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Advances in Agronomy

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ISSN (Print) 0065-2113
Published by Elsevier

[2564 journals]

Index
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Six Discoveries Leading to Conventional Chemical Kinetics for Pesticides in Soils A Review
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Donald S. Gamble
  The purpose of applying chemical kinetics to pesticides in soils is to permit quantitative predictions that can contribute to the best possible protection of crops and the environment considered together. In this case, soils include related aquatic sediments. An agricultural soil is the ultimate example of physically and chemically irregular mixtures. That has to be taken into account in any adaptation of conventional chemical kinetics to pesticides in soils. A large number of scientists have published a sequence of discoveries that have now led to an adaptation of conventional chemical kinetics to the sorption–desorption-reaction mechanisms of agricultural pesticides in soils. The discoveries have made it possible to determine the sorption stoichiometry and variable rate coefficients with which chemical kinetics can be done in irregular mixtures. The discoveries are outlined here in a logical sequence rather than a chronological sequence. The whole pesticide literature is too large for the citation of everything that might be relevant. Some authors not cited might be as important as those that have been selected as representative. This review is a progress report that describes some of the user-friendly spreadsheet models that have been based on conventional chemical kinetics. They instantly give graphical predictions. Experimental tests of predictions indicate that empirical parameters can be replaced by conventional chemical kinetics. The type of model needs to be improved and extended in several ways, using modern analytical chemical instrumentation. That includes especially LC/MS/MS.
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Five A Review of the Use of Organic Amendments and the Risk to Human Health
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Michael J. Goss , Ashraf Tubeileh , Dave Goorahoo
  Historically, organic amendments—organic wastes—have been the main source of plant nutrients, especially N. Their use allows better management of often-finite resources to counter changes in soils that result from essential practices for crop production. Organic amendments provide macro- and micronutrients, including carbon for the restoration of soil physical and chemical properties. Challenges from the use of organic amendments arise from the presence of heavy metals and the inability to control the transformations required to convert the organic forms of N and P into the minerals available to crops, and particularly to minimize the losses of these nutrients in forms that may present a threat to human health. Animal manure and sewage biosolids, the organic amendments in greatest abundance, contain components that can be hazardous to human health, other animals and plants. Pathogens pose an immediate threat. Antibiotics, other pharmaceuticals and naturally produced hormones may pose a threat if they increase the number of zoonotic disease organisms that are resistant to multiple antimicrobial drugs or interfere with reproductive processes. Some approaches aimed at limiting N losses (e.g. covered liquid or slurry storage, rapid incorporation into the soil, timing applications to minimize delay before plant uptake) also tend to favor survival of pathogens. Risks to human health, through the food chain and drinking water, from the pathogens, antibiotics and hormonal substances that may be present in organic amendments can be reduced by treatment before land application, such as in the case of sewage biosolids. Other sources, such as livestock and poultry manures, are largely managed by ensuring that they are applied at the rate, time and place most appropriate to the crops and soils. A more holistic approach to management is required as intensification of agriculture increases.
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Four The Role of Bioretention Systems in the Treatment of Stormwater
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Georgina Laurenson , Seth Laurenson , Nanthi Bolan , Simon Beecham , Ian Clark
  Urbanization leads to water catchments becoming more impervious and channelized. These modifications to the natural landscape result in reduced water infiltration into soils and base flow components that cause a greater volume and rate of surface water runoff. In contrast to conventional stormwater management systems, water-sensitive urban design (WSUD) technologies manage rainfall where it falls, through enhancement of infiltration capacity of impervious areas and rerouting runoff across pervious areas. WSUD aims to better incorporate several urban water sources, including stormwater, into the local hydrological cycle so as to (1) reduce demand on potable water, (2) minimize pollutant loading to surface waters, and (3) restore or maintain predevelopment hydrological processes. Bioretention systems are designed to remove both dissolved pollutants and particulate matter from stormwater runoff and reduce the volume and rate of stormwater discharged. Treatment is achieved via a number of chemical, biological and physical processes including sedimentation, filtration, sorption, reduction, vegetative uptake and microbial biomass assimilation. The efficiency of bioretention systems in the treatment of contaminants in stormwater depends on a number of factors including substrate conditions, type of vegetation, climatic conditions and on the volume and rate of stormwater infiltrated and discharged. This chapter discusses the various processes involved in the treatment of stormwater within bioretention systems; in particular, the fate of nutrients such as nitrogen and phosphorus, and metals, and the soil–plant processes involved in their retention. The factors affecting treatment efficiency are also examined.
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Three Ecological Restoration Approaches and Impacts on Vegetation, Soils and Society
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Asa L. Aradottir , Dagmar Hagen
  Ecological restoration has a growing role in policy aimed at reversing the widespread effects of environmental degradation. It includes activities to assist the recovery of ecosystem structure and function, and the associated provision of goods and services. Rooted in ecological theory, ecological restoration requires an integrated approach of different disciplines; including soil science, hydrology and conservation biology, together with the relevant socioeconomical and political frameworks. Ecological restoration interventions also rely on applied fields such as agronomy, horticulture and forestry. We clarify some of the main approaches and challenges of ecological restoration in order to encourage cooperation of professionals with a wide array of background and skills needed for successful restoration practices. We also discuss the diverse impacts of ecological restoration on ecosystems and societies. Restoration of soil quality together with improved nutrient cycling, water retention, pollination services and regulation of soil erosion can benefit traditional agricultural production through improved crop or forage production. It also enhances the provision of other important ecosystem services, including clean water, wildlife habitat, carbon sequestration and recreation. Payments for such ecosystem services are a growing source of income for rural inhabitants. Ecological restoration can also create new job opportunities in rural areas, e.g. nature-based tourism, game hunting and businesses based on native plant materials. Agricultural extension services should support these kinds of initiatives by putting ecological restoration to a larger degree on their agenda and provide expertise in this field.
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Two Chromium Contamination and Its Risk Management in Complex Environmental Settings
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Girish Choppala , Nanthi Bolan , Jin Hee Park
  Chromium reaches the soil environment through waste disposal emanating from a number of industrial activities, including coal-fired power production, electroplating, leather tanning, timber treatment, pulp production, and mineral ore and petroleum refining. Of the heavy metals, chromium (Cr) is a major pollutant, poses a great threat to flora and fauna and persists for long time. The most abundant species of Cr—Cr(III) and Cr(VI)—have very different properties. The toxicity, mobility, and bioavailability of Cr mainly depend on its speciation. In the natural environment, Cr(III) is most immobile, less soluble and stable, whereas Cr(VI) is highly mobile, soluble and bioavailable. Redox reactions play an important role in the interconversion of Cr(VI) and Cr(III). As our awareness of the rising toxicity of Cr increases, it is necessary to develop new and advanced strategies to mitigate this toxicity in the environment. Several physicochemical methods have been developed but these techniques are expensive and are not readily applicable to large contaminated zones. This chapter provides an overview of the concepts of Cr biogeochemistry, bioavailability and integrated risk management. The physicochemical factors, speciation and toxicity have been discussed with special emphasis on the remediation methods due to the complex reactions associated with Cr toxicity mitigation. Furthermore, this study identified systematically the future needs for understanding Cr biogeochemistry and low-cost remediation methods.
  
