Analysis of the changes in medium moisture content according to a crop irrigation strategy and the medium properties for precise moisture content control in rock wool

Abstract

The substrate moisture content affects crop absorption, microorganisms, oxygen concentration, water stress, and the ultimate evaporation amount. The moisture content in the rhizosphere can be controlled by the amount of water, the frequency of water supply, the time of water supply, and the rate of water supply provided to the crops. The purpose of this study was to investigate the physical properties of a rock wool medium and to investigate the water movement characteristics of the medium according to different watering conditions. To measure the moisture content of the substrate and the drainage amount, load cells were used as weight sensors, and the total irrigation capacity was 99 and 198 mL/min, respectively. The moisture content at each irrigation starting point was set from 30 to 80% of the substrate moisture content at each 5%. The relationship of the starting point of drainage, the 30% drainage rate, the point of the first saturation according to the two different irrigation rates, and the point of moisture content at the start of irrigation showed a sigmoidal relationship. When reviewing the irrigation to the first saturation point, the substrate moisture content got higher as the moisture content at the irrigation start increased. Also, it was shown that the higher the irrigation rate, the higher the saturated moisture content seen in the substrate. The high irrigation rate is useful for the saturation of the substrate, but a large amount of water was needed to adjust the drainage rate. For this reason, we analyzed the irrigation rate under various cultivation conditions.