Nutrient losses from agricultural areas in the Gulf of Riga drainage basin

Leaching and runoff losses of nitrogen and phosphorus were measured in four catchments in Estonia and Latvia during the period 1994–1997. The losses varied considerably depending on land use and farming practices. In two catchments characterised by cereal production and moderate inputs of plant nutrients, the losses were found to be at a low level, compared to measurements in similar catchments in Norway and Sweden. Very large leaching and runoff losses were recorded in two catchments characterised by heavy applications of pig slurry. In one of these catchments, high losses were recorded even though farming activities ceased in 1991–1992. The effects of slurry applications seem more marked for P than for N. The study shows that the former large state and collective farms that specialised in animal production may still be potential risks for the environmental quality of Estonian and Latvian waters.     

Soil Erosion Impact on Agronomic Productivity and Environment Quality

Soil erosion is a global issue because of its severe adverse economic and environmental impacts. Economic impacts on productivity may be due to direct effects on crops/plants on-site and off-site, and environmental consequences are primarily off-site due either to pollution of natural waters or adverse effects on air quality due to dust and emissions of radiatively active gases. Off-site economic effects of erosion are related to the damage to civil structure, siltation of water ways and reservoirs, and additional costs involved in water treatment. There are numerous reports regarding the on-site effects of erosion on productivity. However, a vast majority of these are from the U.S., Canada, Australia, and Europe, and only a few from soils of the tropics and subtropics. On-site effects of erosion on agronomic productivity are assessed with a wide range of methods, which can be broadly grouped into three categories: agronomic/soil quality evaluation, economic assessment, and knowledge surveys. Agronomic methods involve greenhouse and field experiments to assess erosion-induced changes in soil quality in relation to productivity. A widely used technique is to establish field plots on the same soil series but with different severity of past erosion. Different erosional phases must be located on the same landscape position. Impact of past erosion on productivity can also be assessed by relating plant growth to the depth of a root-restrictive horizon. Impact of current erosion rate on productivity can be assessed using field runoff plots or paired watersheds, and that of future erosion using topsoil removal and addition technique. Economic evaluation of the on-site impact involves assessment of the losses of plant available water and nutrients and other additional inputs needed due to erosion. Knowledge surveys are conducted as a qualitative substitute for locations where quantitative data are not available. Results obtained from these different techniques are not comparable, and there is a need to standardize the methods and develop scaling procedures to extrapolate the data from plot or soil level to regional and global scale. There is also a need to assess on-site impact of erosion in relation to soil loss tolerance, soil life, soil resilience or ease of restoration, and soil management options for sustainable use of soil and water resources. Restoration of degraded soils is a high global priority. If about 1.5×10⁹?ha of soils in the world prone to erosion can be managed to effectively control soil erosion, it would improve air and water quality, sequester C in the pedosphere at the rate of about 1.5?Pg/year, and increase food production. The risks of global annual loss of food production due to accelerated erosion may be as high as 190×10⁶?Mg of cereals, 6×10⁶?Mg of soybeans, 3×10⁶?Mg of pulses, and 73×10⁶?Mg of roots and tubers. The actual loss may depend on weather conditions during the growing season, farming systems, soil management, and soil ameliorative input used. Erosion-caused losses of food production are most severe in Asia, Sub-Saharan Africa, and elsewhere in the tropics rather than in other regions.     

