adequate soil quality standards for heavy metals as highlighted by the European Thematic Strategy for Soil Protection.     

Heavy metal contents in horticultural crops of a representative area of the European Mediterranean region

Heavy metal content (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) was analysed in the edible parts of two types of horticultural crops (leaf and inflorescence crops) from 30 agricultural fields in Castellón (Spain), a representative area of the European Mediterranean region. Selected soil properties relevant to control the mobility and bioavaibility of heavy metals were analysed for the general characterisation of these agricultural soils. The levels of clay, high percentages of organic matter and the presence of carbonate seem to suggest an important retention of heavy metals by these components in most of these soils. However, the high salinity in some fields (>4 dS/m) seems to facilitate the mobility of some heavy metals (e.g. Cu). The mean values of total contents of heavy metals in soils were similar to values obtained in other works on Spanish agricultural soils. However, there were some fields with a metal content (particularly Cu, Pb or Zn) higher than these works, reflecting an important anthropogenic source. In seven fields, the crop contents of Cd and/or Pb were higher than the maximum levels established by the Commission Regulation no. 466/2001 for horticultural crops. Heavy metal contents in leaf crops were higher than in inflorescence crops, except for Zn. The differences for Cd, Cr, Cu, Fe and Mn contents between these two types of crops were statistically significant. The analysis of crop heavy metal contents showed a higher absorption and/or accumulation of heavy metals in leaf crops than in inflorescence crops. Differences in crop characteristics seem to be responsible for the differential accumulation of heavy metals. Furthermore, agronomic practices and other sources of heavy metals (e.g. atmospheric deposition for Cd and Pb) may also have some influence on crop accumulation. Given the relevance of horticultural crops in the Mediterranean diet, it is highly necessary to extend the experience of this work to other areas of the European Mediterranean region.     

Environmental implications of three modern agricultural practices: Conservation Agriculture,the System of Rice Intensification and Precision Agriculture

Substantial and rapid changes in agricultural land management practices are being made in many countries on all five inhabited continents: Conservation Agriculture, comprising practices that avoid or minimise mechanical soil disturbance, maintain a protective soil mulch cover, and produce crops in rotations or associations; the System of Rice Intensification, in which rice is grown in mainly moist, aerobic soils; and Precision Agriculture, using practices that optimise the use of seed, fertilisers and other production inputs. These management systems provide considerable financial benefits to farmers as well as important environmental benefits, including reversal of land degradation, reduction of river pollution, increased carbon sequestration and reduced greenhouse gas emissions. The nature and scale of these benefits need to be measured and monitored in different agro-ecological and socio-political environments. The reasons for different rates of adoption of these improved practices between and within countries also deserve examination.     

Impacts of climate change on the fate and behaviour of pesticides in surface and groundwater--A UK perspective

Over the last two decades significant effort has been dedicated to understanding the fate and transport of pesticides in surface water and groundwater and to use this understanding in the development of environmental policy and regulation. However, there have been few studies that have investigated the relationships between pesticides and climate change, and where this work has been undertaken it has principally been in relation to the impacts of climate change on agricultural production rather than in the context of environmental protection. This study addresses that gap by reviewing how climate change may impact the fate and transport of pesticides in surface and groundwaters as a pre-cursor to quantitative studies. In order to structure the review, we have adopted a source-pathway-receptor approach where climate sensitivities of pesticide source terms, environmental pathways and receptors are reviewed. The main climate drivers for changing pesticide fate and behaviour are thought to be changes in rainfall seasonality and intensity and increased temperatures, but the effect of climate change on pesticide fate and transport is likely to be very variable and difficult to predict. In the long-term, indirect impacts, such as land-use change driven by changes in climate, may have a more significant effect on pesticides in surface and groundwaters than the direct impacts of climate change on pesticide fate and transport. The review focuses on climate change scenarios and case studies from the UK; however, the general conclusions can be applied more widely.     

