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Organic Farming  

Theodore J. K. Radovich

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.


Agriculture and Biodiversity in Latin America in Historical Perspective  

Angus Wright

Latin America is thought to be the world’s most biodiverse region, but as in the rest of the world, the number of species and the size of their populations is generally in sharp decline. Most experts consider agriculture to be the most important cause of biodiversity decline. At one extreme of policy argument regarding biodiversity conservation are those who argue that the only path to species protection is the establishment of many more and larger “protected areas” in which human activities will be severely restricted. On the remaining land agriculture will be carried out largely with the presently prevailing methods of “industrial agriculture,” including heavy reliance on synthetic pesticides and fertilizers, heavy machine use, large-scale irrigation schemes, limited crop diversity, and crops genetically engineered to maximize returns from these tools and techniques. Those who argue for these policies largely accept that industrial agriculture of this sort is severely hostile to biodiversity, but argue that the high productivity of such methods makes it possible to limit agriculture to a relatively small land base, leaving the rest for protected areas and other human activities. On the other side of the argument are those who argue that agricultural techniques are either available or can be created to make agricultural areas more favorable to species survival. They argue that even with a desirable expansion of protected areas, such reserves cannot successfully maintain high biodiversity levels if protected reserves are not complemented by an agriculture more friendly to species survival and migration. The policy arguments on these issues are of major human and biological importance. They are also very complex and depend on theoretical perspectives and data that do not provide definitive guidance. One way to enrich the debate is to develop a specifically historical perspective that illuminates the relationship between human actions and species diversity. In Latin America, humans have been modifying landscapes and species composition of landscapes for thousands of years. Even in areas of presently low human population density and extraordinarily high species diversity, such as remaining tropical rainforests, humans may have been active in shaping species composition for millennia. After 1492, human population levels in Latin America plummeted with the introduction of Old-World diseases. It is often assumed that this led to a blossoming of species diversity, but the historical evidence from 1492 to the present strongly suggests the combination of European technologies and the integration of agriculture into world markets meant more damaging use of soils, widespread deforestation, and subsequent decline in species numbers. The exploitation and consequent despoliation of Latin American resources were integral to colonialism and intensified later by national governments focused on rapid economic growth. High species diversity remained in areas that were too difficult to exploit and/or were used by indigenous populations or smallholders whose production techniques were often favorable to species survival. Many of these techniques provide clues for how agriculture might be reshaped to be more friendly both to biodiversity and social equity.


Geography and Chronology of the Transition to Agriculture  

Peter Bogucki

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 and Climate Change Communication  

Linda S. Prokopy, Wendy-Lin Bartels, Gary Burniske, and Rebecca Power

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.


Terracing: From Agriculture to Multiple Ecosystem Services  

Paolo Socci, Alessandro Errico, Giulio Castelli, Daniele Penna, and Federico Preti

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.


DDT and Pesticides  

Frederick Rowe Davis

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 Impacts on Agriculture across Africa  

Laura Pereira

Confidence in the projected impacts of climate change on agricultural systems has increased substantially since the first Intergovernmental Panel on Climate Change (IPCC) reports. In Africa, much work has gone into downscaling global climate models to understand regional impacts, but there remains a dearth of local level understanding of impacts and communities’ capacity to adapt. It is well understood that Africa is vulnerable to climate change, not only because of its high exposure to climate change, but also because many African communities lack the capacity to respond or adapt to the impacts of climate change. Warming trends have already become evident across the continent, and it is likely that the continent’s 2000 mean annual temperature change will exceed +2°C by 2100. Added to this warming trend, changes in precipitation patterns are also of concern: Even if rainfall remains constant, due to increasing temperatures, existing water stress will be amplified, putting even more pressure on agricultural systems, especially in semiarid areas. In general, high temperatures and changes in rainfall patterns are likely to reduce cereal crop productivity, and new evidence is emerging that high-value perennial crops will also be negatively impacted by rising temperatures. Pressures from pests, weeds, and diseases are also expected to increase, with detrimental effects on crops and livestock. Much of African agriculture’s vulnerability to climate change lies in the fact that its agricultural systems remain largely rain-fed and underdeveloped, as the majority of Africa’s farmers are small-scale farmers with few financial resources, limited access to infrastructure, and disparate access to information. At the same time, as these systems are highly reliant on their environment, and farmers are dependent on farming for their livelihoods, their diversity, context specificity, and the existence of generations of traditional knowledge offer elements of resilience in the face of climate change. Overall, however, the combination of climatic and nonclimatic drivers and stressors will exacerbate the vulnerability of Africa’s agricultural systems to climate change, but the impacts will not be universally felt. Climate change will impact farmers and their agricultural systems in different ways, and adapting to these impacts will need to be context-specific. Current adaptation efforts on the continent are increasing across the continent, but it is expected that in the long term these will be insufficient in enabling communities to cope with the changes due to longer-term climate change. African famers are increasingly adopting a variety of conservation and agroecological practices such as agroforestry, contouring, terracing, mulching, and no-till. These practices have the twin benefits of lowering carbon emissions while adapting to climate change as well as broadening the sources of livelihoods for poor farmers, but there are constraints to their widespread adoption. These challenges vary from insecure land tenure to difficulties with knowledge-sharing. While African agriculture faces exposure to climate change as well as broader socioeconomic and political challenges, many of its diverse agricultural systems remain resilient. As the continent with the highest population growth rate, rapid urbanization trends, and rising GDP in many countries, Africa’s agricultural systems will need to become adaptive to more than just climate change as the uncertainties of the 21st century unfold.


