Showing papers in "Agronomy for Sustainable Development in 2009"

Plant drought stress: effects, mechanisms and management

Abstract: Scarcity of water is a severe environmental constraint to plant productivity. Drought-induced loss in crop yield probably exceeds losses from all other causes, since both the severity and duration of the stress are critical. Here, we have reviewed the effects of drought stress on the growth, phenology, water and nutrient relations, photosynthesis, assimilate partitioning, and respiration in plants. This article also describes the mechanism of drought resistance in plants on a morphological, physiological and molecular basis. Various management strategies have been proposed to cope with drought stress. Drought stress reduces leaf size, stem extension and root proliferation, disturbs plant water relations and reduces water-use efficiency. Plants display a variety of physiological and biochemical responses at cellular and whole-organism levels towards prevailing drought stress, thus making it a complex phenomenon. CO2 assimilation by leaves is reduced mainly by stomatal closure, membrane damage and disturbed activity of various enzymes, especially those of CO2 fixation and adenosine triphosphate synthesis. Enhanced metabolite flux through the photorespiratory pathway increases the oxidative load on the tissues as both processes generate reactive oxygen species. Injury caused by reactive oxygen species to biological macromolecules under drought stress is among the major deterrents to growth. Plants display a range of mechanisms to withstand drought stress. The major mechanisms include curtailed water loss by increased diffusive resistance, enhanced water uptake with prolific and deep root systems and its efficient use, and smaller and succulent leaves to reduce the transpirational loss. Among the nutrients, potassium ions help in osmotic adjustment; silicon increases root endodermal silicification and improves the cell water balance. Low-molecular-weight osmolytes, including glycinebetaine, proline and other amino acids, organic acids, and polyols, are crucial to sustain cellular functions under drought. Plant growth substances such as salicylic acid, auxins, gibberrellins, cytokinin and abscisic acid modulate the plant responses towards drought. Polyamines, citrulline and several enzymes act as antioxidants and reduce the adverse effects of water deficit. At molecular levels several drought-responsive genes and transcription factors have been identified, such as the dehydration-responsive element-binding gene, aquaporin, late embryogenesis abundant proteins and dehydrins. Plant drought tolerance can be managed by adopting strategies such as mass screening and breeding, marker-assisted selection and exogenous application of hormones and osmoprotectants to seed or growing plants, as well as engineering for drought resistance.

Agroecology as a science, a movement and a practice. A review

Abstract: Agroecology involves various approaches to solve actual challenges of agricultural production. Though agroecology initially dealt primarily with crop production and protection aspects, in recent decades new dimensions such as environmental, social, economic, ethical and development issues are becoming relevant. Today, the term 'agroecology' means either a scientific discipline, agricultural practice, or political or social movement. Here we study the different meanings of agroecology. For that we analyse the historical development of agroecology. We present examples from USA, Brazil, Germany, and France. We study and discuss the evolution of different meanings agroecology. The use of the term agroecology can be traced back to the 1930s. Until the 1960s agroecology referred only as a purely scientific discipline. Then, different branches of agroecology developed. Following environmental movements in the 1960s that went against industrial agriculture, agroecology evolved and fostered agroecological movements in the 1990s. Agroecology as an agricultural practice emerged in the 1980s, and was often intertwined with movements. Further, the scales and dimensions of agroecological investigations changed over the past 80 years from the plot and field scales to the farm and agroecosystem scales. Actually three approaches persist: (1) investigations at plot and field scales, (2) investigations at the agroecosystem and farm scales, and (3) investigations covering the whole food system. These different approaches of agroecological science can be explained by the history of nations. In France, agroecology was mainly understood as a farming practice and to certain extent as a movement, whereas the corresponding scientific discipline was agronomy. In Germany, agroecology has a long tradition as a scientific discipline. In the USA and in Brazil all three interpretations of agroecology occur, albeit with a predominance of agroecology as a science in the USA and a stronger emphasis on movement and agricultural practice in Brazil. These varied meanings of the term agroecology cause confusion among scientists and the public, and we recommend that those who publish using this term be explicit in their interpretation. agroecosystem / Brazil / food system / France / Germany / rural development / scientific discipline / sustainable agriculture / USA

Mixing plant species in cropping systems: concepts, tools and models. A review

Abstract: The evolution of natural ecosystems is controled by a high level of biodiversity, In sharp contrast, intensive agricultural systems involve monocultures associated with high input of chemical fertilisers and pesticides. Intensive agricultural systems have clearly negative impacts on soil and water quality and on biodiversity conservation. Alternatively, cropping systems based on carefully designed species mixtures reveal many potential advantages under various conditions, both in temperate and tropical agriculture. This article reviews those potential advantages by addressing the reasons for mixing plant species; the concepts and tools required for understanding and designing cropping systems with mixed species; and the ways of simulating multispecies cropping systems with models. Multispecies systems are diverse and may include annual and perennial crops on a gradient of complexity from 2 to n species. A literature survey shows potential advantages such as (1) higher overall productivity, (2) better control of pests and diseases, (3) enhanced ecological services and (4) greater economic profitability. Agronomic and ecological conceptual frameworks are examined for a clearer understanding of cropping systems, including the concepts of competition and facilitation, above- and belowground interactions and the types of biological interactions between species that enable better pest management in the system. After a review of existing models, future directions in modelling plant mixtures are proposed. We conclude on the need to enhance agricultural research on these multispecies systems, combining both agronomic and ecological concepts and tools.

