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Sieglinde S. Snapp

Bio: Sieglinde S. Snapp is an academic researcher from Michigan State University. The author has contributed to research in topics: Agriculture & Soil organic matter. The author has an hindex of 49, co-authored 228 publications receiving 8998 citations. Previous affiliations of Sieglinde S. Snapp include Washington State University & University of California, Davis.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors reviewed the literature along with Michigan farmer experience to evaluate promising cover crop species for four niches: Northern winter (USDA Hardiness Zones 5-6), Northern summer (Zones 5 -6), Southern winter (Zone 7-8), and Southern summer (Zone 6 -8).
Abstract: The integration of cover crops into cropping systems brings costs and benefits, both internal and external to the farm. Benefits include promoting pest-suppression, soil and water quality, nutrient cycling efficiency, and cash crop productivity. Costs of adopting cover crops include increased direct costs, potentially reduced income if cover crops interfere with other attractive crops, slow soil warming, difficulties in predicting N mineralization, and production expenses. Cover crop benefits tend to be higher in irrigated systems. The literature is reviewed here along with Michigan farmer experience to evaluate promising cover crop species for four niches: Northern winter (USDA Hardiness Zones 5-6), Northern summer (Zones 5-6), Southern winter (Zones 7-8), and Southern summer (Zones 7-8). Warm season C 4 grasses are outstanding performers for summer niches (6-9 Mg ha -1 ), and rye (Secale cereale L.) is the most promising for winter niches (0.8-6 Mg ha -1 ) across all hardiness zones reviewed. Legume-cereal mixtures such as sudangrass (Sorghum sudanese L.)-cowpea (Vigna unguiculata L.) and wheat (Triticum aestivum L.)-red clover (Trifolium pretense L.) are the most effective means to produce substantial amounts (28 Mg ha -1 ) of mixed quality residues. Legume covers are slow growers and expensive to establish. At the same time, legumes fix N, produce high quality but limited amounts (0.5-4 Mg ha -1 ) of residues, and enhance beneficial insect habitat. Brassica species produce glucosinolate-containing residues (2-6 Mg ha -1 ) and suppress plant-parasitic nematodes and soil-borne disease. Legume cover crops are the most reliable means to enhance cash crop yields compared with fallows or other cover crop species. However, farmer goals and circumstances must be considered. If soil pests are a major yield limiting factor in cash crop production, then use of brassica cover crops should be considered. Cereal cover crops produce the largest amount of biomass and should be considered when the goal is to rapidly build soil organic matter. Legume-cereal or brassica-cereal mixtures show promise over a wide range of niches.

824 citations

Journal ArticleDOI
TL;DR: This article measured POXC across a wide range of soil types, ecosystems, and geographic areas (12 studies, 53 total sites, = 1379) to determine the relationship between POXc and POC, microbial biomass C (MBC), and soil organic C (SOC) fractions, and determine the relative sensitivity as a labile soil C metric across a range of environmental and management conditions.
Abstract: Permanganate oxidizable C (POXC; i.e., active C) is a relatively new method that can quantify labile soil C rapidly and inexpensively. Despite limited reports of positive correlations with particulate organic C (POC), microbial biomass C (MBC), and other soil C fractions, little is known about what soil fractions POXC most closely reflects. We measured POXC across a wide range of soil types, ecosystems, and geographic areas (12 studies, 53 total sites, = 1379) to: (i) determine the relationship between POXC and POC, MBC and soil organic C (SOC) fractions, and (ii) determine the relative sensitivity of POXC as a labile soil C metric across a range of environmental and management conditions. Permanganate oxidizable C was significantly related to POC, MBC, and SOC, and these relationships were strongest when data were analyzed by individual studies. Permanganate oxidizable C was more closely related to smaller-sized (53–250 μm) than larger POC fractions (250–2000 μm), and more closely related to heavier (>1.7 g cm) than lighter POC fractions, indicating that it reflects a relatively processed pool of labile soil C. Compared with POC, MBC, or SOC, POXC demonstrated greater sensitivity to changes in management or environmental variation in 42% of the significant experimental factors examined across the 12 studies. Our analysis demonstrates the usefulness of POXC in quickly and inexpensively assessing changes in the labile soil C pool.

