Showing papers in "Advances in Agronomy in 2010"

A review of biochar and its use and function in soil

Abstract: Agricultural activities and soils release greenhouse gases, and additional emissions occur in the conversion of land from other uses. Unlike natural lands, active management offers the possibility to increase terrestrial stores of carbon in various forms in soil. The potential to sequester carbon as thermally stabilized (charred) biomass using existing organic resource is estimated to be at least 1 Gt yr − 1 and “biochar,” defined by its useful application to soil, is expected to provide a benefit from enduring physical and chemical properties. Studies of charcoal tend to suggest stability in the order of 1000 years in the natural environment, and various analytical techniques inform quantification and an understanding of turnover processes. Other types of biochar, such as those produced under zero-oxygen conditions have been studied less, but costs associated with logistics and opportunity costs from diversion from energy or an active form in soil demand certainty and predictability of the agronomic return, especially until eligibility for carbon credits has been established. The mechanisms of biochar function in soil, which appear to be sensitive to the conditions prevailing during its formation or manufacture, are also affected by the material from which it is produced. Proposed mechanisms and some experimental evidence point to added environmental function in the mitigation of diffuse pollution and emissions of trace gases from soil; precluding the possibility of contaminants accumulating in soil from the incorporation of biochar is important to ensure safety and regulatory compliance.

Visible and Near Infrared Spectroscopy in Soil Science

Abstract: This chapter provides a review on the state of soil visible–near infrared (vis–NIR) spectroscopy Our intention is for the review to serve as a source of up-to-date information on the past and current role of vis–NIR spectroscopy in soil science It should also provide critical discussion on issues surrounding the use of vis–NIR for soil analysis and on future directions To this end, we describe the fundamentals of visible and infrared diffuse reflectance spectroscopy and spectroscopic multivariate calibrations A review of the past and current role of vis–NIR spectroscopy in soil analysis is provided, focusing on important soil attributes such as soil organic matter (SOM), minerals, texture, nutrients, water, pH, and heavy metals We then discuss the performance and generalization capacity of vis–NIR calibrations, with particular attention on sample pretratments, covariations in data sets, and mathematical data preprocessing Field analyses and strategies for the practical use of vis–NIR are considered We conclude that the technique is useful to measure soil water and mineral composition and to derive robust calibrations for SOM and clay content Many studies show that we also can predict properties such as pH and nutrients, although their robustness may be questioned For future work we recommend that research should focus on: (i) moving forward with more theoretical calibrations, (ii) better understanding of the complexity of soil and the physical basis for soil reflection, and (iii) applications and the use of spectra for soil mapping and monitoring, and for making inferences about soils quality, fertility and function To do this, research in soil spectroscopy needs to be more collaborative and strategic The development of the Global Soil Spectral Library might be a step in the right direction

How the Plant Growth-Promoting Bacterium Azospirillum Promotes Plant Growth—A Critical Assessment

Abstract: During the last 35 years of studies of Azospirillum–plant interaction, over 20 proposals were suggested for the mechanism of action by which Azospirillum spp., the most intensively studied plant growth-promoting bacteria, enhances plant growth. The proposals include a single phytohormone activity, multiple phytohormones, nitrogen fixation, assortments of small-sized molecules and enzymes, enhanced membrane activity, proliferation of the root system, enhanced water and mineral uptake, mobilization of minerals, mitigation of environmental stressors of plants, and direct and indirect biological control of numerous phytopathogens. By volume, the largest number of published information involves hormonal activities, nitrogen fixation, and root proliferation. After analyzing the accumulated knowledge, it was concluded that this versatile genus possesses a large array of potential mechanisms by which it can effect plant growth. Consequently, this review proposes the “Multiple Mechanisms Theory,” based on the assumption that there is no single mechanism involved in promotion of plant growth by Azospirillum, but a combination of a few or many mechanisms in each case of inoculation. These may vary according to the plant species, the Azospirillum strain, and environmental conditions when the interaction occurred. The effect can be cumulative, an “additive hypothesis” (proposed before), where the effects of small mechanisms operating at the same time or consecutively create a larger final effect on plant. Additionally, the observed effect on plant growth can be the result of a tandem or a cascade of mechanisms in which one mechanism stimulates another, yielding enhanced plant growth, such as the plausible relations among phytohormones, nitric oxide, membrane activities, and proliferation of roots. Finally, the growth promotion can also be a combination of unrelated mechanisms that operate under environmental or agricultural conditions needed by the crop at particular locations, such as mitigating stress (salt, drought, toxic compounds, adverse environment), and the need for biological control of or reducing pathogenic microflora.

