Investigating into the effect of ph on the availability of trace elements in soil

Abstract

The hydrogen ion concentration (pH) changes in soil can be very important in determining the yield of plants. Linear relationships have been found between the soil- and the plant-avai lable trace elements. Induced ion-chlorosi s has been associated with excess (toxic) levels of cobalt and copper in soils and consequently in plants. "Bronz inq" disease in rice has been associated with high iron levels while both an excess and deficiency of molybdenum and zinc lead to stunted plant growth. Manganese disorder leads to necrosis of young leaves and stunted root growth. To observe the effect of pH on the availability of these trace elements in soil, liming and acidification of both the acidic and the basic soils respectively were done. The available contents were then obtained after pH analyses, extraction using O.lM HCI, complexation using both APDC (pH 2) and NaDDTc (pH 6) and irradiating following the EDXRF analysis technique. Total contents of the elements 'In different soils were obtained by pelletilization. Two binding agents (PVP and starch) were tried out and compared for the low organicmatter soils. While no obvious relationships were observed between the total and available contents of these elements, the available ., contents changed, though not linearly with the pH variation. Thus one can predict and pick out the pH at which a higher or lower elemental concentration may be obtained as desired hence a way of varying its amounts in soils and plants. PVP was found to be a good substitute for starch while making pellets of very dry, low organic-matter soils (eg. sands) . EDXRF technique was found to be a fast, precise and accurate method of soil analysis.