How did the development of efficient agricultural practices, including the nile rivers fluding patterns, change egyptian work life ?

Every year in the Nile east of flood before dams were built. And when it did it flood it brought many things that were in the water light silt that were very nutritious for the soil, it brought it up to the surface and when it flooded it went on to the soil and then became very nutritious to the nearby Farms. but once dams were built to stop happening so people start using chemicals which started making their plants grow but slowly started killing the nutrients in the soil.