Soils and food sufficiency. A review

Abstract: Soil degradation, caused by land misuse and soil mismanagement, has plagued humanity since the dawn of settled agriculture. Many once thriving civilizations collapsed due to erosion, salinization, nutrient depletion and other soil degradation processes. The Green Revolution of the 1960s and 1970s, that saved hundreds of millions from starvation in Asia and elsewhere, by-passed Sub-Saharan Africa. This remains the only region in the world where the number of hungry and food-insecure populations will still be on the increase even by 2020. The serious technological and political challenges are being exacerbated by the rising energy costs. Resource-poor and small-size land-holders can neither afford the expensive input nor are they sure of their effectiveness because of degraded soils and the harsh, changing climate. Consequently, crop yields are adversely impacted by accelerated erosion, and depletion of soil organic matter (SOM) and nutrients because of the extractive farming practices. Low crop yields, despite growing improved varieties, are due to the severe soil degradation, especially the low SOM reserves and poor soil structure that aggravate drought stress. Components of recommended technology include: no-till; residue mulch and cover crops; integrated nutrient management; and biochar used in conjunction with improved crops (genetically modified, biotechnology) and cropping systems, and energy plantation for biofuel production. However, its low acceptance, e.g. for no-till farming, is due to a range of biophysical, social and economic factors. Competing uses of crop residues for other needs is among numerous factors limiting the adoption of no-till farming. Creating another income stream for resource-poor farmers, through payments for ecosystem services, e.g., C sequestration in terrestrial ecosystems, is an important strategy for promoting the adoption of recommended technologies. Adoption of improved soil management practices is essential to adapt to the changing climate, and meeting the needs of growing populations for food, fodder, fuel and fabrics. Soil restoration and sustainable management are essential to achieving food security, and global peace and stability.

Agronomy for sustainable agriculture. A review

Abstract: Sustainability rests on the principle that we must meet the needs of the present without compromising the ability of future generations to meet their own needs. Starving people in poor nations, obesity in rich nations, increasing food prices, on-going climate changes, increasing fuel and transportation costs, flaws of the global market, worldwide pesticide pollution, pest adaptation and resistance, loss of soil fertility and organic carbon, soil erosion, decreasing biodiversity, desertification, and so on. Despite unprecedented advances in sciences allowing us to visit planets and disclose subatomic particles, serious terrestrial issues about food show clearly that conventional agriculture is no longer suited to feeding humans and preserving ecosystems. Sustainable agriculture is an alternative for solving fundamental and applied issues related to food production in an ecological way (Lal (2008) Agron. Sustain. Dev. 28, 57–64.). While conventional agriculture is driven almost solely by productivity and profit, sustainable agriculture integrates biological, chemical, physical, ecological, economic and social sciences in a comprehensive way to develop new farming practices that are safe and do not degrade our environment. To address current agronomical issues and to promote worldwide discussions and cooperation we implemented sharp changes at the journal Agronomy for Sustainable Development from 2003 to 2006. Here we report (1) the results of the renovation of the journal and (2) a short overview of current concepts of agronomical research for sustainable agriculture. Considered for a long time as a soft, side science, agronomy is rising fast as a central science because current issues are about food, and humans eat food. This report is the introductory article of the book Sustainable Agriculture, volume 1, published by EDP Sciences and Springer (Lichtfouse et al. (2009) Sustainable Agriculture, Vol. 1, Springer, EDP Sciences, in press).

Comparison of methods to assess the sustainability of agricultural systems. A review

Abstract: Since the 1990s, numerous agri-environmental indicators and indicator-based methods have been developed to assess the adverse effects of cropping and farming systems such as water pollution by nitrates and pesticides, and gaseous emissions due to nitrogen inputs. This wealth of environmental indicators and assessment methods based on indicators raises issues on the quality of the methods and of the indicators, and on the relevancy of results. Evaluation and comparative studies are therefore needed to answer such issues. Here, we present four recent comparative studies selected for their illustrative value, first, to analyse the methodologies used for comparison of methods, and second, to highlight the main results of the four comparisons. The first study involves 23 indicators to address nitrate leaching. The second study involves 43 indicators to address pesticide risk. The third and fourth studies compare environmental assessment methods based on 4–5 indicators used in French and Upper Rhine plains (France, Germany and Switzerland). Both studies also compare the outputs of the methods and highlight the low degree of convergence between them. The approach proposed in the last study is the most elaborate among the four case studies. It could be used to develop a generic evaluation and comparison methodology. The review of those four case studies shows the need to formalise the methodology underlying any comparison work of indicators or evaluation methods.

Conversion to organic farming: a multidimensional research object at the crossroads of agricultural and social sciences. A review

Abstract: Literature on the conversion to organic farming is scattered. However, both the conversion of farmers to organic farming and of consumers to organic food are the driving forces for the development of the organic sector. In this review, we combine agricultural and social scientists’ viewpoints for a critical appraisal of literature on conversion to organic food and farming. First, a brief historical retrospective enables us to refer the scientific production to the institutional and economic context over the past decades. Secondly, we review the methods used to analyse conversion in agricultural and social sciences, and show that emphasis is most often laid upon the effects of conversion and the motivations to convert, on the basis of comparative approaches with so-called conventional agriculture. Therefore, the literature minimises the importance of transitional aspects and trajectories, and rarely approaches conversion as a longer process than its legal duration and from a wider point of view. Thirdly, we examine the paradigms of input efficiency and system redesign, which frame discussions about transitions in agriculture, beyond organics, and therefore helps shed light on sustainability issues. We suggest that analysing conversion and more generally transitions in agriculture as multidimensional issues, involving both production and social practices, entails interdisciplinary approaches and the redefinition of some central research topics.

