Search Results

Organic farming occupies a unique position among the world’s agricultural systems. While not the only available model for sustainable food production, organic farmers and their supporters have been the most vocal advocates for a fully integrated agriculture that recognizes a link between the health of the land, the food it produces, and those that consume it. Advocacy for the biological basis of agriculture and the deliberate restriction or prohibition of many agricultural inputs arose in response to potential and observed negative environmental impacts of new agricultural technologies introduced in the 20th century. A primary focus of organic farming is to enhance soil ecological function by building soil organic matter that in turn enhances the biota that soil health and the health of the agroecosystem depends on. The rapid growth in demand for organic products in the late 20th and early 21st centuries is based on consumer perception that organically grown food is better for the environment and human health. Although there have been some documented trends in chemical quality differences between organic and non-organic products, the meaningful impact of the magnitude of these differences is unclear. There is stronger evidence to suggest that organic systems pose less risk to the environment, particularly with regard to water quality; however, as intensity of management in organic farming increases, the potential risk to the environment is expected to also increase. In the early 21st century there has been much discussion centered on the apparent bifurcation of organic farming into two approaches: “input substitution” and “system redesign.” The former approach is a more recent phenomenon associated with pragmatic considerations of scaling up the size of operations and long distance shipping to take advantage of distant markets. Critics argue that this approach represents a “conventionalization” of organic agriculture that will erode potential benefits of organic farming to the environment, human health, and social welfare. A current challenge of organic farming systems is to reconcile the different views among organic producers regarding issues arising from the rapid growth of organic farming.

After millennia of hunting and gathering, prehistoric human societies around the world made the transition to food production using domesticated plants and animals. Several key areas for the initial domestication of plants and animals can be identified: southwestern Asia, Mesoamerica, China, Neotropical South America, eastern North America, Highland New Guinea, and sub-Saharan Africa. In the Old World, wheat, barley, millet, rice, sheep, goats, cattle, and pigs were the major founding crops, while in the New World, maize, squashes, beans, and many other seed and tuber plants were brought into cultivation. Although each area had its own distinct pathway to agriculture, it typically followed a standard path from resource management by hunter-gatherers, incipient cultivation (and livestock herding in some areas), domestication, to commitment to agriculture. Many theories to explain the transition to agriculture have been proposed. Early single-factor hypotheses have been largely discarded in favor models drawn from human evolutionary biology that emphasize the interplay between humans and the species targeted for domestication. Although within the long span of human history, the transition from hunting and gathering to farming in the last 10,000 years can be considered extraordinarily rapid, usually this process took decades, centuries, or even millennia when considered from the perspective of the human factors involved. From these core areas, agricultural practices dispersed, both through their integration into the plant and animal economies of hunter-gatherer societies and through the spread of farming populations. The transition to agriculture had consequences on a global scale, leading to social complexity and, in many cases, urban societies that would be impossible to imagine without agriculture.

Agricultural extension has evolved over the last 200 years from a system of top-down dissemination of information from experts to farmers to a more complex system, in which a diversity of knowledge producers and farmers work together to co-produce information. Following a detailed history of the evolution of extension in the United States, this article describes an example from the southeastern United States that illustrates how innovative institutional arrangements enable land-grant universities to actively engage farmers and extension agents as key partners in the knowledge generation process. A second U.S. example shows that private retailers are more influential than extension in influencing large-scale farmers’ farm management decisions in the midwestern United States. However, these private retailers trust extension as a source of climate change information and thus partnerships are important for extension. Nongovernmental organizations (NGOs) have been an important source of extension services for smallholder farmers across the world, and examples from the NGO CARE indicate that a participatory and facilitative approach works well for climate change communication. Collectively, these examples emphasize that the role of agricultural extension in climate change communication is essential in the context of both developed and developing countries and with both smallholder farmers and large-scale farmers. These case studies illustrate the effectiveness of a co-production approach, the importance of partners and donors, and the changing landscape of agricultural extension delivery.