Economics of Low Carbon Agriculture  

Dominic Moran and Jorie Knook

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.


Agricultural Nitrogen and Phosphorus Pollution in Surface Waters  

Marianne Bechmann and Per Stålnacke

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.


CAFOs: Farm Animals and Industrialized Livestock Production  

James M. MacDonald

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.


Soil Tilth and Management  

Lars J. Munkholm, Mansonia Pulido-Moncada, and Peter Bilson Obour

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.


Soviet Collectivization in Central Asia  

Marianne Kamp

In Soviet Central Asia, efforts at the mass collectivization of agriculture began in early 1930, and by 1935, more than 80 percent of all farming and herding households joined collective farms (kolkhoz) or state farms (sovkhoz). The Communist Party’s main purpose was to control peasant lives and labor. Collectivization was supposed to lead to increased agricultural production due to modernized methods and intensification. The USSR’s Central Asian republics were given unachievable plans to raise their output of cotton, wheat, and meat, while wealthier herders and peasants were threatened with arrest and exile if they resisted collectivization. Collectivization was devastating for Kazakh nomadic herders, whose livestock numbers plummeted, and who endured a three-year long famine that killed more than one-fourth of the Kazakh population. Investments went into expanding irrigation canals and irrigable fields, forcing an ever-increasing number of kolkhoz members to expend most of their labor on cotton cultivation.


Economy in Brazil in the 20th Century  

Herbert S. Klein and Francisco Vidal Luna

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.


Malthusian Thought  

Glenn Davis Stone

Robert Malthus’s 1798 Population has proven to be one of the most influential publications in history. Challenging ideas popular among Enlightenment writers, including the perfectibility of human institutions, he argued that since population could grow exponentially and agriculture only linearly, there was an inherent and irresolvable imbalance in nature that unavoidably led to population being checked by mortality among the poor. The policy implication was that aid to the hungry would only create more misery. The most famous “proof” of the theory came in Ireland in the 1840s, and Malthus’s policy recommendations were followed. However, Ireland was setting food export records during the famine, and agriculture has grown much more rapidly than population ever since. The basic tenets of Malthus’s have been debunked, but it continues to be influential, especially in the form of neo-Malthusianism, largely because of the interests it serves.