Coexistence of genetically modified (GM) and non-GM crops in the European Union. A review

Abstract: The adoption of genetically modified (GM) crops in the European Union (EU) raises questions on the feasibility of coexistence between GM and non-GM crops. Regulations to ensure that different cropping systems can develop side-by-side without excluding any agricultural option are currently implemented or developed by member states. The aim of this review is to explore whether nationally or regionally proposed coexistence strategies comply with the general principles established by the European Commission that ask for science-based and proportionate coexistence measures. In the first part, existing legal requirements and potential sources of adventitious mixing are reviewed. It is discussed what type of coexistence measures might be necessary to keep GM inputs below the legal tolerance threshold of 0.9%. Concentrating on cross-fertilisation as the major biological source of adventitious mixing in maize, it is then assessed to which extent available scientific data on cross-fertilisation can explain the diversity of currently proposed isolation distances by several member states. In the second part, it is analysed whether currently proposed isolation distances reflect contending policy objectives towards GM crops that largely exceed the economic scope of coexistence. It is investigated how coexistence is intersecting with a wider debate about the role of GM crops in agriculture. Based on the analysis of existing cross-fertilisation data, it is concluded that some of the currently proposed isolation distances are not in line with the coexistence principles laid down by the European Commission: they are (i) excessive from a scientific point of view; (ii) difficult to implement in practice; (iii) rarely proportional to the regional heterogeneity in the agricultural landscape; and (iv) not proportional to the farmers’ basic economic incentives for coexistence. Hence, the range of proposed isolation distances cannot simply be explained by different interpretations of available scientific data, possible error intervals and remaining uncertainties inherent in the scientific process. It is argued that other than scientific issues must be at play. One might thus claim that coexistence has become an arena of contending values and visions on the future of agriculture and on the role GM crops might play therein.

MASC, a qualitative multi-attribute decision model for ex ante assessment of the sustainability of cropping systems

Abstract: Realistic assessments of sustainability are often viewed as typical decision-making problems requiring multi-criteria decision-aid (MCDA) methods taking into account the conflicting objectives underlying the economic, social and environmental dimensions of sustainability, and the different sources of knowledge representing them. Some MCDA-based studies have resulted in the development of sustainable agricultural systems, but the new challenges facing agriculture and the increasing unpredictability of their driving forces highlight the need for faster ex ante ('Before-the-event') assessment frameworks. These frameworks should also (i) provide a more realistic assessment of sustainability, by integrating a wider range of informal knowledge, via the use of qualitative information; (ii) address alternative scales, such as cropping system level, improving granularity for the handling of sustainability issues and (iii) target a larger panel of decision-makers and contexts. We describe here the MASC model, which is at the center of a framework addressing these objectives. The MASC model has at its core a decision tree that breaks the sustainability assessment decisional problem down into simpler units as a function of sustainability dimensional structure (economic, social and environmental), generating a vector of 32 holistic 'mixed' (quantitative and qualitative) elementary criteria rating cropping systems. The assessment process involves the calculation of these criteria, their homogenization into qualitative information for input into the model and their aggregation throughout the decision tree based on 'If-Then' decision rules, entered by the user. We present the model and describe its first implementation for the evaluation of four cropping systems generated from expert knowledge, and discuss its relevance to the objectives cited above. The MASC model has several advantages over existing methods, due to its ability to handle qualitative information, its transparency, flexibility and feasibility.

Climate change in Europe. 3. Impact on agriculture and forestry. A review

Abstract: This article reviews major impacts of climate change on agriculture and forestry.

A 25-year record of carbon sequestration and soil properties in intensive agriculture.

Abstract: As a major carbon pool on earth, soil organic carbon may act either as a sink or a source of atmospheric CO2, a greenhouse gas. Soil organic carbon is also impacting fertility, and, in turn, crop yields. However, knowledge of the impact of cropping techniques on the long-term behavior of soil carbon is scarce. Several studies have shown that continuous cropping decreases soil organic carbon stocks, rapidly in the initial years then at a slower rate, approaching a new equilibrium after 30 to 50 years. For instance, a study of intensive corn cropping for 35 years on temperate soils showed a 50% decrease in soil organic carbon. Our study is located in the North Indian state of Punjab. It is the most intensively cultivated region in the country with a cropping intensity of 190%, predominantly of a rice-wheat system. Due to high nutrient demand and its continuous cultivation, the cropping system is presumed to adversely affect soil organic carbon and other soil properties. However, this has been postulated without any real-time data analysis on a regional scale. Therefore, we evaluated soil data for 25 years from 1981/82 to 2005/06 to investigate the impact of intensive agriculture on C sequestration and soil properties on a regional scale. The results showed that, unexpectedly, intensive agriculture has resulted in improved soil organic carbon (SOC) status. As a weighted average for the whole state, SOC increased from 2.9 g kg−1 in 1981/82 to 4.0 g kg−1 in 2005/06, an increase of 38%. Increased productivity of rice and wheat resulted in enhanced C sequestration in the plough layer by 0.8 tC ha−1 per ton of increased grain production. Soil pH declined by 0.8 pH units from 8.5 in 1981/82 to 7.7 in 2005/06. This pH decline has positive implications for availability of phosphorus and micronutrients such as Zn, Fe and Mn. Changes in plant-available P in soil were related to the amount of fertilizer P applied. The status of available P in soils increased from 19.9 kg ha−1 in 1981/82 to 29.2 kg P ha−1 during 2005/06. The status of plant-available K in soil remained almost unaltered and averaged 106 and 123 mg kg−1 soil in 1981/82 and 2005/06, respectively. The analysis showed that intensive cultivation of a rice-wheat system unexpectedly resulted in improved C sequestration, a favorable pH environment and amelioration of the soil salinity.