Carbon Sequestration in Agroforestry Systems

Abstract: Agroforestry—the practice of growing trees and crops in interacting combinations—is recognized worldwide as an integrated approach to sustainable land-use. It is estimated to be practiced over 1 billion hectares in developing countries, and to a lesser extent in the industrialized countries. Agroforestry systems (AFSs) are believed to have a higher potential to sequester carbon (C) because of their perceived ability for greater capture and utilization of growth resources (light, nutrients, and water) than single-species crop or pasture systems. The estimates of C stored in AFSs range from 0.29 to 15.21 Mg ha − 1 yr − 1 aboveground, and 30 to 300 Mg C ha − 1 up to 1-m depth in the soil. Recent studies under various AFSs in diverse ecological conditions showed that tree-based agricultural systems, compared to treeless systems, stored more C in deeper soil layers near the tree than away from the tree; higher soil organic carbon content was associated with higher species richness and tree density; and C3 plants (trees) contributed to more C in the silt- + clay-sized (

Improving Productivity of Crops in Water-Limited Environments

Abstract: This review deals with improving the performance of dryland crops in dry, mainly semiarid, environments. Although such crops are often limited by water, the development of the notion of water-limited potential yield has shown that their yields are often limited strongly by other factors. These factors are explored by dissecting the water-limited potential yield into a framework involving four largely independent components, namely, the potential water supply for the crop; the fraction of that water supply that is transpired; the efficiency with which the crop exchanges water for CO 2 in producing biomass (Transpiration Efficiency); and the fraction of the biomass that ends up in the grain (Harvest Index). This framework is used to explore a wide range of agronomic possibilities for managing crops so as to get close to the water-limited potential, including managing previous crops, forages and fallows to increase soil water at sowing; reducing evaporative losses from the soil surface; ensuring that sowing and flowering occur at the right times; maximizing soil water extraction by the crop; and ensuring that there is adequate water available during late floral development and grain filling. Such operations often involve trade-offs and risks that must be managed.

The role of seed ecology in improving weed management strategies in the tropics

Abstract: Weed seed banks reflect past weed populations and management practices and are the source of weed infestations to come. The factors affecting weed seed germination, however, are often poorly understood. Depleting the soil seed bank and influencing germination patterns are common goals of enduring cultural weed management practices. Greater understanding of the factors influencing the germination of weed seeds could facilitate the development of more effective cultural weed management practices through either suppressing germination or encouraging germination at times when seedlings can be readily controlled. Such cultural methods may contribute to overcoming problems such as feral crops (e.g., weedy rice), crop volunteers, and the evolution of herbicide resistance in weeds that have, in some systems, increased to a point where the lack of sustainable practices is a threat to productivity. Weed seed germination is commonly influenced by light exposure, soil moisture, burial depth through tillage, the use of mulches, fire for land clearance, and flooding of the soil. Harnessing these factors to influence germination can serve as major entry points for improved weed management. Diverse crop production systems provide a wide range of examples to illustrate how recent advances in the understanding of the responses of weed seed germination can be used to develop new and sustainable cultural management of weeds. Crop management practices, such as adopting no-till crops or delaying tillage, that increase weed seed exposure to predators (ants, beetles, etc.) could be incorporated into integrated weed management programs. Retention of crop residue on the soil surface under no-till systems can suppress weed seedling emergence, delay the time of emergence, and allow the crop to gain an advantage over weeds, and reduce the need for control. Rotation of tillage or crop establishment system could also be adopted to deflect the “trajectories” of likely weed population shifts. In rice, flooding after herbicide application or hand weeding can largely prevent the growth of weeds and reduce the need for further interventions.

Halting the groundwater decline in north-west India--which crop technologies will be winners?

Abstract: Increasing the productivity of the rice–wheat (RW) system in north-west India is critical for the food security of India. However, yields are stagnating or declining, and the rate of groundwater use is not sustainable. Many improved technologies are under development for RW systems, with multiple objectives including increased production, improved soil fertility, greater input use efficiency, reduced environmental pollution, and higher profitability for farmers. There are large reductions in irrigation amount with many of these technologies compared with conventional practice, such as laser land leveling, alternate wetting and drying (AWD) water management in rice, delayed rice transplanting, shorter duration rice varieties, zero till wheat, raised beds, and replacing rice with other crops. However, the nature of the irrigation water savings has seldom been determined. It is often likely to be due to reduced deep drainage, with little effect on evapotranspiration (ET). Reducing deep drainage has major benefits, including reduced energy consumption to pump groundwater, nutrient loss by leaching, and groundwater pollution. The impacts of alternative technologies on deep drainage (and thus on irrigation water savings) vary greatly depending on site conditions, especially soil permeability, depth to the watertable, and water management. More than 90% of the major RW areas in north-west India are irrigated using groundwater. Here, reducing deep drainage will not “save water” nor reduce the rate of decline of the watertable. In these regions, it is critical that technologies that decrease ET and increase the amount of crop produced per amount of water lost as ET (i.e., crop water productivity, WPET) are implemented. The best technologies for achieving this are delaying rice transplanting and short duration rice varieties. The potential for replacing rice with other crops with lower ET is less clear.

