Impact of calcium and magnesium concentration on irrigator clogging in drip fertigation using brackish water and humic acid fertilizer

【Objective】 Drip fertigation is an irrigation technique increasingly used to simultaneously irrigate and fertilize crops grown in different environments. However, calcium and magnesium in the water could react chemically to precipitate, clogging the irrigator as a result. In this paper, we experimentally study the impact of calcium and magnesium concentration on irrigator clogging in drip fertigation using brackish water and humic acid fertilizer. 【Method】 In this experiment, four types of irrigators (FE1, FE2, FE3, FE4) with different rated flow rates (1.6, 1.1, 1.4, 1.75 L/h) were selected, in which three groups of brackish water treatments with calcium ion mass concentration, with ion mass concentrations of 100, 150 and 200 mg/L (G1, G2, G3), and three groups of brackish water treatments with magnesium ion mass concentration, with ion mass concentrations of 100, 150 and 200 mg/L (M1, M2, M3). In each treatment, fertigation using local groundwater was taken as the control (CK), we measured the average flow rate in the irrigator (Dra), clogging distribution in the irrigator, the dry mass of clogging materials (DW), and mineral fraction of the clogging materials in the irrigator. 【Result】 Compared to CK, fertigation using water with elaborated Ca2+ and Mg2+ concentration and humic acid fertilizer increased Dra by 21.58% to 56.75%, and DW by 67.14% to 270.09%, respectively, with the increase depending on dripping rate and Ca2+ and Mg2+ concentration. When Ca2+ and Mg2+concentration was the same, increasing dripping rate reduced DW by 4.77% to 27.26%, with the reduction depending on Ca2+ and Mg2+ concentration. 【Conclusion】 Increasing calcium and magnesium concentration in the fertigation water significantly increased irrigator clogging. When calcium and magnesium concentration was the same, an increase in magnesium concentration significantly reduced the mass of clogged materials due to the reduced carbonate. Thus, increasing magnesium ion can ameliorate irrigator clogging and reduce the risk of irrigator blockage.