Effects of Previous Rice Cropping History on Salt Accumulation of Surface Soils in the Middle Nile Delta, Egypt

Agriculture in Egypt mostly depends on crop production in the Nile Delta, but problems of salinization in the surface soil become obvious due to development of Aswan High dam and irrigation agriculture. In this situation, rice cultivation is considered as a salt leaching method because it uses larger amounts of water than field crops. The present study was conducted to investigate the effects of previous rice cropping history on salt accumulation of surface soils on 15 farms in the middle Nile Delta. These surface soil samples were collected from the Agriculture Research Center (ARC) near Sakha and 14 private farms near ARC, and categorized by the record of previous rice cropping history. In addition, farmers were asked about the field conditions, such as fertilization and subsurface drainage. Irrigation water was also sampled in each area. As results of soil analysis, there were little differences in pH, total carbon (T-C), total nitrogen (T-N), and cation exchange capacity (CEC) of the soil samples, showing the basic properties of soils were similar. However, exchangeable bases showed some differences, and electrical conductivity (EC) and exchangeable Na＋ revealed correlations, but these differences were not related to previous rice cropping history. Ion concentrations in irrigation water were also different among areas. Based on statistical results, there were significant differences in salt accumulation of surface soils depending on area and especially in the conditions of subsurface drainage. However, previous rice cropping was seen to have had little effect on salt accumulation in the surface soils. These results show that other factors, such as subsurface drainage conditions or quality of irrigation water, affect soil salinity in these study sites rather than rice cultivation.