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  • 1
    Electronic Resource
    Electronic Resource
    Agricultural soils as a sink to mitigate CO2 emissions (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Soil use and management 13 (1997), S. 0 
    Details
    ISSN: 1475-2743
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract. Agricultural soils, having been depleted of much of their native carbon stocks, have a significant CO2 sink capacity. Global estimates of this sink capacity are in the order of 20-30 Pg C over the next 50-100 years. Management practices to build up soil C must increase the input of organic matter to soil and/or decrease soil organic matter decomposition rates. The most appropriate management practices to increase soil C vary regionally, dependent on both environmental and socioeconomic factors.In temperate regions, key strategies involve increasing cropping frequency and reducing bare fallow, increasing the use of perennial forages (including N-fixing species) in crop rotations, retaining crop residues and reducing or eliminating tillage (i.e. no-till). In North America and Europe, conversion of marginal arable land to permanent perennial vegetation, to protect fragile soils and landscapes and/or reduce agricultural surpluses, provides additional opportunities for C sequestration.In the tropics, increasing C inputs to soil through improving the fertility and productivity of cropland and pastures is essential. In extensive systems with vegetated fallow periods (e.g. shifting cultivation), planted fallows and cover crops can increase C levels over the cropping cycle. Use of no-till, green manures and agroforestry are other beneficial practices. Overall, improving the productivity and sustainability of existing agricultural lands is crucial to help reduce the rate of new land clearing, from which large amounts of CO2 from biomass and soil are emitted to the atmosphere.Some regional analyses of soil C sequestration and sequestration potential have been performed, mainly for temperate industrialized countries. More are needed, especially for the tropics, to capture region-specific interactions between climate, soil and management resources that are lost in global level assessments.By itself, C sequestration in agricultural soils can make only modest contributions (e.g. 3-6% of total fossil C emissions) to mitigating greenhouse gas emissions. However, effective mitigation policies will not be based on any single ‘magic bullet’ solutions, but rather on many modest reductions which are economically efficient and which confer additional benefits to society. In this context, soil C sequestration is a significant mitigation option. Additional advantages of pursuing strategies to increase soil C are the added benefits of improved soil quality for improving agricultural productivity and sustainability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00594.x
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  • 2
    Electronic Resource
    Electronic Resource
    The inherent ‘safety-net’ of an Acrisol: measuring and modelling retarded leaching of mineral nitrogen (2002)
    Oxford, UK : Blackwell Science Ltd
    European journal of soil science 53 (2002), S. 0 
    Details
    ISSN: 1365-2389
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The inherent features of Acrisols with their increasing clay content with depth are conducive to reducing nutrient losses by nutrient adsorption on the matrix soil surfaces. Ammonium (NH4+) and nitrate (NO3−) adsorption by a Plinthic Acrisol from Lampung, Indonesia was studied in column experiments. The peak of the H218O breakthrough occurred at 1 pore volume, whereas the median pore volumes for NH4+ and NO3− ranged from 6.4 to 6.9 and 1.1 to 1.6, respectively. The adsorption coefficients (Ka in cm3 g–1) measured were 1.81, 1.51, 1.64 and 1.47 for NH4+ and 0.03, 0.09, 0.10 and 0.17 for NO3−, respectively, in the 0–0.2, 0.2–0.4, 0.4–0.6 and 0.6–0.8 m soil depth layers. The NH4+ and NO3− adsorption coefficients derived from this study were put in to the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model to evaluate their effect on leaching in the context of several cropping systems in the humid tropics. The resulting simulations indicate that the inherent ‘safety-net’ (retardation mechanism) of a shallow (0.8–1 m) Plinthic Acrisol can reduce the leaching of mineral N by between 5 and 33% (or up to 2.1 g m−2), mainly due to the NH4+ retardation factor, and that the effectiveness in reducing N leaching increases with increasing depth. However, the inherent ‘safety-net’ is useful only if deep-rooted plants can recover the N subsequently.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2389.2002.00447.x
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  • 3
    Electronic Resource
    Electronic Resource
    Production and decay of structural root material of winter wheat and sugar beet in conventional and integrated cropping systems
    Amsterdam : Elsevier
    Agriculture, Ecosystems and Environment 51 (1994), S. 99-113 
    Details