不同耕作和覆盖方式对紫色丘陵区坡耕地水土及养分流失的影响

采用随机区组试验,研究了四川紫色丘陵区坡耕地不同耕作和覆盖方式对玉米生育期中水土及养分流失的影响。结果表明:秸秆覆盖对减少水土流失和增加玉米产量的效果均优于地膜覆盖。秸秆覆盖能显著减少地表径流(73.9%—86.2%),但增加了壤中流(15.4%—156.4%);使径流总量降低32.5%—66.6%,并极显著降低土壤侵蚀总量达96.4%—98.1%。地膜覆盖虽能在一定程度上减少壤中流和径流总深,但差异未达到显著水平。土壤N平均损失量达37.4kg/hm2,其中70.1%经由壤中流流失。秸秆覆盖虽然增加了一定的壤中流N损失,但能减少N流失总量达12.8%—65.1%。土壤P素损失量相对较小,仅为9.32kg/hm2,并主要随侵蚀泥沙迁移,占流失总量的92.1%。土壤K损失量达183.3kg/hm2,其流失载体也主要是侵蚀泥沙,占96.5%。因此,两种覆盖方式均能显著控制土壤P和K的损失。无论是秸秆还是地膜覆盖,与顺坡垄作相比,横坡垄作均能减少地表径流、地下径流、土壤侵蚀量及氮、磷、钾素总流失量,同时还能提高玉米产量。从简便、增产和防治面源污染的角度考虑,紫色土区坡耕地最适宜的种植方式为平作+秸秆覆盖。     

Mixed crop-livestock systems: an economic and environmental-friendly way of farming?

Intensification and specialisation of agriculture in developed countries enabled productivity to be improved but had detrimental impacts on the environment and threatened the economic viability of a huge number of farms. The combination of livestock and crops, which was very common in the past, is assumed to be a viable alternative to specialised livestock or cropping systems. Mixed crop-livestock systems can improve nutrient cycling while reducing chemical inputs and generate economies of scope at farm level. Most assumptions underlying these views are based on theoretical and experimental evidence. Very few assessments of their environmental and economic advantages have nevertheless been undertaken in real-world farming conditions. In this paper, we present a comparative assessment of the environmental and economic performances of mixed crop-livestock farms v. specialised farms among the farm population of the French ‘Coteaux de Gascogne’. In this hilly region, half of the farms currently use a mixed crop-livestock system including beef cattle and cash crops, the remaining farms being specialised in either crops or cattle. Data were collected through an exhaustive survey of farms located in our study area. The economic performances of farming systems were assessed on 48 farms on the basis of (i) overall gross margin, (ii) production costs and (iii) analysis of the sensitivity of gross margins to fluctuations in the price of inputs and outputs. The environmental dimension was analysed through (i) characterisation of farmers’ crop management practices, (ii) analysis of farm land use diversity and (iii) nitrogen farm-gate balance. Local mixed crop-livestock farms did not have significantly higher overall gross margins than specialised farms but were less sensitive than dairy and crop farms to fluctuations in the price of inputs and outputs considered. Mixed crop-livestock farms had lower costs than crop farms, while beef farms had the lowest costs as they are grass-based systems. Concerning crop management practices, our results revealed an intensification gradient from low to high input farming systems. Beyond some general trends, a wide range of management practices and levels of intensification were observed among farms with a similar production system. Mixed crop-livestock farms were very heterogeneous with respect to the use of inputs. Nevertheless, our study revealed a lower potential for nitrogen pollution in mixed crop-livestock and beef production systems than in dairy and crop farming systems. Even if a wide variability exists within system, mixed crop-livestock systems appear to be a way for an environmental and economical sustainable agriculture.     

Phosphorus budget in the Marne Watershed (France): urban vs. diffuse sources,dissolved vs. particulate forms

We evaluated the P sources (point, diffuse), through a nested watershed approach investigating the Blaise (607 km²), dominated by livestock farming, the Grand Morin (1202 km²), dominated by crop farming, and the Marne (12,762 km²), influenced by both agriculture and urbanization. Fertilizers account for the main P inputs (>60%) to the soils. An agricultural P surplus (0.5–8 kg P ha^–1 year^–1) contributes to P enrichment of the soil. The downstream urbanized zone is dominated by point sources (60%, mainly in dissolved forms), whereas in the upstream basin diffuse sources dominate (60%, mostly particulate). Among the diffuse sources (losses by forests, drainage and runoff), losses by runoff clearly dominate (>90%). P retention in the alluvial plain and the reservoir represents 15–30% of the total P inputs. Dissolved and particulate P fluxes at the outlet of the Marne are similar (340 and 319 tons of P year^–1, respectively). The Blaise sub-basin receives P from point and diffuse sources in equal proportions, and retention is negligible. The Grand-Morin sub-basin, influenced by the urbanized zone receives, as does to the whole Marne basin, 60% of P inputs as point sources. The total particulate phosphorus in suspended sediments averaged 1.28 g P kg^–1, of which about 60% are inorganic and 40% organic P. Particulate phosphorus exchangeable in 1 week and 1 year (³²P isotopic method) accounts for between almost 26% and 54% of the particulate inorganic phosphorus in the suspended sediment and might represent an important source of dissolved P, possibly directly assimilated by the vegetation.     

