The role of soil organic matter in maintaining soil quality in continuous cropping systems
TL;DR: In this paper, the authors focus on lessons learned from long-term continuous cropping experiments, focusing on the importance of maintaining and improving soil quality in a continuous crop system, which is critical to sustaining agricultural productivity and environmental quality for future generations.
Abstract: Maintenance and improvement of soil quality in continuous cropping systems is critical to sustaining agricultural productivity and environmental quality for future generations. This review focuses on lessons learned from long-term continuous cropping experiments. Soil organic carbon (SOC) is the most often reported attribute from long-term studies and is chosen as the most important indicator of soil quality and agronomic sustainability because of its impact on other physical, chemical and biological indicators of soil quality. Long-term studies have consistently shown the benefit of manures, adequate fertilization, and crop rotation on maintaining agronomic productivity by increasing C inputs into the soil. However, even with crop rotation and manure additions, continuous cropping results in a decline in SOC, although the rate and magnitude of the decline is affected by cropping and tillage system, climate and soil. In the oldest of these studies, the influence of tillage on SOC and dependent soil quality indicators can only be inferred from rotation treatments which included ley rotations (with their reduced frequency of tillage). The impact of tillage per se on SOC and soil quality has only been tested in the ‘long-term’ for about 30 yrs, since the advent of conservation tillage techniques, and only in developed countries in temperate regions. Long-term conservation tillage studies have shown that, within climatic limits: Conservation tillage can sustain or actually increase SOC when coupled with intensive cropping systems; and the need for sound rotation practices in order to maintain agronomic productivity and economic sustainability is more critical in conservation tillage systems than conventional tillage systems. Long-term tillage studies are in their infancy. Preserving and improving these valuable resources is critical to our development of soil management practices for sustaining soil quality in continuous cropping systems.
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TL;DR: In this article, the authors quantify potential soil organic carbon sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur.
Abstract: Changes in agricultural management can potentially increase the accumulation rate of soil organic C (SOC), thereby sequestering CO 2 from the atmosphere. This study was conducted to quantify potential soil C sequestration rates for different crops in response to decreasing tillage intensity or enhancing rotation complexity, and to estimate the duration of time over which sequestration may occur. Analyses of C sequestration rates were completed using a global database of 67 long-term agricultural experiments, consisting of 276 paired treatments. Results indicate, on average, that a change from conventional tillage (CT) to no-till (NT) can sequester 57 ± 14 g C m -2 yr -1 , excluding wheat (Triticum aestivum L.)-fallow systems which may not result in SOC accumulation with a change from CT to NT. Enhancing rotation complexity can sequester an average 20 ± 12 g C m -2 yr -1 , excluding a change from continuous corn (Zea mays L.) to corn-soybean (Glycine max L.) which may not result in a significant accumulation of SOC. Carbon sequestration rates, with a change from CT to NT, can be expected to peak in 5 to 10 yr with SOC reaching a new equilibrium in 15 to 20 yr. Following initiation of an enhancement in rotation complexity, SOC may reach a new equilibrium in approximately 40 to 60 yr. Carbon sequestration rates, estimated for a number of individual crops and crop rotations in this study, can be used in spatial modeling analyses to more accurately predict regional, national, and global C sequestration potentials.
2,097 citations
Cites background from "The role of soil organic matter in ..."
...…agricultural soils contributes positively at a rate of 130 g C m 2 yr 1 for the first 20 yr, and thento soil fertility, soil tilth, crop production, and overat an average rate of 41 g C m 2 yr 1 for the followingall soil sustainability (Bauer and Black, 1994; Lal et al., 80 yr.1997; Reeves, 1997)....
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TL;DR: In this paper, a full C cycle analysis has been completed for agricultural inputs, resulting in estimates of net C flux for three crop types across three tillage intensities, including primary fuels, electricity, fertilizers, lime, pesticides, irrigation, seed production, and farm machinery.
1,199 citations
Cites background from "The role of soil organic matter in ..."
...Changes in tillage practice can lead to sequestration of C in agricultural soils (Kern and Johnson, 1993; Reeves, 1997; Smith et al., 1998)....
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TL;DR: A 10-year US Department of Energy sponsored research program designed to evaluate and develop switchgrass ( Panicum virgatum ), a native perennial warm-season grass, as a dedicated energy crop is reviewed in this paper.
