The researchers studied different ways of tilling soil and how they affect its physical properties in Northern Sudan. They tested five tillage methods and two irrigation levels over two summers. They found that disc plowing and chisel plowing were the most effective methods. The soil was hardest to penetrate after using a disc harrow. The soil was less dense after conventional tillage compared to minimum tillage. Overall, disc plowing had the lowest bulk density at a depth of 0-15 cm.