Saturday, 15 July 2006

Plant Growth in a Chromium Contaminated Site Affected by Different Fertilizers.

Farideh Karbasi, Bu- Ali Sina Univ, Hamadan, Iran

Dispersion of dust in dry weather of bare chromium contaminated soils can cause high chromium dust problems in dry weather, which is toxic and carcinogenic. Contaminated land represents a potential hazard to health or the environment as a result of current or previous misuse. There is increasing concern about our natural environment and the need to protect it for the benefit of future generations. A poorly vegetated soil in a former industrial site raised concern about the safety of residential area and their people around the site and lead to this research. There was necessitated a remedial action in order to render the site safe. Amongst the different suggestions to overcome the problem, cheaper solution was breaking the link between source of the contamination and the target. Vegetation cover can reduce the dust in dry weather and also reduce the runoff water. Trees and bushes also can discourage access to the area. The establishment and maintenance of vegetation as a part of the reconstruction of a contaminated or industrial land involves generation of functioning soil ecosystem containing adequate amounts of major nutrients. Three soil samples from 0-15 cm depth from three sampling points (one flat, one sloped and one at the base of the slope) were taken. The profiles were contaminated with chromium and contained calcium carbonate waste materials at different depths. Primary analysis such as pH, available nutrients, total and available chromium were carried out on the two mm sieved soils. The effects of fertilizer additions were evaluated in two pot experiment studies of these soils using ryegrass as a test crop. The first pot experiment was carried out to look at the response of the soil samples at different combinations of N, P and K fertilizers to determine which fertilizer is limiting the plant growth. The response was measured by dry matter production. Nitrogen was shown to be the limiting factor for growth of the grass in these soils. Alleviating the limiting factor can result in a yield increase. Since the trend of this increase can not be fully applied to all types of soils and spoils due to differences in nature of the material, a second pot experiment was carried out to look at the response of the vegetation to addition of the different rates of nitrogen fertilizer. The results showed that the application of 100 /50 /50 of N/P/K kg/ha fertilizer could obtain the higher yield for some soils and lesser for some others. In this paper the correlation of yield with chromium content and other factors of the soils are discussed.

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