diagnose your sick marijuana plants
Signs of Low pH
Low pH symptoms may vary among plants. However, soils with low pH may cause a release of aluminum that can stunt a plant’s growth and alter nutrient intake. Some plants may also suffer with manganese and iron toxicity that causes yellow spots and leads to browning and leaf death. Other symptoms you may notice include wilting leaves, stunted growth, blighted leaf tips, yellowing of foliage or other leaf discoloration and poor stem development.
Why pH Matters
Acidic soils have a low pH, and this affects the plant’s ability to absorb essential nutrients from the soil. Normal ranges for soil pH are between 5.0 and 8.5. It is when the levels go above or below these numbers that problems occur. For example, at pH values lower than 5.0, manganese and aluminum can become toxic to plants growing in that soil. Plants can get overloaded with these liberated nutrients and cannot process the excess quickly enough, leading to plant death.
Causes of Low pH
Several factors can affect a soil’s pH level, causing it to drop. One such factor is rainfall that is naturally acidic because of the presence of carbonic acid, which results from the atmosphere’s carbon dioxide and moisture. Environmental factors, such as where the rain falls, also has an effect on pH. It tends to be lower in cities, because the atmosphere near cities has more sulfuric and nitric acid from burning fossil fuels. The use of nitrogen fertilizers that contain ammonia also lowers a soil’s pH level, and so does decomposing organic matter, which produces carbonic acid.
Adjusting Low Soil pH
A soil test can help you determine what your soil pH is. It is also important to know the soil texture, as the type of soil helps determine the amount of limestone needed. For example, clay soil requires more limestone than sandy soil. To raise pH, use dolomitic limestone, a combination of magnesium and calcium carbonate, which neutralize more acid and add magnesium to the soil. You can also use oyster shells or wood ashes to raise pH.
Nitrogen (N) Mobile Element and Macro Element
Benefit: Nitrogen plays a very big role in your plants; this one element is directly responsible for production of chlorophyll, photosynthesis, Amino Acids, which are the building block of Proteins. The myriad of enzymes which help the plants growth in leaves stems and the how well the vigour of your plants is.
Nitrogen is the biggest mobile element meaning it can travel anywhere on the plant.
Usually the def will start on the lower to middle part of the plant, and then will usually happen to older leaves first. Then the deficiency will work its way up the plant. Your plant can be green on top, then yellowing on the lower leaves when the deficiency is starting out. Yield will be greatly reduced without good amounts of nitrogen in your plants. Sometimes in bad cases the leaves will turn a purplish colour along with the yellowing.
Unlike a magnesium deficiency, nitrogen def will start from the tips and work its way back to the leaf node. Nitrogen and Magnesium get confused. The best way to tell them apart is, nitrogen deficiency starts around the tips and works its way to the back of the leaves, where a magnesium deficiency will cover the entire outer part of the leave and make the entire leaves yellow leaving the veins to stay green. If your plants are having a slow growth rate and have yellowing of the leaves, then most likely it’s a nitrogen deficiency.
Towards the middle to end of flowering stages, the plant will show a nitrogen deficiency almost always. This process is completely normal and just let the plant naturally yellow out as it uses it’s stored nutrients. This actually helps you by getting ready for final flushing and then harvesting. At this point DO NOT not use nitrogen to fix the problem. The yellowing leaves will then eventually drop off after the plant is done with them.
Parts affected by a nitrogen deficiency are: Older foliage, going to whole plant, Petioles (rare) cases.
Now for having too much nitrogen in your growing mediums or soil. The plant will have like an overall DARK green look and have delayed maturity. Due to Nitrogen being involved in vegetative growth, to much nitrogen will result in tall plants with weak stems. New growth will be very lively and plant transpiration will be high, but not always. Nitrogen toxicity can be seen when there are very very dry conditions almost as if there was a drought, which may show a burning effect. If you give your plants ammonium based nutrients they may show NH4+ toxicity, which will show a smaller plant growth and lesions that occur on stems and roots, leaf margins that will roll downward. Also the big fan leaves will have “the claw” look. The tips will point down but the leaves will stay up as if when you bend your fingers downwards. Leaves can be twisted when growing… mainly new growths. Roots will be under developed along with the slowing of flowering. Yields will be decreased, because to much nitrogen in early stages of flowering slows down bud growth. Water uptake is slowing down from the vascular breakdown of the plants as well. Too much potassium and nitrogen will lock out calcium as well.
