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GM-related sustainability: agro-ecological impacts, risk and opportunities of soy production in Argentina and Brazil
... Besides, the use of fertilizers and agrochemicals represents great source of contamination for water reservoirs. They can permeate the soil and affect water streams and underground aquifers, causing eutrophication or making the water toxic [39,45]. The amount of water used to assimilate the pollutant loads, also known as gray water, is around 40 m 3 per ton in North America, considering a rain regime of 2000 m 3 per ton [42]. ...
... Most of them are severely toxic chemical compounds that impair not only the pests themselves but also the surrounding fauna, flora, and water sources. In the case of soybean, the main pesticide applied is the glyphosate, a herbicide, in addition to others applied in lower quantities, for example, metsulfuron, metribuzin, haloxyfop (herbicides), endosulfan, cypermethirin, chlorpyrifos (insecticides), curasemilla, trifloxistrobin, and cyproconazole (fungicides) [39,45]. ...
... The GM crops usually stimulate an intense use of glyphosate in countries like Brazil, the United States, Argentina, and Paraguay. Other insecticides and fungicides together sum up to 0.6 kg per ha, less than half of the amount of herbicides used for conventional soy and 6 times lower than the value for GM soy [45]. In terms of greenhouse effects increase, glyphosate represents alone 15 kg CO 2 eq per soy kg, while other pesticides sum up 40 kg CO 2 eq per kg, with exception of curasemilla, which represents more than 5000 kg CO 2 eq per kg [39]. ...
Soybean is one of the most abundant and cheap sources of high-quality vegetable protein. The most important suppliers of this commodity, as predicted for 2020/2021, are Brazil, the United States and Argentina, with 131, 112 and 53 million tons, respectively. China is expected to remain the greatest consumer (112 million tons). The main products obtained from soybean are the oil, the defatted bran, lecithin and in some cases the protein-concentrate bran. Soybean hulls and soybean molasses are the main residues to be valorized in a soybean biorefinery. This chapter will present the industrial processing of soybean, the variety of soy-derived products and the possible valorization strategies for soybean hulls and molasses. Socio-economic and environmental aspects within the soybean production chain will be addressed in a circular bioeconomy approach.
... We found that in Brazil the 49 % (about 415 Mha) of the total country area is potentially available for soybean expansion, the 56 % of which is currently covered by forests and intact forests and the 26 % are shrublands belonging to the cerrado biome, a unique and important ecosystem in Latin American (Bindraban et al., 2009;Coutinho et al., 2014;Modernel et al., 2016;de Souza Medeiros et al., 2022) with many relevant environmental functions including carbon sequestration (Table 8). A similar trend is observed in Argentina, where the 44 % of the available area for soybean expansion (16 Mha) and the 31 % of area for sunflower expansion (8 Mha) are forests, i.e., together the 81 % of the total national forests. ...
... A similar trend is observed in Argentina, where the 44 % of the available area for soybean expansion (16 Mha) and the 31 % of area for sunflower expansion (8 Mha) are forests, i.e., together the 81 % of the total national forests. Moreover, the 38 % (14 Mha) and the 40 % (11 Mha) of the available area for soybean and sunflower expansion, respectively, are shrublands mostly included in the pampa biome which, likewise the cerrado biome, is a relevant ecosystem for carbon sequestration in Latin American (Bindraban et al., 2009;Alvarez et al., 2014;Coutinho et al., 2014;Modernel et al., 2016). ...
... Soybean production in Brazil increased from 16 million to 61 million tons from 1990 to 2007. China and EU are the world's largest soybean importers (Bindraban et al., 2009). However, the sector there has been criticized for its typical mono-cropping in which biodiversity is jeopardized to support the cultivation of one single genetically manipulated soybean type (Bindraban et al., 2009). ...
... China and EU are the world's largest soybean importers (Bindraban et al., 2009). However, the sector there has been criticized for its typical mono-cropping in which biodiversity is jeopardized to support the cultivation of one single genetically manipulated soybean type (Bindraban et al., 2009). ...
Soybean value chains are an important means to supply the growing demand for protein in Africa and a source of income for farmers and processors. In Benin, the functioning of chains is however hindered by heterogeneous quality levels, the entrance of foreign traders, and a lack of support from the government and macro-level organizations. The local nongovernmental organization Sojagnon (the association of development of soybeans in Benin) has the mission to reorganize the Beninese soy system. It worked among others on the improvement of seed quality, the professionalization of farmers and processors, the development of a soybean value chain. In this case study, Patrice Sèwadé, Sojagnon’s chairman reflects on the interventions of the past years and wonders what the next actions should be. The case highlights the role of local entrepreneurs and organizations in the rapid transformation of the African agri-food environment.
... This is evident from numbers of different sources. For example, Bindraban et al. [12] report 3.84 kg (a.i.)/ha in 2007, Benbrook [10] reports around 4 kg (a.i.)/ha to be sprayed in Argentina and Brazil in 2014, while Monsanto, in its product label, recommends about 7 kg (a.i.)/ha to be sprayed [13]. Official figures from the USDA database [14] show that up to 6-7 kg (a.i.)/ha of glyphosate can be expected in soybean cultivation, including pre-and post-emergence applications. ...
The introduction of herbicide-tolerant (HT) genetically engineered (GE) soybeans has raised new challenges for the European risk assessment of imported food and feed. Food and feed products derived from these plants may show specific patterns of chemical residues and altered nutritional composition. Furthermore, there has been a substantial increase in the usage of herbicides in soybean production due to the emergence of resistant weeds. This concerns particular glyphosate-based herbicides and also other herbicides. In this review, we give an overview of available data regarding glyphosate application on HT GE soybeans in North and South America. We have further compared this data with herbicide applications in experimental field trials conducted by the industry. We conclude that field trials carried out for risk assessment purposes do not generally represent the real agronomic conditions in commercial HT GE plant cultivation. In most cases, neither the applied dose nor the number of applications match real conditions. This finding is especially relevant for risk assessment since a review of relevant publications shows that the amount and timing of spraying glyphosate as a complementary herbicide onto HT GE plants can impact their composition; this is relevant to EFSA comparative risk assessment of GMOs. Further, closely related issues were identified that overlap with EU GMO and pesticide regulation, but are not currently considered. These issues concern indirect, cumulative and combinatorial effects as well as the assessment of mixed toxicity. Consequently, current risk assessment practice for HT GE plants cannot be considered to fulfil EU regulatory standards which require the safety of food and feed to be demonstrated. It is much more likely that concerns about the health risks of HT GE plant material used for food and feed have been underestimated. We therefore conclude that the EU risk assessment of food and feed derived from HT GE plants needs substantial improvement.
... Thus, the concentration of IMZT employed in this investigation would be expected to be almost improbable in the environment. However, considering the recommended application field ratios of 100-150 g a.i./ha reported for Argentina (Bindraban et al. 2009;CASAFE 2017CASAFE -2019, it cannot be ruled out the possibility that L. latinasus populations could be exposed accidentally to IMZT at this range of concentrations when specific events occurred (e.g., direct application, drainage into ditches, or accidental discharge). ...