  PubDate: 2013-04-29T19:46:31Z
Front Matter
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  
  PubDate: 2013-04-29T19:46:31Z
Advances in Agronomy
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  
  PubDate: 2013-04-29T19:46:31Z
Copyright
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  
  PubDate: 2013-04-29T19:46:31Z
Contributors
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  
  PubDate: 2013-04-29T19:46:31Z
Preface
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Donald L. Sparks
  
  PubDate: 2013-04-29T19:46:31Z
Chapter One Food, Nutrition and Agrobiodiversity Under Global Climate Change
- Abstract: Publication date: 2013
  Source:Advances in Agronomy, Volume 120
  Author(s): Sangam Dwivedi , Kanwar Sahrawat , Hari Upadhyaya , Rodomiro Ortiz
  Available evidence and predictions suggest overall negative effects on agricultural production as a result of climate change, especially when more food is required by a growing population. Information on the effects of global warming on pests and pathogens affecting agricultural crops is limited, though crop–pest models could offer means to predict changes in pest dynamics, and help design sound plant health management practices. Host-plant resistance should continue to receive high priority as global warming may favor emergence of new pest epidemics. There is increased risk, due to climate change, to food and feed contaminated by mycotoxin-producing fungi. Mycotoxin biosynthesis gene-specific microarray is being used to identify food-born fungi and associated mycotoxins, and investigate the influence of environmental parameters and their interactions for control of mycotoxin in food crops. Some crop wild relatives are threatened plant species and efforts should be made for their in situ conservation to ensure evolution of new variants, which may contribute to addressing new challenges to agricultural production. There should be more emphasis on germplasm enhancement to develop intermediate products with specific characteristics to support plant breeding. Abiotic stress response is routinely dissected to component physiological traits. Use of transgene(s) has led to the development of transgenic events, which could provide enhanced adaptation to abiotic stresses that are exacerbated by climate change. Global warming is also associated with declining nutritional quality of food crops. Micronutrient-dense cultivars have been released in selected areas of the developing world, while various nutritionally enhanced lines are in the release pipeline. The high-throughput phenomic platforms are allowing researchers to accurately measure plant growth and development, analyze nutritional traits, and assess response to stresses on large sets of individuals. Analogs for tomorrow’s agriculture offer a virtual natural laboratory to innovate and test technological options to develop climate resilience production systems. Increased use of agrobiodiversity is crucial to coping with adverse impacts of global warming on food and feed production and quality. No one solution will suffice to adapt to climate change and its variability. Suits of technological innovations, including climate-resilient crop cultivars, will be needed to feed 9 billion people who will be living in the Earth by the middle of the twenty-first century.
  
