Just started a grow in a location with around 200 ppm out of the tap. After reading the local water analysis, I have come to the conclusion that the tap water contains high levels of calcium which in turn is locking out the magnesium and causing purple stems on all of the strains I am running. Though I am a very experienced grower, I have never been faced with this issue before. I have read many times about blades adding epsom salt to there hard tap, just not sure how this solves the problem of calcium toxicity. I know that Cal and Mag need to be given at an equal rate to avoid locking out the Mag but how do you find the correct dosage for individual tap levels? Any help from pros that are currently growing with hardwater would be appreciated, I refuse to begin flower with these levels of calcium, as I am a perfectionist but this is not my level of expertise.
not sure how to interpret the chart, though the hardness levels which is noted as calcium is the highest number on the chart. Im not familiar with the unit of measurement they are testing with. At this grow the mothers are in soil and the flowering room is flood and drain. Not sure how that relates to my problem. Id like to understand how adding epsom salts help solve the issue with high calcium HARD water? I keep reading 1 Tbsp per gallon but how was this number arrived at? How much of a difference can Cal and Mag be added before an issue arises? And will 1 Tbsp somehow "Magically" balance these two important micro-nutes? Id like to be able to use this water straight from the tap as water is monitored some what in this area and I think RO would be such a waste if I am able to use what is provided.
I equate purple stems with high nute levels and watch the leaves for signs of lockout or toxicities. I run high PPM levels and almost always see purple stems on my strain. I mix my nutes from 5 dry chemicals and a chelated micro nutrient product. During veg stage the Calcium Nitrate is used at almost 1-1 volumes with Magnesium Sulfate ( Epsom Salts) but the ratio changes to almost 2-1 for bud stage so perhaps your high calcium water will benefit the plants during bud?
AFAIK purple stems is no indication of a Ca toxicity or locking out Mg.. Could be genetics, cold temps , P deficient or all the above..I think you're over-worrying regarding purple stems.. W/O knowing your actual water analysis, IMO your tap is not all that hard.. Even if your tap contains Ca it doesn't mean it is completely soluble/useable to your plant(s), b/c the molecules are too large to be absorbed by the roots..hence why even some tap users supplement Ca..Plants need readily available Ca to be absorbed immediately, b/c it is an immobile element, and a constant supply is necessary..If your base nutes contain enough Ca from source and in your base nute , what I would do is at least maintain a 2:1 Ca:Mg ratio, if it means adding additional Mg via ES, sweet etc..But not at 1:1 or equal rate as you've stated..However nothing is set in stone, and there is a range of ratios that work..also depends on plant stage.. google plant tissue analysis for more info.. IOW w/o knowing where you base nute levels/ratios are at, no one can recommend how much additional Ca or Mg you should supply to your girls.. Hope that helps..