Nutrient use efficiency and biomass production of tree species for rotational woodlot systems in semi-arid Morogoro, Tanzania

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 À1 ) 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.

Nutrient dynamics through fine litterfall in three plantations in Sabah, Malaysia, in relation to nutrient supply to surface soil

“…The effects of Acacia plantations on soils have been investigated in many studies, especially recently. Some studies have reported positive effects on topsoil of N accumulation (Fisher 1995;BernhardReversat 1996;Majalap 1999;Garay et al 2004;Jang et al 2004;Xue et al 2005;Kimaro et al 2007;Macedo et al 2008;Kunhamu et al 2009) and/or N mineralization (Majalap 1999Li et al 2001;Kimaro et al 2007). Vitousek et al (2002) pointed out the importance of N 2 fixation as a source of N cycling in tropical ecosystems, and a large organic N flux through litterfall is likely to enhance N availability in tropical forest plantations.…”

“…Understanding of the effect of N 2 -fixing trees, particularly A. mangium, on soil conditions has recently improved (Fisher 1995;Bernhard-Reversat 1996;Majalap 1999;Li et al 2001;Garay et al 2004;Jang et al 2004;Xue et al 2005;Kimaro et al 2007;Abdu et al 2008;Macedo et al 2008;Yamashita et al 2008;Kunhamu et al 2009). Some studies have found more organic matter and N accumulation in soils of A. mangium stands than in those of non-legume tree stands.…”

Nitrogen and phosphorus retranslocation and N:P ratios of litterfall in three tropical plantations: luxurious N and efficient P use by Acacia mangium

“…Therefore, such efficient P cycling likely occurs at a field level and such differences in N and P cycling may be reflected in N:P ratios. We anticipated that plantation forests would exhibit different N:P ratios for each planted species as has been shown in natural tropical forests (Townsend et al 2007) because nutrient demands or N-and P-use efficiency differ among species (Kimaro et al 2007;). Litterfall of N 2 -fixers is expected to have higher N:P ratios; e.g.…”

Impact of Soil Fertility Replenishment Agroforestry Technology Adoption on the Livelihoods and Food Security of Smallholder Farmers in Central and Southern Malawi

“…The same study reported fuelwood production amounts of 1 MT ha ֿ◌¹ after a 2 year Gliricida/maize intercrop and 3.3 and 5.0 MT ha ֿ◌¹ after 3 years of Gliricida/maize/pigeon pea and Gliricidia/maize intercrop, respectively (Chirwa et al, 2003). A 5 year Gliricidia rotational woodlot in Tanzania was found to produce over 30 MT of woody biomass (Kimaro et al, 2007). Faidherbia albida and Leucaena leucocephala are two other SFR species planted in the southern Africa region that are managed for the dual purpose of soil fertility and woody biomass production (AFT, 2008).…”