الفهرس 
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Abstract
The aim of this study is to calibrate the DTPA soil test for extractable iron and manganese in the soils of Egypt. This calibration will result in establishing the critical levels of both nutrients to be used in the interpretation of the soil test results in soil laboratories.
Fourty nine soil samples were carefully selected to represent the magor types of soil of Egypt covering the ”old land” in the Nile valley and delta, as well as the ” new land” in the most important reclamation areas of Egypt. These soil samples were grouped in to three subgroups, namely, alluvial soils of the Nile valley and delta desert sandy non calcareous soils and calcareous soils.
The collected samples were analysed for relevant physical and chemical properties as well as their contents of DTPA – extractable iron and manganese. Pot experiment were carried out to study the response of corn plants to application of iron and manganese.
The three known approaches for calibration of soil test, i.e. yield response; nutrient up take and nutrient concentration, were used in this work for the evaluation of DTPA- soil test. The quartering method of cate and Nelson (1965, 1971) was used to determine the critical level of Fe and Mn.