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| 2. |
- Kätterer, Thomas, et al.
(författare)
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Carbon loss from Brachystegia spiciformis leaf litter in the sandy soils of southern Mozambique
- 2009
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Ingår i: Nutrient cycling in agroecosystems. - : Springer Science and Business Media LLC. - 1385-1314 .- 1573-0867. ; 83, s. 13-26
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Tidskriftsartikel (refereegranskat)abstract
- Leaves of Brachystegia spiciformis represent a substantial fraction of the total aboveground litter in bush fallow fields with sandy soils in southern Mozambique, where annual rainfall exceeds 600 mm. This species is one of the most important in the miombo woodland that is the natural vegetation of the region. Proper knowledge of the decomposition of its litter is therefore crucial for understanding processes responsible for natural build-up of fertility in agricultural soils abandoned to bush fallow during shifting cultivation. This study investigated the effects of soil water content and soil temperature on loss of organic carbon (C) from decomposing leaves in litterbags with 1 mm mesh size. The litterbags were buried 50 mm deep in recently abandoned agricultural fields cleared of any vegetation (Bare) and in more than 15-year-old bush fallow fields (Fallow) of sites covering a climatic transect with annual rainfall from <400 mm to >1,000 mm. Two patterns of C loss were observed, one in coastal and wetter agroecosystems (rainfall >600 mm) and the other in inland and drier agroecosystems (rainfall <600 mm). In the wetter agroecosystems C loss was faster, whereas in drier agroecosystems it was more sensitive to rainfall pulses. Similarly, C loss was faster in fallow fields than in bare fields. During summer, bare fields reached soil temperatures higher than the estimated upper boundary favourable for C loss from decomposing leaf litter at all sites. A simple dynamic decomposition model describing the C fraction remaining in the litterbags was developed. Coefficients of determination (R 2) for the individual experimental units varied between 0.79 and 0.97. The general model for all sites and fields improved explanation of total variation from 81% to 86% when measured soil temperature and soil water content were used as modifiers of decomposition rate, compared with the standard negative exponential model. Root-mean-square error and systematic bias were 9.7% and 0.5% of initial C, respectively. Decomposition was more strongly affected by soil water content than by soil temperature and explained 75% of total variation. Thus, rainfall is the main driver of C loss from leaf litter in these agroecosystems.
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| 3. |
- Ledin, Stig, et al.
(författare)
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Effectiveness of crop-waste compost on a Eutric Ferralsol
- 2011
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Ingår i: Journal of Plant Nutrition and Soil Science. - : Wiley. - 1436-8730 .- 1522-2624. ; 174, s. 430-436
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Tidskriftsartikel (refereegranskat)abstract
- Lack of environmentally safe handling of garbage is a growing problem in urban sub-Saharan Africa (SSA). Composting the garbage for soil-fertility management presents an opportunity for reducing the risks of environmental pollution. This study aimed at evaluating the agronomic effectiveness and nutrient-utilization efficiency of urban market crop-waste compost on a Eutric Ferralsol. The study was conducted in central Uganda with treatments including compost applied at 0, 5, and 10 t ha(-1) (d. w. basis); inorganic N fertilizer at rates of 0, 40, and 80 kg ha(-1) and inorganic P fertilizer at 0, 9, and 18 kg ha(-1). Maize (Zea mays L.), variety Longe 4 was used as the test crop. The nutrient quality of the compost was medium with total N of 0.9% and total P of 0.45%. Compost significantly increased plant height, LAI, stover weight, and grain yield; however, there were no significant differences between the 5 and 10 t ha(-1) rates. Nitrogen also had a significant effect on LAI and stover yield, though there was no significant difference between the 40 and 80 kg ha(-1) rates. Likewise, P increased plant height with no significant difference between the 9 and 18 kg ha(-1) rates. Mineral N at 40 kg ha(-1) led to the highest increase in N uptake by plants (76%) above the control. Nitrogen-and P-utilization efficiencies for the 5 t ha(-1) compost rate were more than twice that of the 10 t ha(-1) rate. The highest P-utilization efficiency (69%) was obtained where 9 kg ha(-1) P was applied with 40 kg ha(-1) N, while the highest N-utilization efficiency (48%) was obtained with the 5 t ha(-1) compost applied together with N at 40 kg ha(-1). From the above studies, it is clear that effectiveness of the 5 t ha(-1) compost rate is the most promising.
