Using Right Fertilizer

FERTILIZER - UNDERSTANDING IT’S CHEMICAL COMPOSITION:

It it important to select the most appropriate fertilizer to use on a specific type of orchid. The chemical components used in different fertilizers varies greatly from one brand to another. Additionally, the type of fertilizer, and amount that you use will need to be adjusted to suite the seasonal growth phase which the plant is currently in.

What do the numbers really mean?
The first thing to understand when selecting fertilizers is the chemical composition code labeled on the container. These numbers are almost always listed as a sequence of 3 numbers, such as 30-10-10, or 10-50-10.

NITROGEN (N) - The first number in the sequence specifys the nitrogen content of the fertilizer. and is given as a percentage. Nitrogen promotes vegitative growth in plants.

PHOSPHORUS (P) - The second number in the sequence specifys the phosphorus content of the fertilizer. Phosphorus promotes flowering. Fertilizers labeled with disproportionatally high amounts of phosphorus are sometimes labeled as “bloom booster”.

SOLUBLE POTASH (K) - The third number in the chemical sequence referrs to % soluble potash, K₂O, contained in the fertilizer.

A fertilizer labeled as 30-10-10 would contain 30% nitrogen, 10% phosphate, and 10% soluble potash, and would generally be used during a plant’s active growth cycle. While a fertilizer labeled as 10-50-10, would contain 10% nitrogen, 50% phosphate, and 10% soluble potash, and would typically be used prior to and during a plant’s blooming season.

Once your understand the basic composition of fertilizers, there are a number of additional factors to consider:

UREA VS NON-UREA BASED NITROGEN:
While the first number of the code on the label tells you what percentage of the fertilizer is Nitrogen, the number alone does not tell you the entire story. There are 2 primary sources of nitrogen which fertilizer manufactureres use; urea based, and non-urea based nitrogen.

Urea is a nitrogen based chemical. There is some evidence to indicate that, in its natural form, the nitrogen contained in urea is not able to be utilized by plants. In order for the nitrogen in urea to be used, it must be broken down by a chemical process and normally, this process is accompolished by bacteria residing in the soil or potting medium.

Non-urea based fertilizer is believed to be a more readily usable form of nitrogen, than urea based nitrogen. While there is much debate surrounding whether or not urea based nitrogen can be absorbed by plants, there is no one who will dispute the fact that non-urea based nitrogen is utilized by plants without further need for chemical decomposition. Two common used non-urea based nitrogen components of fertilizer are Ammoniacal Nitrogen, and Nitrate Nitrogen.

Why the debate over urea and non-urea based nitrogen? What it really comes down to is cost. If urea based and non-urea based nitrogen cost the same abount, there would probably be no debate. Most people would probably just use non-urea based fertilizers. However, urea is a bi-product of a chemical manufacturing process, and so urea is abundant and available at a very low cost. This makes urea derived nitrogen fertilizer relatively inexpensive to produce, compared to fertilizers derived from more costly non-urea based chemical components. Ultimately, you will have decide for yourself, whether or not the added expense of non-urea based fertilizer is justified.

ESSENTIAL TRACE ELEMENTS:
In addition to the primary 3 chemical components which I have listed above, some fertilizers contain additinal micronutrients and other essential trace elements. While the role of these trace elements is not as clearly defined as the role of nitrogen, phosphorus and potash, the presence of these trace elements could have a beneficial effect on your plants. It is a good idea to include fertilizers of this type from time to time.

SALTS:
When the chemicals contained in fertilizers interact with each other, interact with chemicals in the soil or potting medium, or are involved in biological processes, the chemical interactions can result in the formation of salts. The fertilizers themselves may also contain salts. The presence of salts can damage or burn plants roots, and you should endeavor to use low salt fertilizers, as well as vigorously flush the soil or potting medium with water, when possible.

POTENTIAL ACIDITY:
A measure of the potential acidity of the fertilizer is sometimes supplied on the lable, and is typically given in terms of pounds of calcium carbonate per ton of fertilizer.