Agricultural terraces are widely spread all over the world and are among the most evident landscape signatures of the human fingerprint, in many cases dating back to several centuries. Agricultural terraces create complex anthropogenic landscapes traditionally built to obtain land for cultivation in steep terrains, typically prone to runoff production and soil erosion, and thus hardly suitable for rain-fed farming practices. In addition to acquiring new land for cultivation, terracing can provide a wide array of ecosystem services, including runoff reduction, water conservation, erosion control, soil conservation and increase of soil quality, carbon sequestration, enhancement of biodiversity, enhancement of soil fertility and land productivity, increase of crop yield and food security, development of aesthetic landscapes and recreational options. Moreover, some terraced areas in the world can be considered as a cultural and historical heritage that increases the asset of the local landscape. Terraced slopes may be prone to failure and degradation issues, such as localized erosion, wall or riser collapse, piping, and landsliding, mainly related to runoff concentration processes. Degradation phenomena, which are exacerbated by progressive land abandonment, reduce the efficiency of benefits provided by terraces. Therefore, understanding the physical processes occurring in terraced slopes is essential to find the most effective maintenance criteria necessary to accurately and adequately preserve agricultural terraces worldwide.

The history of DDT and pesticides in America is overshadowed by four broad myths. The first myth suggests that DDT was the first insecticide deployed widely by American farmers. The second indicates that DDT was the most toxic pesticide to wildlife and humans alike. The third myth assumes that Rachel Carson’s Silent Spring (1962) was an exposé of the problems of DDT rather than a broad indictment of American dependency on chemical insecticides. The fourth and final myth reassures Americans that the ban on DDT late in 1972 resolved the pesticide paradox in America. Over the course of the 20th century, agricultural chemists have developed insecticides from plants with phytotoxic properties (“botanical” insecticides) and a range of chemicals including heavy metals such as lead and arsenic, chlorinated hydrocarbons like DDT, and organophosphates like parathion. All of the synthetic insecticides carried profound unintended consequences for landscapes and wildlife alike. More recently, chemists have returned to nature and developed chemical analogs of the botanical insecticides, first with the synthetic pyrethroids and now with the neonicotinoids. Despite recent introduction, neonics have become widely used in agriculture and there are suspicions that these chemicals contribute to declines in bees and grassland birds.

Climate change is already having a significant impact on agriculture through greater weather variability and the increasing frequency of extreme events. International policy is rightly focused on adapting and transforming agricultural and food production systems to reduce vulnerability. But agriculture also has a role in terms of climate change mitigation. The agricultural sector accounts for approximately a third of global anthropogenic greenhouse gas emissions, including related emissions from land-use change and deforestation. Farmers and land managers have a significant role to play because emissions reduction measures can be taken to increase soil carbon sequestration, manage fertilizer application, and improve ruminant nutrition and waste. There is also potential to improve overall productivity in some systems, thereby reducing emissions per unit of product. The global significance of such actions should not be underestimated. Existing research shows that some of these measures are low cost relative to the costs of reducing emissions in other sectors such as energy or heavy industry. Some measures are apparently cost-negative or win–win, in that they have the potential to reduce emissions and save production costs. However, the mitigation potential is also hindered by the biophysical complexity of agricultural systems and institutional and behavioral barriers limiting the adoption of these measures in developed and developing countries. This includes formal agreement on how agricultural mitigation should be treated in national obligations, commitments or targets, and the nature of policy incentives that can be deployed in different farming systems and along food chains beyond the farm gate. These challenges also overlap growing concern about global food security, which highlights additional stressors, including demographic change, natural resource scarcity, and economic convergence in consumption preferences, particularly for livestock products. The focus on reducing emissions through modified food consumption and reduced waste is a recent agenda that is proving more controversial than dealing with emissions related to production.

Nutrient pollution can have a negative impact on the aquatic environment, with loss of biodiversity, toxic algal blooms, and a deficiency in dissolved oxygen in surface waters. Agricultural production is one of the main contributors to these problems; this article provides an overview of and background for the main biogeochemical processes causing agricultural nutrient pollution of surface waters. It discusses the main features of the agricultural impact on nutrient loads to surface waters, focusing on nitrogen and phosphorus, and describes some of the main characteristics of agricultural management, including processes and pathways from soil to surface waters. An overview of mitigation measures to reduce pollution, retention in the landscape, and challenges regarding quantification of nutrient losses are also dealt with. Examples are presented from different spatial scales, from field and catchment to river basin scale.