Genotoxic, biochemical and individual organizational effects on Leptodactylus latinasus tadpoles were evaluated after exposure to an imazethapyr (IMZT)-based commercial herbicide formulation, Pivot® H (10.59% IMZT). A determination of the value of the lethal concentration (LC50) was determined as a toxicological endpoint. Alterations in animal behaviour and morphological abnormalities as well as cholinesterase (ChE), catalase (CAT) and glutathione S-transferase (GST) activities were employed as individual sublethal endpoints. Micronuclei frequencies (MNs), binucleated cells (BNs), blebbed nuclei (BLs), lobed nuclei (LBs), notched nuclei (NTs), erythroplastids (EPs), and evaluation of DNA strand breaks were employed as genotoxic endpoints. All biomarkers were evaluated after 48 and 96 h of exposure to concentrations of IMZT within 0.07-4.89 mg/L. LC5096h values of 1.01 and 0.29 mg/L IMZT were obtained for Gosner stages 25 and 36, respectively. Irregular swimming, diamond body shape and decreased frequency of keratodonts were detected at both sampling times. Results showed that IMZT increased GST activity and MNs frequency at 48 and 96 h of exposure. Other nuclear abnormalities were also observed in the circulating erythrocytes of tadpoles, i.e., NTs and BLs values after 48 h, and LNs, BLs and EPs values after 96 h. Finally, results showed that IMZT within 0.07-0.22 mg/L increased the genetic damage index in tadpoles exposed for both exposure times (48 and 96 h). This study is the first to report the sublethal biochemical effects of IMZT in anurans and is also the first report using L. latinasus tadpoles as a bioindicator for ecotoxicological studies.
... Native grasslands throughout this ecoregion were gradually turned into agro-ecosystems over the past two centuries, leaving almost no pristine grassland areas (15). The introduction of GMO glyphosate-resistant crops and the use of no-till technologies have promoted an unprecedented growth of the agricultural frontier (16). The last remaining patches of semi-natural habitats are small and isolated, frequently in unproductive or marginal locations, like roadsides, train lines or around lakes (17). ...
... Native grasslands throughout this ecoregion were gradually turned into agro-ecosystems over the past two centuries, leaving almost no pristine grassland areas (15). The introduction of GMO glyphosate-resistant crops and the use of no-till technologies have promoted an unprecedented growth of the agricultural frontier (16). The last remaining patches of semi-natural habitats are small and isolated, frequently in unproductive or marginal locations, like roadsides, train lines or around lakes (17). ...
... Agricultural practices underwent a paradigmatic shift with the ad- vent of the "new green revolution" including the implementation of genetically modified seeds, zero tillage and direct seeding (Atlin et al., 2017;Bindraban et al., 2009;Evenson and Gollin, 2003). The use of transgenic seeds has led to the increase in the consumption of agro- chemicals, and as a consequence in a rise of the concentration of agro- chemicals into the different ecosystemic compartments (Etchegoyen et al., 2017;Li et al., 2014). ...
In the last years, the agricultural expansion has led to an increased use of pesticides, with glyphosate as the most widely used worldwide. This is also the situation in Argentina, where glyphosate formulations are the most commercialized herbicides. It is known that glyphosate formulations are much more toxic than the active ingredient, and this difference in toxicity can be attributed to the adjuvants present in the formula. In this context, the aim of the present study was to evaluate and compare sub-lethal histological effects of the glyphosate formulation Roundup Ultramax and glyphosate active ingredient on Leptodactylus latrans tadpoles at Gosner-stage 36. Semi-static bioassays were performed using 96 h of exposure with Roundup Ultramax formulation (RU; 0.37-5.25 mg a.e./L), glyphosate (GLY; 3-300 mg/L), and a control group. RU exposure showed an increment in the melanomacrophagic cells (MMc) and melanomacrophagic centers (MMCs) from 0.37 mg a.e./L. GLY exposure showed a significant increment in the number of MMc from 15 mg/L, and of MMCs from 3 mg/L. Also, histopathological lesions were observed in the liver of tadpoles exposed to both, GLY and RU. These lesions included: lipidosis and hepatic congestion, but only RU showed significant differences respect to control, with a LOEC value of 2.22 mg a.e./L for both effects. In sum, this study represents the first evidence of adverse effects of glyphosate and RU formulation on the liver of anuran larvae at concentrations frequently found in the environment.
... However, the main economic driver for this expansion appeared to be the worldwide increasing demand for soy products. The review concluded that, at most, the availability of GM soybean has facilitated the expansion of soybean acreage, for large-scale cultivation of non-GM soybean has also expanded enormously, e.g. in the northern Mato Grosso province of Brazil [8]. ...
A global challenge for the coming decades is to feed the world in a sustainable way. This will require major steps forward across the food production chain, including plant breeding, farming practices, and storage and logistics. Sustainable agriculture requires the implementation of agro-ecological and agronomic knowledge and methods in combination with optimal plant material, optimal in the sense that it is most suitable for a certain place, in a particular farming system, and in relation to market demand. To breed such plant varieties plant breeders need to employ the largest toolkit possible [1]. Among the wide array of tools available to the breeder, genetic modification (GM) receives most attention in public debates on sustainability. In Europe, practically the only GM crop sown, Bt MON810 maize, was grown on 114,000 ha (
... This looping relation between GMO crops and ecosystems by weed responses was introduced by Lehmann and Pengue (2000) and later reported by Binimelis et al. (2009) as a new phenomenon of intensification that the authors named "transgenic treadmill". Bindraban et al. (2009) reported, as a first approach, the higher use of herbicides in GMO soybean than in conventional in one in the major production region of Argentina. Benbrook (2012) argued that use of GMO crops with herbicide resistance eventually generates increased use of pesticides, thus increased input use as a consequence of this new technology will likely increase production costs, both in seed research and farmer use of chemicals. ...
... Problems sometimes arise when soybean shipments contain traces of unapproved GM maize varieties. Bindraban et al. (2009) looked into 12 popular claims regarding the agro-ecological impacts of genetically modified soy production in Argentina and Brazil. The GM soy that is currently commercially grown in these countries is Roundup TM Ready (RR) soy, which is tolerant of the herbicide glyphosate. ...
In het rapport 'The protein puzzle. The consumption and production of meat, dairy and fish in the European Union' brengen onderzoekers van het Planbureau voor de Leefomgeving (PBL) in kaart wat de gevolgen van de productie en consumptie van dierlijke eiwitten zijn voor milieu, natuur en gezondheid. Vervolgens schetst het PBL welke opties er in Europees verband zijn om de negatieve effecten te verminderen. Met deze studie verschaft het PBL relevante feiten en cijfers ten behoeve van het debat over eiwitconsumptie, inclusief een indicatie van de onzekerheden daarbij.
The rapidly expanding field of commercial transgenic cultivation has its greatest concern related to environmental well being as transgenic crops are seen as a threat to the biodiversity in the agricultural fields. Since transgenic technology is continuing to witness a rapid growth in terms of developing novel varieties, it is imperative to examine whether the developed varieties contribute to preserving biodiversity. Further, it is also necessary to focus future research towards developing transgenic varieties to contribute to preserving and enhancing the biodiversity. The present review aims to present an overview of the current status of transgenic technology in contributing to biodiversity and suggest future research strategies enabling the preservation of biodiversity.
The potential impact of GM crops on biodiversity has been a topic of interest both in general as well as specifically in the context of the Convention on Biological Diversity. Agricultural biodiversity has been defined at levels from genes to ecosystems that are involved or impacted by agricultural production (www.cbd.int/agro/whatis.shtml). After fifteen years of commercial cultivation, a substantial body of literature now exists addressing the potential impacts of GM crops on the environment. This review takes a biodiversity lens to this literature, considering the impacts at three levels: the crop, farm and landscape scales. Within that framework, this review covers potential impacts of the introduction of genetically engineered crops on: crop diversity, biodiversity of wild relatives, non-target soil organisms, weeds, land use, non-target above-ground organisms, and area-wide pest suppression. The emphasis of the review is peer-reviewed literature that presents direct measures of impacts on biodiversity. In addition, possible impacts of changes in management practises such as tillage and pesticide use are also discussed to complement the literature on direct measures. The focus of the review is on technologies that have been commercialized somewhere in the world, while results may emanate from non-adopting countries and regions. Overall, the review finds that currently commercialized GM crops have reduced the impacts of agriculture on biodiversity, through enhanced adoption of conservation tillage practices, reduction of insecticide use and use of more environmentally benign herbicides and increasing yields to alleviate pressure to convert additional land into agricultural use.