    ISSN: 0167-8809
    Keywords: Decomposition ; Farming system, conventional ; Farming system, integrated ; Minirhizotron technique ; Root turnover ; Sugar beet ; Triticum aestivum
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1016/0167-8809(94)90037-X
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  • 4
    Electronic Resource
    Electronic Resource
    Effects of fertilizer price on feasibility of efficiency improvement: Case study for an urea injector for lowland rice (1994)
    Springer
    Nutrient cycling in agroecosystems 39 (1994), S. 1-9 
    Details
    ISSN: 1573-0867
    Keywords: Economic analysis ; fertilizer subsidies ; nitrogen use efficiency ; optimization ; price policy ; rice ; yield model
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efficiency improving techniques, such as the introduction of a urea injector for lowland rice production, appear to lead to higher yields, lower fertilizer use and less environmental pollution at the same time. If farmers are free to decide on the amount of fertilizer they use, economic rationality leads to a choice between using the improved technique for saving fertilizer while obtaining the same yield, for increasing yield (at the same fertilizer rate) or for a mixed strategy (a slightly higher yield and a different fertilizer rate). The ‘economic optimum fertilizer rate’ was calculated with a simple yield model for a low and a high fertilizer application efficiency to predict which strategy would be best for the farmer. Calculations for a ‘standard’ data set for lowland rice show that the greatest benefit from an increase in application efficiency by urea deep placement instead of broadcast application can be expected when a marginal efficiency of about 9 kg rice per kg fertilizer N is used for determining the fertilizer rate. For a marginal efficiency of less than 6, savings on fertilizer are the main benefit of efficiency improvement; for higher marginal efficiencies yield increases become the main component of total benefit; for marginal efficiencies above 9, fertilizer use will increase when a more efficient technique is used, but increased yields compensate for their costs. In the four countries where a manually operated pneumatic urea injector was tested (Togo, Bangladesh, Indonesia and Ivory Coast) the price ratio of rice and fertilizer N ranged from 1.1 to 2.5. Even when a ‘risk-avoidance’ multiplier of 2 is used, we may conclude that fertilizer prices were too low relative to rice to make optimum use of the existing techniques for efficiency improvement. An equation is derived for estimating the price ratio at which the probability of farmer acceptance of techniques for improving fertilizer use efficiency is highest.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00750151
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  • 5
    Electronic Resource
    Electronic Resource
    The Imperata grasslands of tropical Asia: area, distribution, and typology (1996)
    Springer
    Agroforestry systems 36 (1996), S. 3-29 
    Details
    ISSN: 1572-9680
    Keywords: alang-alang ; area estimates ; cogon ; degraded lands ; Imperata cylindrica (L.) ; uplands
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The rehabilitation or intensified use of Imperata grasslands will require a much better understanding of their area, distribution, and characteristics. We generated estimates of the area of Imperata grasslands in tropical Asia, and suggested a typology of Imperata grasslands that may be useful to define the pathways toward appropriate land use intensification. We conclude that the area of Imperata grasslands in Asia is about 35 million ha. This about 4% of the total land area. The countries with the largest area of Imperata grasslands are Indonesia (8.5 million ha) and India (8.0 million ha). Those with the largest proportion of their surface area covered with Imperata are Sri Lanka (23%), the Philippines (17%), and Vietnam (9%). Laos, Thailand, Myanmar, and Bangladesh evidently all have similar proportions of their land area infested with Imperata (about 3 to 4%). Malaysia (〈 1%), Cambodia (1%), and the southern part of China (2%) have but a minor proportion of their total land area in Imperata. The species was found widely distributed on the full range of soil orders. It occupied both fertile (e.g. some of the Inceptisols and Andisols) and infertile soils (Ultisols and Oxisols) across a wide range of climates and elevations. Imperata lands fall into four mapping scale-related categories: Mega-grasslands, itmacro-grasslands, meso-grasslands, and micro-grasslands. The mega-grasslands are often referred to as ‘sheet Imperata’. They are the large contiguous areas of Imperata that would appear on small-scale maps of say 1:1,000,000. We propose that this basic typology be supplemented with a number of additional components that have a key influence on intensification pathways: land quality, market access, and the source of power for tillage. The typology was applied in a case study of Indonesian villages in the vicinity of Imperata grasslands. We propose an international initiative to map and derive a more complete and uniform picture of the area of the Imperata grasslands. This should include selected studies to understand conditions at the local level. These are critical to build the appreciation of change agents for the indigenous systems of resource exploitation, and how they relate to local needs, values and constraints.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00142865