  PubDate: 2013-04-29T19:46:31Z
Chapter Two Advances in Understanding Organic Nitrogen Chemistry in Soils Using State-of-the-art Analytical Techniques
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  During the past decade, soil and geochemists have adopted a variety of novel chemical–analytical methods to explore the chemistry of soil organic N (Norg). This chapter summarizes some of the more recent developments in the use of wet-chemical and instrumental methods to determine total Norg concentrations as well as to speciate the Norg in soils. A critical evaluation of 15N nuclear magnetic resonance (NMR) spectroscopy found the technique to be wanting, in terms of its sensitivity and ability to identify classes of Norg compounds in soils. Complementary mass spectrometric techniques are described briefly, and improved data evaluations based on broad applications of high-resolution pyrolysis-field ionization mass spectrometry are presented and discussed. A reassessment of older data sets using the new spectral evaluation algorithms provides strong evidence of fire- and management-induced changes in Norg speciation. Isotope-ratio mass spectrometry, Fourier transform ion cyclotron resonance mass spectrometry, and nanoscale secondary ion mass spectrometry (Nano-SIMS) also are discussed, with the latter two techniques having potential to (1) identify Norg compounds and (2) provide spatially resolved information on the molecular, elemental and isotopic composition of soil Norg. The use of 15N labeling techniques is discussed both from a methodological standpoint and in terms of tracking the fate of plant-derived (residue or rhizodeposit) N in the soil. Indeed, coupling 15N labeling with analytical techniques such as 15N NMR, Nano-SIMS and high- or ultrahigh-resolution mass spectrometry can provide information on how N is incorporated into soil organic matter. Analytical and instrumental innovations have resulted in new insights into the chemistry of Norg—together with a revised summary of the relative amounts of the different Norg compound classes present in soils (e.g. aliphatic amine and amide N, aromatic heterocyclic N), as well as their ecophysiological functions. Particular emphasis is given to the use of multitechnique analyses and the outstanding molecular–chemical diversity of biogenic heterocyclic Norg compounds. Examples are given of the new insights obtained using multi-analytical research approaches to explore microbial utilization of heterocyclic N and organic–mineral interactions, as well as the ability of human and environmental intervention to alter the composition of soil Norg. Finally, we examine future challenges and propose analytical approaches to tackle open questions regarding the basic chemistry and cycling of Norg in soils, as well as the agronomic and environmental consequences associated with N transformations in agro-ecosystems.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter One Use of Synchrotron-Based Techniques to Elucidate Metal Uptake and Metabolism in Plants
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  Synchrotron techniques have become key components of the toolbox for studying the mechanisms involved in metal(loid) uptake and metabolism in plants. Most widely used techniques in this field include micro-X-ray fluorescence (µXRF) for imaging the distribution of elements in plant tissues and cells and quantifying them, and X-ray absorption spectroscopy (XAS) for determining their chemical forms. Recent advances in terms of spatial resolution, sensitivity and versatility of the sample environment have opened new perspectives for the study of trace elements at the micro- and nanoscale with a minimal perturbation of the sample. Sample conditioning remains a key issue for the study of metals in plants. Cryogenic sample environments allow work on hydrated systems, with a limited risk of metal remobilization and changes in speciation. Still, radiation damage should be monitored carefully, especially for high-flux spectrometers. In addition, progress in software for data analysis has facilitated data mining and integration of results from various techniques. This chapter presents the principle and the basics of data analysis for µXRF imaging and tomography, XAS and micro-Fourier transform infrared spectromicroscopy (µFTIR). Major results obtained on Ni, Cd, Zn, Se, As, Cu, Mn and nanoparticles in hyperaccumulating and nonaccumulating plants are presented. Complementary approaches including histochemical techniques, micro and nanoscopic techniques using electron- or ion beams, and laser ablation coupled with inductively coupled plasma mass spectrometry (ICP-MS) are also presented, and key results reviewed. Finally, there is also great interest in coupling synchrotron techniques, which is possible on more and more beamlines, and also in coupling synchrotron techniques with other approaches such as the ones mentioned above; perspectives in this area are discussed.
  
  PubDate: 2013-01-19T20:22:06Z
Preface
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Advisory Board
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Front Matter
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Copyright
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Contributors
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Index
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Color Plate
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Seven An Assessment of the Variation of Manure Nitrogen Efficiency throughout Europe and an Appraisal of Means to Increase Manure-N Efficiency
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  Using the nitrogen (N) in organic manures more effectively reduces losses to the environment. A requirement to take allowance of the N conserved by reduced ammonia (NH3)-emission techniques would increase manure-N efficiency by up to 15%. Covering manure stores and land application of slurry by injection beneath the soil surface and by rapid incorporation of both slurries and solid manures into uncropped soil reduce NH3 emissions. Injection of cattle slurry also reduces N immobilization compared with application methods, which mix the slurry with soil and increases manure-N efficiency by ca 10–15%. In growing cereals, NH3 emissions can be reduced by band spreading within the canopy. Anaerobic digestion of slurry may also increase manure-N availability in the season of application by 10–20%, compared with undigested slurry. Slurry acidification may increase manure-N efficiency by 35–65% by reducing total NH3 losses by 70% compared with unacidified slurry stored without cover and not incorporated after spreading. To fully utilize the fertilizer value of manure-N, uptake over more than 1 year needs to be accounted for. This is particularly important for solid manures which provide less-available N in the season after application than slurries but release more N to crops in subsequent years. Using manure-N as a sole N source may limit overall manure-N efficiency. Applying manures at reduced rates over a larger crop area, using N fertilizer at times when crop recovery of manure-N may be limited, may give the greatest overall manure-N efficiency.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Five Transport and Retention of Heavy Metal in Soils Competitive Sorption
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  Appreciable amounts of various heavy metals (e.g. As, Cu, Ni, and Zn) are found in surface soils of lands as a result of accidental spills or industrial waste and sewage sludge applications. Such conditions often create environmental risks and potential contamination of soil, surface and groundwater resources. Competitive adsorption and desorption processes of heavy metals by the soil matrix have significant importance on their fate and mobility in soils. In this contribution, equilibrium and kinetic models governing competitive heavy-metal sorption and transport in soils were presented. Several examples were discussed to illustrate the impact of competing ions on the reactivities and mobility of heavy metals in the soil–water environment. The examples exhibited that competition among various heavy-metal species for available adsorption sites on soil matrix surfaces often results in the enhancement of the mobility of contaminants in the soil environment. Competitive sorption based on equilibrium Freundlich and Langmuir models were derived in order to account for competitive sorption of cations and anions in soils. Competitive models of the multiple reaction type including the two-site nonlinear equilibrium-kinetic models, the concurrent- and consecutive multireaction models were modified to describe kinetic adsorption–desorption of heavy metals behavior in soil. It was shown that equilibrium Langmuir and kinetic second-order models can be extended to simulate the competitive sorption and transport in soils. A drawback of Freundlich and Langmuir approaches is that their associated parameters are specific for each soil. Moreover, since predictions of the transport of heavy metals were sometime inadequate, improved competitive modeling approaches are needed. On the other hand, geochemical models, which are based on ion exchange and surface complexation concepts, are frequently utilized to quantify competitive behavior of several chemical species under a wide range of environmental conditions. However, further research is also needed since geochemical models are incapable of describing kinetic sorption–desorption of heavy metal ions in competitive systems.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Six Clean Coal Technology Combustion Products Properties, Agricultural and Environmental Applications, and Risk Management
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  Coal combustion products (CCPs), as the name suggests, are residues derived from the burning of coal in power generation industries. Traditionally, they have been dumped in large piles and/or ash-ponds mostly around the power stations. The CCPs are generally ash materials, mostly made of fine particles but some are also generated as coarse particles. Generation of these products poses serious threats to air, water and soil, and consequently to living organisms. The extent of the environmental effects caused by CCPs depends on (1) the coal source, (2) the combustion technology used and (3) the collection and segregation of the residues. Over the past two decades, there have been progressive research on the quality of power generation in terms of economic viability and environmental safety, and the effective usage of the waste products generated as a result of the power generation. This resulted in the emergence of clean coal technologies (CCTs), which aim at minimal environmental impacts, especially in curbing air pollution and ensuring more beneficial residues compared to conventional methods of combustion. In the global perspective, CCTs also reduce emission of several pollutants, decrease waste generation and increase the amount of energy gained per unit amount of coal combustion. This chapter will focus on the recent developments in CCTs and the applications of CCPs arising from those technologies, particularly agricultural and environmental applications. This chapter outlines the coal economy, their importance in power generation, latest technologies in the coal-fired power stations addressing emission control, the properties of CCPs generated, applications of CCPs and threats posed by the products. Each section will start with the products of conventional combustion technology (e.g. fly ash) and will later cover the applications pertaining to the products from CCTs (e.g. fluidized bed combustion ash). Future research should aim to focus more on the biological implications of CCPs addition to soil, long-term trials and a repository on ash information.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Four Cadmium Contamination and Its Risk Management in Rice Ecosystems
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  Cadmium (Cd) has been identified as one of the major heavy metals reaching the food chain through various geogenic and anthropogenic activities. In many East and South Asian countries including Japan, Bangladesh, Indonesia, and Korea, Cd accumulation in rice (Oryza sativa L.) ecosystems and its subsequent transfer to the human food chain is a major environmental issue. Rice soils in these countries have been affected by Cd accumulation derived from fertilizer and manure application, mine tailings, and refining plants. Excessive intake of Cd into the human body is detrimental to human health, causing serious illnesses such as itai-itai disease. To ensure the safety of foods, the concentrations of Cd in staple crops should be below a standard value; this applies particularly to rice because 34–50% of the Cd intake by people in many Asian countries has been derived from rice. Therefore, development of remediation methods for Cd-contaminated rice soils has become an urgent task to ensure food safety. This chapter provides an overview of the various sources of Cd in rice ecosystems and the biogeochemical processes that regulate Cd bioavailability to organisms, including microbes, plants, animals, and humans. Because of the complexity involved in dealing with Cd in rice ecosystems, exacerbated by the Cd source, site characteristics, and the nature of water management strategies, we have attempted to describe an “integrated” approach that employs a combination of remediation technologies, with the aim of securing methods that are economically and technologically viable.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Three The Role of Nitrate in Human Health
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 119
  
