Hydraulic characteristics of porous clay capsules and their effects on soil water distribution

Buried porous clay capsule irrigation is one of the most important traditional methods that could be of great use on small and medium sized farms and gardens. Hydraulic characteristics of porous clay capsules are affected by clay type, clay percent, sand percent, T.N.V. %, wall thickness, soaking time, firing temperature and hydrostatic pressure. The present paper has attempted to evaluate the hydraulic characteristics of porous clay capsules based on firing temperature, soaking time, and hydrostatic pressure. Raw materials used for making porous clay capsules were obtained from calcareous soil of Nasr-Abad village of Gorgan city. The amount of sand added for improving hydraulic properties was 0, 200, 400, 600, and 800g into 1000g of Nasr Abad of Gorgan soils respectively. These produced clay capsules were named Gorgan-0, Gorgan-200, Gorgan-400, Gorgan-600, and Gorgan-800 respectively. Results showed that with increasing firing temperature, the soaking time of porous clay capsules decreased. Also the discharge of porous clay capsules, with increasing firing temperature increased. The relationship between discharge of Gorgan-0 and Gorgan-200 with hydrostatic pressures is linear and with increasing fine sand in Gorgan-400, Gorgan-600 and Gorgan-800, the relationship became non-linear. Meanwhile soil wetting shape with clay capsules followed a spherical trend, which is due to the low discharge of clay capsules.