Recently, spray drift and its effects have become an important aspect of risk assessment in the registration process of pesticides in Belgium. In this regulation, drift reducing spray application techniques can be used to reduce buffer zones. The purpose of this research is to measure and compare the amount of drift sediment for different spray application techniques under field conditions. A drift prediction equation for the reference spraying was used to compare other spraying techniques with the reference spraying, under different weather conditions. Drift measurements were performed for several combinations of nozzle type (flat fan, low-drift, air injection) and size (ISO 02, 03, 04 and 06), spray pressure (2, 3 and 4 bar), driving speed (4, 6, 8 and 10 km.h-1) and spray boom height (0.3, 0.5 and 0.75 m). Nozzle type as well as spray pressure, driving speed and spray boom height, have an important effect on the amount of spray drift. Larger nozzle sizes, lower spray pressures and driving speeds and lower spray boom heights generally reduce spray drift. Concerning nozzle types, air injection nozzles have the highest drift reduction potential followed by the low-drift nozzles and the standard flat fan nozzles.
Pesticides constitute a major anthropogenic addition to natural communities. In aquatic communities, a great majority of pesticide impacts are determined from single-species experiments conducted under laboratory conditions. Although this is an essential protocol to rapidly identify the direct impacts of pesticides on organisms, it prevents an assessment of direct and indirect pesticide effects on organisms embedded in their natural ecological contexts. In this study, I examined the impact of four globally common pesticides (two insecticides, carbaryl [Sevin] and malathion; two herbicides, glyphosate [Roundup] and 2,4-D) on the biodiversity of aquatic communities containing algae and 25 species of animals.
Species richness was reduced by 15% with Sevin, 30% with malathion, and 22% with Roundup, whereas 2,4-D had no effect. Both insecticides reduced zooplankton diversity by eliminating cladocerans but not copepods (the latter increased in abundance). The insecticides also reduced the diversity and biomass of predatory insects and had an apparent indirect positive effect on several species of tadpoles, but had no effect on snails. The two herbicides had no effects on zooplankton, insect predators, or snails. Moreover, the herbicide 2,4-D had no effect on tadpoles. However, Roundup completely eliminated two species of tadpoles and nearly exterminated a third species, resulting in a 70% decline in the species richness of tadpoles. This study represents one of the most extensive experimental investigations of pesticide effects on aquatic communities and offers a comprehensive perspective on the impacts of pesticides when nontarget organisms are examined under ecologically relevant conditions.
Theobjective of this work was to evaluate soybean gene flow in the Western Region of Paraná. Five concentric circles were sowed with the CD219RR cultivar, which contains the CP4EPSPS gene. The circles were spaced in 50cm and the central circle had 50cm in diameter. Externally to the CD219RR circles, five concentric circles were sowed with CD211 cultivar, a no genetically modified soybean, spaced of 1m. The CD211 plants were harvested and threshed separately and the seeds were sowed again. After the emergency, 151,772seedlings were obtained, which with 15days were sprayed with 900gha-1 a.i. of glyphosate. After one week, the surviving plants were analysed by PCR to verify the CP4 EPSPS gene presence. The cross-pollinating rate was 0.61, 0.29, 0.23, 0.22 and 0.23% in 1, 2, 3, 4 and 5m distance of the genetically modified plants, respectively.
In Argentina, deforestation due to agriculture expan-sion is threatening the Semi-arid Chaco, one of the largest forested biomes of South America. This study focuses on the north-west boundary of the Argentine Semi-arid Chaco, where soybean is the most important crop. Deforestation was estimated for areas with dif-ferent levels of soil and rainfall limitation for agricul-ture between 1972 and 2001, with a finer analysis in three periods starting in 1984, which are characterized by differences in rainfall, soybean price, production cost, technology-driven yield and national gross domestic product. Between 1972 and 2001, 588 900 ha (c. 20% of the forests) were deforested. Deforestation has been accelerating, reaching >28 000 ha yr −1 after 1997. The initial deforestation was associated with black bean cultivation following an increase in rainfall during the 1970s. In the 1980s, high soybean prices stimulated fur-ther deforestation. Finally, the introduction of soybean transgenic cultivars in 1997 reduced plantation costs and stimulated a further increase in deforestation. The domestic economy had little association with defo-restation. Although deforestation was more intense in the moister (rainfall >600 mm yr −1) areas, more than 300 000 ha have already been deforested in the drier areas, suggesting that climatic limitations are being overcome by technological and genetic improvement. Furthermore, more than 300 000 ha of forest occur in sectors without major soil and rainfall limitations. If global trends of technology, soybean markets and climate continue, and no active conservation policies are applied, vast areas of the Chaco will be deforested in the coming decades.
Soil organic carbon (SOC) was assessed in a long-term (19 yr) experiment comparing conventional tillage (CT) and no-tillage (NT) management systems and various winter cover crop treatments in a Rhodic Hapludox in southern Brazil. After 19 yr, NT resulted in 6.84 Mg C ha(-1), in the upper soil layer (0-10 cm), which represented 64.6% more than CT. In the 0 to 20 cm soil layer, the NT system sequestered 1.24 Mg C ha(-1) yr(-1), while CT sequestered 0.96 Mg C ha(-1) yr(-1). Independent of soil management, the fallow treatment resulted in the lowest SOC stocks to the 40-cm soil depth compared to all other winter treatments. We compared SOC levels of the experimental site with a nearby-forested area, which has never been cleared. No-till management combined with winter cover crops resulted in soil properties that most closely resembled the undisturbed forest. Maize grain yields and soybean seed yields were 6 and 5% higher, respectively, under NT than CT. Our results point to NT management combined with winter cover crops as the management system of choice to achieve sustainable crop production on Oxisols in the subtropical and tropical regions of the world.
This study assesses the socioeconomic and biodiversity impacts associated with the production of selected agro-commodities in their production countries and areas. Selected agro-commodities are soy (in Argentina and Brazil), palm oil (in Indonesia and Malaysia), beef (in Argentina and Brazil), and coffee (in Honduras and Vietnam). In each of the countries specific production areas and regions were selected, where production of the agro-commodity has shown strong expansion during the last 5 to 8 years. Using data and information on biodiversity and socioeconomic indicators available at the subnational level, a loss of biodiversity as well as a decline of critical socioeconomic indicators was observed in 54% of the studied production areas. Because in the mid-1990s several production areas had lower values for important socioeconomic indicators compared to the national average, a widening of the gap between the socioeconomic situation in production areas as compared to the national average was found in 26% of the cases studied. This corresponds to 59% of areas with a poor initial development situation. We found that factors explaining these patterns are characteristics of the commodities, macroeconomic and governance issues of the countries, as well as the history of the production area and whether production increase occurs through frontier expansion or intensification. Overall these results contradict the neoliberal assumption that export-oriented development will generally stimulate economic growth and reduce poverty in the production areas.
Land-use change for human settlement and agricultural purposes,
especially pasture establishment, has caused major impacts on the Amazon Basin's
environment. Development of strategies for reformation and restoration of already
degraded pastures constitutes the main goal of the authors' research work. For some
of this work, a homogeneous area of land in terms of soil characteristics was selected
at Nova Vida ranch in Rondônia state to conduct a multidisciplinary experiment,
which included agronomic, environmental and economic analyses. Since July 2001,
the authors have monitored five treatments: control, herbicide, tillage, no-till rice
and no-till soybean, arranged in four blocks. Early results on carbon and nitrogen
stocks, nitrogen mineralization, trace-gas fluxes, dissolved organic carbon and
microbial biomass are briefly presented.