Soil tilth is a dynamic and multifaceted concept that refers to the suitability of a soil for planting and growing crops. A soil with good tilth is “usually loose, friable and well granulated”; a condition that can also be described as the soil’s having a good “self-mulching” ability. On the other hand soils with poor tilth are usually dense (compacted), with hard, blocky, or massive structural characteristics. Poor soil tilth is generally associated with compaction, induced by wheel traffic, animal trampling, and/or to natural soil consolidation (i.e., so-called hard-setting behavior). The soil-tilth concept dates back to the early days of arable farming and has been addressed in soil-science literature since the 1920s. Soil tilth is generally associated with soil’s physical properties and processes rather than the more holistic concepts of soil quality and soil health. Improved soil tilth has been associated with deep and intensive tillage, as those practices were traditionally considered the primary method for creating a suitable soil condition for plant growth. Therefore, for millennia there has been a strong focus both in practice and in research on developing tillage tools that create suitable growing conditions for different crops, soil types, and climatic conditions. Deep and intensive tillage may be appropriate for producing a good, short-term tilth, but may also lead to severe long-term degradation of the soil structure. The failure of methods relying on physical manipulation as means of sustaining good tilth has increased the recognition given to the important role that soil biota have in soil-structure formation and stabilization. Soil biology has only received substantial attention in soil science during the last few decades. One result of this is that this knowledge is now being used to optimize soil management through strategies such as more diverse rotations, cover crops, and crop-residue management, with these being applied either as single management components or more preferably as part of an integrated system (i.e., either conservation agriculture or organic farming).Traditionally, farmers have evaluated soil tilth qualitatively in the field. However, a number of quantitative or semi-quantitative procedures for assessing soil tilth has been developed over the last 80 years. These procedures vary from simply determining soil cloddiness to more detailed evaluations whereby soil’s physical properties (e.g., porosity, strength, and aggregate characteristics) are combined with its consistency and organic-matter measurements in soil-tilth indices. Semi-quantitative visual soil-evaluation methods have also been developed for field evaluation of soil tilth, and are now used in many countries worldwide.

Industrialized livestock production can be characterized by five key attributes: confinement feeding of animals, separation of feed and livestock production, specialization, large size, and close vertical linkages with buyers. Industrialized livestock operations—popularly known as CAFOs, for Concentrated Animal Feeding Operations—have spread rapidly in developed and developing countries; by the early 21st century, they accounted for three quarters of poultry production and over half of global pork production, and held a growing foothold in dairy production. Industrialized systems have created significant improvements in agricultural productivity, leading to greater output of meat and dairy products for given commitments of land, feed, labor, housing, and equipment. They have also been effective at developing, applying, and disseminating research leading to persistent improvements in animal genetics, breeding, feed formulations, and biosecurity. The reduced prices associated with productivity improvements support increased meat and dairy product consumption in low and middle income countries, while reducing the resources used for such consumption in higher income countries. The high-stocking densities associated with confined feeding also exacerbate several social costs associated with livestock production. Animals in high-density environments may be exposed to diseases, subject to attacks from other animals, and unable to engage in natural behaviors, raising concerns about higher levels of fear, pain, stress, and boredom. Such animal welfare concerns have realized greater salience in recent years. By consolidating large numbers of animals in a location, industrial systems also concentrate animal wastes, often in levels that exceed the capacity of local cropland to absorb the nutrients in manure. While the productivity improvements associated with industrial systems reduce the resource demands of agriculture, excessive localized concentrations of manure can lean to environmental damage through contamination of ground and surface water and through volatilization of nitrogen nutrients into airborne pollutants. Finally, animals in industrialized systems are often provided with antibiotics in their feed or water, in order to treat and prevent disease, but also to realize improved feed absorption (“a production purpose”). Bacteria are developing resistance to many important antibiotic drugs; the extensive use of such drugs in human and animal medicine has contributed to the spread of antibiotic resistance, with consequent health risks to humans. The social costs associated with industrialized production have led to a range of regulatory interventions, primarily in North America and Europe, as well as private sector attempts to alter the incentives that producers face through the development of labels and through associated adjustments within supply chains.

