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  • 1
    Electronic Resource
    Electronic Resource
    Net flux of carbon dioxide from tropical forests in 1980 (1985)
    [s.l.] : Nature Publishing Group
    Nature 316 (1985), S. 617-620 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The FAO/UNEFs8'9 estimate of deforestation in the tropics is compared in Table 1 with estimates made by Myers10'12 and the FAO's Production Yearbook13. Comparison of the rates given by FAO/UNEP and the Production Yearbook assumes that deforestation of the open and closed forests of the former is ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/316617a0
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  • 2
    Electronic Resource
    Electronic Resource
    Inorganic fertilizer enrichment of soil: effect on decomposition of plant litter under subhumid tropical conditions (1999)
    Springer
    Biology and fertility of soils 30 (1999), S. 224-231 
    Details
    ISSN: 1432-0789
    Keywords: Key words Decomposition ; Mineralization ; Residue quality ; Mineral fertilizer ; Soil microbial biomass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  Litter decomposition is controlled by many factors, including the quality of the litter and conditions within the soil environment. The decomposition and N and P release from prunings of three agroforestry plant species (Sesbania sesban, Croton megalocarpus, and Calliandra calothyrsus) were evaluated on field plots which were amended with: (1) no fertilizer (control), (2) 120 kg N ha–1 applied as urea (urea), and (3) 150 kg P ha–1 applied as triple superphosphate (TSP) over a period of 77 days. For all litters, the percentage of initial mass, N and P remaining (dry weight basis) over time followed the single exponential model and was strongly influenced by the interaction of plant species and fertilizer. Decay rate constants (k) of loss of litter mass (k B), and release of N (k N), and P (k P) varied among litters and fertility regimes. The k B, k N and k P of Sesbania and Croton were enhanced more by urea than by TSP and control treatments. For Calliandra, k B with TSP was higher (0.016 day–1) than with urea (0.012 day–1) and control (0.012 day–1). Sesbania and Croton showed no differences in k B, k N and k P between control and TSP. For Sesbania and Croton, leaching may have accelerated the release of P to meet the needs of decomposer organisms, resulting in no significant effects of TSP on their decomposition processes. The low rate of decomposition of Calliandra may be partly due to its high lignin content. In conclusion, the higher the total N or P of litter, the less likely would be the significant effects of additions of the inorganic form of fertilizer on the decomposition processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050612
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  • 3
    Electronic Resource
    Electronic Resource
    Tithonia and senna green manures and inorganic fertilizers as phosphorus sources for maize in Western Kenya (1998)
    Springer
    Agroforestry systems 44 (1998), S. 21-35 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; decomposition ; mineralization ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Efforts to overcome declining soil fertility on small holder farms in western Kenya must be consistent with the reality of low utilization of inorganic fertilizers. Likewise organic inputs alone cannot supply adequate nutrients. The use of two organic resources, Tithonia diversifolia (tithonia) and Senna spectabilis (senna) leaves, and their combination with inorganic P for improving soil fertility and maize yields was investigated on a P limiting soil in Western Kenya. Treatments included: 1) control, no inputs; 2) 5 t ha−1 (dry matter) tithonia leaves; 3) 5 t ha−1 senna leaves; 4) 5 t ha−1 tithonia leaves + 25 kg P ha−1 as triple superphosphate (TSP); 5) 5 t ha−1 senna leaves + 25 kg P ha−1 (as TSP); and 6) 25 kg P ha−1 of TSP. Maize was used as a test crop. Decomposition and P and N release of tithonia and senna leaves were determined in a litterbag study. Tithonia + TSP applications tripled maize yields compared to the control, senna + TSP and tithonia sole application doubled yields, while senna sole applications did not increase yields substantially. A large residual yield was produced in the tithonia treatments in a subsequent crop. These yield results were consistent with the higher quality and faster release of N and P from the tithonia leaves compared to senna. The tithonia biomass transfer system can improve yields in the short term but has limitations because of the large amount of biomass and the associated labor requirements.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006123404071
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  • 4
    Electronic Resource
    Electronic Resource
    Tithonia diversifolia as a green manure for soil fertility improvement in western Kenya: A review (2000)
    Springer
    Agroforestry systems 49 (2000), S. 201-221 
    Details
    ISSN: 1572-9680