Summary Weeds are major constraints on crop production, yet as part of the primary producers within farming systems, they may be important components of the agroecosystem. Using published literature, the role of weeds in arable systems for other above-ground trophic levels are examined. In the UK, there is evidence that weed flora have changed over the past century, with some species declining in abundance, whereas others have increased. There is also some evidence for a decline in the size of arable weed seedbanks. Some of these changes reflect improved agricultural efficiency, changes to more winter-sown crops in arable rotations and the use of more broad-spectrum herbicide combinations. Interrogation of a database of records of phytophagous insects associated with plant species in the UK reveals that many arable weed species support a high diversity of insect species. Reductions in abundances of host plants may affect associated insects and other taxa. A number of insect groups and farmland birds have shown marked population declines over the past 30 years. Correlational studies indicate that many of these declines are associated with changes in agricultural practices. Certainly reductions in food availability in winter and for nestling birds in spring are implicated in the declines of several bird species, notably the grey partridge, Perdix perdix. Thus weeds have a role within agroecosystems in supporting biodiversity more generally. An understanding of weed competitivity and the importance of weeds for insects and birds may allow the identification of the most important weed species. This may form the first step in balancing the needs for weed control with the requirements for biodiversity and more sustainable production methods.
The growing human population and the increase in per capita food consumption are driving agriculture expansion and affecting natural ecosystems around the world. To balance increasing agriculture production and nature conservation, we must assess the efficiency of land-use strategies. Soybean production, mainly exported to China and Europe, has become the major driver of deforestation in dry forest/savanna ecosystems of South America. In this article we compared land cover patterns (based on satellite imagery) and land-use and human population trends (based on government statistics) in regions with two contrasting development pathways in the Chaco dry forests of northern Argentina, since the early 1970s. The area (ca. 13 million hectares) includes one of the largest continuous patches of tropical dry forests and has experienced rapid land-use change. In the region where land use has been driven by government-sponsored colonization programs, the expansion of extensive grazing has led to a growing rural population, low food production, and widespread environmental degradation. In contrast, in the region dominated by market-driven soybean expansion, the rural population has decreased, food production is between 300% and 800% greater, and low-density extensive cattle production has declined over extensive remaining forested areas, resulting in a land-use trend that appears to better balance food production and nature conservation.
Most agricultural landscapes are a mosaic of farmers' fields, semi-natural habitats, human infrastructures (e.g. roads) and occasional natural habitats. Within such landscapes, linear semi-natural habitats often define the edges of agricultural fields. This paper reviews the role and interactions within and between the flora of these elements. In temperate, intensive agriculture, such field margin habitats, which historically had true agricultural functions, now are important refugia for biodiversity. As manmade habitats, field margins may also have important cultural roles as part of our landscape heritage, e.g. hedges in Britain. Whilst field margins are not usually specific habitat types, they contain a variety of plant communities in a variety of structures. These may range from aquatic elements to ruderal and woodland communities. Studies demonstrate a variety of interactions between fields and their margins. Agricultural operations, such as fertiliser and pesticide application, have effects on the flora. Some margin flora may spread into crops, becoming field weeds. Margins also have a range of associated fauna, some of which may be pest species, while many are beneficial, either as crop pollinators or as pest predators. The biodiversity of the margin may be of particular importance for the maintenance of species at higher trophic levels, notably farmland birds, at the landscape scale. Margins contribute to the sustainability of production, by enhancing beneficial species within crops and reducing pesticide use. In northwestern Europe, a variety of methods to enhance diversity at field edges have been introduced, including sown grass and flower strips. The impact of these on weed flora and arthropods indicate mostly beneficial effects though conflicts exist, notably for the conservation of rare arable weed species. © 2002 Elsevier Science B.V. All rights reserved.
Spray drift can be defined as the quantity of plant protection product that is carried out of the sprayed (treated) area by the action of air currents during the application process. This continues to be a major problem in applying agricultural pesticides. The purpose of this research is to measure and compare the amount of drift for different climatological conditions under field conditions. Sedimenting spray drift was determined by sampling in a defined downwind area at different positions in a flat meadow using horizontal drift collectors for a reference spraying. Meteorological conditions were monitored during each experiment. A drift prediction equation for the reference spraying was set up to predict the expected magnitude of sedimenting at various drift distances and atmospheric conditions. The measurements proved the important effect of weather conditions (temperature, relative humidity and wind speed) on the amount of spray drift. A lower wind speed or a higher relative humidity decreases the amount of spray drift. Taking into account the correlation between temperature and relative humidity, a lower temperature will also result in lower drift values due to the cumulative effect of relative humidity. This equation can be used to quantify the effect of meteorological conditions, to compare measurements using other spraying techniques under different weather conditions to the reference spraying and to perform spray drift risk assessments.
Fields left fallow after harvest (i.e. stubble fields) support high wintering densities of many species of granivorous bird. We examined correlates of use by eight such species of different types of intensively managed wheat and barley stubble fields, organic wheat fields and set‐aside fields on mixed lowland farmland in central England. Field occupancy was studied in relation to the physical characteristics of fields and seed abundance.
Higher seed abundance was associated with greater occupancy by linnet Carduelis cannabina , grey partridge Perdix perdix , chaffinch Fringilla coelebs , yellowhammer Emberiza citrinella , reed bunting Emberiza schoeniclus and corn bunting Miliaria calandra . Larger areas of bare earth within stubble fields were associated with greater occupancy by linnet, yellowhammer, reed bunting and corn bunting, but lower occupancy by woodpigeon Columba palumbus .
On conventional intensively farmed sites, seed abundance and area of bare earth were significantly greater on barley stubbles than on wheat stubbles.
Seed numbers fell throughout the winter in all stubble types, although reductions were greatest on intensive barley stubbles, intermediate on intensive wheat stubble and lowest on undersown organic wheat stubbles.
Within fields occupied by linnets, areas used for feeding had significantly greater quantities of seeds known to be important in their diet. Feeding areas also had a greater area of bare earth than randomly selected ‘non‐feeding areas’.
Linnets and reed buntings were rarely found on fields where densities of weed seeds important in their diets fell below 250 seeds m ⁻² . In autumn, yellowhammers and grey partridges rarely fed on fields where cereal grain density was below 50 m ⁻² . However, in spring, both species fed on these fields irrespective of grain density, perhaps indicating a switch to other food sources.
We suggest that land managers wishing to maximize the value of overwinter stubble fields for granivorous birds locate such fields where there is a substantial natural regeneration of weed flora and where previous cropping (e.g. barley) is likely to offer a sparse stubble with substantial areas of bare ground.
The development and use of genetically modified plants (GMPs) has been a topic of considerable public debate in recent years. GMPs hold great promise for improving agricultural output, but the potential for unwanted effects of GMP use is still not fully understood. The majority of studies addressing potential risks of GMP cultivation have addressed only aboveground effects. However, recent methodological advances in soil microbial ecology have allowed research focus to move underground to try to gain knowledge of GMP-driven effects on the microbial communities and processes in soil that are essential to key terrestrial ecosystem functions. This review gives an overview of the research performed to date on this timely topic, highlighting a number of case studies. Although such research has advanced our understanding of this topic, a number of knowledge gaps still prevent full interpretation of results, as highlighted by the failure of most studies to assign a definitively negative, positive or neutral effect to GMP introduction. Based upon our accumulating, yet incomplete, understanding of soil microbes and processes, we propose a synthesis for the case-by-case study of GMP effects, incorporating assessment of the potential plant/ecosystem interactions, accessible and relevant indicators, and tests for unforeseen effects.
Assessing the sustainability of complex development processes requires multi-causal and integrated analyses. We develop a
system-based methodology, rooted in interdisciplinary discussion and consensus building between 15 experts, to construct a
multi-causal diagram which examines the sustainability of the Argentine Pampas´ process of agriculturization. The resulting
diagram includes 25 factors and provides a big-picture of the multiple dimensions and interrelations affecting sustainability.
