It's the fourth most common element in the Earth's crust, and all plant and animal life depend on nitrogen to survive and thrive. It's also the first element in the NPK formula.
Nitrogen has been used in agriculture since farming began, and is still one of the most common supplements used in agriculture today. So yes, nitrogen is a big deal.
If you're growing any sort of plant, you are likely familiar with the process of photosynthesis. Put simply, photosynthesis is the process that plants use to break down energy from sunlight into digestible sugars from water and carbon dioxide.
An essential compound used in photosynthesis is chlorophyll. Can you guess what element is essential for chlorophyll to function? That's right, nitrogen.
In other words, without nitrogen your plants will not be able to efficiently breakdown the light they receive, whether from the sun or your indoor lights. When your plants can't convert light into energy, they can't grow, and you can guess what happens next.
It is clear by now that nitrogen is essential throughout all stages of your plants' growth, but it serves a greater purpose in the early development of your plants growth.
Without high amounts of nitrogen, especially during the vegetative growth stage, your plants' yield will greatly reduced as water up-take slows from vascular breakdown in your plants.
And don't be fooled; nitrogen issues can happen throughout the entire growth cycle. Most importantly though, plants should never experience a nitrogen deficiency during vegetative growth. However, over-fertilizing with N causes problems too.
One of the toughest obstacles a grower will inevitably deal with is nutrient deficiencies. In a lot of cases, nutrient deficiencies can look very similar to each other, which makes dealing with them a little bit of a guessing game.
With nitrogen however it is actually relatively easy to spot a deficiency compared to other nutrients. The most noticeable sign of a nitrogen deficiency is yellowing in your leaves.
The yellowing will start on your older leaves that are lower on the plant, and as the deficiency progresses the leaves will eventually wilt and fall off. On the leaf itself, the yellowing wills start from the vein of the leaf and spread outward, but the vein will maintain its green color.
Because your plants value their tops more (that's where most of the light is received), your leaves on the top of your plant will actually steal nitrogen from your lower leaves, which is what causes them to die off.
If your plants are in their later stage of growth, lower leaves falling off and focusing energy to the top isn't actually a bad thing as you want more energy focused on your flower sites.
However if this problem begins in your vegetative stage, it's a problem that needs to be dealt with quickly.
Fixing a nitrogen deficiency is very simple. With a nitrogen supplement added in to your feeding regiment you can give your plants the nitrogen they are missing.
Be careful not to go overboard with the supplements though. It's not uncommon to see your plants hurting and give them a little extra in the hopes they bounce back quicker.
However giving your plants too much nitrogen can have just as negative results. Your plants can take a lot of nitrogen during their vegetative stage, making a problem like nitrogen lockout or nitrogen toxicity less likely to occur. But keep this in mind if you encounter a nitrogen deficiency in your flower stage as the opposite is the case, and giving too much nitrogen can have a negative impact.