  The enrichment of the biosphere with reactive nitrogen from anthropogenic origin, in combination with increased consumption of vegetables and (preserved) animal products, has led to increased intake by humans of nitrite and nitrate. Nitrate and nitrate-forming salts are among the key components of fertilizers and the increased dependency of farming practices on such fertilizers over several decades has led to increasing levels of human exposure. This arises from consumption of crops and from nitrate-contaminated drinking water due to agricultural land runoff. For years, people have viewed dietary sources of nitrate as harmful to humans causing methemoglobinemia and cancers. However, methemoglobinemia is rare and evidence suggests a relation with infective enteritis rather than with nitrate alone. Also, epidemiological evidence for an association between cancers of the digestive tract and nitrate intake is inconclusive in terms of increased risks of cancer although the International Agency for Research on Cancer concluded “ingested nitrite or nitrate under conditions that result in endogenous nitrosation is probably carcinogenic to humans (Group 2A)”. The discovery of the nitric oxide pathway in the early 1980s revealed that nitrate is produced endogenously in the body changing our perception of nitrate safety. Recently benefits of dietary sources of nitrate for cardiovascular health and protection against infections have been unveiled, calling for an assessment of the risk and benefits associated with nitrate in our food and water supply. The scope of this article is to review the current state of the science on nitrate in human health and disease.
  
  PubDate: 2013-01-19T20:22:06Z
Chapter Six Flaming as an Alternative Weed Control Method for Conventional and Organic Agronomic Crop Production Systems A Review
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  The interest for organic crop production is in the increase due to a strong demand for organic food from consumers and an attractive income potential for farmers. Weeds pose one of the major problems in crop production and are responsible for significant crop yield reduction. The problem of controlling weeds without synthetic herbicides under the rules of organic agriculture is challenging. The increase in the number of herbicide-resistant weeds, the increase in herbicide cost, and the movement of herbicides into surface and ground water have sparked public awareness and restrictions on herbicide use. For these reasons, weed scientists are considering alternative and integrated weed management practices to reduce herbicide inputs and impacts. The use of propane for flame weeding can be adopted as one of the alternatives to chemical weed control, as it eliminates concerns over direct residual effects on soil, water, and food quality and can lessen the reliance on herbicides, hand weeding, and/or mechanical cultivation. Flame weeding is an acceptable weed control option in both organic and conventional production systems. A greater knowledge on the development of dose–response curves for determining the appropriate propane dose for effective weed control in major agronomic crops is needed to improve flame-weeding strategies. The dose–response curves for weeds and crops are important so that the lowest effective dose of propane can be applied for weed control in agronomic crops, which saves energy and reduces production costs. Depending on the desired level of weed control or tolerable crop injury level, a propane dose could be selected to either control the weed, or reduce its competitive ability against the crop. In this chapter, we will provide an overview of the findings from the flaming research that has been conducted for the last six years at the University of Nebraska, USA, or reported in pertinent newest literature. This chapter will improve our existing knowledge about flame weeding and will present better general guidelines for both organic and conventional crop producers interested in flaming techniques for weed control.
  