According to this examination, the increasing concentration of production and the incorporation of technological innovations,
triggered by economic and institutional factors, are the cause of environmental distresses and social changes, whose consequences
for sustainability are still highly disputed. Nevertheless, the symptoms of both environmental and social unsustainability
are more evident in the case of the extra-Pampean regions than in the Pampas. This suggests that the Pampean agriculture model
should not be transferred to these regions without substantial modifications. The experts did not reach consensus on whether
the agriculturization process is overall sustainable or unsustainable. Lack of consensus revolved mainly around opposing perspectives
regarding the significance of the threats to environmental sustainability. The magnitude of socio-distributive unbalance and
loss of rural jobs were also contentious. Yet, the paper shows how the exercise of building a joint causal diagram was undoubtedly
helpful for linking piece-meal disciplinary facts, brought in from all fronts, into a comprehensive and coherent picture.
A summary is given of research within the field of application technology for crop protection products for the past 10years
in The Netherlands. Results are presented for greenhouse, orchard, nursery tree and arable field spraying for the typical
Dutch situation. Research predominantly focussed on the quantification of spray deposition in crop canopy and the emissions
into the environment, especially spray drift. The risk of spray drift is related to defined distances and dimensions of the
surface water adjacent to a sprayed field. Spray deposition and spray drift research was setup in order to identify and quantify
drift-reducing technologies. Results are presented for cross-flow sprayers, tunnel sprayers and air-assisted field sprayers.
For field crop spraying with a boom sprayer the effect of nozzle type on spray deposition in crop canopy and spray drift is
highlighted both with a modelling approach as based on field experiments. The use of spray drift data in regulation is discussed.
A relation between spray deposition and biological efficacy is outlined for drift-reducing spray techniques. The effect of
spray drift-reducing technologies in combination with crop- and spray-free buffer zones is outlined. It is concluded that
spray technology plays an important role to minimise spray- and crop-free buffer zones, and to maintain biological efficacy
and acceptable levels of ecotoxicological risk in the surface water.
Two decades of extensive research and experimentation with zero‐till methods has allowed “ideal” zero‐till systems to emerge in Brazil, involving no soil turning, maintenance of a permanent vegetative cover, and rotations of both cash and cover crops. By exploiting rapid successions of suitable crops, for example, as well as through careful temporal and spatial planning, Brazilian examples show that it is possible to continuously cover soil, gradually increase soil organic matter (SOM) stocks, integrate livestock, move surface‐applied lime through the soil profile, break compact soil layers, and reduce reliance on agrochemicals in zero‐till, all under a variety of edaphic and climatic conditions, and levels of mechanization/farm sizes. Various such technologies and systems are reviewed in this chapter. However, we also note that among smallholder zero‐till farmers, for example, the adaptations of “ideal” zero‐till systems are manifold and complex, partial adoption of certain components and technologies rather than full adoption of zero‐till systems being the norm. By examining farmers' experiences and practice, we ascertain that in many cases there is perhaps a divorce between the ideal, originating mainly from individual technology research on agricultural research stations, and farmers' reality, given the complexity of socioeconomical constraints facing the latter. We conclude that although there is a wealth of valuable zero‐till experience and technologies precipitating from the Brazilian zero‐till “revolution,” numerous challenges in zero‐till research, especially in respect to resource‐poor smallholder farmers, still remain, and perhaps more holistic, participatory and adaptive on farm‐research is necessary in future. © 2006, Elsevier Inc.
The current annual rates of tropical deforestation from Brazil and Indonesia alone would equal four-fifths of the emissions reductions gained by implementing the Kyoto Protocol in its first commitment period, jeopardizing the goal of Protocol to avoid dangerous anthropogenic interference with the climate system. We propose the novel concept of compensated reduction, whereby countries that elect to reduce national level deforestation to below a previously determined historical level would receive post facto compensation, and commit to stabilize or further reduce deforestation in the future. Such a program could create large-scale incentives to reduce tropical deforestation, as well as for broader developing country participation in the Kyoto Protocol, and leverage support for the continuity of the Protocol beyond the 20082012 first commitment period. Pages: 267-276
Franke AC, Lotz LAP, vander Burg WJ & van Overbeek L (2009). The role of arable weed seeds for agroecosystem functioning. Weed Research49, 131–141.
A literature study was conducted to gather knowledge on the impact of weed seeds on agroecosystem functioning other than effects related to the production of weed seedlings and plants. The results of the review suggested that a larger and more diverse weed seedbank can contribute to the biodiversity of various groups of macrofauna and microbiota, with a positive or negative impact on the agroecosystem. However, relationships between weed seed availability and functional biodiversity in the field have generally not been established, with the exception of case studies of seeds sustaining populations of granivorous farmland birds or acting as reservoirs and vectors of plant pathogens. To value the contribution of different weed seeds to sustaining populations of functional biota, more detailed information on their relationships with seeds is essential. Hypotheses and related questions that can be used to explore the impact of weed seeds on functional biodiversity have been identified. The identification of weed seed species that are a key to sustaining functional biota may lead to a weed management strategy aiming to minimise the damage of weeds to crops while taking the alternative ecological roles of weed seeds into account.
Since the early 1990s, Argentinean grain production underwent a dramatic increase in grains production (from 26 million tons in 1988/89 to over 75 million tons in 2002/2003). Several factors contributed to this "revolution," but probably one of the most important was the introduction of new genetic modification (GM) technologies, specifically herbicide-tolerant soybeans. This article analyses this process, reporting on the economic benefits accruing to producers and other participating actors as well as some of the environmental and social impacts that could be associated with the introduction of the new technologies. In doing so, it lends attention to the synergies between GM soybeans and reduced-tillage technologies and also explores some of the institutional factors that shed light on the success of this case, including aspects such as the early availability of a reliable biosafety mechanism and a special intellectual property rights (IPR) situation. In its concluding comments, this article also posts a number of questions about the replicability of the experience and some pending policy issues regarding the future exploitation of GM technologies in Argentina.
The effect of regular and exclusive application of glyphosate in crop sequences on associated weed composition, richness and diversity was studied over five years. Three sequences (wheat–soybean, soybean monoculture and soybean–maize) including soybean and maize glyphosate-resistant cultivars were investigated under two tillage systems (conventional or no-tillage). Regardless of sequence and tillage system, regular glyphosate application appeared to reduce richness and density of the most competitive weeds such as early-emergence annual broad-leaved and grassy annuals and increase that of the less competitive late-emerging annual broad-leaved weeds in no-tillage systems. Some late-emerging annual broad-leaved species, e.g. Bowlesia incana Ruiz et Pav. were present from the beginning of the experiment and others species, e.g. Parietaria debilis G. Foster were not present before initiating the study. This species was the only tolerant to glyphosate at the recommended dose of the herbicide. Species richness in pre-glyphosate application counts showed no response in the wheat–soybean rotation but decreased in the soybean–maize rotation and soybean monoculture in both tillage systems. In post-glyphosate application counts, richness increased for all sequences. Diversity showed an inconsistent response with time. It can be concluded that the effect of glyphosate application was a more important factor than crop sequence to explain weed community changes in summer crops. It may be predicted that continual glyphosate application for longer periods of time might lead to the development or higher increases in abundance of weeds tolerant to the herbicide.
Pesticide use is an important component of agricultural and non-agricultural pest control in tropical areas. However, the fate of pesticides in tropical soils is not as well understood as that for soils from temperate regions. Tropical soils defy easy generalizations, but they are typically very old soils characterized by year-round uniformity of temperature regime. Although only a few studies have directly compared pesticide fate in tropical and temperate soils, there is no evidence that pesticides degrade more slowly under tropical conditions. Laboratory studies in which soils have been held under standardized conditions reveal that pesticide degradation rate and pathway are comparable between tropical and temperate soils. However, field investigations of tropical pesticide soil fate indicate that dissipation occurs more rapidly, in some cases much more rapidly, than for pesticides used under similar temperate conditions. The most prominent mechanisms for this acceleration in pesticide dissipation appear to be related to the effect of tropical climates, and would include increased volatility and enhanced chemical and microbial degradation rates on an annualized basis.