General Trends of Technological Changes in Agriculture

In this article we show that technological development in agriculture exhibits general trends when assessed on a large scale. These trends are generated by changes in the larger socioeconomic context in which the farming system operates. We characterize agricultural performance by land and farm labor productivity and the pattern of use of technological inputs. By means of a cross-sectional analysis of agricultural performance of 20 countries (at the national level), we show that increases in demographic pressure and socioeconomic pressure (increases in average income and labor productivity) in society are the main driving forces of technological development in agriculture. Further, it is shown that the ecological impact of farming (environmental loading) is linked to the particular combination of land productivity and labor productivity at which the agricultural sector operates (through the particular mix and the level of inputs used in agricultural production). Briefly we discuss the role of international trade in agricultural policies and performance. Special attention is given to the situation of Chinese agriculture.     

Closing the phosphorus cycle in a food system: insights from a modelling exercise

Mineral phosphorus (P) used to fertilise crops is derived from phosphate rock, which is a finite resource. Preventing and recycling mineral P waste in the food system, therefore, are essential to sustain future food security and long-term availability of mineral P. The aim of our modelling exercise was to assess the potential of preventing and recycling P waste in a food system, in order to reduce the dependency on phosphate rock. To this end, we modelled a hypothetical food system designed to produce sufficient food for a fixed population with a minimum input requirement of mineral P. This model included representative crop and animal production systems, and was parameterised using data from the Netherlands. We assumed no import or export of feed and food. We furthermore assumed small P soil losses and no net P accumulation in soils, which is typical for northwest European conditions. We first assessed the minimum P requirement in a baseline situation, that is 42% of crop waste is recycled, and humans derived 60% of their dietary protein from animals (PA). Results showed that about 60% of the P waste in this food system resulted from wasting P in human excreta. We subsequently evaluated P input for alternative situations to assess the (combined) effect of: (1) preventing waste of crop and animal products, (2) fully recycling waste of crop products, (3) fully recycling waste of animal products and (4) fully recycling human excreta and industrial processing water. Recycling of human excreta showed most potential to reduce P waste from the food system, followed by prevention and finally recycling of agricultural waste. Fully recycling P could reduce mineral P input by 90%. Finally, for each situation, we studied the impact of consumption of PA in the human diet from 0% to 80%. The optimal amount of animal protein in the diet depended on whether P waste from animal products was prevented or fully recycled: if it was, then a small amount of animal protein in the human diet resulted in the most sustainable use of P; but if it was not, then the most sustainable use of P would result from a complete absence of animal protein in the human diet. Our results apply to our hypothetical situation. The principles included in our model however, also hold for food systems with, for example, different climatic and soil conditions, farming practices, representative types of crops and animals and population densities.     

Theory and Practice of the Cropping Systems Approach to Reducing Nematode Problems in the Tropics

Plant-parasitic nematodes are major constraints to the productivity of tropical farming operations. Intensive land use and climatic conditions favorable to nematode development contribute to increased crop losses due to these pests. Many farmers in developing tropical countries have limited resources and management options. Cropping systems research is a relatively low-cost, low-input method of optimizing existing agricultural practices with respect to limiting losses due to plant-parasitic nematodes. Specific tropical farming practices are discussed along with problems they pose for research in quantitative hematology. Comprehensive, systematic research methods for delineating and using nematode-host relationships are described, and new ways of dealing with complex multicropping systems are suggested.     

