Abstract
In order to develop an irrigation method for rockwool culture, the flow of the solution and movement of the solvent in the rockwool mat caused by drip irrigation were examined. It was important to set the dripping sites at one side on the surface of the 30 cm width mat, and open the drainage slit near the opposite side of the mat bottom. Then the solution flowed evenly in the mat from the dripping sites to the drainage slit, and the nutrient composition in the mat was uniform. When the dripping sites were moved to the center of the mat surface, only a small amount of the dripped solution flowed to the opposite side of the drainage slit. Consequently, the nutrient composition in the mat was not uniform. When the drainage slits were opened in both sides, or the width of the mat decreased to 20 cm, the composition of the nutrients remained uniform. When half of the mat volume was adequately irrigated, 50% of the solvent drained from the mat, regardless of the water content of the mat and the irrigation intensity. When the irrigation intensity exceeded the plant water uptake, the application of continuous irrigation resulted in a difference in the nutrient composition in the mat depending on the distance from the dripping site. At that time the difference in the nutrient composition between the dripping solution and the drainage one was maximum in the mat. Under such conditions of irrigation, it may be possible to estimate the nutrient composition in the mat by analyzing the composition of the drainage solution.