Crops have been grown in the subhumid and semiarid Argentinean Pampas for over 50 years using tillage methods (intensive plowing) introduced from more humid regions. As a result, soil degradation due to erosion by wind and water has been moderate to severe. Experiments to control erosion through use of conservation systems were initiated at six semiarid and subhumid sites in the Argentinean Pampas between 1976 and 1990 and conducted for 5 to 11 years. In this paper, we summarize the effect of conventional and conservation tillage treatments on some soil properties and crop yields. Most soil physical, chemical, and biological properties were improved by conservation systems, but the rate of change differed due to climatic and soil differences among sites, with the difference due to tillage generally being greater at the more humid sites with loamy soils than at the drier sites with sandier soils. Crops with a large N requirement yielded less with conservation than with conventional tillage systems. Use of conservation tillage can improve or stabilize soil conditions in the region, but crop nutrient requirements must be met to achieve optimum crop yields when conservation tillage is used. Research regarding the plant nutrient requirements under conservation tillage is being conducted. Also, conservation tillage is gaining acceptance in the Argentinean Pampas region.
There are several recent trends in North American soybean [Glycine max (L.) Merr.] breeding that call for a new evaluation of the pedigree structure of this population. These are the introduction of Roundup Ready (RR) soybean and restricted exchange of germplasm between breeding programs. The objectives of this study were to assess the genetic structure of the current elite North American soybean population and the current and potential affect of RR soybean and crossing restrictions on this population. This study used coefficient of parentage (CP) analysis of 312 current RR and conventional lines. The RR trait was initially backcrossed into elite lines from a total of 30 different recurrent parents. Many of the intermediates of the backcrossing were also crossed to other elite lines and it is from such crosses that many of the current RR lines derive. Only 1% of the total variation in CP among lines from the northern or southern regions was accounted for by differences between conventional lines, RR lines, and the recurrent parents used to initiate RR breeding programs. The advent of RR cultivars has had little impact on diversity because of the wide use of this technology by many programs and its incorporation into many lines. In contrast, 19% of the variation in CP among northern lines, and 14% among southern lines, was due to difference between lines from different companies and institutions. Diversity was limited among elite lines from some companies. The restricted diversity within some companies coupled with limited exchange of germplasm could affect the soybean industry if marketplace shifts favor one company. Public programs can work to ensure and expand diversity.
SummaryA large proportion of the world tropical region is covered by savannas, which have been little used for agriculture. Locally known as Cerrado, this ecosystem occupies about 20% of Brazilian territory. Preliminary surveys indicate that at least 50 × 106 ha of the Cerrado are of potential use for intensive mechanized agriculture, but development has been limited by soil-related constraints. Most soils are acid and with very low native fertility, especially in terms of phosphorus. Chemical barriers to root growth may cause severe yield losses during dry periods. Field crop responses to lime and fertilizers, obtained during the last 5–8 years, show that once soil-related constraints are removed, high yields can be achieved. This review gives an account of the main lines of research which are leading to economic methods of developing the agricultural use of the Cerrado, and gives future research needs.
A large area (180 Mha) of central Brazil is occupied by a savanna biome known as the Cerrado. Annual rainfall in this region varies from 1200 to 2000 mm, although there is a long (∼5 month) dry season with almost no rain. This region is regarded by Brazilians as their agricultural frontier and there is a steady growth in the area dedicated to permanent cropping in the region, which today is estimated to occupy 14 Mha. Owing to the dearth of long-term experiments, the impact of continuous cropping on soil carbon stocks remains unclear. The objective of this study was to evaluate the effects of different tillage systems (zero till (ZT) and conventional tillage (CT)) on the change in soil carbon stocks over a 20-year period of the same crop sequence compared to that under a neighbouring area of native vegetation (NV). Only approximately 10 Mg ha−1 of soil carbon in the 0–100 cm depth interval was lost under continuous ZT. However, under CT systems losses were greater (up to 30 Mg C ha−1) when the mouldboard plough was used and/or tillage was performed twice a year. We did not have access to instrumentation to accurately assess soil charcoal but the C/N data and peroxide and dichromate oxidative techniques suggested that ∼40% of soil C was in this form. The 13C natural abundance of soil profiles indicated that residues of crops (maize) and the spontaneous annual fallow of Brachiaria spp. resulted in integration of significant C4 residues to a depth of at least 40 cm. It would appear that zero tillage, which is already widely adopted in the Cerrado region of Brazil, will have only a small negative long-term impact on soil C stocks, but ploughing, especially more than once a year, will lead to considerably larger soil C losses.
Conservation tillage (CT) is practised on 45 million ha world-wide, predominantly in North and South America but its uptake is also increasing in South Africa, Australia and other semi-arid areas of the world. It is primarily used as a means to protect soils from erosion and compaction, to conserve moisture and reduce production costs. In Europe, the area cultivated using minimum tillage is increasing primarily in an effort to reduce production costs, but also as a way of preventing soil erosion and retain soil moisture. A large proportion (16%) of Europe's cultivated land is also prone to soil degradation but farmers and governments are being slow to recognise and address the problem, despite the widespread environmental problems that can occur when soils become degraded. Conservation tillage can improve soil structure and stability thereby facilitating better drainage and water holding capacity that reduces the extremes of water logging and drought. These improvements to soil structure also reduce the risk of runoff and pollution of surface waters with sediment, pesticides and nutrients. Reducing the intensity of soil cultivation lowers energy consumption and the emission of carbon dioxide, while carbon sequestration is raised though the increase in soil organic matter (SOM). Under conservation tillage, a richer soil biota develops that can improve nutrient recycling and this may also help combat crop pests and diseases. The greater availability of crop residues and weed seeds improves food supplies for insects, birds and small mammals. All these aspects are reviewed but detailed information on the environmental benefits of conservation tillage is sparse and disparate from European studies. No detailed studies have been conducted at the catchment scale in Europe, therefore some findings must be treated with caution until they can be verified at a larger scale and for a greater range of climatic, cropping and soil conditions.
There is growing concern about declining species diversity in agro‐ecosystems caused by agricultural intensification at the field and landscape scales. Species diversity of arable weeds is classically related to local abiotic factors and resource conditions. It is believed to be enhanced by organic farming but the surrounding landscape may also be important.
This study assessed the ruderal vegetation, seed bank and seed rain in 24 winter wheat fields to examine the relative importance of organic vs. conventional farming and landscape complexity for weed species diversity. Diversity was partitioned into its additive components: alpha, beta and gamma diversity. Percentage arable land in a circular landscape sector of 1‐km radius around each study site was used as an indicator of landscape complexity.
Weed species diversity in the vegetation, seed rain and seed bank was higher in organic than in conventional fields. Increasing landscape complexity enhanced species diversity more strongly in the vegetation of conventional than organic fields, to the extent that diversity was similar in both farming systems when the landscape was complex. Species diversity of the seed bank was increased by landscape complexity irrespective of farming system.
Overall diversity was largely determined by the high heterogeneity between and within the fields (beta diversity). Only in very few cases could higher weed species diversity in complex landscapes and/or organic farming be related to species dependence on landscape or farming system.
Synthesis and applications. Local weed species diversity was influenced by both landscape complexity and farming system. Species diversity under organic farming systems was clearly higher in simple landscapes. Conventional vegetation reached similar diversity levels when the surrounding landscape was complex through the presence of refugia for weed populations. Consequently, agri‐environment schemes designed to preserve and enhance biodiversity should not only consider the management of single fields but also of the surrounding landscape.