Problems with Nitrogen being locked out by pH troubles.
Waterlogged soil and Soil with low organic matter.
Nitrogen is a very important element in the plant, all of them are but some are more important than others. For soil the best pH to have is 6.8. Why? Because at 6.8, that’s the best number for ALL available nutrients to be absorbed into the plant without any of them being locked out. For hydro and soil less mediums best pH to have is around 5.8.
Try not to keep your plants to cold, because the cold temps will cause the nitrogen harder for the plant to be absorbed.
pH levels for Nitrogen:
Nitrogen gets locked out of soil growing at pH levels of 4.0- 5.5.
Nitrogen is absorbed best in soil at a pH level of 6.0-8.0. ( wouldn’t recommend having a pH of over 7.0 in soil) best range to have nitrogen is a pH of 6-7. Anything out of that range will contribute to a nitrogen def.
Hydro and Soil less Mediums
Nitrogen gets locked out of Hydro, Soil less mediums at the levels of 4.5-5.0.
Nitrogen has the best absorption rate at a pH of 5.5 to 8.0
(Wouldn’t recommend having a pH over 6.5 in hydro and soil less mediums.) Best range to have Nitrogen is: 5.0-7.0. Anything out of that range will contribute to a nitrogen def.
Solution to fixing a Nitrogen deficiency
Avoid excessive ammonium nitrogen, which can interfere with other nutrients. Too much N delays flowering. Plants should be allowed to become N-deficient late in flowering for best flavour.
A goof solid N-P-K ratio will fix any nitrogen deficiency. Any chemical or organic fertilizers that have Nitrogen in them will fix a nitrogen deficiency., Peters all purpose plant food 20-20-20 is good, Miracle grow All purpose plant food, Miracle grow Tomato plant food, (Only mixing at ½ strength when using chemical nutrients, or it will cause nutrient burn!) as well and blood meal! If you need to give your plants a quick solution to nitrogen and you want to use blood meal, I suggest making it into a tea for faster use, where blood meal is slow acting, but when made into a tea it works quicker! Other sources of nitrogen are dried blood, Cotton seed meal which is slow acting, Insect eating bat guano which is fast acting. Bone meal which is a gradual absorption when not made into a tea.( also excellent source of phosphorus). Fish Meal Or Fish Emulsion is a good source of nitrogen and is medium acting. Worm castings, which is gradual absorption. Seabird guano, All purpose Millennia Seabird guano, Original Seabird guano All Purpose, Crabshell ,which is slow absorption. Fox Farm Grow Big, which is fast acting. ( can bring down your pH as well)
Nutrient burn is one of the most common beginner cannabis growing problems. The yellow or brown leaf tips are caused by too-high levels of nutrients accumulating in the leaves.
(Nutrient burn is often called “Nute Burn” in the cannabis growing community).
When the roots take in more nutrients than a cannabis plant can use, the overabundance causes a brown or yellow “burn” on the tips of your leaves. If nutrient levels are not lowered, the burnt tips start traveling inwards and the ends of leaves start becoming crispy and twisted
Problem: You will notice the tips of your marijuana leaves showing the first signs of nutrient burn by turning yellow, tan, gold or brown. A light case of nutrient burn will only affect the tips of your leaves.
The yellow tips will eventually turn rusty brown and crispy. If you do not correct the problem, you may also notice the burn slowly spreading from the tips to the whole leaf. At this point, if you haven’t done so already, you should immediately treat your plant (directions below) before there’s more damage.