  PubDate: 2012-12-22T22:44:51Z
Chapter Seven Ridge-Furrow Mulching Systems—An Innovative Technique for Boosting Crop Productivity in Semiarid Rain-Fed Environments
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  Increasing food demands by a growing human population require substantial increases in crop productivity. In rain-fed arid and semiarid areas where the water supply is limited, an increase in the precipitation use efficiency (PUE) is the key to reach this goal. This chapter examines the scientific basis of a ridge-furrow mulching system (RF system) for increasing PUE, and summarizes the effects of this system on crop performance, microclimates, soil attributes, and environmental sustainability. Studies have shown that using crop straw, plastic film, or gravel–sand materials to mulch the soil surface significantly reduces the evaporation of soil moisture, increases water availability to crop plants, and decreases soil erosion caused by wind and water. Plastic mulching increases topsoil temperature during cool spring, promoting plant growth; during hot summer, straw mulching can moderate soil temperature, preventing the topsoil from reaching temperatures that inhibit plant growth. Ridge furrows with plastic mulching on the ridges and crop straw covering the furrows channel water to the furrows, and enhance soil water infiltration and water availability to the crop. Microclimates under mulched ridges and furrows favor soil microbial activity, increase soil biodiversity, and improve environmental benefits. The effectiveness of ridge-furrow systems is reflected in increased crop yields (20–180%) compared with that of the conventional-flat planting. Although more research is required to document physiochemical strengths, technique details and potential drawbacks, and more importantly to define long-term sustainability, we strongly suggest that RF systems are an innovative approach for increasing crop water availability, improving soil productivity, and enhancing food security for arid and semiarid rain-fed areas.
  
  PubDate: 2012-12-22T22:44:51Z
Chapter Five Responses of Crop Plants to Ammonium and Nitrate N
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  Nitrogen (N) is the most important, essential nutrient for all living organisms on earth; it is present in a number of complex organic molecules and plays extremely important roles in their activities. Ammonium N (NH4 +–N) and nitrate N (NO3 −–N) are the main forms taken up by plants in addition to some organic N compounds. More than 90% soil N is in organic form. The intermediate products of complicated organic N substances can be absorbed by plants. Organic N nutrition affects plant product quality and plant metabolism. Organic N passes through the cell wall and arrives at the plasma membrane through the apoplast and cytoplast systems and, in addition to endocytosis, may get transported across the plasma membrane by an active (sugar/proton cotransport) or passive process. After uptake by plants, simple organic N compounds such as amino acids can be rapidly assimilated and transformed into other amino acids by transamination and deamination. The uptake of NH4 +–N and NO3 −–N can be described by the Michaelis–Menten equation, and two parameters, the maximum absorption velocity (Vmax) and affinity constant or Michaelis constant (Km), have been used to measure the ability and efficiency of roots absorbing the two ions of crop plants. The uptake amounts of both NH4 +–N and NO3 −–N at the seedling stage are well in agreement with their absorption kinetic parameters, particularly at low concentrations, but are not fully in agreement with the entire growing periods of crops. In addition to root interception, NH4 + and NO3 − can move from bulk soil to the root surface by mass flow and diffusion. Diffusion is more important to NH4 +–N than NO3 −–N, while NO3 −–N movement mainly depends on mass flow. Roots are the major organs for the uptake of NH4 + and NO3 − ions. On arriving at the root surface, the two N forms can passively enter the root epidermis cell wall through the symplast and apoplast and then radically and vertically move across the cortex where the two ions in the apoplast enter the cortex symplast for passing through the endodermal Casparian trip to the endodermis. From the endodermis, the two ions go to the stele and empty into the xylem, or flow to the apoplast or get stored in vacuoles in addition to reduction or direct assimilation. The movement occurs from cell to cell. On emptying into the xylem, NH4 + and NO3 − are transported to the shoots via the transpiration stream. NO3 −–N is the dominant form of the mineral N with high concentrations in soil solutions, and is usually taken up in great amounts by crops and is readily mobile in the xylem. Transport of NO3 − across the plasma membrane along the electrochemical gradient is thought to be by H+/NO3 − cotransport, or by transport proteins or carriers or by specific ion channels. NH4 + is in equilibrium with NH3, and in most soils, the pH is considerably low and NH3 concentrations are usually very low. NH4 + uptake through the plasma membrane has been assumed to occur in three ways: either active or passive, or both. Passive uptake may occur at the initial stage of uptake, while at the second stage, active uptake may be predominating. For passive uptake, NH4 + ions passing through the membrane are thought to be present in either NH4 + or NH3 form, and in this way may be related to the facilitated diffusion through channels. The NH4 + ion resembles the K+ ion in terms of the ionic radius and size of the hydration shell, and therefore, it may be able to permeate the plasma membrane through K+ channels. The active uptake includes the H+/NH4 + cotransport, and specific transporters. Nitrate N cannot be directly used by plants until it is reduced to ammonia. The reduction is catalyzed by enzymes in two steps: the first step takes place in the cytoplasm by nitrate reductase (NR) transforming NO3
  PubDate: 2012-12-22T22:44:51Z
Chapter Four Insights from the Soybean (Glycine max and Glycine soja) Genome Past, Present, and Future
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  The complete assembly of the soybean genome sequence was a paradigm-shifting event for legume genomicists and offered a promising new resource for breeders and geneticists. Subsequent and ongoing resequencing of additional soybean accessions and wild relatives is building a comprehensive infrastructure for understanding soybean gene content and germplasm diversity. In this chapter, we first revisit the major events in soybean genomics that preceded and led to the soybean-sequencing project. Next, we delve into the important and unique features of the soybean genome that have been revealed through recent sequencing and resequencing efforts. We highlight the immediate impacts of the genome sequence, including the integration of the soybean genetic and physical maps and how the genome sequence has accelerated gene cloning. Last, we address ongoing and new projects that are leveraging the genome sequence to address previously inaccessible questions, and providing new genetic resources. The purpose of this chapter is to give an insight into the ways that the soybean genome has enabled the research community to address standing issues in both fundamental and applied areas.
  