Iron and zinc biofortification strategies in dicot plants by intercropping with gramineous species. A review

Abstract: The lack of micronutrients such as iron and zinc is a widespread nutrition and health problem in developing countries. Biofortification is the process of enriching the nutrient content of staple crops. Biofortification provides a sustainable solution to iron and zinc deficiency in food around the world. Reports have highlighted the current strategies for the biofortification of crops, including mineral fertilization, conventional breeding and transgenic approaches. Any approach which could increase root growth and result in a high transfer of Fe and Zn from the soil to the plant is crucial for biofortification. In addition to these approaches, we draw attention to another important aspect of Fe and Zn biofortification: intercropping between dicots and gramineous species. Intercropping, in which at least two crop species are grown on the same plot of land simultaneously, can improve utilization of resources while significantly enhancing crop productivity, whereas monocropping is a traditional cropping system of only one crop growth. Monocropping has maintained crop productivity through heavy chemical inputs including the application of fertilizers and pesticides. Monocropping has therefore resulted in substantial eutrophication, environmental pollution, a food security crisis and economic burdens on farmers. Monocropping has also reduced the plant and microorganism diversity in the ecosystem. Compared with monocropped plants, intercropped plants can use nutrients, water and light better due to the spatial and temporal differences in the growth factors and a variety of species-specific mechanisms of physiological response to environmental stress. Intercropping is common in developing countries such as China, India, Southeast Asia, Latin America and Africa. In particular, interspecific interaction facilitates the iron and zinc nutrition of intercropping systems such as peanut/maize, wheat/chickpea and guava/sorghum or maize. Intercropping also increases iron and zinc content in the seeds. In a peanut/maize case study, the Fe concentrations in peanut shoots and seed were 1.47–2.28 and 1.43 times higher than those of peanut in monocropping, respectively. In intercropping of chickpea and wheat, the Fe contents in wheat and chickpea seed were increased 1.26 and 1.21 times, respectively, and Zn concentration in chickpea seed was 2.82 times higher than that in monocropping. In this review, we focus on exemplary cases of dicot/gramineous species intercropping that result in improved iron and zinc nutrition of the plants. We present the current understanding of the mechanisms of improvement of iron and zinc in intercropping. The available literature shows that a reasonable intercropping system of nutrient-efficient species could prevent or mitigate iron and zinc deficiency of plants. Here, we propose that intercropping can potentially offer an effective and sustainable pathway to iron and zinc biofortification.

Alternative control of wild oat and canary grass in wheat fields by allelopathic plant water extracts

Abstract: The increasing concern about the toxicity of synthetic herbicides has boosted the search for eco-friendly and sustainable weed management practices. Allelopathic control of weeds has received great attention in recent years as a possible alternative for weed management. Here, a two-year field study was conducted to explore the herbicidal potential of sorghum water extract alone and in combination with water extracts of other allelopathic plants: eucalyptus, sesame, sunflower, tobacco and brassica, against wild oat (Avena fatua) and canary grass (Phalaris minor), two noxious weeds of wheat fields. Water extracts were applied twice 30 and 40 days after sowing. Our results show that application of sorghum and sunflower extracts at 12 L ha−1 each was more effective than other combinations. This treatment reduced wild oat dry matter by 42–62%, and canary grass by 36–55%. Application of sorghum and sunflower at 6 L ha−1 each increased the wheat grain yield by 89% during the first year, and by 35% during the second year. Application of the synthetic herbicide isoproturon at 1000 g active ingredient ha−1 was more effective for weed inhibition and yield increase than allelopathic water extracts. Nevertheless, application of sorghum and sunflower at 6 L ha−1 was economically more viable than the other treatments, with the highest marginal rate of return of 2824%.

Iterative design and evaluation of rule-based cropping systems: methodology and case studies. A review

Abstract: The economic and regulatory context of crop production changes rapidly, but concerns about agricultural sustainability, including environmental impacts, are increasing steadily. To cope with complexity and uncertainty, innovative methodologies are required for designing, managing and evaluating prototype cropping systems. A generic approach combining iteratively design of cropping systems and evaluation of their performances is presented in this review article. It includes 5 main steps: (1) defining the set of goals and constraints for each cropping system, (2) identifying a suitable agronomic strategy, (3) formulating the consistent set of technical decision rules, (4) applying and evaluating the rule-based system, and (5) validating or refining the strategy and the rules. This methodology was applied to a range of environmental and production contexts, in a perspective of integrated crop production (ICP) prototyping. Three cropping system experiments conducted in France were brought together to demonstrate the potentialities of this system approach and discuss the methodological bottlenecks to address. The three case studies differed by the context of crop production and resource use: adaptation to limited irrigation water (Toulouse), introduction of innovative cropping systems (Versailles), and substitution of herbicides by non-chemical methods (Dijon). The consequences of the specific objectives in each case study on the experimental design and the evaluation process were discussed. Special attention was paid to the time step of the evaluation process, the duration of the improvement loops when prototyping cropping systems, the global evaluation of the systems and the evaluation of individual decision rules.

Effect of cropping systems and crop rotations on weeds

Abstract: Dynamics of weed populations in arable fields are influenced by environmental and soil characteristics and also by cropping system and management practices. Manipulation of cropping systems to improve weed management requires a better understanding of the spatial and temporal dynamics of weeds, seed losses and seed production. To assess the effect of different cropping systems and various crop rotations on the weed population and seed bank, we conducted a field study at the experimental farm in Khorasan Agricultural Research Center, Mashhad, Iran. The experimental design was a split plot with 3 crop rotations as the main plots, and five cropping systems consisting of high-input, medium-input, low-input, organic and integrated systems applied to the sub-plots. Our results show that weed seed densities in organic and integrated cropping systems, of about 5000-6000 seeds/m 2 were higher than conventional and high-input cropping systems showing about 2000 seeds/m 2 . Weed seed density in continuous winter wheat of approximately 6300 seeds/m 2 was higher than other rotations with about 5000 seeds/m 2 . Weed composition in the high-input system was 11 species with 66 plants/m 2 . Whereas in the low-input and organic systems, the weed populations were 15 and 13 species with 145 and 220 plants/m 2 , respectively. Changes in weed seed bank density and species composition often occur when crop management practices and crop rotations are altered. For example, continuous winter wheat fields showed more annual grass weeds, but broadleaf weeds were more abundant in sugar beet-winter wheat rotation. The weed population in continuous winter wheat plots comprised 90% grass and sedge weeds, while in sugar beet-wheat rotation, it was only 43% of total weed density. Broadleaf weeds were 55.2% in sugar beet-winter wheat but 9.4% of total weed density in continuous winter wheat. Different rotations that include crops with different life cycles such as winter wheat-maize and winter wheat-sugar beet could lead to additional benefits of reducing the weed seed bank. conventional agriculture / ecological farming / integrated crop management / low-input crop production / organic farming