Strategies for farmers and policy makers to control nitrogen losses whilst maintaining crop production

The nitrogen (N) cycle is essentially 'leaky'. The losses of small amounts of nitrate to waters and of ammonia and nitrous oxide to the atmosphere are a part of the global biogeochemical N cycle. However, intensive agricultural production, industry and vehicle use have more tem change and health concerns. Research has identified agricultural practices that cause large losses of N and, in some cases, developed solutions. This paper discusses the problems of maintaining productivity while reducing N losses, compares conventional with low input (integrated) and organic farming systems, and discusses wider options. It also looks at the need to integrate studies on N with other environmental impacts, set in the context of the whole farm system, to provide truly sustainable agricultural systems.     

Soil biochemical properties and crop productivity following application of locally produced biochar at organic farms on Waldron Island,WA

Biochar (a carbon-rich product from pyrolysis of organic materials) additions to agricultural soils have been shown to often result in neutral to positive influences on soil properties and processes; however, the only a limited number of studies have been conducted on active organic farming systems and of those, none have used multivariate analytical methods to examine the influence of biochar on soil microbial activity, nutrient cycling, and crop performance. In this study, biochar produced from local timber harvest residues on Waldron Island, WA was applied in factorial combination with a poultry litter based fertilizer to replicated plots on six organic farms that were all growing Kabocha squash (Cucurbita maxima) in the summer of 2016. A series of soil physicochemical and biochemical properties were examined after 5 months of biochar application; squash samples were evaluated for productivity and nutrient uptake. Factorial multivariate analysis of variance (MANOVA) revealed a significant influence of biochar on soil properties as well as a synergistic effect of biochar and poultry litter during a 5 month field trial. Principle component analysis (PCA) highlighted soil total C content, microbial biomass C, enzyme activities, bioavailable P, and phosphatase enzyme activity as the variables most influenced by biochar incorporation into surface mineral soil. Redundancy analysis (RDA) further indicated that better soil biochemical conditions, particularly soil enzyme activities and available P concentrations, were associated with higher crop productivity in biochar-treated plots. Overall, our study demonstrates that locally produced wood biochar, in addition to improving soil C storage, has the potential to significantly improve soil fertility and crop productivity in organic farming systems on sandy soils.     

Strategies for farmers and policy makers to control nitrogen losses whilst maintaining crop production

The nitrogen (N) cycle is essentially ‘leaky’. The losses of small amounts of nitrate to waters and of ammonia and nitrous oxide to the atmosphere are a part of the global biogeochemical N cycle. However, intensive agricultural production, industry and vehicle use have more than doubled the amount of ‘reactive’ N in the environment, resulting in eutrophication, ecosystem change and health concerns. Research has identified agricultural practices that cause large losses of N and, in some cases, developed solutions. This paper discusses the problems of maintaining productivity while reducing N losses, compares conventional with low input (integrated) and organic farming systems, and discusses wider options. It also looks at the need to integrate studies on N with other environmental impacts, set in the context of the whole farm system, to provide truly sustainable agricultural systems.     

Strategies for farmers and policy makers to control nitro-gen losses whilst maintaining crop production

The nitrogen (N) cycle is essentially 'leaky'. The losses of small amounts of nitrate to waters and of ammonia and nitrous oxide to the atmosphere are a part of the global biogeo-chemical N cycle. However, intensive agricultural production, industry and vehicle use have more than doubled the amount of 'reactive' N in the environment, resulting in eutrophication, ecosystem change and health concerns. Research has identified agricultural practices that cause large losses of N and, in some cases, developed solutions. This paper discusses the problems of maintaining productivity while reducing N losses, compares conventional with low input (integrated) and organic farming systems, and discusses wider options. It also looks at the need to integrate studies on N with other environmental impacts, set in the context of the whole farm system, to provide truly sustainable agricultural systems.     

