Salinity management under a capillary-driven automatic irrigation system

抄録

To automatically meet crop water requirement and regulate drought stress to enhance sugar content, a capillary-driven automatic irrigation system (new sand ponics, NSP) was invented. This system keeps water level below the root zone which is packed with a non-woven fabric and water is automatically supplied by capillary force responding to root water uptake. However, this upward capillary movement irreversibly accumulates salts unless leaching is carried out. To examine whether NSP can still be profitable in spite of additionally required water for leaching, we carried out an experiment under green houses. Tomato was cultivated using 1000 ppm NaCl solution containing fertilizer at constant daily application rate. Leaching was carried out when estimated root zone salinity reached prescribed limit. Income was calculated assuming that 30 USD/kg of sugar while water price was assumed to be 1 USD/t. Results showed that NSP can still be more profitable than SP even when frequent leaching is required.