We have a very special guest on the show, Dr. Glen Harris of the University of Georgia. Glen specializes in Environmental Soil & Fertilizers. Tonight, Greg and Glen do a deep dive into what exactly is in fertilizers. It’s time to plant cool weather cover crops and short maturing greens (Mustard, Turnips, Kohlrabi, and Spinach).
What’s In Fertilizer?
A generic label in most garden centers uses 13-13-13. With any and all labels, the first number you see on a fertilizer label is for Nitrogen, the second number is phosphorous, and the third is Potassium. (N, P, K) Glen states that the numbers on these labels are all the same around the world! For it to be a “complete fertilizer” it will need to also include micronutrients as the secondary, such as calcium, magnesium, sulfur, and iron (to name a few).
Ammoniacal Nitrogen (NH3-N) is nitrogen derived from ammonia. One form of nitrogen that your plants regularly use. Most commonly found in the soil is ammonium. It is naturally created by the nitrogen cycle (or introduced) through synthesized fertilizers and deposited into the soil. If you have a high PH in your soil, it can “gas up” and leave the soil (volatilization).
Plants have the ability to take up many chemical forms of nitrogen. Most common, Ammonium (NH-4) which has a positive charge and can be held by the soil; Nitrate (NO-3) which has a negative charge and will have trouble holding onto the soil (too much rain can cause this issue), and Urea ((NH-2)CO)) which has no charge. Many commercial fertilizers contain mixes of a combination of all three of these nitrogen forms. Plants need both Ammonium and Nitrate. Nitrate is very important for your soil and it is the main driver for proteins in your plant.
Urea Nitrogen, when applied to your soil, begins to break down as soon as it is applied. It will hydrolyze and convert into ammonium and carbon dioxide. The main drawback with Urea is the tendency to be lost through volatilization, which is the loss of applied nitrogen to the atmosphere as ammonia gas.
Phosphorous plays a primary role in storing and transferring energy produced by photosynthesis for use in the growth and reproductive process in your plants. Rock Phosphate is an organic source of phosphorous and an issue with this source when putting it directly into your garden. Other types include wood ash, bone meal, manure, and vermicomposted manure. Wood Ash is the most rapidly available organic source of phosphate.
“Phosphorous should be managed. It is immobile in our soil, will build up and get bound in our soil.”, Glen Harris states. It is important for early seed/seedling growth. The roots of the seedlings will have to intercept with the phosphorous and that is mainly why there is phosphorous used in started fertilizers.
Potassium Chloride is the most widely used potassium source worldwide, this aids healthy plant growth disease resistance. It is associated with the movement of water, carbohydrates, and nutrients in plant tissue. The common salt often referred to as potash, is widely used as a major fertilizer. Potassium also helps in reducing water loss and wilting, it also reduces respiration, preventing energy losses.
Potassium chloride is a naturally mined salt, and surprisingly it is considered non-organic. You do not want too much or it could potentially kill the microbes in your soil but if used correctly, it will be very beneficial to your soil.
Just as Important
Boron is a secondary element and many of the vegetable crops need and love boron in the soil. Beets and corn are two of those that need boron.
Sulfur is an anion, and it is very leachable. 90% of sulfur in soil is found in organic matter, which mineralizes and releases sulfur to the plants. Onions and Garlic love sulfur. Sweet onions like sulfur in the early stages of growth.
Calcium plays a vital role in plant growth, promotes healthy soil structure by loosening soils and stabilizing organic matter. Blossom End Rot is a major issue when it comes to growing tomatoes and peppers. Calcium Nitrate and Gypsum Soil Conditioner are great ways to add calcium to your soil. You need to make sure you have enough irrigation going to your plant when you add your calcium, this element needs to be able to move throughout the plant.
Organic Fertilizer vs. Conventional Fertilizer
A member of our Row By Row Group on Facebook asked a question a couple of weeks back, “does a plant know the difference of an element if it comes from an organic versus a conventional source?”, Greg asks. Dr. Glen Harris states, “After being in this field a long time, I can tell you that a plant does not care where nutrate or ammonium came from. Once it gets to the nitrate or ammonium molecule, it’s going to take it up, so I would answer that question with that it may have a preference for nitrate or ammonium but it does not care where it comes from.”