Modelling of soil nutrient budgets: an assessment of agricultural sustainability in Nepal |
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| Authors: | S Brown H Schreier PB Shah LM Lavkulich |
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| Institution: | Institute for Resources and Environment, University of British Columbia, 436E-2206 East Mall, Vancouver, Canada. Fax: 011-604-822-9250.;International Centre for Integrated Mountain Development, P.O. Box 3226, Kathmandu, Nepal. |
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| Abstract: | Abstract. Sustaining soil fertility under agricultural intensification and expansion onto marginal lands is a significant challenge in the Nepalese Middle Mountains. In a detailed watershed study it was shown that the overall soil fertility is poor, forest soils display the poorest conditions as a result of biomass removal, and sustaining agriculture is questionable due to the transformation from traditional to multiple cropping systems. Parent material is a significant factor influencing low phosphorus status while insufficient inputs create deficiencies in total carbon, nitrogen and bases. A nutrient budget model was developed to assess inputs, redistribution and losses relative to soil fertility. Yield, input and management data obtained from farm interviews, and soil analysis data were used in the calculation of nutrient budgets. Results from modelling indicate declining soil fertility under rainfed agriculture, forest and rangelands, and marginal conditions under irrigated agriculture subject to intensive cultivation. Nutrient deficits were relatively low for irrigated rice-wheat systems, which benefit from nutrient inputs via sediments and irrigation waters, but the introduction of triple cropping showed greater deficits. Nutrient balances were most critical under rainfed maize production where 94% of the farms were in deficit. Current shortages of organic matter make elimination of nutrient deficits problematic but improvement of composting, biological N-fixation and fertilizer efficiency and reducing erosion were found to be potential options. |
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| Keywords: | Soil fertility nutrient balance soils models sustainability agriculture land management Nepal |
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