Environmental, Social, and Management Drivers of Soil Nutrient Mass Balances in an Extensive Andean Cropping System

Sustainable nutrient cycling in agroecosystems combining grazing and crops has global ramifications for protecting these ecosystems and for the livelihoods they support. We sought to understand environmental, management, and social drivers of nutrient management and sustainability in Andean grazing/crop systems. We assessed the impact of farmer wealth, fields’ proximity to villages, topography, and rangeland net primary productivity (NPP) on mass balances for nitrogen (N), phosphorus (P), and potassium (K) of 43 fields. Wealthier farmers applied greater total amounts (kg) of manure nutrients. However, higher manure application rates (kg ha^?1) were associated with field proximity and NPP rather than wealth. Manure P inputs in far fields (> 500-m distant) were half those in near fields. Harvest exports increased with manure inputs (P < 0.001) so that balances varied less than either of these flows. Erosion nutrient losses in steeper far fields matched crop exports, and yields declined with increasing field slope (P < 0.001), suggesting that erosion reduces productivity. Balances for P were slightly positive in near and far fields (+2.2 kg P ha^?1 y^?1, combined mean) when calculated without erosion, but zero in near fields and negative in far fields with erosion included (?6.1 kg P ha^?1 y^?1 in far fields). Near/far differences in both inputs and erosion thus drove P limitation. Crop K exports dominated K balances, which were negative even without accounting for erosion. Modeled intensification scenarios showed that remediating far field deficits would require P addition and erosion reduction. Management nested within environmental constraints (NPP, erosion) rather than socioeconomic status drives soil nutrient sustainability in these agroecosystems. Time-lags between management and long-term degradation are a principal sustainability challenge to farming in these montane grazing/crop agroecosystems.     

Managing agricultural phosphorus for water quality protection: principles for progress

Background

The eutrophication of aquatic systems due to diffuse pollution of agricultural phosphorus (P) is a local, even regional, water quality problem that can be found world-wide.

Scope

Sustainable management of P requires prudent tempering of agronomic practices, recognizing that additional steps are often required to reduce the downstream impacts of most production systems.

Conclusions

Strategies to mitigate diffuse losses of P must consider chronic (edaphic) and acute, temporary (fertilizer, manure, vegetation) sources. Even then, hydrology can readily convert modest sources into significant loads, including via subsurface pathways. Systemic drivers, particularly P surpluses that result in long-term over-application of P to soils, are the most recalcitrant causes of diffuse P loss. Even in systems where P application is in balance with withdrawal, diffuse pollution can be exacerbated by management systems that promote accumulation of P within the effective layer of effective interaction between soils and runoff water. Indeed, conventional conservation practices aimed at controlling soil erosion must be evaluated in light of their ability to exacerbate dissolved P pollution. Understanding the opportunities and limitations of P management strategies is essential to ensure that water quality expectations are realistic and that our beneficial management practices are both efficient and effective.     

Opportunities for improving phosphorus-use efficiency in crop plants

Limitation of grain crop productivity by phosphorus (P) is widespread and will probably increase in the future. Enhanced P efficiency can be achieved by improved uptake of phosphate from soil (P-acquisition efficiency) and by improved productivity per unit P taken up (P-use efficiency). This review focuses on improved P-use efficiency, which can be achieved by plants that have overall lower P concentrations, and by optimal distribution and redistribution of P in the plant allowing maximum growth and biomass allocation to harvestable plant parts. Significant decreases in plant P pools may be possible, for example, through reductions of superfluous ribosomal RNA and replacement of phospholipids by sulfolipids and galactolipids. Improvements in P distribution within the plant may be possible by increased remobilization from tissues that no longer need it (e.g. senescing leaves) and reduced partitioning of P to developing grains. Such changes would prolong and enhance the productive use of P in photosynthesis and have nutritional and environmental benefits. Research considering physiological, metabolic, molecular biological, genetic and phylogenetic aspects of P-use efficiency is urgently needed to allow significant progress to be made in our understanding of this complex trait.     