Advances in understanding the molecular structure of soil organic matter: implications for interactions in the environment.

Abstract: We take a historic approach to explore how concepts of the chemical and physical nature of soil organic matter have evolved over time. We emphasize conceptual and analytical achievements in organic matter research over the last two decades and demonstrate how these developments have led to increased skepticism toward the humification concept and question the usefulness of operationally defined and artificially prepared “humic substances” as models of fractions of soil organic matter in real soils. We identify some of the still open questions about organic matter, and point out future research directions that are likely to refine those concepts of the physicochemical nature of soil organic matter which we put before the reader today.

Biological Control of Insect Pests in Agroecosystems: Effects of Crop Management, Farming Systems, and Seminatural Habitats at the Landscape Scale: A Review

Abstract: There is a growing body of evidence to suggest that the simplification of land uses associated with a strong dependence on agrochemical inputs is decreasing environmental quality, threatening biodiversity, and increasing the likelihood of pest outbreaks. The development of farming systems with greater reliance on ecosystem services, such as biological control of insect pests, should increase the sustainability of agroecosystems. However, the factors responsible for the maintenance or enhancement of natural pest control remain unclear. The goal of this review is, therefore, to expose which elements, from the field to the landscape scale, influence natural enemy populations and pest regulation. We present here the principal effects of seminatural habitats, farming systems, and crop management on the abundance of insect pests and their biological control, with a view to evaluating their relative importance and identifying key elements that regulate natural pest control interactions. Because of the range of spatial and temporal scales experienced by these organisms, we advocate, in studies investigating trophic relations and biological pest control, a clear description of cropping systems and an explicit consideration of seminatural habitats and more generally of the surrounding landscape. Through this review, we also indicate gaps in knowledge and demonstrate the interest of linking agronomy and landscape ecology to understand trophic interactions, maximize natural pest control, and limit pesticide applications. Quantifying the relative importance of both local and landscape scales is a fundamental step in the design and assessment of ecologically sound integrated pest management strategies for farmers.

Rhizosphere Processes and Management for Improving Nutrient Use Efficiency and Crop Productivity: Implications for China

Abstract: Rhizosphere dynamics have been widely investigated since the beginning of last century but little attention has been paid to process-based rhizosphere management at an agroecosystem level. High inputs, high outputs, low nutrient use efficiency, and increasing environmental pressure are typical characteristics of intensive farming systems in China. Achievement of high nutrient use efficiency and high crop productivity together is a major challenge for sustainability of Chinese intensive agriculture. Over the last 20 years crop yield has not increased proportionately with increasing fertilizer inputs, leading to low nutrient use efficiency and increasing environmental risk. Traditional nutrient management is highly dependent on the external fertilizer inputs but ignores exploiting the intrinsic biological potential of rhizosphere processes for efficient mobilization and acquisition of soil nutrients by crops. Several successful case studies on rhizosphere processes and management have been summarized in this chapter, and the results demonstrate that rhizosphere management provides a unique opportunity to harmonize crop productivity, nutrient efficiency, and environmental impact. Rhizosphere management strategies emphasize maximizing the efficiency of root and rhizosphere processes in nutrient acquisition and use by crops rather than solely depending on excessive application of chemical fertilizers. The strategies mainly include manipulating root system, rhizosphere acidification, carboxylate exudation, microbial associations with plants, rhizosphere interactions in terms of intercropping and rotation, localized application of nutrients, use of efficient crop genotypes, and synchronizing rhizosphere nutrient supply with crop demands. Rhizosphere management has been proved to be an effective approach to increasing nutrient use efficiency and crop productivity for sustainable agricultural production.

