What kind of soil did the Nile floods deposit on Egyptian farmland?

The Nile floods historically deposited silt on Egyptian farmland, which constitutes the highly fertile soil found in the Nile valley and the delta region.12

This silt is carried down from the Ethiopian Highlands by the river's upper tributary system, specifically the Blue Nile and the Atbara rivers. While this deposit is generally very fertile, the composition of the soil can vary:1

• Texture and Composition: The soil often has a high clay content, which can make it difficult to work. Toward the edges of cultivated areas, the soil tends to be more sandy.1
• Variations: In some regions, concentrations of sodium carbonate can create infertile black-alkali soils, and in the northern delta, salinization has resulted in sterile regions known as barārī (barren).1

Before the completion of the Aswan High Dam in 1970, these annual inundations were essential for maintaining the fertility and prosperity of the land, effectively defining the agricultural seasons of the Egyptian year.3