Biological nitrogen fixation: An efficient source of nitrogen for sustainable agricultural production?

A fundamental shift has taken place in agricultural research and world food production. In the past, the principal driving force was to increase the yield potential of food crops and to maximize productivity. Today, the drive for productivity is increasingly combined with a desire for sustainability. For farming systems to remain productive, and to be sustainable in the long-term, it will be necessary to replenish the reserves of nutrients which are removed or lost from the soil. In the case of nitrogen (N), inputs into agricultural systems may be in the form of N-fertilizer, or be derived from atmospheric N₂ via biological N₂ fixation (BNF).Although BNF has long been a component of many farming systems throughout the world, its importance as a primary source of N for agriculture has diminished in recent decades as increasing amounts of fertilizer-N are used for the production of food and cash crops. However, international emphasis on environmentally sustainable development with the use of renewable resources is likely to focus attention on the potential role of BNF in supplying N for agriculture. This paper documents inputs of N via symbiotic N₂ fixation measured in experimental plots and in farmers' fields in tropical and temperate regions. It considers contributions of fixed N from legumes (crop, pasture, green manures and trees), Casuarina, and Azolla, and compares the relative utilization of N derived from these sources with fertilizer N.     

Reducing soil erosion and the loss of soil fertility for environmentally-sustainable agricultural cropping and livestock production systems

My proposals for reducing soil erosion are based on my experience of assessing erosion, largely in Britain, both of cultivated land and of upland grazings. I have assessed the extent and rates of erosion in the field mostly by using easily‐ and rapidly‐used photographic and measurement techniques, rather than by using experimental plots set up either in the field or laboratory which overstate erosion. Policies which have governed the economics of agricultural production have also been examined. Much of the increase in occurrence of runoff and soil erosion in Britain is due to changes in land use and in intensity of use since the Agriculture Act was passed in 1947, and especially since joining the Common Market in 1973, with its even greater emphasis on paying for increased production. The increasing numbers of animals grazing the land, especially sheep, led to the initiation and erosion of bare soil in the uplands and to trampling and puddling of soils in lowland pastures. There is evidence that runoff from the land, and sedimentation of water courses have also increased. In the cultivated lowlands, the expansion in area of land drilled to winter cereals, the increase in area of land sown to maize or used to rear outdoor pigs, changes in farming techniques, and larger machines working in larger fields can explain much of the increase in erosion. Reversing some of these changes, for example by lowering the intensity of grazing and inserting grass (set‐aside) into the arable rotation will reduce the extent of erosion. Other techniques to reduce erosion are well‐known but need national and international agricultural policies that improve farmers' incomes to bring them into use. In developed countries, erosion need not reduce soil fertility, as nutrients removed from the soil by animals or crops can be affordably replaced. This may not be so in other parts of the world. Education of farmers also has a vital role to play in persuading them to use the land more sustainably, for many of the impacts of erosion such as flooding and pollution of water supplies bear on society as a whole, not just farmers who are themselves little affected. The principles devised to reduce erosion in developed countries are likely to be successful in developing countries. However, it may take many years for better and more sustainable agricultural policies at national and international level to be devised and brought into being.     

