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- Nakagawa, K., et al.
(författare)
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Modelling reactive solute transport from groundwater to soil surface under evaporation
- 2010
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Ingår i: Hydrological Processes. - : Wiley. - 1099-1085 .- 0885-6087. ; 24:5, s. 608-617
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Tidskriftsartikel (refereegranskat)abstract
- Two-stage soil column experiments involving capillary rise and evaporation were conducted to improve understanding of salt and water movement from groundwater to soil surface. In total, 64 soil columns were placed in a tank partly filled with water in order to mimic the groundwater table in soil. Each soil column was analysed by dividing it into 27 segments to analyse pore water and ion distribution in both liquid and solid phases after prescribed time periods. The water and solute transport behaviour in the columns was simulated by a one-dimensional numerical model. The model considers the cation exchange of four cations (Ca2+, Mg2+, Na+ and K+) in both dissolved and exchangeable forms and anion retardation for one anion (SO42-). The Cl- is treated as a conservative solute without retardation. The numerical results of the cation distributions in both liquid and solid phases, anions in the liquid phase, and volumetric water contents were in relatively good agreement with the experimental results. To achieve a better model fit to these experimental results, a variable cation exchange capacity (CEC) distribution may be required. When a simple calculation scheme for evaporation intensity was applied, better predictions in terms of daily variation were achieved. The soil water profile displayed a steady state behaviour approximately 10 days after the start of the experiments. This was in agreement with numerical results and calculated distribution of velocity vectors. The final model includes cation exchange, anion retardation, and unsaturated water flow. Consequently, the model can be applied to study sequential irrigation effects on salt accumulation or reactive transport during major ion concentration changes in groundwater. Copyright (C) 2009 John Wiley & Sons, Ltd.
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| 2. |
- Karltun, Erik
(författare)
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COMPARING FARMERS' PERCEPTION OF SOIL FERTILITY CHANGE WITH SOIL PROPERTIES AND CROP PERFORMANCE IN BESEKU, ETHIOPIA
- 2013
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Ingår i: Land Degradation and Development. - : Wiley. - 1085-3278 .- 1099-145X. ; 24, s. 228-235
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Tidskriftsartikel (refereegranskat)abstract
- Farmers' perceptions of soil fertility change were compared with observations on soil quality changes and crop performance in soils from a chronosequence representing a range of soil ages since conversion from forest to cropland (0 to 57years). A majority of the farmers, 92 per cent, had observed a decline in soil fertility on their land. Farmers use crop yield, indicator plants, soil softness and soil colour to judge soil fertility. They identified 11 plants that they used to indicate high soil fertility and four plants that they used to indicate low soil fertility. There was a strong correlation (r=0 center dot 96) between soil organic matter content (loss on ignition) and farmers' ranking of soil fertility based on colour and softness of soil samples from the chronosequence. The biotest experiment with maize showed an exponential decline in biomass production along the chronosequence, confirming the results of farmers' soil fertility ranking. In the biotest, total soil N predicted produced biomass well (r2=0 center dot 95), whereas the relationship with soil available P (Olsen) was less obvious. Among the eight analysed plant nutrients in the maize leaves, N content was found to correlate best with biomass production (r2=0 center dot 94). We conclude (i) that there is good agreement between farmers' knowledge and scientific indicators of soil fertility and (ii) that the major reason for declining soil fertility in Beseku is the decrease in N mineralization over time. Interventions should focus on supporting farmers to implement a diversified nutrient management strategy that can maintain or increase long-term productivity of the soil. Copyright (c) 2011 John Wiley & Sons, Ltd.
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