An improved model to simulate rice yield

Abstract: Rice is the staple food for about half of the world’s population. Although global production has more than doubled in the last 40 years, food security problems still persist and need to be managed based on early and reliable forecasting activities. This is especially true since the frequency of extreme weather events is forecasted to increase by the intergovernmental panel on climate change (IPCC). The most advanced crop yield forecasting systems are based on simulation models. However, examples of operational systems implementing models which are suitable for reproducing the peculiarities of paddy rice, especially on small scales, are missing. The rice model WARM is used within the crop yield forecasting system of the European Commission. In this article we evaluated the WARM model for the simulation of rice growth under flooded and unflooded conditions in China and Italy. The WARM model simulates crop growth and development, floodwater effect on the vertical thermal profile, blast disease, cold-shock induced spikelet sterility during the pre-flowering period and hydrological peculiarities of paddy soils. We identified the most relevant model parameters through sensitivity analyses carried out using the Sobol’ method and then calibrated using the simplex algorithm. Data from 11 published experiments, covering 13 locations and 10 years, were used. Two groups of rice varieties were identified for each country. Our results show that the model was able to reproduce rice growth in both countries. Specifically, the average relative root mean square error calculated on aboveground biomass curves was 21.9% for the calibration and 23.6% for validation. The parameters of the linear regression equation between measured and simulated values were always satisfactory. Indeed, intercept and slope were always close to their optima and R2 was always higher than 0.79. For some of the combinations of country and simulated variable, the indices of agreement calculated for the validation datasets were better then the corresponding ones computed at the end of the calibration, indirectly proving the robustness of the modeling approach. WARM’s robustness and accuracy, combined with the low requirements in terms of inputs and the implementation of modules for reproducing biophysical processes strongly influencing the year-to-year yield variation, make the model suitable for forecasting rice yields on regional, national and international scales.

Earthworm community in conventional, organic and direct seeding with living mulch cropping systems

Abstract: The loss of biodiversity by intensification of agricultural practices is a major environmental issue that calls for the design of new cropping systems. For instance, negative effects of tillage on earthworm populations have been reported. However, few field studies have compared full cropping systems. Here, we assessed diversity, density and biomass of earthworm populations for 3 years. We use a combined method involving a diluted solution of allyl isothiocyanate to expel earthworms followed by hand sorting. In a long-term trial, we compared 3 systems: (1) a conventional system, (2) a direct seeding living mulch-based cropping system, named a living mulch cropping system, and (3) an organic system. These three cropping systems differed in terms of soil tillage, pesticide and nitrogen use, and crop biomass production. The results showed that measured variables, except diversity, varied depending on the year of sampling. Further, anecic and epigeic density was 3.2–7.2 times higher in the living mulch cropping system than in the conventional and organic systems. There were 3.4–12.5 times more anecic and epigeic earthworm biomass in the living mulch cropping system. The conventional and organic systems showed, respectively, 2.8 and 2.2 times more earthworm density, and 1.9 and 1.8 times more endogeic earthworm biomass than in the living mulch cropping system. Shannon-Wiener and equitability indices were superior in the living mulch cropping system compared with the conventional and organic systems. Cropping systems thus modified specific and functional diversity as well as earthworm community biomass. On the other hand, the organic and conventional systems did not differ in their earthworm density, biomass or diversity.

Triggering transitions towards sustainable development of the Dutch agricultural sector : TransForum's approach : review article

Abstract: TransForum is an innovation program which aims to make a substantial contribution to the transition towards more sustainable development of the Dutch agricultural sector. This article describes the scientific foundation and architecture of this program. TransForum operates on the basis of five working hypotheses which together constitute one integrated analytical framework. These hypotheses are: (1) sustainable development is a dynamic system property; (2) sustainable development needs system innovation; (3) system innovation is a non-linear learning process; (4) system innovation requires active participation of relevant key players from knowledge institutes, governmental bodies, civil society organisations and the business community; (5) the program requires transdisciplinary collaboration of all players. TransForum identifies three new innovation strategies: (1) vital clusters; (2) regional development; (3) international agro-food networks; as alternatives to the current arrangements. Innovative projects are organised in these innovation strategies. The aim of the scientific program is threefold: (1) it addresses research questions raised in the innovative projects; (2) it investigates the need for system-innovations and the way in which they can be realized; (3) it designs research projects to test the 5 main working hypotheses of the program. The scientific program is organised in four themes following a cyclic innovation process which is constantly monitored. The cycle starts with people’s preferences and images, followed by studies on which inventions are required to achieve a successful innovation. Subsequently, it is investigated how to organize new innovations and transitions and finally, how citizen/consumers behaviour and preferences mobilizes sustainable development, closing the loop.

Triggering transitions towards sustainable development of the Dutch agricultural sector: TransForum's approach.