Trees,soils, and food security

Trees have a different impact on soil properties than annual crops, because of their longer residence time, larger biomass accumulation, and longer-lasting, more extensive root systems. In natural forests nutrients are efficiently cycled with very small inputs and outputs from the system. In most agricultural systems the opposite happens. Agroforestry encompasses the continuum between these extremes, and emerging hard data is showing that successful agroforestry systems increase nutrient inputs, enhance internal flows, decrease nutrient losses and provide environmental benefits: when the competition for growth resources between the tree and the crop component is well managed. The three main determinants for overcoming rural poverty in Africa are (i) reversing soil fertility depletion, (ii) intensifying and diversifying land use with high-value products, and (iii) providing an enabling policy environment for the smallholder farming sector. Agroforestry practices can improve food production in a sustainable way through their contribution to soil fertility replenishment. The use of organic inputs as a source of biologically-fixed nitrogen, together with deep nitrate that is captured by trees, plays a major role in nitrogen replenishment. The combination of commercial phosphorus fertilizers with available organic resources may be the key to increasing and sustaining phosphorus capital. High-value trees, ''Cinderella'' species, can fit in specific niches on farms, thereby making the system ecologically stable and more rewarding economically, in addition to diversifying and increasing rural incomes and improving food security. In the most heavily populated areas of East Africa, where farm size is extremely small, the number of trees on farms is increasing as farmers seek to reduce labour demands, compatible with the drift of some members of the family into the towns to earn off-farm income. Contrary to the concept that population pressure promotes deforestation, there is evidence that demonstrates that there are conditions under which increasing tree planting is occurring on farms in the tropics through successful agroforestry as human population density increases. <br>     

Organic Farming: Biodiversity Impacts Can Depend on Dispersal Characteristics and Landscape Context

Organic farming, a low intensity system, may offer benefits for a range of taxa, but what affects the extent of those benefits is imperfectly understood. We explored the effects of organic farming and landscape on the activity density and species density of spiders and carabid beetles, using a large sample of paired organic and conventional farms in the UK. Spider activity density and species density were influenced by both farming system and surrounding landscape. Hunting spiders, which tend to have lower dispersal capabilities, had higher activity density, and more species were captured, on organic compared to conventional farms. There was also evidence for an interaction, as the farming system effect was particularly marked in the cropped area before harvest and was more pronounced in complex landscapes (those with little arable land). There was no evidence for any effect of farming system or landscape on web-building spiders (which include the linyphiids, many of which have high dispersal capabilities). For carabid beetles, the farming system effects were inconsistent. Before harvest, higher activity densities were observed in the crops on organic farms compared with conventional farms. After harvest, no difference was detected in the cropped area, but more carabids were captured on conventional compared to organic boundaries. Carabids were more species-dense in complex landscapes, and farming system did not affect this. There was little evidence that non-cropped habitat differences explained the farming system effects for either spiders or carabid beetles. For spiders, the farming system effects in the cropped area were probably largely attributable to differences in crop management; reduced inputs of pesticides (herbicides and insecticides) and fertilisers are possible influences, and there was some evidence for an effect of non-crop plant species richness on hunting spider activity density. The benefits of organic farming may be greatest for taxa with lower dispersal abilities generally. The evidence for interactions among landscape and farming system in their effects on spiders highlights the importance of developing strategies for managing farmland at the landscape-scale for most effective conservation of biodiversity.     

The opening of Pandora’s Box: climate change impacts on soil fertility and crop nutrition in developing countries

Feeding the world’s growing population is a serious challenge. Food insecurity is concentrated in developing nations, where drought and low soil fertility are primary constraints to food production. Many crops in developing countries are supported by weathered soils in which nutrient deficiencies and ion toxicities are common. Many systems have declining soil fertility due to inadequate use of fertility inputs, ongoing soil degradation, and increasingly intense resource use by burgeoning populations. Climate models predict that warmer temperatures and increases in the frequency and duration of drought during the 21st century will have net negative effects on agricultural productivity. The potential effects of climate change on soil fertility and the ability of crops to acquire and utilize soil nutrients is poorly understood, but is essential for understanding the future of global agriculture. This paper explores how rising temperature, drought and more intense precipitation events projected in climate change scenarios for the 21st century might affect soil fertility and the mineral nutrition of crops in developing countries. The effects of climate change on erosion rates, soil organic carbon losses, soil moisture, root growth and function, root-microbe associations and plant phenology as they relate to mineral nutrition are discussed. Our analysis suggests that the negative impacts of climate change on soil fertility and mineral nutrition of crops will far exceed beneficial effects, which would intensify food insecurity, particularly in developing countries.