Agronomic evaluation of some industrial wastes as alternative sources of plant nutrients in Morogoro District, Tanzania
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Date
2001
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Publisher
Sokoine University of Agriculture
Abstract
A study’ was conducted at Magadu. Morogoro. Tanzania to evaluate the industrial wastes
as alternative sources of plant nutrients and/or soil conditioners. The soil of Magadu was
classified by Kaaya (1989) as Oxic Haplustult. The soil was characterised in this study
for its physical and chemical properties prior to planting of the test crop. The analytical
data showed that the soil was strongly acidic with a pH of 5.1. Total N. available P.
%OC, exchangeable Ca and Na. CEC. and DTPA extractable Zn were in the low range.
Exchangeable Mg was in the medium range, while exchangeable K. DTPA extractable
Fe, Mn and Cu were high. In the field a randomised complete block design was used to evaluate the wastes using maize as test crop. The rate of waste application were
5.24 4.8, 4.25, 4.5 and 3.7 tonnes/ha of waste tea, wattle bark chippings, waste tobacco, wood
ash and saw dust respectively. Prior to soil incorporation, the wastes were analysed for
their chemical properties. Maize dry matter yields were significantly higher in plots
which received 5.24 tonnes/ha of waste tea followed by plots which received 4.25 and
4.5 tonnes/ha of waste tobacco and wood ash respectively. Maize grain yields were
significantly higher in waste tea and wattle bark chippings amended plots than in the
other waste amended plots. At the end of the growing season the soil was analysed to
evaluate the residual effect of wastes on soil properties. Soil pH, available water
capacity, available P, % OC, total N, exchangeable bases, CEC, DTPA extractable Zn
and Cu in waste amended plots increased in the top 15 cm of soil relative to the control
plots. DTPA extractable Fe and Mn, exchangeable Al and acidity were significantly
reduced in all waste treatments. Total N and % OC in wood ash and saw dust amended plots were at par with those found in control plots. The results from the field suggested
that when applied at agronomic rates, industrial wastes can produce satisfactory plant
growth and yields. The results revealed further that waste application on a long term
basis will allow good build up of soil organic matter and plant nutrients which in turn
will improve on soil productivity. It is recommended that N supplement to wood ash
which is rich in almost all macro and micronutrients (except N) would balance its
nutrient supply to plants. A glasshouse decomposition experiment was carried out with
some wastes including sawdust and wattle bark chippings in perforated plastic litter
bags. The wastes were either surface applied or buried to 10 cm depth in wooden
troughs. The decomposition process which was monitored at 0. 3, 6, 9, and 12 weeks of
incubation revealed that soil incorporated wastes decomposed and released nutrients
faster than surface applied ones.
Description
A dissertation submitted in partial fulfilment of the requirement for the degree of master of science in soil science and land management
Keywords
Industrial wastes, Agronomic evaluation, Llternative sources, plant nutrients, Morogoro District, Tanzania