Hi so this is my first time growing in coco coir (not full hydroponics I am watering by hand). So a little background. I have 16 plants (seeds, OG Cheese) under a 600w hps. I have done 12 days of good vegging and am into day 2 of 12/12. I had to start flowering a week or two earlier than I would have liked because of my crappy time managment skills, in 90 days I'll be away from home for a week. The nutrients that I use (Gold label hydro/coco A+B) recommend a pH of 5.2 during veg. That is really friking low, goes against everything I have read, but I decided to go with it as it's the recommendation of the manufacturer. My tap water EC is 550uS/cm, which is very high but I contacted the manufacturer and they said that their nutrients are made for hard water and that it's fine. My temps are fine (20-26 celcius) however my humidity is very low at around 25%rh but there's not a whole lot I can do about that right now. Anyway here's the problem, three of my plants have had rusty/blotchy looking leaves since they sprouted. It looks like a calcium deficiency but I'm not too sure. At first I thought that it was just going to sort itself out (not too sure why I thought that, could have solved this a week ago). It was only getting worse. I read that low pH can cause calcium lockout and that's what it looks like, so three days ago I decide to increase pH day by day, first to 5.4 and today I fed at about 5.7. My nutrient manufacturer is the only source I found that recommends 5.2 anyway... I have no idea why. I also decided to check my runoff EC only about 4 days ago (just after repotting) and it was 4000uS/cm ! I think this was due to the substrate itself because I had been fertigating daily with 30-40% runoff, using an EC of 1200uS/cm. I did not flush, because to be completely honest I couldn't get bothered to deal with preparing a huge amount of nutrient solution and then dealing with huge amounts of runoff (yep I'm lazy lol). Instead, I reduced my nutrient solution EC to 900 and continued fertigating daily with 30-40% runoff. Today, my runoff EC read 2000. I will wait till it reads 1500 before increasing my nutrients again. It looks like the new growth on the plants is healthy, but it's a bit too soon to tell. Have I taken the right steps to solve this ?
You have to add extra calmag to coco, because its notorious for sucking calmag out of nutrient solution. Keep your ph between 5.5 to 6.0 and fluctuate periodically to get the best nutrient uptake.
I think a lot of folks get into coco not knowing that many coco coir’s have to be loaded with Ca+ & Mg+ prior to using to thwart this. I made this mistake my first grow too good luck man. If you haven’t read Dr Coco’s work I suggest you check out CocoForCannabis.com ✌
I don't think you have a calcium deficiency. Pre charging is necessary to replace the sodium and potassium cations with calcium and magnesium. I even pre charge when the coco is already buffered, just to be safe. Feed daily to run off with a nute solution pH'd at 5.8 - 6.0. Good luck.
Hi Fred, I felt like coming back and offering a great suggestion for ya regarding your humidity. 20’s is really low. My grow room stays at 20’s all the time too. So after a bit of research I landed on this: This is a Levoit 6L (1.5 gallon) humidifier with awesome features. I can dial this thing in for multiple uses around my grow room at different stages in my grow. What I love about it most is it holds enough water to get by for 12-13 hrs while I’m away under heavy use, I.e., when I first take clones. Otherwise I can go about a day before needing to refill. I hope you have access to it if you need one cause I think you’d really like it here’s the amazon link if you’d like to check it out. Best of luck to you and your grow Fred