    Keywords: biomass transfer ; integrated nutrient management ; nitrogen ; nutrient cycling ; phosphorus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Tithonia diversifolia, a shrub in the family Asteraceae, is widely distributed along farm boundaries in the humid and subhumid tropics of Africa. Green biomass of tithonia has been recognized as an effective source of nutrients for lowland rice (Oryza sativa) in Asia and more recently for maize (Zea mays) and vegetables in eastern and southern Africa. This paper reviews the potential of tithonia green biomass for soil fertility improvement based on recent research in western Kenya. Green leaf biomass of tithonia is high in nutrients, averaging about 3.5% N, 0.37% P and 4.1% K on a dry matter basis. Boundary hedges of sole tithonia can produce about 1 kg biomass (tender stems + leaves) m−1 yr−1 on a dry weight basis. Tithonia biomass decomposes rapidly after application to soil, and incorporated biomass can be an effective source of N, P and K for crops. In some cases, maize yields were even higher with incorporation of tithonia biomass than with commercial mineral fertilizer at equivalent rates of N, P and K. In addition to providing nutrients, tithonia incorporated at 5 t dry matter ha−1 can reduce P sorption and increase soil microbial biomass. Because of high labor requirements for cutting and carrying the biomass to fields, the use of tithonia biomass as a nutrient source is more profitable with high-value crops such as vegetables than with relatively low-valued maize. The transfer of tithonia biomass to fields constitutes the redistribution of nutrients within the landscape rather than a net input of nutrients. External inputs of nutrients would eventually be required to sustain production of tithonia when biomass is continually cut and transferred to agricultural land.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006339025728
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  • 5
    Electronic Resource
    Electronic Resource
    Organic residues affect phosphorus availability and maize yields in a Nitisol of western Kenya (2000)
    Springer
    Biology and fertility of soils 32 (2000), S. 328-339 
    Details
    ISSN: 1432-0789
    Keywords: Key words Biomass transfer ; Maize ; Phosphorus ; Resin extractable phosphorus ; Triple superphosphate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract  The effects of organic residues and inorganic fertilizers on P availability and maize yield were compared in a Nitisol of western Kenya. Leaf biomass of Calliandra calothyrsus, Senna spectabilis, Croton megalocarpus, Lantana camara, Sesbania sesban, and Tithonia diversifolia were incorporated into the soil at 5 Mg ha–1 for six consecutive seasons in 3 years and responses compared with those following the application of 120 kg N ha–1, 0 kg P ha–1 (0P); 120 kg N ha–1, 10 kg P ha–1; and 120 kg N ha–1 25 kg P ha–1 as urea and triple superphosphate (TSP); K was supplied in all treatments. Addition of Tithonia, Lantana and Croton increased soil resin-extractable P over that of fertilizer-amended soil throughout the first crop, but the amounts in the former treatments became similar to those for soils amended with inorganic fertilizers for subsequent crops. Addition of Sesbania, Calliandra and Senna had a similar effect on resin P as inorganic fertilizers. Total maize yields after six seasons were tripled by the application of Tithonia compared to 0P, and were higher than those of the Calliandra, Senna, Sesbania and Lantana treatments, and similar only to that of the Croton treatment. P recovered in the above-ground biomass and resin P, immediately after the implementation of the treatments, was higher in the Senna, Sesbania, Croton, Lantana and Tithonia (35–77%) treatments than in the inorganic fertilizer treatments (21–27%). The P content of organic residues, and the soluble C:total P ratio, were the main residue parameters predicting soil P availability and maize yield. All organic residues used in this study can replace inorganic fertilizers for the enhancement of P availability and maize production, while an additional benefit could be obtained from the use of Croton, Lantana and Tithonia.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740000256
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  • 6
    Electronic Resource
    Electronic Resource
    Contribution of agroforestry trees to nutrient requirements of intercropped plants (1995)
    Springer
    Agroforestry systems 30 (1995), S. 105-124 
    Details
    ISSN: 1572-9680
