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Vol. 16 No. 2 - April 2010

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 itís 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]

This article has been reproduced from the archives of EnviroNews - Newsletter of ISEB India.

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