Abstract: TransForum is an innovation program which aims to make a substantial contribution to the transition towards more sustainable development of the Dutch agricultural sector. This article describes the scientific foundation and architecture of this program. TransForum operates on the basis of five working hypotheses which together constitute one integrated analytical framework. These hypotheses are: (1) sustainable development is a dynamic system property; (2) sustainable development needs system innovation; (3) system innovation is a non-linear learning process; (4) system innovation requires active participation of relevant key players from knowledge institutes, governmental bodies, civil society organisations and the business community; (5) the program requires transdisciplinary collaboration of all players. TransForum identifies three new innovation strategies: (1) vital clusters; (2) regional development; (3) international agro-food networks; as alternatives to the current arrangements. Innovative projects are organised in these innovation strategies. The aim of the scientific program is threefold: (1) it addresses research questions raised in the innovative projects; (2) it investigates the need for system-innovations and the way in which they can be realized; (3) it designs research projects to test the five main working hypotheses of the program. The scientific program is organised in four themes following a cyclic innovation process which is constantly monitored. The cycle starts with people’s preferences and images, followed by studies on which inventions are required to achieve a successful innovation. Subsequently, it is investigated how to organize new innovations and transitions and finally, how citizen/consumers behaviour and preferences mobilizes sustainable development, closing the loop.

Climate change in Europe. 1. Impact on terrestrial ecosystems and biodiversity. A review

Abstract: Ecosystems have an essential role in providing services to humankind such as nutrient cycling, pest control, pollination, quality of life, and hydrological, atmospheric and climatic regulation. About 60% of the world’s known ecosystems are currently used unsustainably. In Europe, the richness and abundance of biodiversity is undergoing significant decline, partly due to climate change. This article outlines the impacts of climate change on biodiversity by showing both observed and projected changes in the distribution and phenology of plants and animals (phenology refers to changes in the timing of seasonal events). The four major findings are the following. (1) Concerning the distribution of plant species, climate change is responsible for the observed northward and uphill distribution shifts of many European plant species. By the late 21st century, distributions of European plant species are projected to have shifted several hundred kilometres to the north, forests are likely to have contracted in the south and expanded in the north, and 60% of mountain plant species may face extinction. The rate of change will exceed the ability of many species to adapt. (2) Concerning plant phenology, the timing of seasonal events in plants is changing across Europe due to changes in climate conditions. For instance, 78% of leaf unfolding and flowering records show advancing trends. Between 1971 and 2000, the average advance of spring and summer was 2.5 days per decade. The pollen season starts on average 10 days earlier and is longer than 50 years ago. Trends in seasonal events will continue to advance as climate warming increases in the years and decades to come. (3) Concerning the distribution of animal species, Europe’s birds, insects, and mammals are moving northwards and uphill in response to observed climate change. Rate of climate change, habitat fragmentation and other obstacles will impede the movement of many animal species. Distribution changes are projected to continue. Suitable climatic conditions for Europe’s breeding birds are projected to shift nearly 550 km northeast by the end of the century. Projections for 120 native European mammals suggest that up to 9% face extinction during the 21st century. (4) Concerning animal phenology, climatic warming has caused advancement in the life cycles of many animal groups, including frogs spawning, birds nesting and the arrival of migrant birds and butterflies. Seasonal advancement is particularly strong and rapid in the Arctic. Breeding seasons are lengthening, allowing extra generations of temperature-sensitive insects such as butterflies, dragonflies and pest species to be produced during the year. These trends are projected to continue as climate warming increases in the decades to come. Populations may explode if the young are not exposed to normal predation pressures. Conversely, populations may crash if the emergence of vulnerable young is not in synchrony with their main food source or if shorter hibernation times lead to declines in body condition.

Nutrient value, odour emission and energy production of manure as influenced by anaerobic digestion and separation

Abstract: Crop fields can be fertilised by application of manure because manure contains fertilising elements such as N and P, and organic matter that enhances soil physical properties. However, application of manure may also cause P and N pollution of surroundings, odour emission and waste of energy. A solution may be to apply an improved liquid manure fraction resulting from manure separation and anaerobic digestion. As previous studies have only focused on the factors individually, we carried out here a system analysis with the aim of optimising all the factors simultaneously. We tested three solid-liquid separations on raw manure and manure pre-digested in a biogas reactor, with the separation treatments being coagulation, flocculation and filtration, which differed mainly with respect to coagulant volume, and the N:P ratio of the products was measured. The NH3 and odour emission was determined from the liquid fractions during storage and after soil application, while the energy produced at anaerobic digestion of the solid fractions was measured. Our results show that energy production at digestion increased with decreasing coagulant volume, but was largely unaffected by anaerobic digestion whether performed both before and after or only after separation. Odour generation was reduced by pre-digestion. With increasing coagulant volume and without pre-digestion, the nutrient value of the liquid fraction was improved the most, as shown by an increase in the N/P ratio of the liquid fraction and by a decrease in NH3 emissions from stores and fields. The data proved that mechanical separation of raw manure, added coagulant and polymer, followed by anaerobic digestion of the solid fraction was the optimum strategy from a whole animal manure management perspective. The coagulant volume can be adjusted to favour either nutrient value and NH3 emission, or energy production.

Factors limiting the grain protein content of organic winter wheat in south-eastern France: a mixed-model approach

Abstract: Organic agriculture could achieve the objectives of sustainable agriculture by banning the use of synthetic fertilizers and pesticides. However, organic crops generally show lower performances than conventional ones. In France, organic winter wheat production is characterized by low grain protein content. There is a crucial need for better understanding the variability of grain protein content, because millers require batches with values over 10.5% of dry matter. Here, a regional agronomic diagnosis was carried out to identify the limiting factors and crop management practices explaining the variability of grain protein content. The studied field network was a set of 51 organic winter wheat plots in south-eastern France. The mixed-model method was used for identifying and ranking the limiting factors and the crop management practices responsible for variation in limiting factors. Our results show that the grain protein content variation was mostly explained by the baking quality grade of the cultivar, crop nitrogen status and weed density at flowering. There was a positive correlation between grain protein content and both crop nitrogen status and weed density. To a lesser extent, climatic factors also explained grain protein content variability. A lower water stress increased grain protein content, whereas an increase in the photothermal quotient and daily temperature over 25 °C reduced grain protein content. In south-eastern France, grain protein content of organic winter wheat could be increased by improving fertilization management, using an improved baking quality grade cultivar, choosing a legume fodder crop as preceding crop, or by avoiding late sowing dates.