  PubDate: 2012-12-22T22:44:51Z
Chapter Three Elucidating Mechanisms of Competitive Sorption at the Mineral/Water Interface
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  This chapter provides insights into the current state of knowledge on the factors that influence the competitive sorption of different ions on soil components and soils. In soil environments, different cations, anions, and molecules are present together, and then mutual interactions occur among them for sorption on soil components (phyllosilicates, humic substances, variable charge minerals, carbonate, and microorganisms), organo-mineral complexes, and soils. The influence of competitive sorption on ion partitioning between two ions received great attention, but studies on the relative competition for sorption sites onto soil components or soils among various ions are rather scant. In the past decades, many researchers have carried out molecular-scale studies to couple macroscopic sorption investigations with direct characterization by spectroscopic techniques. A wide array of models has been also used to describe chemical species structures and distribution in solution, at the solid–solution interfaces, and in the solid phase. This chapter first gives information on the factors that affect the sorption of cations and anions on phyllosilicates, organic matter, variable charge minerals (mainly Al- and Fe-oxides), and microorganisms, when added alone, and their capacity to form outer- or inner-sphere complexes on the surfaces of the soil components. Then, attention is given to the influence of the nature and concentration of inorganic and organic anions on the sorption of metal cations. The capacity of inorganic and organic ligands to enhance or inhibit cation sorption is discussed. Sorption increase is due to the formation of type A (metal ion bonded to both the sorbent and the ligand) or type B complexes (in which the ligand is bonded to the sorbent between the surface and the metal) on the surfaces of the sorbents or the formation of surfaces precipitates or by electrostatic interactions, whereas sorption decrease of a cation may occur when a ligand blocks common surface sites. The competition of two or more metal cations and the effect of an anion on their competition in sorption have also been discussed. The sorption of an anion inhibits the sorption of the competing anion(s) because it reduces the number of sites available on the sorbent (mainly variable charge minerals) and through changes in the electric potential. The competition in sorption between two or more ligands is affected by many factors such as pH, the nature of the sorbent, the affinity of each anion for the surfaces of the sorbent, the relative concentration of each anion, the surface coverage of the ligands, the sequence of addition of the competing anions, and the residence time. Particular attention has been given to the competitive sorption involving sulfate and phosphate as affected by other inorganic and organic ligands. Competitive sorption involving other ligands (e.g. carbonate, silicate, arsenate, arsenite, selenite, selenate, chromate, humic (HA) and fulvic acids (FAs), and selected low-molecular mass organic ligands (LMMOLs) has been also considered.
  
  PubDate: 2012-12-22T22:44:51Z
Chapter Two Impacts of Changing Climate and Climate Variability on Seed Production and Seed Industry
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  Agriculture is extremely sensitive to climate and weather conditions. The resilience of our crop production systems to changes in climate can be enhanced by improved understanding impacts and responses of crops to changing climates. Several countries in Asia and Africa are at the risk of losing about 280 million tons of potential cereal production as a result of climate change factor, particularly increasing temperatures and prolonged dry periods. The most significant negative changes for developing countries in Asia, where agricultural production declines of about −4% to −10% are anticipated under different socioeconomic and climate change scenarios. Rising temperatures will reduce the amount of fertile farmland, and by 2050, the amount of maize grown is expected to decline by 6–23% and wheat by 40–45%. The majority of the world’s food supply comes from the consumption of seeds from grain crops (wheat, rice, maize, soybean, barley, and sorghum), which are most vulnerable to changing climates. The growth in food production is lower than the population growth; therefore, there will be challenges of food security. Major impacts of climate change will be on rain-fed crops that account for nearly 60% of cropland area. As predicted, South Asia and sub-Saharan Africa will be highly vulnerable to climate change. Crop production can be increased by the use of quality seeds of high-yielding stress-tolerant varieties, combined with judicious use of inputs, particularly water and nutrients. Climate changes affect all four dimensions of food security, that is, availability, access to food, stability of food supplies, and food utilization. The seed industry plays an important role in increasing food production. It provides high-quality seeds of high-yielding varieties in adequate quantities at the right time and right place. Climate change influences the population dynamics of insects, emergence of new pests, changing status of pest and disease development, and evolution of new races of pests. Quality seed production is also affected by crop/weed interactions, loss of pollinator biodiversity, and genetic diversity. The seed crop is also affected by climate change regarding change in crop phenology, reproduction, flowering, anthesis/pollen viability, and pollination/fertilization, length of seed-filling duration, seed setting, seed size, seed dormancy, seed yield, and ultimately seed quality. Therefore, the cost of seed production is likely to increase in changing climate due to scheduling of operations, land and water management, herbicide/insecticide applications, pollination management, and postharvest seed management. Issues regarding intellectual property rights (IPR) related to seed, including patent infringements, prevalence of monocultures, consolidations of transnational corporations through acquisitions and mergers, and biodiversity and pollinator-loss related issues further complicate the problem. The lack of trained conventional plant breeders, crop physiologists, and seed technologists and stronger interdisciplinary collaboration between agronomists and biologists need attention. Further, acceptance of engineered crop or seed, increasing cost of genetically engineered (GE) seed as compared with conventional seed with no yield advantage, increasing number of herbicide applications, culminate in loss in net farm income in developed countries. In this article, the issues regarding the impact of climate change (particularly increasing temperature and carbon dioxide concentrations) on seed production, the present trend of the global seed industry, are discussed.
  
