?When the pilgrims first arrived in America, they were taught by the indigenous people how to grow crops. One of the methods was to drop a small dead fish into the hole where the corn seed was placed,? said Don Johnson, general manager of J.R. Simplot, located in Boise, Idaho. The history of man-made fertilizer began thousands of years ago, when the Chinese applied lime-treated bones to the soil, and the farmers in Britain treated their soil with marl. But, before we get into all the details about fertilizer, let me first ask a question . . . have you ever opened a bag of fertilizer on one of your client?s property and asked yourself, what?s in this bag? What exactly is it that makes the grass so green? Well, here are just a few of the answers. Believe it or not, that bag contains the very same elements that make up the human body. When buying a bag of fertilizer, the first thing you will probably notice on the label are the three major macronutrients needed for plant survival. Those macronutrients, nitrogen (N), phosphorus (P) and potassium (K), are also known as N-P-K, and all are as essential to plants as they are to animals and human life. The amount of each nutrient is usually printed on a bag of fertilizer as a ratio; for example, 5-10-5 or 16-6-8. Each number represents the percentage by weight that each nutrient contributes to the whole product. For example, if a label on a 50-pound bag states that the analysis is 16-6-8, then nitrogen (N) is 16% of 50 pounds, which equals eight pounds of actual N. Phosphorus (P) is 6% of 50 pounds, which is three pounds of actual P, and potassium is 8% of 50 pounds, which is four pounds actual K. The nutrients (active ingredients) equal a grand total of 15 pounds out of the 50 pounds. The balance of weight in the bag of fertilizer is a carrier; the material on to which the fertilizer is sprayed, or impregnated, to permit it to be broadcast easier. The carrier can be designed to break down quickly to release the nutrients rapidly, or to break down slowly to retard the release of nutrients into the soil. ?The formula varies to meet different conditions at different times of the year,? explains Johnson. ?But, it really depends on the manager and what he wants. Some prefer a ?quick-release? fertilizer compared to a ?slow-release fertilizer?. ? Each manufacturer is required by the State Department of Agriculture to list the ?guaranteed? amount of N-P-K in a product. The amount of each nutrient can be more than what?s listed on the label, but should never be less than what the label shows. In addition to N-P-K, many fertilizers contain other nutrient elements as well. Some are deliberately added to give extra value to a product, but most are listed because they are beneficial nutrient contaminants that just happen to be in the parent source mix. A bag of fertilizer contains both macronutrients and micronutrients. Macronutrients include nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and sulfur (S). Micronutrients include iron (Fe), zinc (Zn), copper (Cu), manganese (Mn), molybdenum (Mo), boron (B), and chloride (Cl). These trace elements help the plant in one way or another. For example, iron is essential for the process of photosynthesis, the process by which green plants and other organisms use the energy of light to convert carbon dioxide and water into simple sugar glucose. Photosynthesis provides the basic energy source for virtually all organisms. Plants thirst for a much greater amount of macronutrients than micronutrients, because nitrogen gives plants the ability to grow rapidly and produce large amounts of succulent, green foliage. ?But, before the plants can actually absorb the nitrogen, it must first be converted from a natural gas to ammonium, and further processed to urea,? said Johnson. ?The making of fertilizer involves a lot of chemistry; it?s important that we make the nitrogen in a form that is usable to the plant. If we apply nitrogen that the plant cannot absorb and use, it can have a reverse effect. It can lock up the soil and not allow the plant to feed.? Johnson, who has been in the business for 32 years, and is a former professor of Ventura Community College, Ventura, California, says phosphorus, one of the 16 elements necessary for plant growth, starts out as phosphate rock and then dissolves into a form plants can absorb. Some phosphorus is released as organic matter mineralizes, and some is dissolved from the soil minerals, but the rate of release is very limited. Considered the second most important element, phosphorus plays an important role in seedling development, cell building and root growth. Only about 10 to 20 percent of the applied phosphorus, which usually enters the plant as phosphate, is used by the plant within the year it is applied. Phosphorus sources tend to be one or another form of phosphoric acid, which is very stable in soil. Once it?s applied it stays in the soil, because it does not volatize nor leach through the soil, as do nitrogen and potassium. The most common visible signs of a lack of phosphorus in a plant appear first in the lower leaves because of the movement in the tissues. These are the older leaves, and they show symptoms as a lack of chlorophyll, a deepening of the green color, or a reddish color in the leaves. The third ingredient, potassium, assists plants in forming starches and protein. It is sourced from either rock or water, using the process of evaporation or electrolysis to draw minerals to the region.