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  • 6
    Electronic Resource
    Electronic Resource
    Food-crop-based production systems as sustainable alternatives for Imperata grasslands? (1996)
    Springer
    Agroforestry systems 36 (1996), S. 55-82 
    Details
    ISSN: 1572-9680
    Keywords: erosion ; Imperata cylindrica ; Indonesia ; the Philippines ; rotational hedgerow intercropping ; sustainability criteria ; weed control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Purely annual crop-based production systems have limited scope to be sustainable under upland conditions prone to infestation by Imperata cylindrica if animal or mechanical tillage is not available. Farmers who must rely on manual cultivation of grassland soils can achieve some success in suppressing Imperata for a number of years using intensive relay and intercropping systems that maintain a dense soil cover throughout the year, especially where leguminous cover crops are included in the crop cycle. However, labour investment increases and returns to labour tend to decrease in successive years as weed pressure intensifies and soil quality declines. Continuous crop production has been sustained in many Imperata-infested areas where farmers have access to animal or tractor draft power. Imperata control is not a major problem in such situations. Draft power drastically reduces the labour requirements in weed control. Sustained crop production is then dependent more solely upon soil fertility management. Mixed farming systems that include cattle may also benefit from manure application to the cropped area, and the use of non-cropped fallow areas for grazing. In extensive systems where Imperata infestation is tolerated, cassava or sugarcane are often the crops with the longest period of viable production as the land degrades. On sloping Imperata lands, conservation farming practices are necessary to sustain annual cropping. Pruned tree hedgerows have often been recommended for these situations. On soils that are not strongly acidic they may consistently improve yields. But labour is the scarcest resource on small farms and tree-pruning is usually too labour-intensive to be practical. Buffer strip systems that provide excellent soil conservation but minimize labour have proven much more popular with farmers. Prominent among these are natural vegetative strips, or strips of introduced fodder grasses. The value of Imperata to restore soil fertility is low, particularly compared with woody secondary growth or Compositae species such as Chromolaena odorata or Tithonia diversifolia. Therefore, fallow-rotation systems where farmers can intervene to shift the fallow vegetation toward such naturally-occurring species, or can manage introduced cover crop species such as Mucuna utilis cv. cochinchinensis, enable substantial gains in yields and sustainability. Tree fallows are used successfully to achieve sustained cropping by some upland communities. A variation of this is rotational hedgerow intercropping, where a period of cropping is followed by one or more years of tree growth to generate nutrient-rich biomass, rehabilitate the soil, and suppress Imperata. These options, which suit farmers in quite resource-poor situations, should receive more attention.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00142867
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  • 7
    Electronic Resource
    Electronic Resource
    Fire management on Imperata grasslands as part of agroforestry development in Indonesia (1996)
    Springer
    Agroforestry systems 36 (1996), S. 203-217 
    Details
    ISSN: 1572-9680
    Keywords: fire causation ; fire control ; Imperata cylindrica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Fire is an important factor in the Imperata grassland ecosystem. It prevents or slows down the natural succession to shrubs and/or secondary forest vegetation and is a major threat to (agro)forestry options for Imperata grassland rehabilitation. Forest fires can also be a primary cause of the extension of Imperata grasslands. In this review an attempt is made to integrate biophysical and socioeconomic aspects of the causation of fires in a conceptual model. Fire effects on vegetation are examined. The management options at the level of a farmer, a village community and a national government are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00142874
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  • 8
    Electronic Resource
    Electronic Resource
    Soil fertility management for reclamation of Imperata grasslands by smallholder agroforestry (1996)
    Springer