  PubDate: 2012-12-22T22:44:51Z
Index
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Contributors
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Preface
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Chapter One Digital Mapping of Soil Carbon
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  There is a global demand for soil data and information for food security and global environmental management. There is also great interest in recognizing the soil system as a significant terrestrial sink of carbon. The reliable assessment of soil carbon (C) stocks is of key importance for soil conservation and in mitigation strategies for increased atmospheric carbon. In this article, we review and discuss the recent advances in digital mapping of soil C. The challenge to map carbon is demonstrated with the large variation of soil C concentration at a field, continental, and global scale. This article reviews recent studies in mapping soil C using digital soil mapping approaches. The general activities in digital soil mapping involve collection of a database of soil carbon observations over the area of interest; compilation of relevant covariates (scorpan factors) for the area; calibration or training of a spatial prediction function based on the observed dataset; interpolation and/or extrapolation of the prediction function over the whole area; and finally validation using existing or independent datasets. We discuss several relevant aspects in digital mapping: carbon concentration and carbon density, source of data, sampling density and resolution, depth of investigation, map validation, map uncertainty, and environmental covariates. We demonstrate harmonization of soil depths using the equal-area spline and the use of a material coordinate system to take into consideration the varying bulk density due to management practices. Soil C mapping has evolved from 2-D mapping of soil C stock at particular depth ranges to a semi-3-D soil map allowing the estimation of continuous soil C concentration or density with depth. This review then discusses the dynamics of soil C and the consequences for prediction and mapping of soil C change. Finally, we illustrate the prediction of soil carbon change using a semidynamic scorpan approach.
  
  PubDate: 2012-12-22T22:44:51Z
Copyright
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Front Matter
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Advances in Agronomy
- Abstract: 2013
  Publication year: 2013
  Source:Advances in Agronomy, Volume 118
  
  PubDate: 2012-12-22T22:44:51Z
Chapter Six Productivity and Sustainability of the Rice–Wheat Cropping System in the Indo-Gangetic Plains of the Indian subcontinent Problems, Opportunities, and Strategies
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  Rice and wheat are the staple foods for almost the entire Asian population and therefore they occupy a premium position among all food commodities. The era of the Green Revolution started during the early 1970s with wheat and rice and since then the rice–wheat cropping system of the Indo-Gangetic Plains has played a significant role in the food security of the region. However, recent years have witnessed a significant slowdown in the yield growth rate of this system and the sustainability of this important cropping system is at risk due to second-generation technology problems and mounting pressure on natural resources. Traditional cultivars and conventional agronomic practices are no longer able to even maintain the gains in productivity achieved during the past few decades. Demand for food is increasing with the increasing population and purchasing power of consumers. The rice–wheat cropping system is labor-, water-, and energy-intensive and it becomes less profitable as these resources become increasingly scarce and the problem is aggravated with deterioration of soil health, the emergence of new weeds, and emerging challenges of climate change. Therefore, a paradigm shift is required for enhancing the system's productivity and sustainability. Resource-conserving technologies involving zero- or minimum-tillage in wheat, dry direct seeding in rice, improved water- and nutrient-use efficiency, innovations in residue management to avoid straw burning, and crop diversification should assist in achieving sustainable productivity and allow farmers to reduce inputs, maximize yields, increase profitability, conserve the natural resource base, and reduce risk due to both environmental and economic factors. A number of technological innovation and diversification options have been suggested to overcome the system's sustainability problems but some of them have not been fully embraced by the farmers as these are expensive, knowledge-intensive, or do not fit into the system and have resulted in some other unforeseen problems. Different concerns and possible strategies needed to sustain the rice–wheat cropping system are discussed in this review on the basis of existing evidence and future challenges.
  
  PubDate: 2012-12-15T09:29:12Z
Chapter Five Green and Brown Manures in Dryland Wheat Production Systems in Mediterranean-Type Environments
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  In this review, we draw together research on the use of green and brown manures in wheat cropping systems in Mediterranean-type environments in the light of contemporary pressures on cropping systems including changing climates, increasing costs and declining profit margins. Green and brown manuring have been demonstrated to have benefits in terms of weed control, delaying the development of resistance to herbicides, reducing populations of disease organisms, altering soil water, soil quality and biology, erosion control, and contributing to the nutrition of subsequent crops. However, few researchers have attempted to measure more than one of these variables, which presents difficulties in both interpreting the causes behind results of field trials and in estimating the total benefit of manuring, and hence its consequences for profitability. Well-designed experiments have been reported on component mechanisms (such as weed numbers or N2 fixation). However, these experiments are often not taken through to maturity of the crop following the manuring treatment. As a result, there is limited yield and grain quality data on which to base sound analyses of profitability. A few reports are available which present the impact of manuring on wheat yield and profitability in specific areas and systems but the results vary widely. For such reports to be of value, further research is needed into the factors inducing the changes in response (climate, soil type, or the specifics of the farming system at the time the treatments are imposed) and the mechanisms by which these act. Thus, research is needed into both the mechanisms and yield benefits that flow from the individual responses to manuring. Two further limitations to determining the economic benefit of manuring emerge. Firstly, impacts are primarily reported for a single year after a single manuring treatment. However, if measurements are made over a number of years, effects can often still be detected. More studies aimed to assess the longer-term impacts of manuring on soil health, disease prevalence, and weed populations are required. Secondly, there has been very little effort to explore the whole-farm impact of using manures. These impacts could include effects on other farm enterprises as well as business-level impacts such as potential changes in labor requirements, cash flow, and risk. The incorporation of manuring into wheat production systems may have multiple on-farm and off-farm benefits. However, there is a substantial research requirement before these approaches could be recommended. The highest priority is a sound demonstration of short- to medium-term economic benefits to growers. Without this, adoption can be expected to be poor.
  
