1. What should hemp growers know about micronutrients?
There are different kinds and different categories as far as how they’re made available to the plant. You have straight, raw micronutrients; you have complex micronutrients, which use citric acid and other things to keep them in solution; and then you have fully chelated products, which use chelating agents such as Ethylenediaminetetraacetic acid (EDTA) to hold onto nutrients for even longer. If you utilize straight, raw magnesium sulfate, you have to make multiple applications. Chelated products stick around a lot longer.
2. What are some of the most important micronutrients for hemp growers?
Calcium, magnesium, iron and manganese deficiencies can all be potential problems. Micronutrient deficiencies of molybdenum, copper, zinc and boron can be hard to diagnose. That’s a pretty broad list, and those are nutrients that a lot of our micronutrient packs—we have granulars, liquids and solubles available—have in them.
3. Why is pH important?
pH affects hemp’s micronutrient uptake because at a higher pH, soils and water make a lot of these nutrients unavailable. That really is what leads to deficiencies. Even though you might run a soil test and the micronutrients are there, they’re in a form that the plant can’t use. Most of these have some speckling, spotting or some telltale sign on the leaves in the vegetative state. It’s pretty easy to pick up if you have a micronutrient deficiency because you’ll start to see it consistently through your crop.
4. How can growers ensure micronutrients stay in the soil?
Growers can purchase nutrients with chelation or complexing agents from suppliers. The majority of these are positive cations, so they have a positive charge. They’re being affected by negative charges in [high-pH] soil. So, we want to keep them in that positively charged form for as long as possible. That’s what the chelating and complexing agents will do.
5. What can growers do if they want the plant to produce more flower?
If a plant has micronutrient deficiencies as it starts flowering, it won’t take nutrients in as readily as it did in a vegetative state. The plant starts to put all its energy into flower production, so if there are some micronutrient deficiencies that affect chlorophyll production, you won’t have as healthy a plant. You want to watch and make sure that as the plants starts to flower, you have good, balanced micronutrients.
Because we do have a broad spectrum, growers have used small amounts of a granular early in the season. You can apply small amounts of micronutrients with fertigation. There could still be a little bit of an iron or a manganese issue with some yellowing of the fan leaves as you approach flowering. You can make that correction with a specific micronutrient.