Variability in harvest index of grain crops and potential significance for carbon accounting: examples from Australian agriculture

Abstract: For grain crops, harvest index (HI) is the ratio of harvested grain to total shoot dry matter, and this can be used as a measure of reproductive efficiency. The index can also be used to estimate crop carbon (C) balances by applying it to grain yield statistics to determine total shoot dry matter and then calculating crop residues as the difference between shoot C and grain C. Such an approach is widely used in C-accounting systems. Such a C-accounting practice is sensitive to changes in HI. In Australia, measured variations in HI are large enough to alter C balance calculations for some crops. Much of this variation results from the diverse range of climates and soils, which are a feature of the Australian cereal cropping region. Factors that influence crop HI include the energy and protein content of seeds, long-term breeding achievements, and extreme (either hot or cold) temperatures during crop reproductive development. Crop husbandry can also influence HI, especially delayed sowing, which shortens the length of the vegetative phase and increases HI. For wheat, and perhaps some other C3 cereals, excess nitrogen can enhance the allocation of photosynthate to structural carbon, which cannot be mobilized to grain later, resulting in a decrease in HI. Evidence for the balance between pre and postanthesis water use of field-grown crops having a significant influence on crop HI is equivocal. A dataset containing more than 3000 estimates of HI in Australia has been assembled and used to summarize observed HI variations for each of the principal field crops grown in Australia. There remains a need for more reliable field HI data to be used in C-accounting systems and to aid the development of models to simulate likely regional and seasonal differences in HI for C-accounting purposes.

Phosphorus Solubilization and Potential Transfer to Surface Waters from the Soil Microbial Biomass Following Drying–Rewetting and Freezing–Thawing

Abstract: Drying–rewetting and freezing–thawing are two of the most common forms of abiotic perturbations experienced by soils, and can result in the solubilization of phosphorus (P). There is increasing interest in one particular component of soil P that may be especially susceptible to such stresses: the soil microbial biomass. We examine the evidence for the soil microbial biomass acting as a significant source of P in soils and surface waters by studying the literature on the processes responsible for its solubilization and transfer, resulting from abiotic perturbations. These perturbations have been shown to kill up to circa 70% of the total microbial biomass in some soils, and in some cases nearly all the additional P solubilized has been attributed to the microbial biomass. The degree to which the soil microbial biomass is affected by abiotic perturbations is highly dependent upon many variables, not the least degree, duration, and temporal patterns of stress, as well as the soil type. It is hypothesized that while abiotic perturbations can solubilize large quantities of P from the soil microbial biomass in some soils, only a small proportion is likely to find its way from the soil to surface waters. This is not to say that this small proportion is not significant with regard to surface water quality and nutrient loss from the soil, and may become more prevalent under future climatic change. We conclude that it is likely that only extreme conditions will elicit large responses with regard to the solubilization and transfer of phosphorus to surface waters.

Chapter one. Mitigating nonpoint source pollution in agriculture with constructed and restored wetlands.

Abstract: Nonpoint source pollution (NPSP) from agricultural runoff threatens drinking water quality, aquatic habitats, and a variety of other beneficial uses of water resources. Agricultural runoff often contains a suite of water-quality contaminants, such as nutrients, pesticides, pathogens, sediment, salts, trace metals, and substances, contributing to biological oxygen demand. Increasingly, growers who discharge agricultural runoff must comply with water-quality regulations and implement management practices to reduce NPSP. Constructed and restored wetlands are one of many best management practices that growers can employ to address this problem. This review focuses on the ability of constructed and restored wetlands to mitigate a variety of water-quality contaminants common to most agricultural landscapes. We found that constructed and restored wetlands remove or retain many water-quality contaminants in agricultural runoff if carefully designed and managed. Contaminant removal efficiency generally exceeded 50% for sediment, nitrate, microbial pathogens, particulate phosphorus, hydrophobic pesticides, and selected trace elements when wetlands were placed in the correct settings. There are some potentially adverse effects of constructed and restored wetlands that must be considered, including accumulation of mercury and selenium, increased salinity, mosquito habitat, and greenhouse gas emissions. Proper wetland management and design features are discussed in order to reduce these adverse effects, while optimizing contaminant removal.

