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  • 1
    Digitale Medien
    Digitale Medien
    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
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1111/j.1475-2743.1997.tb00594.x
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    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
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-2389.2002.00447.x
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  • 3
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Decomposition ; Farming system, conventional ; Farming system, integrated ; Minirhizotron technique ; Root turnover ; Sugar beet ; Triticum aestivum
    Quelle: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Thema: Biologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1016/0167-8809(94)90037-X
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  • 4
    Digitale Medien
    Digitale Medien
    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
    Schlagwort(e): Economic analysis ; fertilizer subsidies ; nitrogen use efficiency ; optimization ; price policy ; rice ; yield model
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00750151
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Can the ecosystem mimic hypotheses be applied to farms in African savannahs? (1999)
    Springer
    Agroforestry systems 45 (1999), S. 131-158 
    Details
    ISSN: 1572-9680
    Schlagwort(e): competition ; fertility ; microclimate ; risk ; stability ; water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The first ecosystem mimic hypothesis suggests clear advantages if man-made land use systems do not deviate greatly in their resource use patterns from natural ecosystems typical of a given climatic zone. The second hypothesis claims that additional advantages will accrue if agroecosystems also maintain a substantial part of the diversity of natural systems. We test these hypotheses for the savannah zone of sub-Saharan Africa, with its low soil fertility and variable rainfall. Where annual food crops replace the natural grass understorey of savannah systems, water use will decrease and stream and groundwater flow change, unless tree density increases relative to the natural situation. Increasing tree density, however, will decrease crop yields, unless the trees meet specific criteria. Food crop production in the parkland systems may benefit from lower temperatures under tree canopies, but water use by trees providing this shade will prevent crops from benefiting. In old parkland trees that farmers have traditionally retained when opening fields for crops, water use per unit shade is less than in most fast growing trees introduced for agroforestry trials. Strong competition between plants adapted to years with different rainfall patterns may stabilise total system productivity -- but this will be appreciated by a farmer only if the components are of comparable value. The best precondition for farmers to maintain diversity in their agroecosystem hinges on the availability of a broad basket of choices, without clear winners or 'best bets'.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006245605705
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  • 6
    Digitale Medien
    Digitale Medien
    Productivity of intensified crop—fallow rotations in the Trenbath model (1999)
    Springer
    Agroforestry systems 47 (1999), S. 223-237 
    Details
    ISSN: 1572-9680
    Schlagwort(e): fallow period ; intensification ; soil fertility ; sustainability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: 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.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1023/A:1006223715411
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    The special role of male Cebus monkeys in predation avoidance and its effect on group composition (1989)
    Springer
    Behavioral ecology and sociobiology 24 (1989), S. 265-276 
    Details
    ISSN: 1432-0762
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary Vigilance behavior, predator detection abilities, and responses to real and model predators were studied in two species of capuchin monkeys (Cebus albifrons and C. apella) in a Peruvian lowland rain forest. Adult males were more vigilant than adult females in both species, mainly because the males spent less time feeding and foraging and partly because they were at the periphery more often than the females. The increased vigilance of adult males is reflected in their superior performance in the detection of (model) predators. Adult and subadult males were also far more likely to approach and mob real and model predators. Adults that were outside the center of the group increased foraging activities but cut back an feeding, much of which was done in exposed tree crowns. Current theory suggests that primate groups are multi-male when a single male is unable to defend sexual access to the group of females. In these small capuchin groups, which are multimale, the enhanced safety of females and young provided by extra adult males furnishes a more plausible explanation. A comparison of the two capuchins with the ecologically similar Southeast Asian Macaca fascicularis suggests that the high predation risk outside the group may also have caused the unusual male career profile in capuchins, which have a long tenure of dominants and a very long potential lifespan. Further predictions of this hypothesis are developed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00290902
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Old tree root channels in acid soils in the humid tropics: Important for crop root penetration, water infiltration and nitrogen management (1991)
    Springer
    Plant and soil 134 (1991), S. 37-44 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cassava ; Guelph permeameter ; leaching ; maize ; methylene blue ; rice ; rooting depth ; soybean
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Under high rainfall conditions on acid soils with shallow crop root systems the rate of N leaching is high. A simple model predicts nitrogen uptake efficiency as a function of the amount of rainfall in excess of evapotranspiration, rooting depth and degree to which N leaching is retarded in comparison with water transport. Field observations on acid soils in S.E. Nigeria and S. Sumatera (Indonesia) showed that this model should be amended to include the role of old tree root channels. Crop roots can follow these channels, which are coated with partly decayed organic matter, into the acid subsoil. Measurements of water infiltration with a Guelph permeameter and a methylene blue dye showed that such channels form the major infiltration sites during rainstorms. Implications for nitrogen use efficiency and cropping pattern are discussed.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF00010715
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  • 9
    Digitale Medien
    Digitale Medien
    Heavy-metal uptake by crops from polluted river sediments covered by non-polluted topsoil (1995)
    Springer
    Plant and soil 175 (1995), S. 105-113 
    Details
    ISSN: 1573-5036
    Schlagwort(e): cadmium ; root distribution ; root methods ; soil pollution ; Zea mays
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Cadmium uptake by maize from polluted river sediments covered with a clean top layer of variable thickness is discussed in relation to root distribution. Two pathways for uptake are distinguished: roots penetrating the contaminated layer or contaminants moving into the root zone. Relative Cd uptake proved to be roughly proportional to the fraction of total root length found in the contaminated layer. A deeper water table induced a deeper root development and more Cd uptake for a given thickness of clean topsoil. A model based on exponential decrease of root length density with depth is acceptable as first approximation only. Little or no evidence was found for contaminants moving into the root zone during the ten years of the experiment.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02413015
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  • 10
    Digitale Medien
    Digitale Medien
    Mathematical models on diffusion of oxygen to and within plant roots, with special emphasis on effects of soil-root contact (1984)
    Springer
    Plant and soil 77 (1984), S. 233-241 
    Details
    ISSN: 1573-5036
    Schlagwort(e): Diffusion ; Oxygen ; Soil-root contact
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary In relation to explanations of anaerobiosis in the field, mathematical models presented in part I are evaluated in the light of the disparity between the low oxygen pressure required by plant roots in well-stirred nutrient solutions and the rather high values apparently required in the field. Water film and rhizosphere respiration do not fully explain this disparity. Soil-root contact as described in part I is shown to considerably affect the partial pressure of oxygen required for unrestricted aerobic respiration.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02182926
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