Effect of tillage system and straw management on organic matter dynamics.

Abstract: The choice of cultivation system in arable agriculture exerts a strong influence not only on soil health and crop productivity but also on the wider environment. Conservation tillage using non-inversion methods conserves soil carbon, reduces erosion risk and enhances soil quality. In addition, conservation tillage has been shown to sequester more carbon within the soil than inversion tillage, reducing carbon dioxide losses to the atmosphere. Stable, well structured topsoils that develop following long-term conservation tillage lead to more energy efficient systems due to the reduced power requirements for cultivation. Long-term experiments, e.g. more than 20 years, that confirm the impact of conservation tillage over an extended period are not common. Here we evaluate the impact of different tillage methods and winter wheat straw management, either incorporated or removed, on organic matter turnover and soil quality indicators. No-till, chisel and mouldboard ploughing was carried out for 23 years on a silty clay loam soil in South West England that was not considered suitable for non-inversion tillage due to weak soil structure. In order to assess the effect of contrasting cultivation and straw disposal method on soil carbon dynamics, a range of assays were conducted, including water extractable organic carbon, hot water extractable carbohydrate, microbial biomass carbon, activity of β-glucosidase and acid phosphatase enzymes, C sequestration and the natural abundance of 13C. Our results show that the soil organic carbon concentration in the topsoil was greater under no-till than mouldboard ploughing, while a reverse trend was observed in the lower depths. A 14–17% increase in soil organic carbon was observed in the topsoil for chisel plough and no-till treatments compared to mouldboard ploughing. Water extractable organic carbon was found to constitute only 1–7% of the microbial biomass carbon. Hot water extractable carbohydrate was one of the most sensitive indicators of soil quality and had a significant a negative correlation with bulk density and positive correlation with soil organic carbon microbial biomass carbon β-glucosidase and acid phosphatase. The choice of cultivation method exerted a major control on microbial and carbon dynamics. No-till and chisel ploughing maintained carbon in the soil surface horizons, which will benefit the stability of this weakly structured soil, but mouldboard ploughing distributed carbon more uniformly throughout the soil profile, particularly when straw was incorporated, hence leading to the retention of more carbon in the soil profile.

Climate change in Europe. 2. Impact on soil. A review

Abstract: This article reviews major impacts of climate change on soil.

Laws of Sustainable Soil Management

Abstract: The challenge of doubling the world’s food grain production by 2030 is even more daunting because of the decrease in per capita arable land area and renewable fresh water resources; increase in risks of soil and environmental degradation; and threat of decrease in use efficiency of inputs because of the projected climate change. Thus, the need for identifying processes, practices and policies that govern sustainable management of soil resources is more critical now than ever before. The goal is to minimize risks of soil degradation by enhancing its resilience and improving ecosystem services of the finite and fragile soil resource. Here, 10 principles are given for sustainable management of soil. This report is an introductory article of the book Sustainable Agriculture, published by Springer, EDP Sciences (Lichtfouse et al. 2009).

Digital Imaging Information Technology Applied to Seed Germination Testing: A Review

Abstract: The application of digital imaging information technology to seed germination testing is discussed. This technology is reviewed in light of recent interest on the development and adoption of sustainable agrosystems joined with a modern strategy of “precision agriculture”, which provides new complex information tools for better crop production. Basic concepts on the patterns of image analysis descriptors of imbibing seed performance are described with the objective of demonstrating the potential of this technique to be adequate for overcoming problems encountered with a standard seed germination test. The application of different image analysis system prototypes in monitoring seed germination of Brassica, as well as several other crop species, has provided encouraging results, highlighting the reliability of this technique to quickly acquire digital images and to extract numeric descriptors of germination and radicle growth events. Another aspect of digital imaging is the possibility to determine the colour space of a two-dimensional seed surface. Experiments carried out on lentil seed germination have shown that quantitative changes in Red-Green-Blue (RGB) colour component density may be considered as markers of the start of germination. In addition, the extracted RGB data may be used to trace a virtual three-dimensional surface plot allowing a better analysis of colour distribution on the lentil’s surface. RGB colour density can also be used to determine any variation in colour due to the ‘browning effect’ as a result of advancing seed deterioration. The potential of RGB markers in classifying sub-samples and maintaining high germination quality in aged seed samples represents a non-destructive method in seed testing and sorting. As a conclusion, the information flow deriving from digital image processing should be integrated with other bio-morphological, taxonomic and ‘omic-system’ databases. The final target should be an interrelated and complex database for a deeper functional and structural knowledge of plant species, which can respond to the needs of farmers, seed industries, biodiversity conservation and seed basic research.