    Agroforestry systems 36 (1996), S. 181-202 
    Details
    ISSN: 1572-9680
    Keywords: Imperata cylindrica ; Mucuna pruriens ; phosphorus ; soil organic matter ; Sumatra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Imperata cylindrica grasslands are widely believed to indicate poor soil fertility. Soil fertility improvement may have to be an important component of a reclamation strategy. Data for Sumatra, Indonesia indicate, however, that Imperata occurs on a broad range of soil types and is not confined to the poorest soils. A direct role of Imperata in soil degradation cannot be ascertained. In many instances, however, Imperata soils are low in available P and effective N supply. The use of rock phosphate in combination with erosion control (‘fertility traps’) and legume cover crops can be effective in restoring soil fertility. Case studies for a number of sites in Sumatra have confirmed the practical possibility of reclaiming grasslands for food and tree crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00142873
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  • 9
    Electronic Resource
    Electronic Resource
    Productivity of intensified crop—fallow rotations in the Trenbath model (1999)
    Springer
    Agroforestry systems 47 (1999), S. 223-237 
    Details
    ISSN: 1572-9680
    Keywords: fallow period ; intensification ; soil fertility ; sustainability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Management of crop—fallow rotations should strike a balance between exploitation, during cropping, and restoration of soil fertility during the fallow period. The ‘Trenbath’ model describes build-up of soil fertility during a fallow period by two parameters (a maximum level and a half-recovery time) and decline during cropping as a simple proportion. The model can be used to predict potential crop production for a large number of management options consisting of length of cropping period and duration of fallow. In solving the equations, the model can be restricted to ‘sustainable’ systems, where fallow length is sufficient to restore soil fertility to its value at the start of the previous cropping period. The model outcome suggests that the highest yields per unit of land can be obtained by starting a new cropping period after soil fertility has recovered to 50–60% of its maximum value. This prediction is virtually independent of the growth rate of the fallow vegetation. The nature of the fallow vegetation (natural regrowth, planted trees, or cover crops) mainly influences the crop yield by modifying the required duration of fallow periods. Intensification of land use by shortening fallow periods will initially increase returns per unit land at the likely costs of returns per unit labor. When fallows no longer restore soil fertility to 50% of the maximum, overall productivity will decline both per unit land and per unit labor, unless external inputs replace the soil fertility restoring functions of a fallow.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006223715411
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  • 10
    Electronic Resource
    Electronic Resource
    Scale effects in crop—fallow rotations (1999)
    Springer
    Agroforestry systems 47 (1999), S. 239-251 
    Details
    ISSN: 1572-9680
    Keywords: lateral interaction ; model ; neighborhood effects ; roots ; scaling ; tree—soil—crop interactions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many aspects of ‘scaling up’ must be considered in the spectrum between promising results of new technologies in experimental plots and wide adoption by farmers. These aspects include extrapolating in time to optimize management decisions, extrapolating in space from small plots to large fields and to other farms and regions, and enlarging the range of (presumed) beneficiaries. Models can help in all these aspects to lay a biophysical foundation on which socioeconomic decisions can be built. We focus here on ‘improved fallow’ systems where trees are planted to restore soil fertility for subsequent food crops. The restoration of soil fertility — based on biomass production, litterfall, and build-up of dynamic soil organic matter pools — depends on total resource capture by the fallow vegetation. Where ‘lateral resource capture’ and ‘lateral resource flow’ play a substantive role in the performance of the fallow, the size (scale) of fallow and cropped plots may influence both the build-up and the decline of soil fertility during a cycle. On small farms, fallow systems should not be seen as pure sequential systems, but as mosaics of spatially interacting fallow and cropped plots. Border effects depend on the lateral spread of the root system of the fallow vegetation, as well as on rainfall and N supply. Scale effects in technology adoption include both positive and negative feedback effects, because the spread of a technology may both accelerate innovations as well as increase threats from pest and disease attack.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006227832249
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