Chapter Four - Restoring Soil Fertility in Sub-Sahara Africa

Abstract: Sub-Sahara Africa can overcome the soil fertility depletion that has resulted from decades of nutrient mining by small-scale farmers and threatens the region's food security. Nutrient restoration is now technically feasible because its mechanisms are understood and the rural development community is alerted to this need. Rapid and inexpensive approaches of diagnosing soil fertility limitations are also becoming available and information generated is becoming systematically applied. For example, the recently initiated Africa Soil Information Service project aims at evaluating, mapping, and monitoring Africa's soil qualities for better targeting of soil fertility management technologies to improve crop yields while enhancing the environment. Practical knowledge is available on nutrient management in small-scale farming systems that combines increased biological nitrogen fixation, utilizes agromineral resources such as phosphate rock, better uses organic resources, and more efficiently applies mineral fertilizers. The new approach to managing soil nutrients, recognized as integrated soil fertility management, aims to increase food production through strategic combination of traditional and new technologies and is being stimulated through increased availability and more profitable use of mineral fertilizers by Africa's poorer farmers. This is building on already existing sparks of hope for restoring soil fertility in sub-Saharan Africa derived from such examples as the increasing adoption of the zai-type of pitting system originated in drier parts of West Africa which exemplifies the beneficial effects of integrating harvesting of water and applying nutrient sources at each planting station so as to increase yield in a region where both necessities are key limiting factors. Nitrogen fixation by indigenous and introduced legumes combined with improved agronomic practices has shown potential for kick-starting self-multiplying improvements in soil productivity. Such successes will be accelerated by broader initiatives which improve rural infrastructure, increase accessibility of inputs, improve marketing facilities, and make reinvestment into farming more productive and sustainable. Indeed, experience indicates that investments in farming and, by inference, soil fertility conservation are made when economic returns from smallholder production are sufficient to do so. So, while technical advances leading to improvements in farming practice must continue, policymakers must also recognize that agriculture ultimately forms the basis for economic recovery and act upon past promises to invest in agriculture, including the restoration of nutrient-depleted soils. Investments must address factors that have impacts both on the broad reforms for provision of services such as marketing and trade, as well as those directly constraining the poor farmers such as capacity to access and efficiently apply fertilizers.

The African green revolution: results from the Millennium Villages Project.

Abstract: The Millennium Villages Project (MVP) was initiated in 2005 to implement the recommendations of the UN Millennium Project for achieving the Millennium Development Goals (MDGs). The project is carried out in 14 sites in hunger and poverty hotspots in diverse agroecological zones in sub-Saharan Africa (SSA). The interventions and results for increasing staple crop yields are presented for eight MV sites and cover 52,000 farming households or 310,000 people. By supporting farmers with fertilizers, improved crop germplasm, and intensive training on appropriate agronomic practices, average yields of 3 t ha − 1 were exceeded in all sites where maize is the major crop. Teff yields doubled in the Ethiopian site. In contrast, there was little improvement in millet and groundnut yields in the semiarid and arid sites in West Africa. Over 75% of the farms had maize yields of 3 t ha − 1 and less than 10% of the households had yields lower than 2 t ha − 1 . Households produced enough maize to meet basic caloric requirements, with the exception of farms smaller than 0.2 ha in Sauri, Kenya. Value-to-cost ratios of 2 and above show that the investment in seed and fertilizer is profitable, provided surplus harvests were stored and sold at peak prices. Increased crop yields are the first step in the African Green Revolution, and must be followed by crop diversification for improving nutrition and generating income and a transition to market-based agriculture. A multisector approach that exploits the synergies among improved crop production, nutrition, health, and education is essential to achieving the MDGs.

Interactions among agricultural production and other ecosystem services delivered from European temperate grassland systems

Abstract: Global demand for food is increasing as is the recognition that this must be achieved with minimal negative impacts on the environment or other ecosystem services (ESs). Here we develop an understanding of the relationships among ESs delivered within temperate agricultural grassland systems in lowland Europe. We reviewed the refereed literature on pair-wise interactions between nine different ESs. These were agricultural production, climate regulation, air quality regulation, water quality regulation, hydrological regulation, soil erosion regulation, nutrient cycling, biodiversity conservation, and landscape quality. For each pair, we sought information on how each ES responds to changes in the other. Each interaction was assigned to one of five categories: (i) no direct relationship between the driving ES on the responding ES, (ii) the driving ES has a negative impact on the responding ES, (iii) the driving ES has a positive impact on the responding ES, (iv) the evidence of direction of effect is inconclusive, because of either inadequate information or contradictions in the literature, and (v) there is no current evidence in the current literature for a relationship. Negative relationships resulted only from the effects of increasing the intensity of agricultural production on other ESs. Available evidence infers that erosion regulation and good nutrient cycling were the only two driving ESs shown to enhance agricultural production implying that their protection will enhance our ability to meet future food needs. In order for agriculture to become more sustainable, we need to develop agricultural methods that can minimize the negative impacts of these win–lose relationships.

