Basic Plant Nutrition

Most everyone understands that plants like humans and animals need food to survive. However very few of us understand the science of nutrition and fewer still understand how a plant uptakes the food (fertilizer) that we give them on a regular basis. The nice man on TV says use KA-BLOOM for bigger violets. A few days later everyone is calling and asking “do you have KA-BLOOM?” Sound familiar? The same nice man may appear on your favorite cable channel late at night or early Sunday morning trying to sell you the latest “supplement” for your diet. A little understanding and a little rhyme is all you need to know about plant food.

First off plant food and fertilizer are the same thing. The names are interchangeable. There is no legal definition or labeling requirement I am aware of saying what plant food needs to be called.

Secondly plants cannot tell the difference between organic/natural and commercial chemical fertilizers. Plant roots can only uptake nutrients in their simplest form which is chemical. This is not as drastic as it sounds. While bone meal is a natural source of phosphorous plant roots cannot “chew” the bones nor suck up fish emulsion through a straw. It is the microbial activity going on in the soil (composting ) that breaks down organic fertilizers into their simplest chemical forms. This is where organics give an added benefit in the long run. Microbes tend to multiply when they have something to do like break down bone meal.

One organic/natural fertilizer that can pollute water tables just as easily as chemical forms: fresh animal manure. Fresh manure is loaded with ammonia. This ammonia enters the water table, streams and burns plant roots. Ammonia is also the least expensive form of nitrogen added to fertilizers. Ammonia is “quick acting” released immediately upon contact with soil or water. Although this is the form plants use fresh manure and cheap fertilizers release too much ammonia at one time. (Think soaked baby diapers) What the plants don’t use passes right through the soil into streams and water tables.

Chemical forms of nitrogen can be buffered with different coatings or methods that make them act more like natural ones. SCU stands for sulphur coated urea. Urea is the second fastest released form of nitrogen after ammonia. Coating urea with sulphur slows down the release of nitrogen. Slowing down chemical nitrogen does not give the benefit of increasing microbe populations like organics do. Some sulphur coated urea manufacturers go so far as to call the process synthetic organic!

Remember we said a little rhyme in the beginning? Well here it is: shoots, roots and fruits. Shoots refers to nitrogen and the green “shoots” (leaves) it promotes. Roots refers to phosphorous. Fruits refers to potassium which is responsible for brighter flowers and larger fruits (or vegetables). The order of this rhyme is the order the nutrients appear on a fertilizer package such as 10-6-4. The numbers refer to the percentage by weight of each nutrient. 10-6-4 has 10% nitrogen by weight, 6% phosphorous and 4% potassium.

While organic fertilizers are better for the health of the soil they are also a very expensive way to buy nitrogen. A forty pound bag of 10-10-10 which costs nine dollars contains four pounds of nitrogen. The cost four pounds of nitrogen is roughly ninety nine cents. A fifty pound bag of a popular natural fertilizer costs twenty one ninety nine and contains four percent or two pounds of nitrogen. The cost for that two pounds of natural nitrogen: around one dollar.

Simple nitrogen fertilizer costs twenty five cents per pound in the above example while the natural form runs fifty cents a pound or twice the cost of farm grade nitrogen