ROLE OF CHELATES ON THE AVAILABILITY OF SOME MACRO-AND MICRONUTRIENTS

Abstract

The chelating agents, natural as humic acid and synthetic as EDDHA used to increase the solubility of metal ion in soil such as phosphorus, as macronutrients and Cu, Zn and Mn, as a micronutrients. Increasing solubility and mobility of chelated metals have a major effect on many aspects of soil chemistry and fertility. The movement and availability of these metals to plant roots may be enhanced and remaind a major objective of application for different nutrient metal chelates to soils.

Some problems associated with the application of chelated micronutrients to the soil are the effect of pH, CaC03 and presence of other metal ions in the soil. So that, most of the studies on the use of chelates have been confined to calcareous, and alluvial soils. The chelates led to lowering the pH values and consequently increased the availability of micronutrients such as Cu, Zn and Mn. It can also increase soluble phosphorus from insoluble sources (minerals) such as rock phosphate and basic slag. Stability constants have an important role in chelatirrg reactions with micronutrient cations and thus their mobility in soil. This activity can help in predicting the availability of such cations in the soil-plant ecosystem.

Therefore, the objectives of this investigation are to study the following points:

1- Effect of the chelating agents HA and EDDHA on the extractable P, Zn and Cu in two different soils (alluvial- calcareous). Factors affecting their activities, i.e., concentration of metal ion, pH and shaking time, were also assessed.