by Jorge Cervantes
Nutrient Solutions
To avoid problems, change the nutrient solution in the reservoir every week. Change nutrient solution every two weeks in systems with a large reservoir. You may need to change the nutrient solution more often when plants are in the last stages of flowering because they use more nutrients at that time.
Plants use so much water that nutrient solutions need to be replenished regularly. Water is used at a much faster rate than nutrients. Casually “topping off” the reservoir with pH-balance water will keep the solution relatively balanced for a week or two. Some growers top off the nutrient solution with 500-700 ppm-strength nutrient solution every 2-3 days. Never let the nutrient solution go for more than 4 weeks before draining it and adding fresh solution. Smart growers avoid problems and leach the entire system with weak nutrient solution for an hour or more between changing the reservoir.
Humic and fulvic acids chelate metallic ions, making them readily transportable by water. The (fertilizer) micronutrients – copper, iron, manganese, and zinc – are difficult to dissolve. When mixed in a chelated form, they become readily available for absorption.