The 20th century represents a crucial period in Brazil’s economic history, when an agrarian, rural-dominated society became an urban, industrialized country with a complex financial sector and a large service sector. This economic transformation fueled by coffee exports led to profound demographic and social changes as millions of European and Asian immigrants were integrated into Brazilian society, followed by a massive shift of native-born migrants from the northeast to the dynamic southeast of Brazil, particularly for the state of São Paulo, which became the richest, most industrialized, and most populous state of the nation. The second half of the 20th century saw the creation of a modern industrial sector and the modernization of national agriculture, which in the 21st century made Brazil one of the most important producers of grain and animal protein in the world.

Development is a process that transforms societies. Despite considerable variation across world regions and over time, one commonality of development has been that the initial phase, from 1950 to 1975, likely led to growing inequality between men and women in both opportunities and well-being. The first decades of planning and promotion of development largely excluded women, partly as a result of unequal gender relations in many societies as development began: the slave trade, colonial indifference to women’s rights, and missionary activities may have worsened the status of women. More importantly, the men who controlled the late colonial and early post-independence state saw little reason to promote a pro-woman agenda in development. The initial phase of development thus reinforced male privilege. After 1975, national and international social movements arose to pressure governments and institutions to undo the legacies of gender inequality. Women-centered development flourished in the 2000s. There have been uncertainties, however, over the cost-effectiveness of some of the various policies and programs implemented as a result of the movements to include women in development.

Agriculture has been the principal influence on the physical structure of the English landscape for many thousands of years. Driven by a wider raft of demographic, social, and economic developments, farming has changed in complex ways over this lengthy period, with differing responses to the productive potential and problems of local environments leading to the emergence of distinct regional landscapes. The character and configuration of these, as much as any contemporary influences, have in turn structured the practice of agriculture at particular points in time. The increasing complexity of the wider economy has also been a key influence on the development of the farmed landscape, especially large-scale industrialization in the late 18th and 19th centuries; and, from the late 19th century, globalization and increasing levels of state intervention. Change in agricultural systems has not continued at a constant rate but has displayed periods of more and less innovation.

Agriculture waste can be a significant issue in waste management as its impact can be felt far from its place of origin. Post-harvest crop residues require clearance prior to the next planting and a common practice is burning on the field. The uncontrolled burning results in air pollution and can adversely impact the environment far from the burn site. Agriculture waste can also include animal husbandry waste such as from cattle, swine, and poultry. Animal manure not only causes odors but also pollutes water if discharged untreated. However, agricultural activities, particularly on a large scale, are typically at some distance from urban centers. The environmental impacts associated with production may not be well recognized by the consumers. As the consumption terminal of agricultural produce, urban areas in turn generate food waste, which can contribute significantly to municipal solid wastes. There is a correlation between the quantity of food waste generated and a community’s economic progress. Managing waste carries a cost, which may illustrate cost transfer from waste generators to the public. However, waste need not be seen only as an unwanted material that requires costly treatment before disposal. The waste may instead be perceived as a raw material for resource recovery. For example, the material may have substantial quantities of organic carbon, which can be recovered for energy generation. This offers opportunity for producing and using renewable and environment-friendly fuels. The “waste” may also include quantities of recoverable nutrients such as nitrogen and phosphorus.

