Fertilizer can be a daunting and confusing subject. There are so many options available and even more fields of thought about which ones are the best for different plants. I am not going to address ALL the potential fields of thoughts in this article but I will go over some basics and what I (as only one horticulturist at Nick’s) know to be successful applications.
Fertilizers should consist of both Macro Nutrients and Micro Nutrients. The macro nutrients are the three main numbers which denote in order Nitrogen (N), Phosphorus (P), Potassium (K). Lack of these three elements in a usable form is responsible for limiting the majority of growth in most plants.
In general the first number, Nitrogen, is used mainly for foliage growth. This is why you will see many lawn fertilizers with much higher first numbers than the others. Urea is a type of grass fertilizer that has ONLY Nitrogen in it and LOTS of it at 46%. These are usually what we refer to as “hot fertilizers” and aren’t recommended by many horticulturists in Colorado for residential use. Hot fertilizers can and will burn a yard. Instead look for a more mild fertilizer with slow a release Nitrogen such as Pro-rich by Richlawn. This is one my favorites for a few reasons. I like the slow release Nitrogen, I LOVE that it is a Colorado product made for Colorado lawns, and it has some decent micro nutrients in it like Iron (which I will get to later.)
The Second number on fertilizers is Phosphorus (P). You will usually find high percentages of phosphorus in products like Bloom Booster. That is because this nutrient helps promote three main plant processes: blooming, rooting, fruit production. It does do much more than this, but I am trying to keep it simple. Some bloom booster fertilizers will have as much as 60%. These fertilizers are great for annual flower beds and hanging baskets. Generally fertilizers with phosphorus levels come in liquid or dissolvable powders so that the phosphorus is readily available for plant use. You should also see a high percentage in fertilizers specialized for vegetables new plants, but not in those concentrations.Ferti-Lome As I stated before phosphorus also helps promote root and fruit production as well. Fertilizers balanced for fruits, vegetables, and new plants should have a concentration a little higher or even to the amount of Nitrogen. Too much Nitrogen will cause a plant to expend energy on foliage growth when instead it should be producing fruit or roots to become established.
The Third number of the macro nutrients is Potassium (K). Without getting too in depth it is hard to describe all the functions potassium is responsible for. To keep it simple I will simple say that similar to the human body it helps with chemical communication within the plant. It also helps with photosynthesis, water usage, and protein and starch synthesis. To sum it up there are several essential functions of the plant that require sufficient levels of potassium. When shopping for fertilizers keep this in mind and don’t rule it out as nonessential.
Micronutrients are far too numerous to list all of their uses. A few of the important ones are Calcium (Ca), Iron (Fe), Magnesium (Mg), Sulfur (S), Zinc (Z), Manganese (Mn), Boron (B), and Molybdenum (Mo). Most of these are found in a soil profile deposited by broken down organic material. It is important to note that because Colorado has soils frequently high in pH some of these nutrients get “bound up” and are not available to the plant such as iron, calcium, and sulfur. Not all fertilizers will have trace amounts of all of these micronutrients either. This is one of the many reasons that Colorado plant scientists will encourage the addition of composted organic material when planting anything. Evidence of micronutrient deficiencies can show up in a number of ways. The two most common in Colorado are chlorosis, most often lack of iron in maples, and blossom end rot, most often lack of calcium in Natural Guardtomatoes. Using fertilizers high in the specific micronutrient they are lacking will help avoid these problems. One of my all-time favorite products that helps as a cure all for many problems we face due to lack of available micronutrients in Colorado is Humic Acid.
Humic acid is most easily described as highly broken down organic material. It acts as a one two punch by adding more organic material to the soil, and by simulating a drop in the soil pH to help micronutrients that are there become available for plant uptake. As a test I used this at the beginning of 2012 under my 30 year old maple. This year turned out to be a horrible year for chlorosis in maples. My maple stayed green throughout the season while many around me had faded and looked almost dead. This showed me the powerful beneficial effects humic acid has on plants’ health.
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