الفهرس 
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Abstract
This work aims to study the effect of both individual and combined effects of two organic acids (humic and oxalic acids) applied at different rates and salinity levels of irrigation water under different moisture content of field capacity on some chemical properties of two calcareous soils varied in their content of calcium carbonate and natural carbonate mineral (calcite).This work includes two laboratory experiments. The first experiment was carried out on two calcareous soils which were selected from surface layer (0 – 30 cm) of El-Nobariya - Behara Governorate (soil 1) and Borg El-Arab - Alexandria Governorate (soil 2). The second experiment was carried out on natural calcite mineral which collected from Sammallout Quarry, Minia Governorate. The main properties of the two calcareous soils and calcite were bdetermined. This work used two organic acids i.e. humic acid in this study was isolated and purified from potassium humate for Humintech® Company in Spain and oxalic acids (COOH)2.2H2O). Three types of irrigation water were used in this study. These waters were tap water (W1), mixed water consists of tap water and sea water at a ratio of 1:1 (W2) and sea water (W3). These three waters were varied in their salinity level.