Agriculture is a significant source of methane, contributing about 12% of the global anthropogenic methane emissions. Major sources of methane from agricultural activities are fermentation in the reticulo-rumen of ruminant animals (i.e., enteric methane), fermentation in animal manure, and rice cultivation. Enteric methane is the largest agricultural source of methane and is mainly controlled by feed dry matter intake and composition of the animal diet (i.e., fiber, starch, lipids). Processes that lead to generation of methane from animal manure are similar to those taking place in the reticulo-rumen. Methane emissions from manure, however, are greatly influenced by factors such as manure management system and ambient temperature. Systems that handle manure as a liquid generate much more methane than systems in which manure is handled as a solid. Low ambient temperatures drastically decrease methane emissions from manure. Once applied to soil, animal manure does not generate significant amounts of methane. Globally, methane emissions from rice cultivation represent about 10% of the total agricultural greenhouse gas emissions. In the rice plant, methane dissolves in the soil water surrounding the roots, diffuses into the cell-wall water of the root cells, and is eventually released through the micropores in the leaves. Various strategies have been explored to mitigate agricultural methane emissions. Animal nutrition, including balancing dietary nutrients and replacement of fiber with starch or lipids; alternative sinks for hydrogen; manipulation of ruminal fermentation; and direct inhibition of methanogenesis have been shown to effectively decrease enteric methane emissions. Manure management solutions include solid-liquid separation, manure covers, flaring of generated methane, acidification and cooling of manure, and decreasing manure storage time before soil application. There are also effective mitigation strategies for rice that can be categorized broadly into selection of rice cultivars, water regime, and fertilization. Alternate wetting and drying and mid-season drainage of rice paddies have been shown to be very effective practices for mitigating methane emissions from rice production.

The possibility that native peoples in eastern North America had cultivated plants prior to the introduction of maize was first raised in 1924. Scant evidence was available to support this speculation, however, until the “flotation revolution” of the 1960s and 1970s. As archaeologists involved in large-scale projects began implementing flotation, paleoethnobotanists soon had hundreds of samples and thousands of seeds that demonstrated that indigenous peoples grew a suite of crops, including cucurbit squashes and gourds, sunflower, sumpweed, and chenopod, which displayed signs of domestication. The application of accelerator mass spectrometry (AMS) dating to cucurbit rinds and seeds in the 1980s placed the domestication of these four crops in the Late Archaic period 5000–3800 bp. The presence of wild cucurbits during earlier Archaic periods lent weight to the argument that native peoples in eastern North America domesticated these plants independently of early cultivators in Mesoamerica. Analyses of DNA from chenopods and cucurbits in the 2010s definitively demonstrated that these crops developed from local lineages. With evidence in hand that refuted notions of the diffusion of plant domestication from Mesoamerica, models developed in the 1980s for the transition from foraging to farming in the Eastern Woodlands emphasized the coevolutionary relationship between people and these crop plants. As Archaic-period groups began to occupy river valleys more intensively, in part due to changing climatic patterns during the mid-Holocene that created more stable river systems, their activities created disturbed areas in which these weedy plants thrive. With these useful plants available as more productive stands in closer proximity to base camps, people increasingly used the plants, which in turn responded to people’s selection. Critics noted that these models left little room for intentionality or innovation on the part of early farmers. Models derived from human behavioral ecology explore the circumstances in which foragers choose to start using these small-seeded plants in greater quantities. In contrast to the resource-rich valley settings of the coevolutionary models, human behavioral ecology models posit that foragers would only use these plants, which provide relatively few calories per time spent obtaining them, when existing resources could no longer support growing populations. In these scenarios, Late Archaic peoples cultivated these crops as insurance against shortages in nut supplies. Despite their apparent differences, current iterations of both models recognize humans as agents who actively change their environments, with intentional and unintentional results. Both also are concerned with understanding the social and ecological contexts within which people began cultivating and eventually domesticating plants. The “when” and “where” questions of domestication in eastern North America are relatively well established, although researchers continue to fill significant gaps in geographic data. These primarily include regions where large-scale contract archaeology projects have not been conducted. Researchers are also actively debating the “how” and “why” of domestication, but the cultural ramifications of the transition from foraging to farming have yet to be meaningfully incorporated into the archaeological understanding of the region. The significance of these native crops to the economies of Late Archaic and subsequent Early and Middle Woodland peoples is poorly understood and often woefully underestimated by researchers. The socioeconomic roles of these native crops to past peoples, as well as the possibilities for farmers and cooks to incorporate them into their practices in the early 21st century, are exciting areas for new research.

