Production of Cu-EDTA, Zn-EDTA, CuZn-EDTA as a Micronutrient Fertilizer and its Application to Lettuce

Plants need two types of nutrients, which are macronutrients and micronutrients. Micronutrient needed by plants in small concentration (≤ 100 ppm) i.e. Cu and Zn. This study aims to determine the best composition ratio of Cu:EDTA, Zn:EDTA, and Cu:Zn:EDTA for making the micronutrients, determine the effect of Cu and Zn on lettuce (Lactuca sativa L), and determine the most effective type of micronutrient fertilizer and its concentration for lettuce growth. It was started by dissolving materials with 200 ml distilled water, then stirred and heated at 70-80°C for two hours. After that, the solution was precipitated for two days at room temperature. Methanol was added only before precipitating CuZn-EDTA. The precipitate or micronutrient crystals of Cu-EDTA, Zn-EDTA, and CuZn-EDTA were then filtered and dried in a desiccator for three days. Each of micronutrient crystal was dissolved into 25 ml water then the lettuce will be sprayed with micronutrient solution for two and three sprays once a week. Observations related to the quantity of leaves, plant length, and leaf width were carried out for 25 days and then plant harvested and weighed. The result shows that the best compotition ratio for making micronutrients were Cu:EDTA (1:1.85)w/w; Zn:EDTA (1:3.43)w/w; and Cu:Zn:EDTA (1:1.6:3.85)w/w/w. Concentration of micronutrient solution applied were 5000 and 1000 ppm. Respectively for each concentration, micronutrient CuZn-EDTA affected the leaves quantity growth with the slope of 0.0655 and 0.0642; and yields (g/cm2) with the slope of 0.495 and 0.46. Zn-EDTA had an effect on plant length growth with a slope of 0.1525 and 0.091; and leaf width growth with a slope of 0.0216 and 0.0111. Cu and Zn contained in lettuce leaves then analyzed and was known for Cu-EDTA, Cu and Zn contained (mg/kg) respectively were 37.78 and 50.68; for Zn-EDTA were 32.8 and 61.25; for CuZn-EDTA were 33.23 and 48.16 (mg/kg). The metal content analyzed in lettuce leaves is not suitable for consumption because it exceeds the maximum limit written on the Decree of the Directorate General of POM No 03725/B/SK/VII/89. Application of fertilizer should be more diluted to less than the maximum limit.