I just got into organic growing and admittedly, should have amended my soil better. After 5 weeks Im starting to see alot of yellow on the newer growth and yellow tips. Everything online has been pointing me at nutrient burn but the only thing I feed them is liquid seaweed and molasses in RO water pH 6.8. To me it looks like magnesium deficiency but want to be sure and the best way to fix this. Being my first grow a little guidance would be greatly appreciated.
Im thinking now that messed up by not amending my soil proper in the beginning. Here's what Ive got: 5 x Blue Dream (non-feminized) all started in solo cup at the same time in FFHF, 2 weeks later moved to 3 gal of 1/2 FFHF + 1/2 FFOF, 2 weeks later moved to 100% FFOF. I water every 2-3 days with Liquid Seaweed + Molasses in RO pH 6.6 - 6.8. I also brew a tea every week with COM Lobster Compost + WC + Liquid Seaweed + Molasses. 4x4 with 2 x Maxisun P2000, 18" away at 100% and PAR reading of 800 PPFD avg. I have since lowered the intensity to 60% and my levels are 500-700. I did purchase nutrients in the planning phase, GH Trio but decided on 100% organic grow. I have stocked a wide variety of organic amendments and plan to do a final transplant to 10 gal with properly amended super soil. I have biochar charging for this but it has 12 more days till ready. I was leaning more towards a mag def and was told epsom salts would correct the issue. Im on my way out now to pick some up. Ive picked up alot of my knowledge (limited) lurking here on GC and wouldnt have gotten this far without you guys. The assistance is greatly appreciated.
Here’s a good solid soil recipe that’s economical. no need to waste money on bagged. The Old Soap Box
Very nice, appreciate that. Build a soil does something similiar to this. Curious as to why charging the char is not necessary.
It does look like the beginning stages of a magnesium deficiency but just a reminder that magnesium uptake is slow at 6.8pH I know you’re growing organic, but are you using soil or a hydroponic substrate like peat moss/ coco? Your growing medium will have a huge impact on what pH to shoot for. Before you add or change anything measure and record the runoff pH because this might just be as simple as adjusting what you already have - this is likely the case. here is an awesome chart to reference. Note: there is a big difference in nutrient uptake between soil and hydro! Best of luck my friend
Soil: 90% Ocean Forrest + 10% Happy Frog Very handy thank you. In my notes from research I had to shoot for 6.6 - 6.8. So far every watering has been within that range. I have been using RO water without adding any Cal or Mag. Also, and I cant remember where I got this from but I was told that in a perfect world I should aim for very little runoff if any and thats what I have done so far. I have a soil pH tester that currently reads 6.8 as well but it is a cheaper one, not like the BL METCOM I have for water so I dont trust its accuracy 100%. When I water next should I water enough to test runoff?
In situations like this where pH needs to be confirmed, it’s okay to water enough for runoff. Adjust your water to 6.6pH - 6.8pH and measure the runoff. I’m betting your pH is too acidic, the Happy frog is known for that. But that’s okay because it can be adjusted fairly easily. I mis-spoke earlier when I said magnesium had slow uptake at 6.6pH I was looking at manganese. My apologies. Your target pH (6.6pH - 6.8pH) is perfect.
I don't charge bio-char either, it's just an unneeded step, the bio char will be colonized by the microbes in the soil
if you are feeding molasses that has plenty magnesium it is most likely your ph is off and she cant uptake the magnesium
My guess would be low soil ph, 6.8 ro water combined with organic nutrients that tend to be acidic is going to have you sitting low on ph. I would look into getting some oyster shell flour top dressed and worked into your top inch or so of soil, it will add in some calcium and help to buffer your ph back up to the 7 range. Bear in mind it takes time to breakdown and is not going to be a quick fix, you may need to look at a temporary solution for raising the ph. Also its wont be able to fix the leaves that are already damaged, so watch the new growth.
I would also raise those lights up another 4-6" for the time being to slow down progression until you can get a fix worked.
How is your soil temperature. Mg is one of many nutrients that are taken up very slowly in cool soil. Stick a thermometer in there and see what you have. Cooking type thermometers with a pointy probe and dial indicator on top work great and are cheap. Cheers Os
What is the cheapest way to pH my soil while keeping results accurate enough for this application? The tester I have currently wasnt expensive and only gives me a reading of 6.8 so I cant fully trust it.
How are those commercial soils 'organic'? I reckon MY soil is organic: Peat moss, worm casts, leaf soil, rotted sheep poo, Perlite.
I feel like the answer to that question most likely deserves a thread of its own and I wouldnt belong in the conversation at this point. This being the first time I have ever grown anything limits my experience to research only, much of which I obtained from GC and some highly recommended books. Couple hundred hours later I decided to take the organic path as opposed to using synthetic nutrients. I liked what Build a Soil had to offer but some hands experience now, even if I messed up seemed like a good decision and FFOF and HF allowed me to do that. The were highly recommended as well. They are the only product that Im using that doesnt have the OMRI logo on it though.
My last watering wasnt enough for runoff. So hopefully this will do: I dug into the soil a little bit about 3-4 in down and pulled up about 3-4 tblspn of soil, put it into a clean cup and put a little more than equal that amount of RO water and mixed up. I let it sit for about 5-10 min and tested pH, reading was 7.0 I dont have a way to get the temp deep in the soil. The temp of the water in method above was 68 before adding the soil and 68 after as well. Good idea. Raised 6" now. UPDATE: As recommended from a well known grower, I added epsom salt to the last watering (1 tsp/1 gal) I have not yet seen an improvement and the symptoms have since worsened.
7 is pretty high no matter what, but it also wasn’t an accurate reading. You have to test the water runoff.
Might have overlooked it in one of your responses but Perlite is an essential ingredient in my soil build; helps combat soil compaction and potential root issues which inhibits nutrient uptake.
Something to be aware of when growing with leds and growing organic. Since leds don’t emit infrared radiation the plants and soil don’t feel any warmth from the light. Many functions in the plant are slowed down as the temp drops, including the uptake of P, Ca, and Mg. Air temp at the canopy of 80-82 at that stage of growth and the warmest soil temp you can get will make a big difference. Raising containers or putting insulation under them helps quite a bit. Every degree you can warm your soil will make things better. Ideal soil temp would be 75-80 at this stage. Cheers Os