Biomass, volume and nutrient accumulation by six-year old acacia albi da under agroforestry at Mafiga, Morogoro, Tanzania
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Date
1988
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Sokoine University of Agriculture
Abstract
The study was conducted to evaluate the suitability of Acacia al bi da for fuelwood
and environment fodder at production using Mafiga, Morogoro. agroforestry
in a semi-humid The trial was planted in February, 1980 and arranged in a split - plot design with three main plots:
1)Acacia intercropped with maize, 2)Acacia intercropped with beans, and
3)Acacia monoculture cleanweeded. Each mainplotincluded at4 x4 m, planted four tree
5 x spacing subplots, no trees, trees
5 m and 6 x 6 m.
The experiment had four
replications covering an area of 4.32 ha.
In March 1986, thirty trees representing all the diameter classes in the
trial
content.
root
harvested and used to determine volume, biomass and nutrient
were
addition,
In
di stribution,
biomass
collected
sampleswere
macronutrients.
eight root systems were excavated to determine
and
nutrient
content.
Seventy-two soil
from the different treatments and analysed for
Data on height, diameter growth and food crop yields
(maize and beans) for the past six years was compiled from past records.
At
the
age of
the whole
neither
six years, the mean height and DBH for Acacia al bi da in
trial was 8.41 m and 10.7 cm respectively.
affected
Height growth was
by intercropping nor tree spacing, but.diameter growth
was affected by tree spacing. Volumeproduction varied from 9.9 to
valuesranged
19.6 to 43.1
from
24.9 m3 ha 1 and total biomass
tons
ha'1 .
Intercropping did not
(p < 0.05) influence the production of volume and biomass.
significantly
significantly
Spacing,however,
biomassproduction with
(p
<
0.05) influenced both volume and
higher volume and biomass under lower spacing
and the lowest volume and biomass under the highest spacing.
Nutrient concentrations were high and comparable to other tree legumes.
Generally,nutrient
brushwood,and
least
concentrations were highest
in
the
foliage and
in the stem, with concentrations in the roots and
branches being intermediate.
for
Except
the nutrient
N,
and
brushwood
roots,
The
Thenutrient
accumulation
(4 x 4 m) in Kg ha
spacing
57.6,
with the
Mg
and
were highest in the stem,
least amounts found in the foliage and
highest inventory of N was concentrated in the foliage.
branches.
total
accumulations
73.8,
Na.
in
the aerial biomass at the closest
were 262.9, N; 39.4 P; 156.7, K; 97.4, Ca;
Corresponding values
for the below ground
. -1
biomass were 85.0; 8.1; 54.3; 23.5; 18.1; and 8.1 Kg ha
.
Althoughthere were trends of increasing nutrients under the trees the
presenceof Acacia trees
did not significantly influence the nutrient
status of the soil.
Food
to
-1
crop yields varied from 143.2 to 409.7 Kg ha for beans and 343.8
956.0
Kg
ha-l
for
maize.
The yield of the food crops were not
Description
A dissertation submitted in partial fulfilment of the requirements for the degree of master of science in forestry
Keywords
Biomass, Acacia albi da, Agroforestry, Nutrient accumulation, Mafiga, Morogoro, Tanzania