This measure involves the management of the soil surface by the retention of excess crop residues or the addition of residues or other additives to control the amount and rate of water evaporation. The practice applies to cropland where production is sufficient to produce excess residue to provide adequate cover to bring about the desired effect on water and soil conservation. Studies from Mozambique regarding the savings from mulching showed the following results Table 12. The practice applies for long runs of flood, furrow or levee irrigated fields, especially useful on light loam and sandy soils. Surge irrigation has been shown to produce equal or better yields with 30 to 50 percent less water than continuous flow irrigation.
Surge reduces runoff and deep percolation significantly.
Surge irrigation can reach water use efficiencies of 80 to 85 percent, compared to continuous flow irrigation of 40 to 55 percent. Surge systems can be used for automated fertigation, increasing yields with less use of fertilizers. Field leveling During the 1980s in central Arizona, laser leveling of farmland alone conserved enough water to annually supply water to the half-million residents of the entire city of Tucson. Tailwater Recovery Systems Tailwater recovery can be very useful as long as there is proper salinity control. The amount of Egypt's agricultural drainage water presently re-used in irrigation is 5.0 billion m3 annually.