Climate impacts on European agriculture and water management in the context of adaptation and mitigation—The importance of an integrated approach

We review and qualitatively assess the importance of interactions and feedbacks in assessing climate change impacts on water and agriculture in Europe. We focus particularly on the impact of future hydrological changes on agricultural greenhouse gas (GHG) mitigation and adaptation options. Future projected trends in European agriculture include northward movement of crop suitability zones and increasing crop productivity in Northern Europe, but declining productivity and suitability in Southern Europe. This may be accompanied by a widening of water resource differences between the North and South, and an increase in extreme rainfall events and droughts. Changes in future hydrology and water management practices will influence agricultural adaptation measures and alter the effectiveness of agricultural mitigation strategies. These interactions are often highly complex and influenced by a number of factors which are themselves influenced by climate. Mainly positive impacts may be anticipated for Northern Europe, where agricultural adaptation may be shaped by reduced vulnerability of production, increased water supply and reduced water demand. However, increasing flood hazards may present challenges for agriculture, and summer irrigation shortages may result from earlier spring runoff peaks in some regions. Conversely, the need for effective adaptation will be greatest in Southern Europe as a result of increased production vulnerability, reduced water supply and increased demands for irrigation. Increasing flood and drought risks will further contribute to the need for robust management practices.The impacts of future hydrological changes on agricultural mitigation in Europe will depend on the balance between changes in productivity and rates of decomposition and GHG emission, both of which depend on climatic, land and management factors. Small increases in European soil organic carbon (SOC) stocks per unit land area are anticipated considering changes in climate, management and land use, although an overall reduction in the total stock may result from a smaller agricultural land area. Adaptation in the water sector could potentially provide additional benefits to agricultural production such as reduced flood risk and increased drought resilience.The two main sources of uncertainty in climate impacts on European agriculture and water management are projections of future climate and their resulting impacts on water and agriculture. Since changes in climate, agricultural ecosystems and hydrometeorology depend on complex interactions between the atmosphere, biosphere and hydrological cycle there is a need for more integrated approaches to climate impacts assessments. Methods for assessing options which “moderate” the impact of agriculture in the wider sense will also need to consider cross-sectoral impacts and socio-economic aspects.     

Soil management systems and short term CO₂ emissions in a clayey soil in southern Spain

The soil in general and that destined for agricultural use, more specifically, can act as a source or sink of carbon, hence its direct involvement in strategies for mitigating climate change. A large proportion of this mitigation potential is produced by the sequestration of carbon by soils and, to a lesser extent, by a reduction in emissions from the soil.The most effective practices for increasing the organic carbon in the soils are generally those linked to conservation agriculture, which includes practices of no tillage or minimum tillage and the use of cover crops. During the farming seasons of 2006/07, 2007/08, 2008/09 and 2009/10, a trial was conducted in which the carbon dioxide emissions in soil with a high percentage of clay in the Vega de Carmona (Seville) were estimated, and it was determined how climate conditions and the adoption of conservation agriculture practices vs. the use of traditional tillage influenced the flux of gas into the atmosphere.     

Contact-time-dependent atrazine residue formation in surface soils

The formation of nonextractable atrazine residues was evaluated in sterilized agricultural and woodland soils pre-loaded with ¹⁴C-atrazine for contact periods of 1 h (0.046 days), and 1, 7, 14, 28, 56, and 84 days. Extractability of the pre-loaded atrazine and nonextractable residue formation were determined by subjecting the soils to sequential fill-and-draw extractions with water, ethylacetate/water, and alkali. Nonextractable atrazine residues associated with the fulvic acid (FA), humic acid (HA) and humin/mineral (HM) components of soil were determined by separating FA and HA from the soils and measuring the ¹⁴C-activity associated with each fraction. Longer herbicide–soil contact times resulted in attenuated water extractability and enhanced nonextractable residue formation. At the longest contact periods, residues recovered in the FA, HA and HM components of soil accounted for 35–50% of the pre-loaded herbicide. The woodland soil contained significantly larger amounts of HA and humin than the agricultural soil, and appeared to have contributed significantly to nonextractable residue formation. Results from this study indicate that physicochemical processes occurring at intra-mineral and intra-organic matter sites continue to influence the fate of organic pesticides long after their application on soils.     