Climate Warming-Induced Intensification of the Hydrologic Cycle: An Assessment of the Published Record and Potential Impacts on Agriculture

Abstract: Climate warming is expected to intensify and accelerate the global hydrologic cycle resulting in increases in evaporation, evapotranspiration (ET), atmospheric water-vapor content, and precipitation. The strength of the hydrologic response, or sensitivity of the response for a given degree of warming, is a critical outstanding question in climatology and hydrology. In this review chapter, I examine the published record of trends in various components of the hydrologic cycle and associated variables to assess observed hydrologic responses to warming during the period of observational records. Global and regional trends in evaporation, ET, and atmospheric water-vapor content and several large river basin water-balance studies support an ongoing intensification of the hydrologic cycle. Global trends in precipitation, runoff, and soil moisture are more uncertain than the trends in the variables noted above, in part because of high spatial and temporal variability. Trends in associated variables, such as systematic changes in ocean salinity, the length of the growing season, and the rate of precipitation recycling are generally consistent with intensification of the hydrologic cycle. The evidence for an increase in the frequency, intensity, or duration of extreme-weather events like hurricanes is mixed and remains uncertain. The largest potential impacts to agricultural systems depend greatly on the responses of hydrologic variables that are the most uncertain; for example, intensity and duration of heavy rainfall events; frequency, intensity, and duration of major storms and droughts; and rates of erosion. Impacts on agriculture will depend greatly on how insects, diseases, weeds, nutrient cycling, effectiveness of agrichemicals, and heat stress are affected by an intensification of the hydrologic cycle.

Terrestrial Nanoparticles and Their Controls on Soil-/Geo-Processes and Reactions

Abstract: This review provides insights on some unique properties of nanoparticles (NPs) that are present in soils. In addition, this review discusses the role of NPs in controlling or influencing single and/or coupled chemical, biological, and hydrological soil- and/or geo-processes, which directly or indirectly affect the mobility or may determine the ultimate fate of aqueous and sorbed (adsorbed or precipitated) chemical species of nutrients and contaminants in terrestrial ecosystems. The chapter is composed of five review sections, followed by another section on future research directions, the acknowledgments, and the list of the references. A brief introduction to nanotechnology, nanoscience and environmental soil nanoscience, and definitions of relevant terms and chapter objectives are provided in the first section. A discussion on size-dependent properties and controls, focusing initially on the differences in nanoscale versus bulk scale properties, and later on the properties that change within the nanoscale, is presented in the second section. The important topic of NP origin (natural or manufactured) and occurrence in soils is presented in the third section. The behavior of NPs in soils is discussed in the fourth section. Two subsections are included. In the first one, processes that may affect NPs behavior in soils, such as growth, stability, solid phase transformation, aggregation, and aging are discussed. In the second one, processes that may be affected by the presence of NPs in soils, such as contaminant and/or nutrient sorption, redox reactions, and their advective or diffusive mobility, are discussed. A brief discussion on NPs toxicity is presented in the fifth and last review section of this chapter.

Implications of the Knowledge Paradox for Soil Science

Abstract: Research results that could potentially provide a major contribution to innovation and sustainable development are often not accepted by or implemented in society. This, in short, is the knowledge paradox that is also relevant for soil science. The need to operate in a more interactive mode towards stakeholders and policy makers has been recognized in literature, has become more urgent in our Knowledge Democracy and is accepted by funding agencies. But true transdisciplinarity is difficult to realize and recommendations are discussed for soil science research to improve its effectivity by (i) focusing on unique niches, defined here in terms of seven basic soil functions, some of which have been preempted by others; (ii) considering the policy cycle as a point of reference; (iii) focusing on deriving a series of options (each one with economic, social and environmental tradeoffs) rather than on single solutions of problems related to sustainable development; and (iv) taking the entire knowledge chain into consideration from the tacit to the cutting-edge. Additional attention is suggested for communication and public relations in terms of (i) defining soil quality; (ii) adopting the ecological footprint concept and (iii) presenting storylines for major soil types. Transdisciplinarity requires working in “Communities of Practice” (CoPs); but first, the soil science profession should improve internal cohesion and cooperation by combating current atomization of subdisciplines and by defining mutual responsibilities in soil science “Communities of Scientific Practice” (CSPs) with special attention to quality control, education, and basic research, which is vital for the future of the soil science profession.

Chapter Three - Manufactured Nanoparticles and their Sorption of Organic Chemicals

Abstract: With the rapid development and application of nanotechnology, increasing concern has been raised on the environmental risks of manufactured nanoparticles (MNPs) because they will find their way into the environment during their production, purification, application, and disposal. The interactions between organic chemicals and MNPs will alter the environmental behavior of both organic chemicals and MNPs. Therefore, understanding organic chemical–MNP adsorption mechanisms as well as the consequent influences on organic chemical and MNP environmental behavior is fundamental to assessing their environmental exposure and risks. Thus, current research progress and knowledge gaps regarding adsorption mechanisms of organic chemicals on MNPs are the main focus of this review. In addition, MNP application, general properties, occurrence, and entry pathways to the environment are summarized. MNP colloidal behaviors, which are their unique properties in comparison to other adsorbents, are discussed. The mobility and toxicity of both organic chemicals and MNPs after adsorption are also addressed. Finally, future research directions are presented.