The herbicide Rodeo provides waterfowl managers with an effective chemical tool for creating open water habitats in wetlands if its use does not adversely affect native invertebrate communities. The survival of caged Chironomus spp. (midge), Hyalella azteca (amphipod), Stagnicola elodes (pond snail), and Nephelopsis obscura (leech) was assessed in prairie pothole wetlands treated by air with a tank mixture of Rodeo, the surfactant X-77 Spreader, and the drift retardant Chem-Trol at a rate recommended for controlling cattails. Laboratory studies were then conducted to determine the acute toxicities of Rodeo, X-77 Spreader, and Chem-Trol, individually and in simulated tank mixtures, to the same invertebrates and to Daphnia magna in reconstituted water representative of these wetlands. There was no difference in the survival of caged invertebrates between treated and reference wetlands after 21 days. Based on nominal concentrations of the formulations, X-77 Spreader (LC50s=2.0–14.1 mg/L) was about 83–136 times more toxic than Rodeo (LC50s=218–1216 mg/L) to aquatic invertebrates. Chem-Trol killed 10% of the animals at 10,000 mg/L and 50% of the animals at 28,000 mg/L. Daphnia magna were more sensitive than the other species to X-77 Spreader, Rodeo, and the simulated Rodeo tank mixture (RTM). The joint toxic action of the RTM was additive for amphipods and midges, greater than additive for leeches, and was less than additive for daphnids. X-77 Spreader was the major toxic component in the RTM. Binary mixtures of X-77 Spreader, Rodeo, and Chem-Trol at tank mixture and equitoxic ratios also showed additive toxicity to amphipods. The use of Rodeo (applied as a tank mixture with X-77 Spreader and Chem-Trol) as a management tool in wetlands does not pose an acute hazard to native aquatic invertebrates because the concentrations of Rodeo, X-77 Spreader, and Chem-Trol found to be acutely toxic to these invertebrates were much higher than their expected or measured concentrations in water from wetlands treated with the RTM.
Glyphosate was applied to the water surface of four small boreal forest ponds and sixin situ microcosms at a rate of 0.89 Kg a.i./ha. Water samples collected over a period of up to 255 days were analyzed for glyphosate and its primary metabolite aminomethylphosphonic acid (AMPA). Glyphosate dissipated rapidly from all ponds with first order half-lives ranging from 1.5 to 3.5 days. The slowest dissipation rate occurred in the pond with the most calcareous water and sediments. Glyphosate remained at or above the treatment concentration in microcosms containing only water but decreased rapidly in the presence of sediments. AMPA levels in ponds and microcosms were consistently low. Concentrations on microcosm wall samples were temporally variable, probably a result of adsorption to periphytic biofilms. Glyphosate in the sediments of treated microcosms generally increased with time during the period of observation. These results confirm that glyphosate dissipates rapidly from the surfaces waters of lentic systems, and suggest that sediment adsorption or biodegradation were the major means of glyphosate loss from the water column.
Soil erosion is one of the most serious environmental and public health problems facing human society. Humans obtain more
than 99.7% of their food (calories) from the land and less than 0.3% from the oceans and other aquatic ecosystems. Each year
about 10 millionha of cropland are lost due to soil erosion, thus reducing the cropland available for food production. The
loss of cropland is a serious problem because the World Health Organization reports that more than 3.7 billion people are
malnourished in the world. Overall soil is being lost from land areas 10 to 40 times faster than the rate of soil renewal
imperiling future human food security and environmental quality.
Recent changes in management of soybean production in Argentina may have large impacts on the soil water balance and on crop yield response. Changes in this system have included widespread adoption of a no-till management leaving crop residue on the soil surface, intensive cropping rotations (e.g. double cropping of wheat and soybean) so that the soil may not be fully recharged with water at the time of soybean sowing, and the occurrence of high water tables in a number of areas. The objective of this analysis was to assess the need to account for these factors in simulating soybean yields in Argentina. The influence of no-till management was simulated by simply decreasing the soil evaporation estimated for a bare soil by 70%. However, this alteration resulted in an over prediction in yield in many cases when it was assumed that the soil water content had been fully recharged at the initiation of the simulations. The difficulty with assuming a full soil water profile was confirmed when simulated yields were found to match well with observed yields when measured soil water content was used as an input to the model at the beginning of the soybean season. Finally, even with decreased soil evaporation there were still a few cases where simulated yield was less than observed yield. In these cases, a hypothetical water table, which relieved any drought stress once roots reached a depth of 1 m, resulted in yields that more closely matched observations. Overall, these results highlighted the need to estimate well both the influence of crop residue on soil evaporation and the soil water profile at sowing in simulating soybean yields in Argentina.
Tillage systems affect the soil physical and chemical environment in which soil organisms live, thereby affecting soil organisms. Tillage practices change soil water content, temperature, aeration, and the degree of mixing of crop residues within the soil matrix. These changes in the physical environment and the food supply of the organisms affect different groups of organisms in different ways. One of the challenges of research in soil ecology is to understand the impacts of management on the complex interactions of all organisms at the soil community level. In addition to the response of organisms to soil manipulations, agriculturalists are interested in the actions of soil organisms on the physical and chemical environment in the soil. Soil organisms perform important functions in soil, including structure improvement, nutrient cycling, and organic matter decomposition. This paper discusses the effects of tillage practices on soil organism populations, functions, and interactions. Although there is a wide range of responses among different species, most organism groups have greater abundance or biomass in no-till than in conventional tillage systems. Larger organisms in general appear to be more sensitive to tillage operations than smaller organisms, due to the physical disruption of the soil, burial of crop residue, and the change in soil water and temperature resulting from residue incorporation. Variations in responses found in different studies reflect different magnitudes of tillage disruption and residue burial, timing of the tillage operations, timing of the measurements, and different soil, crop, and climate combinations. The paper concludes with a discussion of challenges for tillage researchers.
The introduction of new agricultural practices (no tillage cropping and soybean transgenic cultivars resistant to glyphosate) to Argentina, together with market factors, have resulted in an increase in the area cropped with soybean and generated a new environment in the Rolling Pampas agroecosystem. During the summers of 1995, 1998, 1999, 2001 and 2003, a total of 120 soybean fields were surveyed, to evaluate the changes in the weed communities of the central Rolling Pampas through the period during which the adoption of these new technologies was increasing exponentially. Floristic structure was analyzed in terms of species composition, and functional structure in terms of morphotypes and physiotypes. Data were summarized by calculating species constancy, and alpha, beta, gamma diversity and functional richness. Alpha (local) diversity and functional richness were linearly related with gamma (regional) diversity and after an initial increase from 1995 to 1998, decreased over time, this being associated with the adoption of the new technologies. Beta diversity was not related to soybean regional pool of weed species, thus it was probably related to the availability of refuges provided by the landscape's habitat. Tillage system and cultivars were the main agronomic variable affecting the occurrence of weeds.
In the humid Pampas of Argentina soybean is cultivated in different soil types, which were changed from conventional- to zero tillage systems in the last decade. Little is known about the response of soybean roots to these different soil physical environments. Pasture, and conventionally- and zero-tilled field lots cropped to soybean (R1 and R2 ontogenic stages) were sampled in February–March 2001 in a sandy clay loam and two silty clay loam Mollisols, and in a clayey Vertisol. In the 0–0.05 m layer of conventionally- and zero-tilled lots soil organic carbon represented 53–72% of that in pasture lots, and showed an incipient recovery after 4–11 years of continuous zero tillage. Soil aggregate stability was 10.1–46.8% lower in conventionally-tilled than in pasture lots, and recovered completely in zero-tilled lots. Soil relative compaction ranged 60.8–83.6%, which was below the threshold limit for crop yields (>90%). In change, soil porosity >50 μm ranged 0.91–5.09% soil volume, well below the minimum critical limit for root aeration and elongation (>10%, v/v). The threshold of soil resistance (about 2–3 MPa) was only over passed in an induced plough pan in the conventionally-tilled Bragado soil (5.9 MPa), and in the conventionally- and zero-tilled Ramallo soils (3.7–4.2 MPa, respectively). However, neither the low macroporosity nor the high soil resistances impeded soybean roots growth in any site. According to a fitted polynomial function, root abundance was negatively related to clay content in the subsoil (R2 = 0.84, P < 0.001). Soybean roots were only abundant in the subsoil of the sandy clay loam Mollisol, which had <350 g kg−1 clay. Results show that subsoil properties, and not tillage systems, were the primary effect of root growth of soybean.
