Abstract

PENA PERALTA, Miguel Ángel; HAHN SCHLAM, Federico  and  YAM TZEC, José Antonio. Fertilizer injection with rotary vane pumps and electrical conductivity control in mixed solutions for fertirrigation. Rev Cie Téc Agr [online]. 2010, vol.19, n.3, pp. 35-42. ISSN 2071-0054.

The injection of fertilizers in fertirrigation is commonly undertaken through Venturi pipes and controlled with the help of conductivity and pH sensors placed at the irrigation outlet point. The Venturi pipes suffer from pressure drops during injection. The fertirrigation equipment was, therefore, redesigned so that pressure drops are controlled by means of a fertilizer injection system powered by rotary vane pumps that provide a continuous volume. A PLC Millennium II XT-20 controls the injection using a program based on the electrical conductivity relationships that exist between the mixed solutions when mixed amongst themselves and when diluted in water in laboratory tests using concentrated solutions for Saladet tomatoes. These relationships allow one to predict the behaviour of the electrical conductivity when varying the percentage of each one of the elements that make it up. According to the equations, a ratio of 3:100 3--3 of fertilizer per 100 of water--must be provided in order to obtain conductivity in the 2 to 3 mS/cm value range, in which the plant has a better opportunity to take advantage of the nutrients. Comparing the pressure drops in the injection outlet point, the Venturi system loses 40 kPa while the system powered by rotary vane pumps does not lose pressure.

Keywords : Fertirrigation; Electrical conductivity; PLC; Rotary vane pump.