    Keywords: lignin ; nutrient content ; nutrient release ; polyphenols ; prunings ; synchrony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A major tenet of agroforestry, that trees maintain soil fertility, is based primarily on observations of higher crop yields near trees or where trees were previously grown. Recently objective analyses and controlled experiments have addressed this topic. This paper examines the issues of tree prunings containing sufficient nutrients to meet crop demands, the timing of nutrient transfer from decomposition to intercrops, the percent of nutrients released that are taken up by the crop, and the fate of nutrients not taken up by the crop. The amount of nutrients provided by prunings are determined by the production rate and nutrient concentrations, both depending on climate, soil type, tree species, plant part, tree density and tree pruning regime. A large number of screening and alley cropping trials in different climate-soil environments indicate that prunings of several tree species contain sufficient nutrients to meet crop demand, with the notable exception of phosphorus. Specific recommendations for the appropriate trees in a given environment await synthesis of existing data, currently only general guidelines can be provided. Tree biomass containing sufficient nutrients to meet crop demand is not enough, the nutrients must be supplied in synchrony to crop needs. Nutrient release patterns from organic materials are, in part, determined by their chemical composition, or quality. Leguminous materials release nitrogen immediately, unless they contain high levels of lignin or polyphenols. Nonlegumes and litter of both legumes and nonlegumes generally immobilize N initially. There is little data on release patterns of other nutrients. Indices that predict nutrient release patterns will assist in the selection of species for synchronizing with crop demand and improve nutrient use-efficiency. Field trials with agroforestry species ranging in quality show that as much as 80% of the nutrients are released during the course of annual crop growth but less than 20% is captured by the crop, a low nutrient-use efficiency. There are insufficient data to determine how much of the N not captured by the crop is captured by the trees or is in the soil organic matter, the availability of that N to subsequent crops, or how much of that N is lost through leaching, volatilization or denitrification. Longer term trials are needed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00708916
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  • 7
    Electronic Resource
    Electronic Resource
    Decomposition and nitrogen release patterns of tree prunings and litter (1997)
    Springer
    Agroforestry systems 38 (1997), S. 77-97 
    Details
    ISSN: 1572-9680
    Keywords: polyphenols ; protein binding capacity ; resource quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Many studies have shown that agroforestry tree prunings can supply sufficient nutrients to meet crop demand, with the exception of phosphorus. The potential of these organic inputs to supply nutrients depends on their resource quality. Various indices have been developed to predict decomposition and nitrogen release patterns of tree prunings. To date the (lignin + polyphenol):N ratio seems to be the most robust ratio for predicting mass loss and nitrogen release. However, no critical value can be given because of the different methods used to analyze polyphenols. Suggested areas of future research include development of robust indices for predicting plant litter quality, decomposition patterns of belowground litter (roots), residual effects of tree biomass additions, and effects of adding mixtures of organic materials of contrasting quality. The overall challenge is to develop ways of managing organic matter decomposition to optimize short- and long-term release of nutrients and the maintenance of soil organic matter.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005978101429
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  • 8
    Electronic Resource
    Electronic Resource
    Crop-tree interactions in alley cropping systems on alluvial soils of the Upper Amazon Basin (1993)
    Springer
    Agroforestry systems 22 (1993), S. 67-82 
    Details
    ISSN: 1572-9680
    Keywords: alley cropping ; competition ; nutrient budgets ; weed control
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Resumen Un diseño de interfase cultivo/hilera de árboles se uso para ensayar tres especies leguminosas:Inga edulis, Leucaena leucocephala, y Erythrina sp. con el propósito de conocer su potencial para ser usadas en cultivos en callejones en suelos aluviales de la parte alta de la cuenca amazónica. Se aplicaron podas en 3 cantidades, 0. 3.3, y 6.7 Mg ha−1 por cultivo. El efecto de competencia, rendimiento del cultivo, balance de nutrientes y control de malezas fueron medidos durante tres cultivos consecutivos de arroz de altura. Reductiones en el rendimiento del cultivo fueron evidenctes hasta 1.5 m de distancia de las hileras de árboles, las reducciones fueron mayores con hileras deLeucaena eInga. Incrementos de las cantidades de podas aplicada fueron capaces de incrementar los rendimientos cerca de las hileras deLeuceana leucocephala yErythrina pero no deInga. En general los rendimientos de arroz fueron más altos con podas deLeucaena yErythrina en comparación con podas deInga, debido quizás a los niveles más altos de nitrógeno disponible proveído por las podas deLeucaena yErythrina, que son de más rápida descomposición. Para las 3 especies estudiadas en interfase, hubo una exportación neta de nutrientes con el grano y rastrojo de arroz que se observó en el declinar de los niveles de P en el suelo y en el declinar de los rendimientos.