Impacts of climate and land‐cover changes on water resources in a humid subtropical watershed: a case study from East Texas,USA

This study investigates the response of water resources regarding the climate and land‐cover changes in a humid subtropical watershed during the period 1970–2009. A 0.7°C increase in temperature and a 16.3% increase in precipitation were observed. Temperature had a lower increase trend, and precipitation showed definite increasing trend compared to previous studies. The main trend of land‐cover change was conversion of vegetation and barren lands to developed and crop lands affected by human intervention, and forest and grass to bush/shrub which considered to be caused by natural climate system. Hydrologic responses to climate and land‐cover changes resulted in increases of surface run‐off (15.0%), soil water content (2.7%), evapotranspiration (20.1%) and a decrease in groundwater discharge (9.2%). We found that surface run‐off is relatively stable with precipitation, whereas groundwater discharge and soil water content are sensitive to changes in land cover, especially land cover brought about by human intervention.     

Projected water consumption in future global agriculture: scenarios and related impacts

Global stress on water and land resources is increasing as a consequence of population growth and higher caloric food demand. Many terrestrial ecosystems have already massively been degraded for providing agricultural land, and water scarcity related to irrigation has damaged water dependent ecosystems. Coping with the food and biomass demand of an increased population, while minimizing the impacts of crop production, is therefore a massive upcoming challenge. In this context, we developed four strategies to deliver the biotic output for feeding mankind in 2050. Expansion on suitable and intensification of existing areas are compared to assess associated environmental impacts, including irrigation demand, water stress under climate change, and the productivity of the occupied land. Based on the agricultural production pattern and impacts of the strategies we identified the trade-offs between land and water use. Intensification in regions currently under deficit irrigation can increase agricultural output by up to 30%. However, intensified crop production causes enormous water stress in many locations and might not be a viable solution. Furthermore, intensification alone will not be able to meet future food demand: additionally, a reduction of waste by 50% along the food supply chain or expansion of agricultural land is required for satisfying current per-capita meat and bioenergy consumption. Suitable areas for such expansion are mainly located in Africa, followed by South America. The increased land stress is of smaller concern than the water stress modeled for the intensification case. Therefore, a combination of waste reduction with expansion on suitable pastures generally results as the best option, along with some intensification on selected areas. Our results suggested that minimizing environmental impacts requires fundamental changes in agricultural systems and international cooperation, by producing crops where it is most environmentally efficient and not where it is closest to demand or cheapest.     

The potential of pesticides to contaminate the groundwater resources of the Axios river basin in Macedonia, Northern Greece. Part I. Monitoring study in the north part of the basin

The Axios river basin is an area of high agricultural importance for Macedonia, Northern Greece. High priced crops such as cotton, corn, sugarbeets, vegetables and rice are rotated with cereals and alfalfa and thus a great variety of pesticides are used annually for the control of pests and diseases. Moreover, the groundwater resources of the specific area constitute the main source of potable water for the surrounding cities and villages. Therefore, a study was initiated to investigate the probable risks of groundwater contamination with pesticides. The leaching of pesticides from agricultural soils was monitored in the phreatic horizon as well as in soil water samples collected with suction lysimeters. In parallel studies, the presence of pesticides in the irrigation water and the water of Axios river was also monitored. Pesticides like carbofuran, atrazine, alachlor and prometryne, which were regularly applied in the northern part of the basin during 1992-1994 were detected at concentrations occasionally exceeding 1 microg/l in soil water from the deeper soil layers and in the phreatic horizon. Residues of pesticides others than the ones applied in the studied area like propanil, terbufos and paraoxon-methyl were also detected at the deeper soil layers and in the phreatic horizon. The latter pesticides were also detected at significant concentrations in the irrigation water which mainly consisted of riverine water. The lack of an independent soil draining system and the use of riverine water for irrigation purposes resulted in the redistribution of residual amounts of these pesticides in the phreatic horizon beneath the agricultural area.     

Erosion of arable soils in Britain

Changing perspectives on erosion problems on British arable soils are reviewed. Current agricultural practices are increasing the magnitude and extent of soil erosion in Britain and other parts of Europe. Current trends in soil erosion research are examined, in particular recent field survey developments and the potential value of radar‐satellite based monitoring of erosive weather systems. More attention should be devoted to assessing levels of erosion on British arable soils and to the implications of current erosion rates on the long‐term ability of soil to act as a medium for sustained crop yield. Proposed strategies for soil conservation include avoiding cultivation of steep slopes, increasing soil organic content, reducing soil compaction, investigating and remedying sub‐soil compaction, developing a mature crop cover before convective storms occur in early summer and reducing cultivations to a minimum.     

