Self Mulching Effect of Dune Sand Small Scale Water Infrastructure

Agriculture consumes about 70 % of the developed fresh water in the world. It is possible to reduce the amount of additional fresh water withdrawals by 40 % if water saving techniques are improved. As the water crisis continues to manifest itself, planners and policy makers will continue to be faced by gaps between supply and demand for water and ultimately food. There is, therefore the need to improve water saving techniques to ensure adequate food for future generations with same or less amount of water than the amount of water that is presently available for agriculture. Surface drip irrigation is the most effective way to supply water and nutrients to the plant and does not only save water but also increases yield of crops. However, irrigation water loss by soil evaporation is inevitable under surface drip irrigation. This study, therefore, attempted to reduce soil evaporation thus improving irrigation water saving through a combination of surface drip irrigation and sand mulch on drip lines. Sand soil was used since it is a readily available material, especially in the sand dune soil areas.
The following aspects were made clear in this study: 1) the quick development of a dry layer on a wet layer of the Tottori sand dune soil and the effect of the dry layer on soil evaporation reduction, 2) the effect of sand mulch on drip lines on the water content of soil, 3) the effect of sand mulch on drip lines on water recharge in the root zone, and 4) estimation of soil evaporation by soil hydraulic factor under sand mulch on drip lines. The quick development of a dry layer of the Tottori sand dune soil was studied to identify its suitability as a self-mulching material to reduce soil evaporation. Enough water was applied to the sand soil and that was naturally dried. The sand soil quickly dried and formed a dry layer near the surface that covered the lower wet layer. The effect of a dry surface layer on soil evaporation was also studied. Sand soil columns were covered with a 2 cm and 5 cm thickness of dry sand soil. The 5 cm thickness was more effective than the 2 cm with soil evaporation reduction of more than 72 %, compared to a sand soil column with no cover.