  PubDate: 2012-12-15T09:29:12Z
Chapter Four Conservation Agriculture in the Semi-Arid Tropics Prospects and Problems
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  Relatively less attention has been paid on the use of conservation agriculture (CA) in the arid and semi-arid tropics (SAT), although a lot of information is available from humid and sub-humid regions globally. The objective of this review is to focus on the use of CA – its status, problems and prospects in the semi-arid tropical regions with emphasis on Asia and Africa. The information on the use of CA in SAT regions is summarized and put in context with the information available and lessons learnt on the use of CA in relatively vast tracts of land, especially in Brazil, North America, and Australia. Clearly, there are several bottlenecks in the use of CA in the SAT regions of Asia and Africa especially under rainfed agriculture. Among the major constraints to the use of CA in these regions include insufficient amounts of residues due to water shortage and degraded nature of soil resource, competing uses of crop residues, resource poor smallholder farmers, and lack of in-depth research in the SAT regions of Africa and to a lesser extent in Asia. The exception in the implementation of CA is of course the wheat–rice system in south Asia under irrigated conditions. The use of CA in the wheat–rice system of the Indo-Gangetic Plains (IGP) of south Asia has been relatively well researched during the last decade or so. However, in rainfed systems of the drier regions, relatively less attention has been given to develop research strategy to overcome the constraints to the adoption of CA. Examples are given from Brazil, Australia and North America as to how CA has been widely adopted in those regions as well as from Africa where CA is being promoted through active support of donor agencies. Obviously, there is need for strategic long-term research in the SAT regions for exploring the prospects in the face of major constraints faced to the adoption of CA, before CA could be taken to the farmers' door steps.
  
  PubDate: 2012-12-15T09:29:12Z
Chapter Three Mechanisms of Nickel Uptake and Hyperaccumulation by Plants and Implications for Soil Remediation
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  Soil contamination by heavy metals like Ni was originally restricted to metalliferous soils but in modern time it has become a general problem due to increasing anthropogenic activities. Because of the characteristics of cost-effectiveness, environmental friendliness, and fewer side-effects, the development of plant based remediation technologies for the cleanup of Ni-contaminated soils has attracted much attention. Nickel is an essential micronutrient, but is toxic to plants at excessive levels. Some plant species can accumulate Ni in the shoots at a high concentration, these plants are called hyperaccumulators. In the past two decades, researchers have endeavored to understand the physiological and molecular mechanisms of Ni uptake, transport, and detoxification in the Ni-hyperaccumulator plants. This is the basis of creating ideal plants for phytoremediation through cell and genetic engineering technologies, which may subsequently improve phytoremediation efficiency for decontaminating Ni-contaminated soils. Both rhizosphere microorganisms and endophytes can play a role in phytoremediation. Optimizing plant and soil management practices, particularly the correction of soil pH and additions of amendments of exogenous chelates and fertilizers, can also enhance phytoremediation of Ni-contaminated soils. The primary objective of this review is to discuss the recent progresses in basic and applied research relevant to phytoremediation of Ni-contaminated soils.
  
  PubDate: 2012-12-15T09:29:12Z
Chapter Two Food Safety Issues for Mineral and Organic Fertilizers
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  Fertilizers and other soil amendments are required to maintain soil fertility, but some may be naturally rich in trace elements, or contaminated. As part of the overall consideration of using fertilizers and soil amendments, one should consider the levels of trace elements present in relation to soil, plant, and food-chain processes (precipitation, adsorption, chelation) which promote or alleviate trace element risks. These natural processes limit plant accumulation of nearly all elements to levels which would not cause harm to humans, livestock, wildlife, or soil organisms. Soils geologically rich or contaminated with Mo can harm ruminants, while those rich in Se may harm all plant consumers; Mo or Se should be applied only when needed. Manures from swine and poultry may be rich in Cu, Zn and/or As from feed additives. Crops except rice accumulate little As from soils, so soil ingestion is the basis for soil As risk except for rice. Pb risk is also through soil ingestion rather than plant uptake. Cd is accumulated by rice to levels which caused human disease (renal tubular dysfunction) where rice soils were contaminated by industrial discharges. Risk from Cd in rice is strongly affected by the high bioavailability of rice Cd. Consumption of similar amounts of Cd have not caused harm from other foods. Because phosphate fertilizers may contain high levels of Cd, and use of high Cd superphosphate in Australia caused significant increase in wheat and potato Cd levels, risk from long-term accumulation of phosphate fertilizer Cd (and other sources) must be controlled. Different control schemes are discussed.
  
  PubDate: 2012-12-15T09:29:12Z
Chapter One Agronomic and Ecological Implications of Biofuels
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  Biofuels can be alternative energy sources which simultaneously reduce dependence on fossil fuels and mitigate climate change by reducing greenhouse gas (GHG) emissions. In the US, over 50 billion liters of ethanol produced in 2010 is mandated to increase to 136 billion liters by 2022. Globally, approximately 33.3millionha (Mha) of land under production of biofuels in 2008 may increase to as much as 82Mha by 2020. Whereas data on the energy efficiency and GHG balances for biofuels are available, information on agronomic and ecological consequences of large-scale production of bioenergy crops is sparse. Thus, this paper describes the potential effects that bioenergy production may have on ecosystems. Conversion of land to biofuel crops may have significant impacts on ecosystem services such soil and water quality, GHG emissions, wildlife habitat, net primary productivity, and biological control, and plant diversity at both the landscape and the regional levels. Production of exotic species for feedstock may increase the risk of escape from agriculture and invasion into natural ecosystems. Several feedstocks, while suitable on the basis of energy and GHG assessments, may have negative ecosystem impacts (i.e., increased N export in the Gulf of Mexico). Bioenergy feedstock may compete with food crops for land, water, and nutrient resources, resulting in higher prices for food as well as potential increases in malnutrition and food insecurity. Biofuels can be a sustainable and renewable source of energy, but assessments must include ecological impacts, economic costs, and energetic efficiencies.
  
  PubDate: 2012-12-15T09:29:12Z
Front Matter
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  PubDate: 2012-12-15T09:29:12Z
Copyright
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  PubDate: 2012-12-15T09:29:12Z
Contributors
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  PubDate: 2012-12-15T09:29:12Z
Preface
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  PubDate: 2012-12-15T09:29:12Z
Advances in Agronomy
- Abstract: 2012
  Publication year: 2012
  Source:Advances in Agronomy, Volume 117
  
  PubDate: 2012-12-15T09:29:12Z