Interactions between abiotic filters,landscape structure and species traits as determinants of dairy farmland plant diversity

Maintaining farmland biodiversity in Europe under scenarios of agricultural intensification is a keystone challenge of nature conservation. The recruitment of species from the regional pool to local landscape mosaics and individual patches is known to be determined by multi-scale ecological filters. Here we aimed at clarifying the relative importance of the physical environment, land use and landscape structure, and species traits, as filters of landscape-level plant species diversity in intensive farmland. Vascular plant species diversity was surveyed in 18 dairy farmland mosaics along a gradient of agricultural specialisation in Northern Portugal. Plant species were grouped according to their life strategy, biogeographic origin, and synecological preferences. Species richness was found to be highest in lowland areas, where warmer climate and nutrient-rich soils contribute to balance the potential negative effects of intensive farming. Multiple predictors, related to physical environment (e.g. climate), land use (e.g. crop area), and landscape structure (e.g. mean patch size), were found to influence diversity patterns, even under the homogenizing effects of agricultural intensification. Dissimilarity models discriminated distinct types of responses, with patterns for biogeographic and synecological groups of species being better predicted by landscape based models. In contrast, a dominant role of physical predictors was observed in explaining diversity patterns for plant strategies. Overall, our results confirmed that physical environmental gradients, land use, landscape structure, and species traits interact in determining landscape-level plant diversity patterns. Such patterns may influence agro-ecosystem responses to environmental changes, and thus should be considered in the development of agri-environmental policies and monitoring schemes.     

Land-use versus natural controls on soil fertility in the Subandean Amazon, Peru

Deforestation to amplify the agricultural frontier is a serious threat to the Amazon forest. Strategies to attain and maintain satisfactory soil fertility, which requires knowledge of spatial and temporal changes caused by land-use, are important for reaching sustainable development. This study highlights these issues by evaluating the relative effects of agricultural land-use and natural factors on chemical fertility of Inceptisols on redbed lithologies in the Subandean Amazon. Macro and micronutrients were determined in topsoil and subsoil in the vicinity of two villages at a total of 80 sites including pastures, coffee plantations, swidden fields, secondary forest and, as a reference, adjacent primary forest. Differences in soil fertility between the land cover classes were investigated by principal component analysis (PCA) and partial least squares regression (PLSR). Primary forest soil was found to be chemically similar to that of coffee plantations, pastures and secondary forests. There were no significant differences between soils of these land cover types in terms of plant nutrients (e.g. N, P, K, Ca, Mg, Mo, Mn, Zn, Cu and Co) or other fertility indicators (OM, pH, BS, EC, CECe and exchangeable acidity). The parent material (as indicated by texture and sample geographical origin) and the slope of the sampled sites were stronger controls on soil fertility than land cover type. Elevated concentrations of a few nutrients (NO₃ and K) were, however detected in soils of swidden fields. Despite being fertile (higher CECe, Ca and P) compared to Oxisols and Ultisols in the Amazon lowland, the Subandean soils frequently showed deficiencies in several nutrients (e.g. P, K, NO₃, Cu and Zn), and high levels of free Al at acidic sites. This paper concludes that deforestation and agricultural land-use has not introduced lasting chemical changes in the studied Subandean soils that are significant in comparison to the natural variability.     

Fate characterization of a novel herbicide ZJ0273 in aerobic soils using multi-position C labeling