Towards a Holistic Classification of Diffuse Agricultural Water Pollution from Intensively Managed Grasslands on Heavy Soils

Abstract: With the increasing demand for food security comes an increasing pressure on the environment. Contamination of surface water by diffuse agricultural pollutants is widely recognized as an area of concern; however, this has still led to a fragmented approach to scientific research. Pollutants tend to be treated in isolation and only infrequently in the context of an environment where other pollutants may be an issue. This is an important concept, as to achieve cost-effective mitigation the effect of any method implemented must take into account the positive as well as the negative effects on other pollutants which exist in the environment in which a method has been implemented. In this chapter, we synthesize the current state of understanding relating to a suite of typical aquatic diffuse pollutants associated with agricultural systems, more specifically those that may originate from intensively managed grassland systems on heavy, clay-rich soil types. This chapter is necessarily wide ranging but tries to draw together the information on each pollutant and present it within a single framework. This is only possible by characterizing the pollutants using shared characteristics along a source–mobilization–delivery (SMD)-continuum. Through this process, we highlight five possible SMD scenarios which can lead to contamination of water bodies. Further information on the nature of these SMD-scenarios can be gained by assessing the relationship between pollutant concentration and discharge of multiple pollutants. In this regard, we highlight the lack of literature available detailing multiple pollutant dynamics and also draw attention to areas of research that we feel need to be addressed if a more holistic approach to diffuse pollution mitigation is to be achieved.

Extent, Impact, and Response to Soil and Water Salinity in Arid and Semiarid Regions

Abstract: Sustainable management of land and water resources in arid and semi-arid regions is of concern as a result of increased population pressure and the need for more food and fiber. Soil and water salinity is widespread across the arid and semi-arid regions of South Asia, Central Asia, Arabian Peninsula, and North Africa and affected agricultural productivity and livelihood of rural population. While natural processes (primary) and anthropogenic activities (secondary) cause salinity, the latter contributed more to agricultural productivity losses in these regions. Recent estimates suggest that up to 50% of irrigated land has become saline in these regions. However, there is cautious optimism for managing salt-affected soils and saline waters for crop and animal production and protection of soil and water resources through research-based interventions using integrated soil–water–plant management practices. The successful use of salt-affected soils and saline water takes the pressure off using freshwater for irrigation. Significant promises for addressing soil and water salinity through an integrated approach include: (1) the use of salt-tolerant crops, forages, and halophytes for human and animal consumption and bio-fuel production, (2) development of agro-forestry through planting forage crops within the interspaces of salt-tolerant trees that co-exist with forage crops and salt-tolerant shrubs, (3) development of appropriate surface and subsurface drainage systems to remove excess water and salt from the soil, (4) alternate and/or blended use of saline and fresh water to minimize salt accumulation in the soil, and (5) maintenance of proper irrigation scheduling to ensure that adequate water is available for crop growth and at the same time removal of excess salt from crop-rooting zone. Monitoring the effectiveness of the above mentioned technologies is important for maximizing the benefits. Finally, appropriate policy and institutional interventions that encourage the general community to accept the technology are required. Isotopic and nuclear techniques play a key role in developing and monitoring the technology for the sustainable use of salt-affected soils and saline waters and protect land and water resources.

Are biofuels antithetic to long-term sustainability of soil and water resources?

Abstract: Sustainability of biofuels is a contentious but old topic that has reemerged with increased use of crops as feedstocks. There are vastly different land requirements for different feedstocks, and disagreement on the energy balance of their conversion to biofuel. To be sustainable, biofuel systems should (1) have favorable economics, (2) conserve natural resources, (3) preserve ecology, and (4) promote social justice. With the possible exception of sugarcane production in Brazil, it seems unlikely that ethanol production from crops will be economically viable without government support. Less is known on cellulosic feedstock economics because there are no commercial-scale plants. Natural resources that may be affected include soil, water, and air. In the United States, agricultural intensification has been associated with greater soil conservation, but this depended on retaining residue that may serve as cellulosic feedstocks. The “water footprint” of bioenergy from crops is much greater than for other forms of energy, although cellulosic feedstocks would have a smaller footprint. Most studies have found that first-generation biofuels reduce greenhouse gas emissions 20–60%, and second generation ones by 70–90%, if effects from land-use change are excluded. But land-use change may incur large carbon losses, and can affect ecological preservation, including biodiversity. Social justice is by far the most contentious sustainability issue. Expanding biofuel production was a major cause of food insecurity and political instability in 2008. There is a large debate on whether biofuels will always contribute to food insecurity, social justice, and environmental degradation in poor countries.