450 citations

Book ChapterDOI
TL;DR: In this paper, an ecosystem-based approach is proposed to optimize organic and mineral reservoirs with longer mean residence times that can be accessed through microbially and plant-mediated processes.
Abstract: Agricultural intensification has greatly increased the productive capacity of agroecosystems, but has had unintended environmental consequences including degradation of soil and water resources, and alteration of biogeochemical cycles. Current nutrient management strategies aim to deliver soluble inorganic nutrients directly to crops and have uncoupled carbon, nitrogen, and phosphorus cycles in space and time. As a result, agricultural ecosystems are maintained in a state of nutrient saturation and are inherently leaky because chronic surplus additions of nitrogen and phosphorus are required to meet yield goals. Significant reductions of nutrient surpluses can only be achieved by managing a variety of intrinsic ecosystem processes at multiple scales to recouple elemental cycles. Rather than focusing solely on soluble, inorganic plant‐available pools, an ecosystem‐based approach would seek to optimize organic and mineral reservoirs with longer mean residence times that can be accessed through microbially and plant‐mediated processes. Strategic use of varied nutrient sources, including inorganic fertilizers, combined with increases in plant diversity aimed at expanding the functional roles of plants in agroecosystems will help restore desired agroecosystem functions. To develop crops that can thrive in this environment, selection of cultivars and their associated microorganisms that are able to access a range of nutrient pools will be critical. Integrated management of biogeochemical processes that regulate the cycling of nutrients and carbon combined with increased reservoirs more readily retained in the soil will greatly reduce the need for surplus nutrient additions in agriculture.

393 citations

Journal ArticleDOI
25 Jun 2010-Science
TL;DR: To ensure food and ecosystem security, farmers need more options to produce grains under different, generally less favorable circumstances than those under which increases in food security were achieved this past century.
Abstract: Despite doubling of yields of major grain crops since the 1950s, more than one in seven people suffer from malnutrition ( 1 ) Global population is growing; demand for food, especially meat, is increasing; much land most suitable for annual crops is already in use; and production of nonfood goods (eg, biofuels) increasingly competes with food production for land ( 2 ) The best lands have soils at low or moderate risk of degradation under annual grain production but make up only 126% of global land area (165 million km2) ( 3 ) Supporting more than 50% of world population is another 437 million km2 of marginal lands (335% of global land area), at high risk of degradation under annual grain production but otherwise capable of producing crops ( 3 ) Global food security depends on annual grains—cereals, oilseeds, and legumes—planted on almost 70% of croplands, which combined supply a similar portion of human calories ( 4 , 5 ) Annual grain production, though, often compromises essential ecosystem services, pushing some beyond sustainable boundaries ( 5 ) To ensure food and ecosystem security, farmers need more options to produce grains under different, generally less favorable circumstances than those under which increases in food security were achieved this past century Development of perennial versions of important grain crops could expand options

374 citations

01 Jan 2010
TL;DR: In this paper, the authors proposed an approach to increase food and ecosystem security via Perennial Grains. But their approach is limited to a limited set of crops and does not consider other types of crops.
Abstract: Increased Food and Ecosystem Security via Perennial Grains J. D. Glover,* J. P. Reganold, L. W. Bell, J. Borevitz, E. C. Brummer, E. S. Buckler, C. M. Cox, T. S. Cox, T. E. Crews, S. W. Culman, L. R. DeHaan, D. Eriksson, B. S. Gill, J. Holland, F. Hu, B. S. Hulke, A. M. H. Ibrahim, W. Jackson, S. S. Jones, S. C. Murray, A. H. Paterson, E. Ploschuk, E. J. Sacks, S. Snapp, D. Tao, D. L. Van Tassel, L. J. Wade, D. L. Wyse, Y. Xu

358 citations


Cited by
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Journal ArticleDOI
TL;DR: Per capita demand for crops, when measured as caloric or protein content of all crops combined, has been a similarly increasing function of per capita real income since 1960 and forecasts a 100–110% increase in global crop demand from 2005 to 2050.
Abstract: Global food demand is increasing rapidly, as are the environmental impacts of agricultural expansion. Here, we project global demand for crop production in 2050 and evaluate the environmental impacts of alternative ways that this demand might be met. We find that per capita demand for crops, when measured as caloric or protein content of all crops combined, has been a similarly increasing function of per capita real income since 1960. This relationship forecasts a 100–110% increase in global crop demand from 2005 to 2050. Quantitative assessments show that the environmental impacts of meeting this demand depend on how global agriculture expands. If current trends of greater agricultural intensification in richer nations and greater land clearing (extensification) in poorer nations were to continue, ∼1 billion ha of land would be cleared globally by 2050, with CO2-C equivalent greenhouse gas emissions reaching ∼3 Gt y−1 and N use ∼250 Mt y−1 by then. In contrast, if 2050 crop demand was met by moderate intensification focused on existing croplands of underyielding nations, adaptation and transfer of high-yielding technologies to these croplands, and global technological improvements, our analyses forecast land clearing of only ∼0.2 billion ha, greenhouse gas emissions of ∼1 Gt y−1, and global N use of ∼225 Mt y−1. Efficient management practices could substantially lower nitrogen use. Attainment of high yields on existing croplands of underyielding nations is of great importance if global crop demand is to be met with minimal environmental impacts.