ZJ0273, propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy)benzylamino)benzoate, is a novel herbicide being developed for use on rape crops. The environmental behavior and fate of ZJ0273, however, are not well understood. In this study, multi-position ¹⁴C-labeled compounds (B-ZJ0273 and C-ZJ0273) were used to investigate the fate of ZJ0273 in aerobic soils, and compare their differences in extractable residues (ER), bound residues (BR), and mineralization. ER for both ¹⁴C labels followed a similar dissipation trend in the same soil, and results showed a strong effect of soil pH, with the ER level being significantly higher in acidic soils than neutral or alkaline soils. The disappearance of parent compound followed first-order dynamics for both labels in the same soils. No difference in BR was observed between the two ¹⁴C-labels. BR increased with time and reached 17.5-35.3% of applied ¹⁴C in the three soils after 100-d incubation, which is much smaller than the non-accumulative criteria (70%) as stated in the directives by the Commission of the European Communities. Mineralization to CO₂ also depended closely on the soil type, with the cumulative mineralized fraction being substantially greater in the neutral and alkaline soils than in the acidic soil. Results also showed that cumulative mineralization rates of the two labels in the acidic soil were much smaller than those in the neutral and alkaline soils. Mineralization of C-ZJ0273 (1.2-9.9%) was found to be more extensive than that of B-ZJ0273 (0.5-6.6%), suggesting that benzyl ring was more susceptible to cleavage than pyrimidine ring. The use of multi-position labeling proved to be valuable; it served the purpose of validating the rigorousness of experimental protocols, and provided insights into the behavior and fate of the different molecular fragments.     

Sewage Sludge Recycling to Agricultural Land: the Environmental Scientist's Perspective

During the next fifteen years, the recycling of sewage sludge to agricultural land will increase significantly in Scotland as a result of EC regulations. This paper describes how soils and related environmental data around Edinburgh can be interrogated and interpreted to assess (a) the suitability of land for sludge utilization, (b) the risk of water pollution in relation to different soil conditions, (c) the ability of soils to adsorb potentially toxic elements in the sludge to prevent transfer to water or plants, and (d) the operational security and environmental sustainability of sludge recycling. The interpretations can make a valuable contribution to the appraisal of sludge disposal policy and implementation, and provide a framework for technology transfer between engineering, environmental and agricultural interests.     

The Impact of Dry Years on Crop Water Requirements in Eastern England

Agricultural water demand is weather and climate driven. Irrigated crop production which makes the largest agricultural demands is highly seasonal, water only being required in a few summer months. A 'droughtiness'factor which is based on crop type and potential soil moisture deficit indicates large differences in the amount and timing of water demand for different crops. Soils with low water retention capacity are shown to be marginal for the potato crop unless irrigation is available in these areas. Economic data are presented which indicate that potato production realizes a considerable benefit from investment in irrigation, but this leads to inertia in the relocation of agricultural production centres in dry years. It is concluded that investment in on-farm winter water storage for irrigation should be a priority investment in eastern England.     

Stream cation concentrations and losses from drainage basins with contrasting land uses in Southern Ontario

The concentration and loss of major cations from 22 watersheds near Toronto, Ontario, was measured over a 27-month period. Calcium and potassium concentrations exhibited a positive relationship with crop area and a negative correlation with abandoned farm land + forest and areas of sand + sandy loam soil. The influence of soil properties and farming activities on streám cation levels could not be separated because of multicollinearity between land use and soils. An absence of correlation between crop area and annual losses of calcium and potassium can be attributed to lower annual stream discharges in agricultural watersheds in comparison to watersheds containing extensive areas of forest and abandoned farm land. Stream concentrations and losses of potassium and sodium were positively correlated with urban land use. Detailed water sampling in the vicinity of urban centres confirmed that these areas are important contributors of sodium, and to a lesser extent, of potassium to streams. Magnesium concentration was influenced mainly by differences in watershed hydrology and no correlation was evident with urban or agricultural land use.     

Carbon losses from soil and its consequences for land-use management

This paper reviews our current knowledge and understanding of carbon processes in the terrestrial ecosystem with a view to reducing soil carbon losses by optimising land-use and land management. Processes that influence the fate of carbon (in both terms of quantity and quality) are important in determining soil fertility, quality and health as well as consequences for future environmental change scenarios. We need to understand the processes that determine soil carbon losses and the fate of the carbon once lost from the soil in order to provide sustainable solutions for mitigating these carbon losses as part of land management "best practice" and balancing national carbon budgets. Here we review the amount of carbon within the UK terrestrial pool, the processes involved and factors influencing carbon transport to and from soils, the fate of the carbon once it has been lost from the soil environment and land-use scenarios that affect carbon losses. We conclude with possible management options to reduce soil carbon loss and identify gaps in knowledge in order to better understand carbon processes in the terrestrial environment.