I’ve got a relatively small marijuana garden with eight indoor plants under a 1,000-watt MH bulb in a space that is 2’ x 4’. I’ve got a commercial soil and I’ve also altered the water so that it’s at a pH of 7 to 7.5. These marijuana plants are only 2 to 3 weeks old, but the older ones are already starting to turn a pale yellow color. The other plants are also starting to turn yellow so I infused a 10-15-10 fertilizer and a single cup of urine per gallon to produce more nitrogen. In addition, I added some Epsom salt for added magnesium. After three days, the marijuana plants still haven’t responded. How is this happening? I don’t want to lose my plants.
Your major problem is that your marijuana plants aren’t receiving as many nutrients because the pH level is too high. When the pH level ranges toward neutral, the nutrients lose some solubility. Indeed, alkalinity (above 7.0) and solubility do not mix.
The dose of fertilizer you have provided the marijuana is so high that it would be toxic if it turned soluble. The first thing you should do is flush the containers with water at a pH of between 6.2 and 6.5. Use a ppm meter to test the runoff water, and stop flushing when you get to below 1,600 ppm. Water the plants with the pH-adjusted water until your plants return to their green color. Then, begin using a full fertilizer that has micronutrients. Any new growth will be normal. Old growth might not recover, however. Be sure to keep the water pH at about 6.2 in the future.
yes indeed - I need to get a pH pen and ppm meter so I can also have a better exact control over my nutrients.
Many of my crops have demonstrated Cal/Mag deficiency - and I’m still struggling to get it right.
As Robert has stated, your pH levels are too high. You are experiencing what in the horticulture industries is called acid lock. Many people keep adding nutrients to try to recover the plant that is exhibiting signs of nutrient deficiencies. inexperienced grower add more and more nutrients and nothing helps. They finally ask an established grower for help to solve this problem, and the answer is check your pH. The pH is checked, and the grower is told add lime to lower the pH. The pH gets back in the range that it should be, and the plant deteriorates extremely fast.
That is because now that the pH is right the soil has enough nutrient in it to grow a redwood tree in 4 hours.
The best way to handle this is to flush the pants as much as possible. It is time consuming, but the only way to salvage the plants.
I take the plants in their container and slowly submerge the plant in a water bath that as close to 7.0 pH. and let them sit for about 20 minutes. I will then take the plant out of the flushing container, then take a reading of the flush solution in ppm. Repeat this until your ppm reading is under 1600.Then I will flush in a solution that has been taken down to a pH of 6.5. Repeat the process, If your ppm stay under 1600, bring the flushing solution to a pH of 6.0. Again repeat until you get ppm readings under 1600.
The best case scenario is to be able to completely flush the plants until the ppm is 0. That is just not that easy to do. At 1600 ppm you are at least at a level that will not burn your plants. The down side is there is no way to determine what the composition of the 1600 ppm are. Could be all Nitrogen, of all Phosphorus.
Once you have to do this to save your plants, you will realize how easy and important it is to check soil pH and ppm.