Agriculture is practiced on 38% of the landmass on Earth, and having replaced natural ecosystems, it is the largest terrestrial biome on Earth. Agricultural biomes are typically focused on annual crops that are produced as a succession of genetically uniform monocultures. Compared to the ecosystems they replaced, agroecosystems provide fewer ecosystem functions and contain much less biodiversity. The large-scale conversion from natural lands to agriculture occurred centuries ago in the Old World (Africa, China, Europe, and India), but in many areas during the latter 20th and early 21st centuries, especially tropical areas with rich biodiversity, agriculture is an emerging industry. Here, displacement of natural ecosystems is also a late 20th-century occurrence, and much of it is ongoing. Regardless of where or when agriculture was established, biodiversity declined and ecosystem services were eroded. Agricultural practices are the second largest contributor to biodiversity loss, due to the loss of habitat, competition for resources, and pesticide use. Most (~96%) of the land used to produce crops is farmed using conventional methods, while smaller percentages are under organic production (~2%) or are producing biotech crops (~4%). Regardless of how agriculture is practiced, it exacts a toll on biodiversity and ecosystem services. While organic agriculture embraces many ecological principals in producing food, it fails to recognize the value of biotechnology as a tool to reduce the environmental impact of agriculture. Herbicide- and/or insect-resistant crops are the most widely planted biotech crops worldwide. Biotech crops in general, but especially insect-resistant crops, reduce pesticide use and increase biodiversity. The widespread adoption of glyphosate-resistant crops increased the use of this herbicide, and resistance evolved in weeds. On the other hand, glyphosate has less environmental impacts than other herbicides. Because of the limited scale of biotech production, it will not have large impacts on mitigating the effects of agriculture on biodiversity and ecosystem services. To have any hope of reducing the environmental impact of agriculture, agro-ecology principals and biotechnology will need to be incorporated. Monetizing biodiversity and ecosystem services through incorporation into commodity prices will incentivize producers to be part of the biodiversity solution. A multi-level biodiversity certification is proposed that is a composite score of the biodiversity and ecosystem services of an individual farm and the growing region were the food is produced. Such a system would add value to the products from farms and ranches proportionate to the level by which their farm and region provides biodiversity and ecosystem services as the natural ecosystem it replaced.

Early agricultural and arboricultural practices in the Pacific are based on vegetative principles, namely, the asexual propagation and transplantation of plants. A vegetative orientation is reflected in the exploitation of underground storage organs (USOs) within Near Oceania, as well as Island Southeast Asia, during the Pleistocene. During the early Holocene, people in the New Guinea region (including Near Oceania) began to intensify the management of plant resources in different landscapes. The increased degree of plant management, as well as associated environmental transformation, is most clearly manifest in the agricultural chronology at Kuk Swamp in the highlands of Papua New Guinea. At Kuk, shifting cultivation was potentially practiced during the early Holocene, with mounded cultivation by c. 7000–6400 cal BP and ditched drainage of wetlands for cultivation by c. 4400–4000 cal BP. Comparable agricultural records are lacking for other regions of Near Oceania; lowland sites indicate a range of arboricultural practices focused on fruit- and nut-bearing trees during the Terminal Pleistocene and throughout the Holocene, as well as potentially sago during the late Holocene. By c. 4000–3000 cal BP, indigenous agricultural and arboricultural elements were integrated with new cultural traits from Southeast Asia, including domestic animals, pottery and potentially new varieties of traditional crops. From c. 3250 to 2800 cal BP, different elements of agricultural and arboricultural practices from lowland New Guinea and Island Melanesia were taken by Lapita pottery–bearing colonists into the western Pacific. A later period of agricultural expansion occurred around c. 1000–750 cal BP with the colonization of eastern Polynesia. Agricultural practices and crops were variably taken and adapted to different islands and island groups across the Pacific. Additional transformations to agriculture occurred with the Polynesian adoption of the sweet potato (Ipomoea batatas), a South American domesticate, as well as following protohistoric and historic encounters.