Nitrogen Deficiency: How to identify and cure your yellowing leaves
Close up of chlorophyll in its natural state

This is a closeup look at chlorophyll in its natural state. As you know, plants need chlorophyll to help absorb light and convert it into usable energy (a processed known as photosynthesis). But do you know where that chlorophyll comes from? Nitrogen, and if you've seen those leaves start turning yellow chances are there's a lack of nitrogen in your nutrients. When your plants aren't getting enough nitrogen they can't keep themselves alive, so it's important to keep nitrogen in your grow.

Identifying Nitrogen Deficiencies:
Example of leaves with different nitrogen consumptions
Nitrogen deficiency will turn a kelly green leaf yellow and that means more than just bad looks. This is often a sign of Chlorosis: a disease that results in the inability to produce chlorophyll. If your plants can't produce chlorophyll they can't eat, and when they start to die all available nitrogen will be used to make new growth. Not only will your plant not be able to keep old plant growth alive, but new growth will come out weaker. Other signs of nitrogen deficiency include:
  • Purple Stalks
  • Yellow leaves on old growth, light green leaves in new growth
  • Leaves begin to fall off
  • Leaves begin to droop while discolored
  • Burned look (in extreme cases of deficiency)
Helping Your Plants Get Back on Track:

So you've identified your plant's problem is a lack of nitrogen. You can already guess that you have to add some sort of extra nutrient to your feeding regimen, but you might be surprised at what you can use to give your plants a boost of nitrogen:

- Cottonseed Meal is high in nitrogen, and when used with Alfalfa you'll stimulate growth and nutrient absorption better than before - Calcium + Magnesium (CalMag) will give your plants a boost of nitrogen, phosphorus, and potassium. This is a good solution in the veg stage of growth, but try not to use it during flowering because it'll throw the pH off - Calcium Nitrate will give your plants a slight boost in nitrogen, helps with calcium deficiencies, and adjusts pH levels of soil - Compost Teas can be used to adjust nitrogen levels in drip systems. The trick is to find the right recipe to fill in the gaps your other nutrients aren't - Urea (yes, from urine) is high in nitrogen and can quickly adjust nitrogen levels. However, most urea needs to be broken down before use. Not only that, but when urea hits soil its chemical composition begins to change, and it'll send off ammonia through your soil. This should be used when your plants are fully grown, and not using the seeding or beginning stages of vegging, as it will burn the roots.

Nitrogen Levels During Vegging vs Flowering Stages

Now that you know a few things on how to restore your plants, we want to remind you that nitrogen deficiencies during the growing/vegging stage and deficiencies in the flowering stage will need different care. When you need to add any nutrients to fight nitrogen deficiency, remember that during the vegging stage your plants will need lots of nitrogen. Even though most nutrients have a good amount of it in them, if you have a nitrogen deficiency it would help using a foliar (foliage, i.e. leaves) growth nutrients, like Humboldt Grow or Compost Teas. If you’re flowering and you start to see a drop in nitrogen, know that during this stage your plants don’t need as much nitrogen, so you’ll want to use a bloom booster to get your plants back on track. A few local hydro growers agree Dyna-Gro Bloom helps give just enough of a boost to get your plants’ leaves back to green without overloading the plant and causing nutrient burn.

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