Urbanism in Mesoamerica  

Verónica Pérez Rodríguez

Urban societies have been defined as stratified, and sometimes literate, societies that build large, densely populated, and monumental centers that serve specialized political, economic, and ritual functions for their regions. Mesoamerica is one of six world regions where urban societies developed, independently, in antiquity. Mesoamerican cities sometimes fit traditional definitions, and other times defy them. There are examples of dispersed low-density urban settlements (Classic Maya, Veracruz) or cities where evidence of writing remains elusive (Teotihuacan). Functional urban definitions have led to debates regarding the urban standing of earlier, Middle Formative Olmec centers, as no contemporary settlements match the monumentality and regional prominence of La Venta or San Lorenzo. The regional settlement studies that have proliferated in the Basin of Mexico and Valley of Oaxaca since the 1960s have helped scholars demonstrate the demographic and political might of Late Formative, Classic, and Postclassic cities such as Monte Albán, Teotihuacan, and Tenochtitlan. Urbanism was demonstrably shown to be a regional phenomenon, one that developed from autochthonous processes as settlements became prominent population centers whose functions, monuments, and institutions served and ruled over their larger regions. While some of the best-known Mesoamerican cities were the capitals of large regional states (Teotihuacan, Tenochtitlán, Monte Albán, and Tzintzuntzan), researchers have documented an even greater number of city-states, which are defined as small states socially and territorially centered around their capital city. The Classic and Postclassic cities of the Maya lowlands, the Postclassic polities or altepemeh of the Basin of Mexico, and the kingdoms of Postclassic Oaxaca are examples of city-states. Among Mesoamerican cities, there was diversity in the form of government, ranging from cities where rulers’ names and royal tombs appear prominently in the archaeological record (Classic Maya cities, Postclassic Oaxacan city-states), to cities where, despite decades of research, no single royal palace or tomb has been found (Teotihuacan). The material record of cities of the latter type suggests that they were governed through more corporate forms of political organization. In the early 21st century research has focused on the role of collectives in city construction, configuration, and governance and the challenge of archaeologically identifying neighborhoods, districts, or other suprahousehold social groups (tlaxilacalli and calpolli, social units above the household in Postclassic Nahuatl polities). Although Classic period Maya centers were not originally considered urban, thanks to settlement studies and, later on, LiDAR technology, scholars have demonstrated that beyond their monumental acropolises there was extensive low-density settlement that was unmistakably urban. The Maya model of low-density lowland urbanism features dispersed populations and extensive urban footprints that integrate complex webs of agricultural areas, terraces, raised fields, hydraulic features, and house mounds. This model may have useful applications for modern-day planning efforts in low-lying cities that need to adapt to climate change. Indeed, Mesoamerican urbanism has much to contribute as the world’s population becomes increasingly urban. Humanity must learn from its past successes, and failures, with urban living.


landscapes, Roman  

Kim Bowes

Roman landscapes exhibited enormous diversity, from the rolling hills of the Mediterranean heartland, to Nile marshlands, Apennine mountain pastures, and African pre-deserts. New work on this diversity has demonstrated the intensive methods with which they were managed for agriculture and artisanal output, as well as their highly periodized histories. While much debate in the study of these landscapes has revolved around ancient climate change, more apparent is robust human intervention, which often reached a peak during the Roman period. Romans thought deeply about landscapes, and their literature and religious rituals used landscape to frame moral, religious, and political values.

Unlike the landscapes of the Greek city states, those encompassed by the Roman empire at its height were diverse in the extreme. Among the empire’s territories were the pre-desert regions of Tripolitania and the Syrian frontier, the mountain pastures of the Apennines, and the marshes of the Egyptian oases, not to mention the rolling limestone landscapes of the Mediterranean heartland. Even within smaller slices of these territories (and even within tiny micro-regions), new work has revealed the remarkable diversity of vegetation, sunlight, rainfall, and topography. It is the plurality of these landscapes that gave Romans material for a rich tradition of literary and religious expression as well as a vast and intensive apparatus for economic exploitation.


Agricultural Methanogenesis  

Alexander N. Hristov

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.


Evolution of Agricultural Practices and the Transformation of the English Landscape  

Tom Williamson

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.


wetlands (bog, marsh)  

Giusto Traina

The most common words to designate a marsh, a swamp, or a bog are helos in ancient Greek and palus in Latin; beside these terms, less common words were also employed. Literary and epigraphic texts give evidence for marshlands in the countryside, in the coastal areas, and also close to urban agglomerations. The sources often give evidence for drainage activity, but cases of extensive drainage are rare. In fact, they were possible only at public expense, by employing free or slave labor. On the other hand, several territories were characterized by a sort of marsh economy. Although rarely portrayed in literature, and despite the risk of malaria, marshy areas presented some economic potential: fishing, hunting, salt extraction, and farming. In many respects, the negative image of wetlands is a modern invention. The contrast between the rational order of the Roman countryside and the “barbaric” medieval landscape was introduced by the Enlightenment, and must be treated with caution.


Food Waste and Biomass Recovery  

Wun Jern Ng, Keke Xiao, Vinay Kumar Tyagi, Chaozhi Pan, and Leong Soon Poh

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.