Effect of fertilizer solution concentrations on filter clogging in drip fertigation systems

Abstract

Drip irrigation using fertilizers is one of the commonly used methods to save fertilizer and minimize the impacts of fertilizer on the soil and the environment. However, the clogging issue of drip fertigation systems has been the major limitation and may lead to system damage if fertilizer solution concentrations are not appropriately selected. Therefore, the head loss, flow rates, and clogging substances of screen and disc filters were analyzed to evaluate the effect of different fertilizer solution concentrations on filter clogging under different injection rates (2%, 3%, and 4%) and fertilizer-water ratios (1:4, 1:5, and 1:6) in drip fertigation systems. The surface morphology and chemical composition of the clogging substances were analyzed by scanning electron microscopy and energy dispersive spectrometry (EDS). The results showed that the large injection rate caused uneven fertilization, and the recommend injection rates of the proportional fertilizer pump were 2% and 3%. In the same fertilizer solution concentration range, the difference in head loss of the screen filter (0.09–7.75 m) was larger than that of the disc filter (0.32–3.88 m), indicating that the anti-clogging performance of the disc filter was better. Meanwhile, the application scope of the fertilizer solution concentration of the screen filter was less than 0.117% and that of the disc filter was between 0.117% and 0.296%. There was a significant effect of the fertilizer solution concentrations on filter clogging (P < 0.05). The interaction between the fertilizer solution concentrations and filter types had a more significant effect on filter clogging (P < 0.01). The clogging substances consisted of undissolved phosphate fertilizers and silicates as well as carbonate and phosphate precipitations generated by chemical reactions. The clogging mechanism was a physical and chemical coupling process when using phosphate fertilizers. Therefore, the use of fertilizers, especially phosphate fertilizers, contributed to the generation of clogging substances. Fertilizer solution concentrations and type of fertilizers should therefore be considered in the anti-clogging performance of filters in drip fertigation systems.