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Cultivation of Tomato plants (Lycopersicon esculentum)
using Municipal
Solid Waste Compost
By: Abida Begum*
Tomato (Lycopersicon esculentum) is considered as one of the most
essential vegetable crops for human nutrition. The deficiency of plant nutrients
causes different changes in the physiological and biochemical processes within
the plant cell resulting in a reduction of growth, delay of development and
qualitative and quantitative decrease of yield, Heavy metal contamination of
soils has markedly increased in the past few decades. Many factors such
as metal-enriched parent materials, mining or industrial activities, non-point
sources of metals, especially automotive emission, and use of metal-enriched
materials, including chemical fertilizer, farm manures, sewage sludge, and
wastewater irrigation, can contribute to this contamination. Waste is a material
that is not needed and it’s economically unstable without further processing,
and it may be in the form of liquid, solid or gas. Waste added to soils
increases the percentage organic matter, the concentration of macro and
micro-nutrients and the activities of micro organism7. Town waste has
a high manurial value and it improves the growth of crops. The addition of urban
waste to soil improves the fertility by acting directly on its biological,
physical and chemical properties which in turn activate the microbial biomass,
improves soil structure, increase water holding capacity and aggregate
stability.
Composting of municipal solid waste (MSW) and its subsequent application to
agricultural land is gaining popularity because of environmental concerns
associated with the disposal of this material in landfills. Several studies have
shown that use of MSW compost in agriculture has many benefits to soil, crops
and environment. However, Heavy metal pollution of agricultural soils and crops
through the applications of MSW (Municipal Solid Waste) compost and sewage
sludge are of great concern. Although MSW compost provides nutrients for plant
growth, its continual use over extended periods can result in the accumulation
of heavy metals in soils and in the crops to levels that are detrimental to the
food chain .As a matter of fact, pollution problems may arise if toxic metals
are mobilized into the soil solution and are either taken up by plants or
transported in drainage waters. Risk for human health may then occur through
consumption of such crops and intake of contaminated waters. In the long term,
the use of MSW compost can also cause a significant accumulation of trace
metals in the soil and plants.
Thus, modifications of
biological properties caused by compost amendments may have an indirect effect
on physico-chemical conditions. Therefore, benefits of compost in relation to
soil restoration are substantial. Due to these positive effects, compost is
applied not only for the improvement of agricultural soils, but for the recovery
of disturbed soils as a consequence of pollution or fires or soils given to
suffer erosion. Nevertheless, since some aspects of the way in which this
positive influence is produced remain unclear, a better understanding of the
process, mainly from a biological point of view, is needed5.
Composting uses very little external energy and in urban areas, especially in
the rapid urbanizing cities of the developing world, problems and issues of
Municipal Solid Waste Management are of immediate importance. Land filling
disposal of wastes contributes flooding, breeding of insect and rodent vectors,
the spread of diseases and polluting ground water quality. Composting is the
simplest yet best process for solid waste management. Information on the heavy
metal loading potentials of MSW compost and its effects on the plants are
scarce.
A pot experiment was carried out in the greenhouse and tomato plants grown in
soil treated with MSW compost. The MSW compost was obtained from the Solid waste
composting plant, Bangalore. Compost was made from sugarcane bagasse, Municipal
solid waste and cattle manure in the proportions 75-0-25, 75-05-20, 75-10-15,
75-15-10 or 75-20-05 75-25-0 (i.e., composts with 0, 5,10,15,20 and 25% MSW)
were air-dried, mixed and sieved through a 2- mm-mesh sieve before filling to
pots. Pots were arranged in triplicate. Before transplanting the plants, all
treatments received supplemental fertilization at a rate of 50, 75, 100, 110 and
120 mg kg-1 of N, P and K, respectively. Pots were maintained around
field capacity by daily watering with distilled water. Leaf samples were taken
at flowering period.Tomato fruits reached maturation after 165 days of
transplanting. Total fruit yield per pot was recorded till the end of harvest.
Samples of root, stem, leaf and fruit samples of tomato plant were subjected to
digestion with HNO3, H2O2, and HCl and the
metal concentration was determined by AAS.
The heavy metal contents of untreated soil are well within the accepted normal
range of values. A comparison of metal contents of MSW compost with that of
untreated soil showed that the metals Cr, Cu, Ni, Pb and Cd were present in MSW
compost in greater concentrations than in the soil. Compared with metal limits
at the highest application of MSW compost (192g/pot), Zn, Cu, Ni and Pb contents
of tomato plant were found in high levels. Nevertheless, all metal
concentrations were below the phytotoxic maximum limits. The concentration of Cd
in the fruit tissues and leaves of tomato plant grown in control treatment was
small and below the detection limit of analytical apparatus. Although
concentration of total Zn, Cu, Ni and Pb in the highest MSW compost treatments
was particularly large and near to toxic level, there was no evidence that plant
growth was affected detrimentally. Roots and stem of tomato plant contained
higher metal concentrations than that of leaf and fruit tissues. This is
important because of edible fraction of plant.
The tomato crop responds very well to manurial and fertilizer application. The
exact requirement of manurial and fertilizers would depend on the fertility
status of the soil in which the crop is being taken. The study revealed that the
use of Municipal solid waste up to 25% during tomato harvest maintains the heavy
metal concentration under permissible limits. The research is being continued
further for upper limit of MSW rates.
* PES School of
engineering, Bangalore
E-Mail: [email protected] |
