Optimization of the capacity of tank in water harvesting using plastic sheet and tank in a sandy field

抄録

In semi-arid climates, rain-fed agriculture often faces long dry spells and crop losses. The use of plastic sheets combined with tanks may enable to harvest water in sandy fields where runoff seldom occurs. To present a methodology to determine an optimal tank capacity, we cultivated garlic (Allium sativum L.) in a sand dune, Japan under three treatments, A, B, and C having the same cultivation and plastic sheet areas of 24 m² and 12.5 m², respectively. Tank capacities for treatment A, B, and C were set as 500, 300, and 200 L, corresponding to storability of 21, 13, and 8 mm, respectively. Water was automatically applied through a drip irrigation system using tensiometers. Results showed that treatment A had larger stored water by 15% and 28%, as well as larger cumulative irrigation depth by 15% and 39% compared to B, and C, respectively. As a result, bulb yield was higher for A by 6% and 18% compared to B, and C, respectively. The optimum storability that gave the highest net income was around 18 mm. Without overflow from gutters, the average collection efficiency was around 95%. The methodology would be suitable to determine the optimal storability of the tank.