There are hundreds of different fertilizers available to gardeners and not all of them are designed to do the same thing. The process of choosing an organic fertilizer can be difficult if you aren't familiar with what the analysis on the label means. First and foremost the most important step to take when building a healthy garden is to add compost to the soil, but compost alone may not be enough until you have spent several years building the soil. You can think of compost as the conditioner of the soil - it builds great soil structure and creates a healthy environment for the plant roots to become established and take up nutrients- but your plants will also need a source of more readily available nutrients for optimal growth. This is where organic fertilizers come in!
Why I choose organic fertilizers over synthetic?
Understanding the Label Analysis
The first thing you will want to look at when choosing an organic fertilizer is the label analysis. The analysis will always include the big three macronutrients: N-P-K
Nitrogen (N): Nitrogen is usually the most limiting nutrient in any soil as it is used by plants for lush green growth and is the nutrient that leaches most easily. Nitrogen is critical for all plants, but is most critical for plants where dark green leafy growth is the main goal: turf, salad greens, onions, cabbage, herbs, etc
Phosphorus (P): Phosphorus is used by plants for healthy root development and flower/fruit development. Having plenty of available phosphorus is beneficial to all plants, but especially those that you want to flower and/or produce fruits.
Potassium (K): Potassium is critical to overall plant health as it serves many functions related to the plants ability to deal with stress. Potassium ions help regulate water balance and the opening and closing of the stomata, which are both crucial for drought tolerance and overall plant turgidity. Potassium also plays a key role in nutrient uptake and protein synthesis.
Percentages: The percentages on the label refer to the percentage of nutrient by weight. For example, if the percentage of of Nitrogen is 4% like in the label above, this means there are 4lbs of nitrogen in every 100lbs of the fertilizer.
Other Macronutrients and Soil pH
The big three nutrients (N-P-K) are definitely the main components of any plant nutrition regimen, but they only make up a part of overall plant health. There are several other macronutrients that are essential to plant health as well. Most of these macronutrients are found naturally in a healthy garden soil, but sometimes their availability is limited because of soil pH. Adding compost to your soil is the best way to regulate and buffer soil pH.
Sulfur: Helps with the development of enzymes, vitamins, amino acids, and chlorophyll.
Calcium: Important for cell wall structure and transport of other nutrients
Magnesium: Essential for photosynthesis and chlorophyll production
Availability of plant nutrients at different pH levels:
As you can see from this chart, even though your soil may have the essential nutrients needed for plant growth sometimes the nutrients aren't available to your plants depending on your soils pH. The best way to regulate this, as mentioned above, is to add compost to your soil at the beginning of each season. Compost helps to regulate and buffer pH in the soil.
If you are curious what the pH of your soil is you can purchase pH monitors to see exactly where your soil is at. They range in price and efficacy, but I have provided a couple examples here:
In addition to the macronutrients, there are several trace elements needed for good plant growth. If your soil has a good balance of organic compost and fertilizers, you will rarely run into deficiencies with these nutrients in your garden, except for maybe iron (which is usually caused by a pH imbalance not an iron deficiency). The micronutrients include:
boron (B), chlorine (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), and zinc (Zn)
These trace minerals are more important when starting seedlings or growing plants in containers and can be supplied by using a good all around liquid fertilizer. More on this later!
Granular fertilizers are applied to the soil at the time of planting, and can be added to the base of established plants if they need a boost mid-way through the season. The benefits of granular fertilizers are as follows:
Remember when I said there are hundreds of fertilizers to choose from? Well really there is one brand you should become familiar with, because basically there is one brand that will provide everything you need in the garden: MicroLife!
MicroLife brand fertilizer is made in Texas (go local!) and is the pinnacle of organic fertilizers. I use MicroLife products on the farm and there really is no need for anything else because they are formulated with an incredible amount of beneficial ingredients for plant health. I swear I do not work for MicroLife and am not endorsed by them, I just know a good product when I find one.
For starters, MicrolLife offers two all-purpose fertilizers for general garden use for all plants. If you want a safe and effective product start with one of these two:
MicroLife also offers a large line of liquid fertilizers to use in the greenhouse and garden. The benefits of liquid fertilizers are as follows:
MicroLife offers a handful of different liquid fertilizers and soil boosters, but the top 3 that I utilize the most frequently are:
I have been using MicroLife products for a couple years now and I have been nothing but impressed with all that they have to offer. In addition to the Maco and Micro nutrients that are available in these formulas, MicroLife is also formulated with billions of beneficial fungi, bacteria, amino acids, plant hormones, and so much more! Healthy plants are strong and resilient, so if you want to get the most out of your garden you need to feed the soil and plants so they can grow to their full potential. All of those nutrients will feed you, in turn, when you harvest the large nutrient dense fruits and vegetables.
There are full-length books written about plant nutrition, so please feel free to contact me with any questions as this has been a very brief introduction to the topic. If you have more in-depth questions about specific nutrients or how to apply organic fertilizers, I would love to help!
Written by Corey Wahl
Related products for applying organic fertilizers
Corey Wahl - director of farm operations at Ronin Farm - Bryan, TX.