Abstract: A 10-year US Department of Energy-sponsored research program designed to evaluate and develop switchgrass ( Panicum virgatum ), a native perennial warm-season grass, as a dedicated energy crop is reviewed. The programmatic objectives were to identify the best varieties and management practices to optimize productivity, while developing an understanding of the basis for long-term improvement of switchgrass through breeding and sustainable production in conventional agroecosystems. This research has reduced the projected production cost of switchgrass by about 25% ($8–9 Mg −1 ) through yield increases of about 50% achieved through selection of the best regionally adapted varieties; through optimizing cutting frequency and timing; and by reducing the level (by about 40%) and timing of nitrogen fertilization. Breeding research has made further gains in productivity of switchgrass that exceed the historical rate of yield improvement of corn. Studies of soil carbon storage under switchgrass indicate significant carbon sequestration will occur in soils that will improve soil productivity and nutrient cycling and can substantially augment greenhouse gas reductions associated with substituting renewable energy for fossil energy. Collaborative research with industry has included fuel production and handling in power production, herbicide testing and licensing, release of new cultivars, and genetic modifications for chemical coproduct enhancement. Economically based life cycle analyses based on this research suggest that switchgrass produced for energy will compete favorably both as an agricultural crop and as fuel for industry.
1,062 citations
TL;DR: In this article, the authors review literature about the impacts of cover crops in cropping systems that affect soil and water quality and present limited new information to help fill knowledge gaps and to provide knowledge gaps.
Abstract: This article reviews literature about the impacts of cover crops in cropping systems that affect soil and water quality and presents limited new information to help fill knowledge gaps. Cover crops grow during periods when the soil might otherwise be fallow. While actively growing, cover crops increase solar energy harvest and carbon flux into the soil, providing food for soil macro and microrganisms, while simultaneously increasing evapotranspiration from the soil. Cover crops reduce sediment production from cropland by intercepting the kinetic energy of rainfall and by reducing the amount and velocity of runoff. Cover crops increase soil quality by improving biological, chemical and physical properties including: organic carbon content, cation exchange capacity, aggregate stability, and water infiltrability. Legume cover crops contribute a nitrogen (N) to subsequent crops. Other cover crops, especially grasses and brassicas, are better at scavenging residual N before it can leach. Because growth of thes...
835 citations
Cites background from "The role of soil organic matter in ..."
...Deep rooted cover crops, such as lupin (Lupinus angustofolius L.) can be particularly effective in increasing effective root depth and subsoil water storage capacity (Reeves, 1994; Calegari and Pavan, 1995; Chan and Heenan, 1996; Reeves, 1997)....
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...Soil Carbon Cover crops increase carbon inputs into agricultural systems (Reeves, 1997; Kuo et al, 1997)....
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...Cover crops increase carbon inputs into agricultural systems (Reeves, 1997; Kuo et al, 1997)....
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...) can be particularly effective in increasing effective root depth and subsoil water storage capacity (Reeves, 1994; Calegari and Pavan, 1995; Chan and Heenan, 1996; Reeves, 1997)....
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TL;DR: In this paper, the importance of soil organic matter (SOM) in Canadian describe quality for that specific use or function is traced. But, it is not possible to make a perfect match and aggregation in sustaining soil functions.
Abstract: is seen as a basic premise of soil quality (Larson and Pierce, 1991, 1994). If a soil is not suitable for a specific Soil quality concepts are commonly used to evaluate sustainable use, then it is not appropriate to attempt to assign or land management in agroecosystems. The objectives of this review were to trace the importance of soil organic matter (SOM) in Canadian describe quality for that specific use or function. In many sustainable land management studies and illustrate the role of SOM cases, however, it is not possible to make a perfect match and aggregation in sustaining soil functions. Canadian studies on soil between the soil and its intended use. Under these cirquality were initiated in the early 1980s and showed that loss of SOM cumstances, quality must be built into the system using and soil aggregate stability were standard features of nonsustainable best management scenarios. land use. Subsequent studies have evaluated SOM quality using the Ecosystem concepts such as function, processes, attrifollowing logical sequence: soil purpose and function, processes, prop- butes, and indicators, have proved to be a useful frameerties and indicators, and methodology. Limiting steps in this soil work to describe soil quality (Larson and Pierce, 1991, quality framework are the questions of critical limits and standardiza1994; Doran and Parkin, 1994; Doran et al., 1996; Carter tion for soil properties. At present, critical limits for SOM are selected et al., 1997; Karlen et al., 1997). However, a precise using a commonly accepted reference value or based on empirically derived relations between SOM and a specific soil process or function definition of soil quality proves to be elusive. This is (e.g., soil fertility, productivity, or erodibility). Organic matter frac- probably related to the innate difficulty in defining soil tions (e.g., macro-organic matter, light fraction, microbial biomass, itself and to the multifaceted nature (i.e., scientific, perand mineralizable C) describe the quality of SOM. These fractions sonal, and social) of environmental concerns. Carter and have biological significance for several soil functions and processes MacEwan (1996) suggested that although soil quality and are sensitive indicators of changes in total SOM. Total SOM describes an objective state or condition of the soil, it influences soil compactibility, friability, and soil water-holding capac- also is subjective, i.e., evaluated partly on the basis of ity while aggregated SOM has major implications for the functioning personal and social determinations. The above frameof soil in regulating air and water infiltration, conserving nutrients, work of soil quality has utility when it is directed or and influencing soil permeability and erodibility. Overall, organic focused towards the manipulation, engineering, and/or matter inputs, the dynamics of the sand-sized macro-organic matter, and the soil aggregation process are important factors in maintaining management of the soil resource. Thus, soil quality is a and regulating organic matter functioning in soil. technology, an applied science, directed towards better soil management. The objective of this paper is to review the context
679 citations
Cites background from "The role of soil organic matter in ..."