Adaptation assessments for crop production in response to climate change in Cameroon

Abstract: The Cameroonian agricultural sector, a critical part of the local ecosystem, is potentially vulnerable to climate change, thus raising concerns about food security in the country’s future. Adaptations policies may be able to mitigate some of this vulnerability. This article addresses the issue of selected adaptation options within the context of Cameroonian food production. A methodology is applied where transient diagnostics of two atmosphere-ocean general circulation models, the NASA/Goddard Institute GISS and the British HadCM3, are coupled to a cropping system simulation model (CropSyst). This methodology simulates current and future (2020, 2080) crop yields for selected key crops such as bambara nut, groundnut, maize, sorghum, and soybean, in eight agricultural regions of Cameroon. Our results show that for the future, substantial yield increases are estimated for bambara groundnut, soybean and groundnut, while little or no change or even decreases for maize and sorghum yields, varying according to the climate scenario and the agricultural region investigated. Taking the “no regrets” principle into consideration, we also explore the advantages of specific adaptation strategies specifically for three crops, maize, sorghum and bambara groundnut, under GISS A2 and B2 marker scenarios only. Here, changing sowing dates may be ineffective in counteracting adverse climatic effects because of the narrow rainfall band that strictly determines the timing of farm operations in Cameroon. In contrast, the possibility of developing later maturing new cultivars proved to be very effective in offsetting adverse impacts, giving the highest increases in productivity under different scenario projections without management changes. For example, under climate change scenario GISS A2 2080, a 14.6% reduction in maize yield was converted to a 32.1% increase; a 39.9% decrease in sorghum yield was converted to a 17.6% increase, and for bambara groundnut, yields were almost trebled due to increase length of growing period and the positive effects of higher CO2 concentrations. These results better inform wider studies and development strategies on sustainable agriculture in the area by providing an indication as to the potential direction in shifts in production capabilities. Our approach highlights the benefit of using models as tools to investigate potential climate change impacts, where results can supplement existing knowledge. The findings also provide useful guidance and motivation to public authorities and development agencies interested in food security issues in Cameroon and elsewhere.

Mobility, turnover and storage of pollutants in soils, sediments and waters : achievements and results of the EU project AquaTerra : a review.

Abstract: AquaTerra is one of the first environmental projects within the 6th Framework program by the European Commission. It began in June 2004 with a multidisciplinary team of 45 partner organizations from 13 EU countries, Switzerland, Serbia, Romania and Montenegro. Results from sampling and modeling in 4 large river basins (Ebro, Danube, Elbe and Meuse) and one catchment of the Brevilles Spring in France led to new evaluations of diffuse and hotspot input of persistent organic and metal pollutants including dynamics of pesticides and polycyclic aromatic hydrocarbons, as well as metal turnover and accumulation. While degradation of selected organic compounds could be demonstrated under controlled conditions in the laboratory, turnover of most persistent pollutants in the field seems to range from decades to centuries. First investigations of long-term cumulative and degradation effects, particularly in the context of climate change, have shown that it is also necessary to consider the predictions of more than one climate model when trying to assess future impacts. This is largely controlled by uncertainties in climate model responses. It is becoming evident, however, that changes to the climate will have important impacts on the diffusion and degradation of pollutants in space and time that are just at the start of their exploration.

Relationships between concentrations of trace metals in wheat grains and soil

Abstract: In order to reduce the amount of trace metals such as cadmium in human food, it is useful to predict the trace metal composition of cereal grains from well-chosen topsoil variables. Statistical relationships between soil properties and metal concentration in plant organs have already been studied. However, such studies involved only a few common soil properties such as pH, organic carbon content and cation exchange capacity. Here, we compared metal contents in grain and in topsoil samples. 198 samples of grains of winter wheat were collected from paired topsoil and crop surveys in the northern half of France. The soils belong to 18 contrasting pedogeological families. Grain and topsoil samples were analysed for Cd, Cr, Cu, Ni, Pb, Zn, Fe, Mg and Mn. For soil samples, three pools of metal were determined: total concentration by HF digestion, and two available pools by partial extraction using either diethylenetriamine pentaacetic acid (DTPA) or NH4NO3. Canonical correlation analysis including multiple linear regression was used to study relationships between soil and grain data. Our findings show the occurrence of six significant and independent relations between the topsoil variables and the grain variables. The adjustment quality of those relations is measured by six coefficients equivalent to individual determination coefficients. The maximum coefficient of 0.79 is higher than any individual ones. Our findings show in particular an excellent regression model for grain Cd with a small number of topsoil variables, thus allowing an accurate prediction for winter wheat grains. Practically, farmers can use the prediction model to increase soil pH and by growing a less metal-accumulating cultivar upon detection of a threat. The strengths of our study are the following: (1) we studied a very large number of sites, including soils with very diverse parent materials, soil-forming processes and geochemical properties; (2) we measured and tested a large number of variables, including in particular available metal fractions; and (3) we applied unusual statistical methods such as canonical correlation analysis.

Integration of soil structure variations with time and space into models for crop management. A review

Abstract: Soil structure plays a major role in the design of new crop management systems. For instance, the transition from conventional to no-tillage changes soil structure, which, in turn, has implications on crop yield greenhouse gas emissions, and pesticide and nitrate leaching. Modelling soil structure at field scale faces two main issues: (1) the spatial variability and (2) the temporal variability. Here, we review how spatial variability of soil structure is taken into account in water transfer models at field scale. We discuss the effects of soil structure on hydraulic properties. We present options to model soil structure effects using pedotransfer functions or calculations based on pore network geometry. Then we review studies on water transfer. Here, we show the utility of one-dimensional (1-D) and 2-D models, and the range of soil profile partitions. In the second part, we study a mean to model the temporal variation of soil structure. We propose an indicator of soil structure dynamics based on the proportion of compacted clods in the tilled layer. This indicator was measured from the observation face of soil pits. We studied this indicator in a long-term field experiment involving various risks of compaction. The results showed that this indicator gave a more precise description of the time course changes in soil structure than the mean soil bulk density measured on the same experimental plots. Lastly, we discuss the principles of a model that predicts the evolution of this indicator under different soil tillage and climatic conditions. This model can be used to evaluate the effects of different crop management systems on soil structure and soil water transfer.