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| 4. |
- Ledin, Stig
(författare)
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Organic matter recovery in sandy soils under bush fallow in southern Mozambique
- 2009
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Ingår i: Nutrient cycling in agroecosystems. - : Springer Science and Business Media LLC. - 1385-1314 .- 1573-0867. ; 83, s. 153-161
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Tidskriftsartikel (refereegranskat)abstract
- Bush fallow under shifting cultivation is commonly practised by subsistence farmers in southern Mozambique. This farming system is likely to persist due to the existence of large sparsely inhabited areas, coupled with financial limitations preventing smallholders from buying fertilisers. The bush fallow is intended to naturally restore soil production capacity lost during the cropping period. This study quantified soil organic matter (OM) content and investigated factors determining its dynamics in sandy soils under varying duration of bush fallow in southern Mozambique. Agroecosystems representing rainfall regions of < 400, 400-600, 600-800, 800-1,000, > 1,000 mm and a transitional agroecosystem of 400-800 mm were selected. Within each agroecosystem, five land uses (virgin, cultivated, < 5 years fallow, 5-15 years fallow and > 15 years fallow) were identified and compared for three shallow soil layers (0-50, 50-100 and 100-200 mm). Organic C and total N were used as indicators of soil OM and the study examined whether OM content increased with higher rainfall or longer bush fallow. Higher rainfall did not consistently increase soil OM content, which was highest in the wettest agroecosystem but did not decline gradually towards the driest. For example, the lowest OM content was found in the second wettest agroecosystem (800-1,000 mm rainfall). Duration of bush fallow was also inconsistent, as OM content continued to decrease for some time after cultivated land was abandoned to bush fallow and an increase in OM content occurred sooner in wetter agroecosystems than drier at a 600 mm rainfall threshold. After 15 years of bush fallow, OM content was still lower than in the virgin land of the agroecosystems. Relative to virgin land, both the loss and gain of OM were smaller in the drier agroecosystems. Further studies are needed to establish optimum bush fallow periods for full recovery of soil OM in southern Mozambique.
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| 6. |
- Stjernman Forsberg, Lovisa, et al.
(författare)
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Effects of sewage sludge on solution chemistry and plant uptake of Cu in sulphide mine tailings at different weathering stages
- 2009
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Ingår i: Applied Geochemistry. - : Elsevier BV. - 0883-2927 .- 1872-9134. ; 24:3, s. 475-482
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Tidskriftsartikel (refereegranskat)abstract
- This climate chamber experiment examines the effects of sewage sludge (SS) on sulphide mine tailings from the Aitik Cu mine in northern Sweden. The effects of SS were determined from Cu in solution and Cu uptake and growth of plants on tailings showing 3 different degrees of weathering. Possible relationships between Cu content in plants and Cu in solution measured in tailings (total dissolved Cu and free Cu) were also evaluated. Red fescue (Festuca rubra) was grown for 6 weeks in pots of the different tailings treated with SS or NPK fertiliser. Soil solution was sampled with Rhizon tension lysimeters and analysed for pH, dissolved organic C (DOC), free Cu, total dissolved Cu and SO42-. The effects of SS on Cu in solution and plants depended on the degree of weathering. In tailings with a low degree of sulphide oxidation, SS application resulted in increased solubility and shoot accumulation of Cu compared with NPK-treated tailings, probably due to DOC forming soluble complexes with Cu. Sewage sludge also seemed to promote translocation of Cu to shoots in those tailings. In highly weathered tailings, lower contents of total dissolved Cu and free Cu in solution and lower Cu levels in shoots were found in SS-treated samples than in NPK-treated. In the moderately weathered tailings, Cu concentrations in solutions were generally similar between treatments, but lower contents of Cu were found in shoots and roots of the fescue grown in the SS-treatment. Irrespective of degree of weathering and treatment, both free Cu and total dissolved Cu concentration in tailings correlated strongly with Cu levels found in fescue shoots.
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| 7. |
- Stjernman Forsberg, Lovisa, et al.
(författare)
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Leaching of metals from oxidising sulphide mine tailings with and without sewage sludge application
- 2008
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Ingår i: Water, Air and Soil Pollution. - : Springer Science and Business Media LLC. - 0049-6979 .- 1573-2932. ; 194:1-4, s. 331-341
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Tidskriftsartikel (refereegranskat)abstract
- A 20-month column experiment investigated leaching of Al, Cu, Mn, Ni, Zn, Cd and Pb during sulphide oxidation in mine tailings with and without sewage sludge (SS) amendment. Leachate pH decreased gradually in all columns during the experiment, irrespective of treatment, due to sulphide oxidation. As the degree of sulphide oxidation, and thus the pH trajectory, differed between replicates (n=3), running data for each column used are reported separately and the relationships between sulphide oxidation, metal leaching and treatment in each column compared. Mean pH in the columns correlated negatively with total amounts of leached SO4 (2-). In the beginning of the experiment the leachate concentrations of Al, Cu, Zn, Ni and Pb were higher in SS-treated columns due to high initial concentrations of dissolved organic carbon. As leaching proceeded, however, the amounts of Al, Cu, Mn and Ni leached from the columns were closely related to the degree of sulphide oxidation in each column, i.e. to its mean pH. There were no statistically significant differences between treatments regarding the total amounts of metals leached and thus addition of sewage sludge to the tailings appeared to play a minor role for metal leaching patterns. Peak concentrations of Al and Cu in the leachate from untreated tailings and of Zn in the leachate from both untreated and SS-treated tailings at pH 4 exceeded national background values for groundwater.
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