The Potential for California Agricultural Crop Soils to Reduce Greenhouse Gas Emissions: A Holistic Evaluation

Abstract: Climate change predictions for California indicate that agriculture will need to substantially adapt to reduced water availability, changing crops, and changes in temperatures, in order to sustain the level and diversity of crop production in California. California legislators recently passed the California Global Warming Solutions Act of 2006 (AB 32) that requires all industries to reduce the three major greenhouse gases (GHGs) (CO2, N2O, and CH4) to 1990 levels by 2020. The great diversity of cropping systems and management practices in California agriculture leads, however, to greater uncertainties in estimates of GHG budgets compared to Midwest agriculture. In light of AB 32, we, here, synthesize all the available information on the potentials for California agriculture to sequester C and reduce GHG emissions through various alternative management practices: minimum or no tillage, organic, cover cropping, manuring, and reduced chemical fertilizer management. Our review indicates that C sequestration and GHG emission reductions are possible, but there is no single land management practice or change in inputs that could mitigate the C released from agricultural practices (e.g., fossil fuel usage, land-use changes, soil erosion, biomass burning, and N fertilizer associated emissions) and meet climate change commitments set out in AB 32. Therefore, it is only the integration of different management strategies that shows considerable potential for C mitigation as well as provides important cobenefits to ensure the future sustainability of California agriculture.

A New GIS Nitrogen Trading Tool Concept for Conservation and Reduction of Reactive Nitrogen Losses to the Environment

Abstract: Nitrogen (N) inputs to agricultural systems are important for their sustainability. However, when N inputs are unnecessarily high, the excess can contribute to greater agricultural N losses that impact air, surface water, and groundwater quality. It is paramount to reduce off-site transport of N by using sound management practices. These practices could potentially be integrated with water and air quality markets, and new tools will be necessary to calculate potential nitrogen savings available for trade. The USDA-NRCS and USDA-ARS Soil Plant Nutrient Research Unit developed a web-based and stand-alone Nitrogen Trading Tool (NTT) prototype. These prototypes have an easy-to-use interface where nitrogen management practices are selected for a given state and the NTT calculates the nitrogen trading potential compared to a given baseline. The stand-alone prototype can also be used to calculate potential savings in direct and indirect carbon sequestration equivalents from practices that reduce N losses. These tools are powerful, versatile, and can run with the USA soil databases from NRCS (SSURGO) and NRCS climate databases. The NTT uses the NLEAP model, which is accurate at the field level and has GIS capabilities. Results indicate that the NTT was able to evaluate management practices for Ohio, Colorado, and Virginia, and that it could be used to quickly conduct assessments of nitrogen savings that can potentially be traded for direct and indirect carbon sequestration equivalents in national and international water and air quality markets. These prototypes could facilitate determining ideal areas to implement management practices that will mitigate N losses in hot spots and provide benefits in trading.

Grassland Fire Management in Future Climate

Abstract: A thorough understanding of the behavior of fire in grasslands is critical to the minimization of the impact of fires on agricultural and pastoral land as well as the successful management of the health, robustness, and species diversity of native grasslands. This is also necessary to understand the impact that a changing climate will have on these fires and the subsequent impacts and adaptation steps needed to protect valuable farmland and grassland ecosystems in the future, a challenge that will soon be facing all land managers. While a number of studies have investigated the impact of climate change on fire danger indices, the fire danger systems used in Australia are actually fire weather indices that provide no information about the likely impact of climate change on fire behavior. This chapter summarizes the state of the knowledge of fire behavior in grass fuels and discusses in detail the factors that influence the behavior of grassfires. The CSIRO Grassland Fire Spread Meter is the recommended operational system for the prediction of grassfire behavior in all Australian grass types. The system is used to assess the impact of a high-emission climate change scenario upon the likely behavior of grassfires throughout the fire season for three major pastoral and agricultural regions of eastern Australia in 2020 and 2050. It was found that mean fire rate of forward spread in ungrazed/natural pastures will increase by a maximum of 10% by 2020 and by 32% by 2050 in southeastern Australia. The implications for grassland management strategies and possible climate adaptation pathways are explored.

Chapter Three - mitigating allergenicity of crops.

Abstract: Reducing the allergenicity of edible crops may be feasible to some extent through genetic means. Allergenicity of different crops varies widely, and consumed components may present multiple allergenic proteins, some of which play essential roles in growth and development of the plant or seeds. Identifying spontaneous or induced mutations in genes for allergenic proteins is facilitated by technological advancements in DNA sequence analysis and proteomics. Furthermore, genetic engineering provides strategies for altering gene expression to study the effects of allergen reduction. In this review, allergens of most concern from major crops within the “Big 8” allergen group are described and approaches for mitigation of allergenicity in these crops are presented.