Nitrogen is one of the nutrients most people have heard of that plants need to grow healthy. It's one of the three macro-nutrients listed on fertilizer labels, so this may be why so many people have heard of it. The "N" on a label that lists N-P-K, is the nitrogen content of that input.
Nitrogen is used by plants for vegetative growth, and contrary to popular belief, nitrogen is still needed when cannabis is flowering. Although in flower, cannabis needs much less nitrogen than in veg.
For vegetable growers, tomatoes, corn, etc., they will need ample supplies of nitrogen for strong healthy growth as well. Depending on the crop, you may need to focus on supplying nitrogen throughout the entire growing season.
The best way to find out what your nitrogen levels are, is to get a soil test. Once you have your soil tests results, you can then use those numbers to help you choose the correct organic soil amendment for your particular application.
Organic Soil Amendments That Provide Nitrogen
Fish meal is a waste product from the fish industry. It is typically high in nitrogen with lesser amounts of phosphorus and potassium. I personally like diverting waste products when appropriate for agricultural use. This is one of those instances. It will give a longer lasting supply of nitrogen, that may be enough for your plants for multiple months. I personally love fish meal as a nitrogen source, and the microbes will love digesting it when applied to the soil.
Soybean meal is a solid choice for nitrogen depleted soils. It is usually domestically procured when in the US, and can be purchased at most coop's. Since it's pretty widely available, it makes a great choice for topping off your nitrogen levels after soil testing. It would be considered plant based, and may can be a great choice when you are looking for vegan nitrogen inputs.
Alfalfa Meal is along the same lines as soybean meals a plant base alternative that is vegan friendly. Typically it is from the US, and is in ample supply. It can be purchased from coop's, feed stores, and many more stores across America. It does provide nitrogen, but not in as a high as an amount as other amendments. One of the great things with alfalfa meal is it won't burn your plants, so if you accidentally over apply, your plants won't suffer.
Feather Meal contains high amounts of nitrogen. It's a diverted waste product from the poultry industry, but commercial cannabis growers need to be careful because of the higher arsenic levels. If passing heavy metals test for cannabis growing is something you are concerned with, I will skip feather meal. Other than that it's usually pretty inexpensive and can be found in most feed stores in the US.
Blood meal may be one of the most well known old school nitrogen sources. It's really high in nitrogen, along the same lines as feather meal. That being said, blood meal can and will burn your plants if over applied. It is a readily available source of nitrogen, and you can get in trouble real fast if you are heavy handed with it. Blood Meal is so readily available it's at most garden centers, and big box stores.
High Nitrogen Bat Guano
Guanos are popular around the world. There are ethical considerations about guano's you need to consider, but they are effective at adding nutrients to soils. A high nitrogen bat guano will give a quick boost to your soils that may be noticed by a plant response within as little as one day. For a quicker way to get the benefits, you can mix powdered High nitrogen bat guano in water and water in the root zone. Always take care to wear a mask when handling any guanos.
The most important take way from this blog post, is to always get a soil test to let you know exactly how much nitrogen you need.. For your average vegetable gardener, a test once per year is plenty. This will ensure you are only applying what you actually need, and nothing else. Long term, this will actually save you money, all while having a happier healthier garden.