Nutrient use efficiency and biomass production of tree species for rotational woodlot systems in semi-arid Morogoro,Tanzania |
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Authors: | Anthony A Kimaro Vic R Timmer Ancelm G Mugasha Shaban A O Chamshama Deborah A Kimaro |
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Institution: | (1) Faculty of Forestry, University of Toronto, 33 Willcocks Street, Toronto, ON, Canada, M5S 3B3;(2) Faculty of Forestry and Nature Conservation, Department of Forest Biology, Sokoine University of Agriculture, P.O. Box 3010, Morogoro, Tanzania;(3) Centre for Sustainable Rural Development, Sokoine University of Agriculture, P.O. Box 3035, Morogoro, Tanzania |
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Abstract: | Frequent nutrient removals accompanying wood and crop harvests from rotational woodlot systems may contribute to declining
site productivity and sustainability because of soil nutrient depletion. However, selecting for nutrient-efficient tree species
may well sustain productivity under this system. To test this hypothesis, a randomized complete block experiment was adopted
to assess effects of five tree species on soil nutrients status, nutrient use efficiency and wood yield in semi-arid Tanzania.
After 5 years rotation, top soils under Gliricidia sepium (Jaqua), Acacia polyacantha Willd. and Acacia mangium Willd. were the most fertile with soil organic carbon and exchangeable cation status raised close to those in natural Miombo
systems. Soil inorganic N and extractable P levels reached sufficiency levels for subsequent maize culture. Wood productivity
in tree fallows averaged three times higher than that of Miombo woodlands indicating the high potential of the woodlot system
to supply fuelwood, and consequently relieve harvesting pressures on the natural forests. Acacia crassicarpa A. Cunn. ex Benth. produced the most wood (51 Mg ha−1) at low nutrient “costs” presumably due to high nutrient use efficiency. Wood yield of this species was 42 and 120% greater
than that of A. polyacantha and A. nilotica, respectively, but contained comparatively less nutrients (42–60% less for P, K, and Ca). Gliricidia sepium and A. polyacantha returned the largest amount of nutrients through slash at harvests. Of all test species, A. crassicarpa exhibited the most promise to sustain wood production under rotational woodlot systems due to relatively high productivity
and low nutrient export at harvest. |
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Keywords: | Acacia Fuelwood Nutrient use efficiency Soil fertility Sustainability |
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