    Notes: Abstract A crop/hedgerow interface design was used to test three leguminous species,Inga edulis, Leucaena leucocephala andErythrina sp., for their potential use for alley cropping on alluvial soils in the upper Amazon Basin. Prunings were applied as mulch at three rates 0, 3.3 and 6.7 Mg dry matter/ha/crop. Competition, crop yields, nutrient budgets, and weed control were monitored for three consecutive crops of upland rice. Crop yield reductions were evident up to 1.5 m from each of the hedgerow species, but were more pronounced withLeucaena hedgerows. Additional mulch was able to compensate for these reduced yields close to the hedges inLeucaena leucocephala andErythrina but not inInga edulis systems. In general rice yields were higher withLeucaena leucocephala andErythrina mulch as compared toInga mulch, perhaps because of higher levels of available N provided by the rapidly decomposing leaves ofLeucaena leucocephala andErythrina sp. as compared toInga. Weed control was greater, however, with the slowly decomposingInga mulch. For all three hedgerow/crop systems there was a net export of P from the system which was exhibited by declining soil P levels and decreasing crop yields.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00707472
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  • 9
    Electronic Resource
    Electronic Resource
    Ecosystem fertility and fallow function in the humid and subhumid tropics (1999)
    Springer
    Agroforestry systems 47 (1999), S. 163-196 
    Details
    ISSN: 1572-9680
    Keywords: biomass accumulation ; improved fallow ; managed fallow ; nutrient budgets ; nutrient cycling ; soil organic matter
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The regeneration of natural vegetation (fallowing) is a traditional practice for restoring fertility of agricultural land in many parts in the tropics. As a result of increasing human population and insufficient fertilizer inputs, the ecosystem fertility functions of traditional fallows must now be improved upon via the use of managed fallows. Interactions between vegetation and soil determine nutrient losses and gains in crop—fallow systems and are influenced by fallow species, patterns and rates of biomass allocation, and crop and fallow management. Nutrient losses occur through offtake in crop harvests during the cropping phase and through leaching, runoff, and erosion in the cropping phase and the initial stage of fallows $#x2014; when nutrient availability exceeds nutrient demand by vegetation. Gains in nutrient stocks in later stages of fallow are generally more rapid on soils with high than low base status due to greater quantities of weatherable minerals and lack of constraints to N2 fixation, deep rooting, and retrieval of subsoil nutrients by fallow vegetation. On low base status soils (exchangeable Ca 〈 1 cmolc kg−1), N2 fixation and atmospheric inputs are likely to be the main sources of nutrient additions. On high base status soils limited by N, gains in N stocks by inputs from N2 fixation and retrieval of subsoil nitrate can occur relatively rapidly; hence short-term fallows can often improve crop performance. Large losses of Ca associated with soil organic matter (SOM) mineralization and soil acidification during cropping and fallow establishment, combined with chemical barriers to root penetration, suggest that long-duration fallows (〉 5 yr) are needed for recovery of cation stocks and crop performance on low base status soils. On both soils, however, residual benefits of fallows on crop yields usually last less than three crops.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006215430432
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  • 10
    Electronic Resource
    Electronic Resource
    Nutrient stocks in managed and natural humid tropical fallows (1996)
    Springer
    Plant and soil 186 (1996), S. 293-309 
    Details
    ISSN: 1573-5036
    Keywords: Amazon ; humid tropics ; improved fallows ; managed fallows ; nutrient balances ; nutrient stocks ; tropical secondary forest
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Managed fallows which recover nutrients more rapidly than natural secondary vegetation may improve the performance of shifting agriculture systems operating under inadequately long fallow cycles. Our objective was to construct nutrient balances for the soil, vegetation, and litter compartments of six planted leguminous fallows and natural secondary vegetation during 53 months. The fallows were planted on a previously cultivated Ultisol (Acrisol) in the Peruvian Amazon and included:Centrosema macrocarpum (Centrosema),Pueraria phaseoloides (Pueraria),Stylosanthes guianensis (Stylosanthes),Desmodium ovalifolium (Desmodium),Cajanus cajan (Cajanus), andInga edulis (Inga). In addition, in the natural fallow treatment secondary vegetation was allowed to establish and grow naturally. Quantities of extractable P, K, Ca, and Mg, total N, and organic C in soil to a 45 cm depth, and macrouttrients in aboveground biomass, roots, and litter were estimated at fallow planting, at 8, 17, and 29 months afterward, and at fallow clearing (53 months). Total N stocks increased by 10% in the Stylosanthes, Desmodium, Pueraria, and Inga treatments, but changed little in the Cajanus, Centrosema and natural fallows. This difference was largely due to greater net increases in both soil and vegetation compartments in the former group of treatments. In the Inga, Desmodium, and natural fallows, total stocks of P and K at 53 months were about 40% to 80% greater and 12% greater, respectively, than initial values, but Ca and Mg stocks were reduced by 25% to 40%. In the other treatments, there was generally little change in P stocks, but large (30% to 60%) reductions in K, Ca, and Mg during the course of the fallow. Although there were net decreases of stocks of P, K, Ca, and Mg in soil in all treatments during the fallow, storage of P and K in vegetation and litter in the Inga, Desmodium, and natural fallows offset losses of these nutrients from soil. These treatments also tended to accumulate more Ca and Mg in biomass and litter than the other treatments. These results suggest that leguminous fallow vegetation that accumulates large amounts of biomass may increase N, P, and K stocks, but that incomplete recuperation of Ca and Mg may limit the sustainability of short-rotation fallow-based systems on acidic, infertile soils. ei]Section editor: G R Stewart
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02415525
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