Sustainable agriculture requires an adequate analysis framework. Fuzzy logic-based and field scale indicators were developed to evaluate the effects of pesticides and tillage on agroecosystems. All the assumptions and rules for making inferences reflect the current knowledge and the expert perception and judgment about the potential environmental impact of pesticides and tillage. The proposed indicators require four input variables: (1) number and type of applied pesticides, (2) rate of applied pesticides, (3) number and type of tillage tools, and (4) land capability class of each field. In regards to pesticide impact, the indicators consider the toxicity effects on: (1) mammals and (2) insects, while the tillage impact is evaluated taking into account the effects of different tillage operations on: (1) the retention of crop stubble on the soil surface, and (2) the stability of soil aggregates. Two overall outputs were obtained: (1) pesticide index and (2) tillage index. The developed indicators were used to compare the potential environmental effect of current practices carried out in Inland Pampa (Argentina). Concerning pesticide use, cropping winter wheat did less harm to the agroecosystem than cropping maize and sunflower. The overall values of tillage index were similar within crops. However, large differences in pesticide and tillage effects were found among tillage systems. Soybean showed the highest variability in both indexes. The type of analysis carried out in this study using farm-level variables may help find more sustainable ways to manage agricultural inputs.
The growth rates of Aporrectodea caliginosa (Savigny) were measured over a 100-day period in soil in culture chambers which were treated with common biocides singly and in combination. The biocides used were: the fungicide Captan, the herbicide, Glyphosate and the insecticide, Azinphos-methyl. The biocides were applied at intervals of 14 days and each treatment was replicated six times. The results are variable, all biocides depressed growth when applied alone but some combinations reduced the effect of other biocides. Azinphos-methyl and Glyphosate applied alone, reduced growth the most over the 100 days and at all rates of application. Azinphos-methyl applied at the highest rate killed worms. Captan applied alone had the least effect on growth and mortality. In combination, Glyphosate and Captan had a lesser effect than Glyphosate alone. Azinphos-methyl and Captan had less effect than Azinphos-methyl alone. After 100 days the combination of all three biocides reduced growth to the same degree as Glyphosate alone.
In the pursuit of more sustainable approaches to agricultural management, there is an obvious need to integrate knowledge of the agricultural sciences and ecology. We used recent findings on ecological correlates of seed characteristics as a framework to discuss the impact of shifting from soil ploughing to farming with reduced or zero tillage on weed communities. In the future, knowledge about seed bank ecology may become increasingly applicable towards improving the way we manage weeds. It is also possible that the effects of cultural activities on moulding weed characteristics will become more apparent.
Risk assessment concerns and recent advances in microbial ecology have spurred a wave of research on the impact of genetically modified (GM) crops on soil-borne microbial community structure and function. Effects have often been observed, but these usually pale in comparison with ‘normal’ sources of variation. In spite of our incomplete knowledge of the microbial communities and processes in plant–soil systems, recent technological and conceptual improvements do offer a way forward. We propose a case-by-case approach within a framework that targets both potentially vulnerable indicators as well as general community parameters for assessing the impact of GM plants on soil microorganisms.
It is widely believed that soil disturbance by tillage was a primary cause of the historical loss of soil organic carbon (SOC) in North America, and that substantial SOC sequestration can be accomplished by changing from conventional plowing to less intensive methods known as conservation tillage. This is based on experiments where changes in carbon storage have been estimated through soil sampling of tillage trials. However, sampling protocol may have biased the results. In essentially all cases where conservation tillage was found to sequester C, soils were only sampled to a depth of 30 cm or less, even though crop roots often extend much deeper. In the few studies where sampling extended deeper than 30 cm, conservation tillage has shown no consistent accrual of SOC, instead showing a difference in the distribution of SOC, with higher concentrations near the surface in conservation tillage and higher concentrations in deeper layers under conventional tillage. These contrasting results may be due to tillage-induced differences in thermal and physical conditions that affect root growth and distribution. Long-term, continuous gas exchange measurements have also been unable to detect C gain due to reduced tillage. Though there are other good reasons to use conservation tillage, evidence that it promotes C sequestration is not compelling.
One of the most important terrestrial pools for carbon (C) storage and exchange with atmospheric CO2 is soil organic carbon (SOC). Following the advent of large-scale cultivation, this long-term balance was disrupted and increased amounts of SOC were exposed to oxidation and loss as atmospheric CO2. The result was a dramatic decrease in SOC. If amounts of C entering the soil exceed that lost to the atmosphere by oxidation, SOC increases. Such an increase can result from practices that include improved: (1) tillage management and cropping systems, (2) management to increase amount of land cover, and (3) efficient use of production inputs, e.g. nutrients and water. Among the most important contributors is conservation tillage (i.e., no-till, ridge-till, and mulch-tillage) whereby higher levels of residue cover are maintained than for conventional-tillage. Gains in amount of land area under conservation tillage between 1989 and 1998 are encouraging because of their contributions to soil and water conservation and for their potential to sequester SOC. Other important contributors are crop residue and biomass management and fallow reduction. Collectively, tillage management and cropping systems in the US are estimated to have the potential to sequester 30–105 million metric tons of carbon (MMTC) yr−1. Two important examples of management strategies whereby land cover is increased include crop rotations with winter cover crops and the conservation reserve program (CRP). Such practices enhance SOC sequestration by increasing the amount and time during which the land is covered by growing plants. Crop rotations, winter cover crops, and the CRP combined have the potential to sequester 14–29 MMTC yr−1. Biomass production is increased by efficient use of production inputs. Optimum fertility levels and water availability in soils can directly affect quantity of crop residues produced for return to the soil and for SOC sequestration. Nutrient inputs and supplemental irrigation are estimated to have the potential to sequester 11–30 MMTC yr−1. In the future, it is important to acquire an improved understanding of SOC sequestration processes, the ability to make quantitative estimates of rates of SOC sequestration, and technology to enhance these rates in an energy- and input-efficient manner. Adoption of improved tillage practices and cropping systems, increased land cover, and efficient use of nutrient and water inputs are examples where such information is necessary.
Transgenic resistance to broad-spectrum herbicides is increasingly seen in various crops. With transgenic herbicide-resistant (THR) cultivars, application of broad-spectrum herbicides is no longer limited to the pre-emergence stage of the crop. Post-emergence application of these herbicides may be more effective in obtaining sufficient weed control compared with currently used herbicides, and herbicide treatment can be delayed compared with that in non-THR crops, thereby controlling weeds at a larger plant size. A well known side effect of glyphosate and glufosinate ammonium is the emergence of so-called 'herbicide-synergists', ie opportunistic root pathogens that accelerate the killing of roots that are herbicide-sensitive. These opportunistic plant pathogens, multiplying in the dying roots of weeds, may affect THR crops. In addition, suppressive effects of glyphosate and/or glufosinate ammonium on the saprophytic and antagonistic microflora have been reported and may enhance the activity of root pathogens. The authors hypothesize that delaying herbicide use in THR cultivars to optimize weed control results in increased infections by root pathogens. Controlled field experiments on the interactions between crops, pathogens and weeds are required to test this hypothesis.