When determining whether a fertilizer product meets the requirements of the USDA Organic Program or of Certified Organic Farming, the decision is often based on the the category of Nitrogen present in the fertilizer. There are four categories:
- Ammoniacal
- Nitrate
- Urea
- Organo-Protein
All four of these have identical representation in the plant: the "certified organic" decision is not based on what the nitrogen sources put in the plant. Further, all four forms when applied in dosages listed on the label are beneficial to both the target plant and other life forms in the soil. In fact, the 1st three are utilized so well that they create an imbalance in the local ecosystem and thus violate the letter of the National Organic Program law: they significantly impact the local environment. Consequently, the only permissible form of Nitrogen in a "certified organic" fertilizer is Organo-Protein.
Organo-Protein nitrogens are found in plant and animal material in varying concentrations. If you are going to use one of these, read the label to avoid any "features" you might not have anticipated. Here are some examples:
- Alfalfa Meal - This is typically from non-GMO alfalfa which you can verify with the manufacturer. The issue here is that the concentration of Nitrogen is so low that the actual cost per net pound of Nitrogen is enormous.
- Blood Meal - This is baked blood from slaughterhouses. It is generally free of pathogens, but can contain active pharmaceutical compounds which some plants may uptake. If this is a concern to you, then verify that the source is from pharmaceutical-free livestock.
- Cottonseed Meal - The USDA reports that 100% of commercial cotton grown in the US is GMO glyphosphate-resistant ("roundup ready"). If this is a concern to you then it is something to avoid. Personally I don't have a problem with it.
- Fish Emulsion - Here you want to insure the product is from a major manufacturer that has performed some secondary processing to remove mercury and other heavy metals from the emulsion, along with the machine oils from the fish factory processing equipment. There are a couple of manufacturers producing Fish Emulsion with added Seaweed Extract: this is an excellent fertilizer for leafy growth.