Evaluating the efficiency of two automatic fertigation systems in soilless crops: substrate moisture sensors vs. timer systems

摘要

Fertigation systems are the main method of nutrition for vegetable production in greenhouses; they allow an efficient and homogeneous distribution of water and nutrients. In most cases when using substrates, it is necessary to apply dissolved nutrients in a large number of low-volume fertigations. Numerous fertigation systems exist based on nutrient input needed at each physiological stage of the crop, the volumetric moisture content of the soil substrate at a given time per the farmers' criteria, solar radiation, evapotranspiration, and the demand tray. In all cases, these variables must be controlled by evaluating the drainage volume, electrical conductivity, and pH of the drainage throughout the crop cycle. Here, a qualitative comparison was madebetween two fertigation systems: the time schedule system, as this is the most common system used in Mediterranean vegetable production, and the volumetric moisture method. For this purpose, a long-cycle tomato crop established in coconut fiber substrate was used. The evaluated variables were: aerial and radical biomass, crop nutritional status, yield, and quality and efficiency of water and fertilizers. Both systems used the same nutrient solution but differed with regard to the frequency and number of irrigations applied. The management of the fertigation system based on the time schedule was determined via climatic demand by checking the drainage percentage and EC of the drainage. However, the fertigation system based on moisture was conducted by using a dielectric probe installed in the substrate that conditioned the demand for fertigation to maintain volumetric moisture in a range between 20 and 28% throughout the production cycle. Results revealed significant differences between the two systemswith regard to the total amount of water used. The volumetric moisture system had a lower consumption of water and fertilizer than the timed system, representing lower production cost, higher productivity, and decreased loss of nutrients by leaching.