5,303 citations

Journal ArticleDOI
TL;DR: The tradeoffs that may occur between provisioning services and other ecosystem services and disservices should be evaluated in terms of spatial scale, temporal scale and reversibility, and the potential for ‘win–win’ scenarios increases.
Abstract: Agricultural ecosystems provide humans with food, forage, bioenergy and pharmaceuticals and are essential to human wellbeing. These systems rely on ecosystem services provided by natural ecosystems, including pollination, biological pest control, maintenance of soil structure and fertility, nutrient cycling and hydrological services. Preliminary assessments indicate that the value of these ecosystem services to agriculture is enormous and often underappreciated. Agroecosystems also produce a variety of ecosystem services, such as regulation of soil and water quality, carbon sequestration, support for biodiversity and cultural services. Depending on management practices, agriculture can also be the source of numerous disservices, including loss of wildlife habitat, nutrient runoff, sedimentation of waterways, greenhouse gas emissions, and pesticide poisoning of humans and non-target species. The tradeoffs that may occur between provisioning services and other ecosystem services and disservices should be evaluated in terms of spatial scale, temporal scale and reversibility. As more effective methods for valuing ecosystem services become available, the potential for ‘win–win’ scenarios increases. Under all scenarios, appropriate agricultural management practices are critical to realizing the benefits of ecosystem services and reducing disservices from agricultural activities.

1,732 citations

Journal ArticleDOI
Ian Scoones1
TL;DR: Livelihoods perspectives have been central to rural development thinking and practice in the past decade But where do such perspectives come from, what are their conceptual roots, and what influences have shaped the way they have emerged? as mentioned in this paper offers an historical review of key moments in debates about rural livelihoods, identifying the tensions, ambiguities and challenges of such approaches.
Abstract: Livelihoods perspectives have been central to rural development thinking and practice in the past decade But where do such perspectives come from, what are their conceptual roots, and what influences have shaped the way they have emerged? This paper offers an historical review of key moments in debates about rural livelihoods, identifying the tensions, ambiguities and challenges of such approaches A number of core challenges are identified, centred on the need to inject a more thorough-going political analysis into the centre of livelihoods perspectives This will enhance the capacity of livelihoods perspectives to address key lacunae in recent discussions, including questions of knowledge, politics, scale and dynamics

1,561 citations

Book Chapter
01 Jan 2010

1,556 citations

Journal ArticleDOI
TL;DR: Free-living soil bacteria beneficial to plant growth, usually referred to as plant growth promoting rhizobacteria (PGPR), are capable of promoting plant growth by colonizing the plant root and can inhibit phytopathogens.
Abstract: Soil bacteria are very important in biogeochemical cycles and have been used for crop production for decades. Plant–bacterial interactions in the rhizosphere are the determinants of plant health and soil fertility. Free-living soil bacteria beneficial to plant growth, usually referred to as plant growth promoting rhizobacteria (PGPR), are capable of promoting plant growth by colonizing the plant root. PGPR are also termed plant health promoting rhizobacteria (PHPR) or nodule promoting rhizobacteria (NPR). These are associated with the rhizosphere, which is an important soil ecological environment for plant–microbe interactions. Symbiotic nitrogen-fixing bacteria include the cyanobacteria of the genera Rhizobium, Bradyrhizobium, Azorhizobium, Allorhizobium, Sinorhizobium and Mesorhizobium. Free-living nitrogen-fixing bacteria or associative nitrogen fixers, for example bacteria belonging to the species Azospirillum, Enterobacter, Klebsiella and Pseudomonas, have been shown to attach to the root and efficiently colonize root surfaces. PGPR have the potential to contribute to sustainable plant growth promotion. Generally, PGPR function in three different ways: synthesizing particular compounds for the plants, facilitating the uptake of certain nutrients from the soil, and lessening or preventing the plants from diseases. Plant growth promotion and development can be facilitated both directly and indirectly. Indirect plant growth promotion includes the prevention of the deleterious effects of phytopathogenic organisms. This can be achieved by the production of siderophores, i.e. small metal-binding molecules. Biological control of soil-borne plant pathogens and the synthesis of antibiotics have also been reported in several bacterial species. Another mechanism by which PGPR can inhibit phytopathogens is the production of hydrogen cyanide (HCN) and/or fungal cell wall degrading enzymes, e.g., chitinase and s-1,3-glucanase. Direct plant growth promotion includes symbiotic and non-symbiotic PGPR which function through production of plant hormones such as auxins, cytokinins, gibberellins, ethylene and abscisic acid. Production of indole-3-ethanol or indole-3-acetic acid (IAA), the compounds belonging to auxins, have been reported for several bacterial genera. Some PGPR function as a sink for 1-aminocyclopropane-1-carboxylate (ACC), the immediate precursor of ethylene in higher plants, by hydrolyzing it into α-ketobutyrate and ammonia, and in this way promote root growth by lowering indigenous ethylene levels in the micro-rhizo environment. PGPR also help in solubilization of mineral phosphates and other nutrients, enhance resistance to stress, stabilize soil aggregates, and improve soil structure and organic matter content. PGPR retain more soil organic N, and other nutrients in the plant–soil system, thus reducing the need for fertilizer N and P and enhancing release of the nutrients.

1,430 citations