College of Agricultural Sciences and Fisheries Technology

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Browsing College of Agricultural Sciences and Fisheries Technology by Author "Ahimana, Celestin"

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    Biomass, volume and nutrient content assessment in three-year old eucalyptus melliodora unweeded, clean-weeded and intercropped with beans, sorghum and maize in Morogoro area, Tanzania
    (University of Dar es Salaam, 1982) Ahimana, Celestin
    In February, 1978, an agroforestry experiment was established at Mafiga, a semi-arid area, in Morogoro Region, Tanzania (37º38' E and 6º49' S). The experiment was a 5 x 5 Latin square in which Eucalyptus melliodora was grown unweeded, clean-weeded and intercropped with beans, sorghum and maize at 2.5 m x 2.5 m espacement. In February, 1981, at the age of three years, the stands were clearfelled and the above crops were grown amongst the coppice. At the time of clearfeelling, the opportunity to assess the volume and biomass of felled treel was taken. The biomass of litter, undergrowth and fallen branches was also assessed. Soil samples were taken for assessment of the nutrient store. Calcium, nitrogen, magnesium, phosphorus, potassium and sodium concentrations and contents in various tree components and liter were determined. Loss of nitrogen by burning was also ascertained. The new bean, sorghum and maize crops were also assessed for biomass and nutrient content when they were harvested in June 1981. Tree and stand volume was estimated using the summation of volumes of equal tree sections and the stand volume also assessed-using the formula V = g x H and by Kio's and Satoo's methods. Above and below-ground tree component biomass was determined by destructive sampling. The allometric regression model in {tree component, kg) = a + a (In dbh, cm) was used to estimate the dry weight of individual trees in the plots. Unweeded trees had the lowest survival rate {53%), volume {8.57 m3 ha-1) and biomass {6,0 t ha-1) , There was no significant difference between clean-weeded trees and those intercropped with beans either in volume or biomass production (respectively 37.41 m3 ha-1 and 37.82 m3 ha-1 and 31.0 t ha-1 and 30.0 t ha-1). Intercropping sorghum and maize significantly (P < 0.05) reduced the tree volume and biomass production (respectively 26.02 m 3 ha-1. and 24.80 m3 ha-1 and 21. 8 t ha-1 and 21 . 0 t ha-1 ). Yields of food crops were as follows: beans, 14'7 kg ha-1; maize, 500 kg ha-1; sorghum, 180 kg ha-1. Beans, sorghum and maize residues had an oiomass of 0.3, 1.7, and 2.2 t ha-1 respectively. The wood yield hectare for planted with beans is sufficient to provide enough fuel for a family of five for a period of at least six years. By removal of stem (overbark) and branches considerable amounts of nutrients are drained from the site, however by leaving the branches and bark on the site, the nutrient drain is insignificant. Nitrogen loss by buring varied from 41% to 91% of the original concentration. Very small amounts to nutrients are lost in food crop harvesting. Techinically, intercropping the above agricultural crops has been found feasible. However, while the espacement of 2.5 m x 2.5 m in this experiment favours tree growth, wider espacements would provide better food crop growth. More reseach is needed to find precisely which tree espacements will give the optimum balance between food crop and wood yields under any specified set of environmental conditions.