...1994; Reeves, 1997), soil erodibility (Feller et al., 1996; Fig....
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..., 1996), crop productivity (Bauer and Black, to changes in SOM. 1994; Reeves, 1997), soil erodibility (Feller et al....
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References
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01 Jan 1982
14,888 citations
14 Feb 1996
8,749 citations
01 Jan 1982
5,659 citations
"The role of soil organic matter in ..." refers background in this paper
...It is commonly estimated from determinations of organic C. Soil organic carbon (SOC)-SOM conversion factors for surface soils range from 1.724 to 2.0 (Nelson and Sommers, 1982)....
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TL;DR: In this article, the effectiveness of various binding agents at different stages in the structural organization of aggregates is described and forms the basis of a model which illustrates the architecture of an aggregate.
Abstract: Summary
The water-stability of aggregates in many soils is shown to depend on organic materials. The organic binding agents have been classified into (a) transient, mainly polysaccharides, (b), temporary, roots and fungal hyphae, and (c) persistent, resistant aromatic components associated with polyvalent metal cations, and strongly sorbed polymers. The effectiveness of various binding agents at different stages in the structural organization of aggregates is described and forms the basis of a model which illustrates the architecture of an aggregate. Roots and hyphae stabilize macro-aggregates, defined as > 250 μm diameter; consequently, macroaggregation is controlled by soil management (i.e. crop rotations), as management influences the growth of plant roots, and the oxidation of organic carbon. The water-stability of micro-aggregates depends on the persistent organic binding agents and appears to be a characteristic of the soil, independent of management.
5,389 citations
"The role of soil organic matter in ..." refers background in this paper
..., 1989; Pikul and Zuzel, 1994) aggregate formation and stability (Tisdall and Oades, 1982; Oades, 1984; MacRae and Mehuys, 1985; Burns and Davies, 1986; Boyle et al., 1989)...
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...…water capacity (Hudson, 1994) infiltration (MacRae and Mehuys, 1985; Boyle et al., 1989; Pikul and Zuzel, 1994) aggregate formation and stability (Tisdall and Oades, 1982; Oades, 1984; MacRae and Mehuys, 1985; Burns and Davies, 1986; Boyle et al., 1989) D.W. Reeues/Soil & Tillage Research 43…...
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...The interrelational role of SOC on soil structure and soil physical properties has been extensively reviewed (Tisdall and Oades, 1982; Oades, 1984; Boyle et al., 1989; Carter and Stewart, 1996) and is beyond the scope of this paper....
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TL;DR: In this article, a model of soil organic matter (SOM) quantity and composition was used to simulate steady-state organic matter levels for 24 grassland locations in the U.S. Great Plains.
Abstract: We analyzed climatic and textural controls of soil organic C and N for soils of the U.S. Great Plains. We used a model of soil organic matter (SOM) quantity and composition to simulate steady-state organic matter levels for 24 grassland locations in the Great Plains. The model was able to simulate the effects of climatic gradients on SOM and productivity. Soil texture was also a major control over organic matter dynamics. The model adequately predicted above-ground plant production and soil C and N levels across soil textures (sandy, medium, and fine); however, the model tended to overestimate soil C and N levels for fine textured soil by 10 to 15%. The impact of grazing on the system was simulated and showed that steady-state soil C and N levels were sensitive to the grazing intensity, with soil C and N levels decreasing with increased grazing rates. Regional trends in SOM can be predicted using four site-specific variables, temperature, moisture, soil texture, and plant lignin content. Nitrogen inputs must also be known. Grazing intensity during soil development is also a significant control over steady-state levels of SOM, and since few data are available on presettlement grazing, some uncertainty is inherent in the model predictions
3,594 citations
"The role of soil organic matter in ..." refers background in this paper
...The authors speculated that several proposed mechanisms for stabilization and protection of SOC by clay (van Veen and Paul, 198 1; Parton et al., 1987; Hassink and Whitmore, 1995 in Campbell et al., 1996a) might offer an explanation for the increased C sequestration with increasing clay content....
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