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NPK Fertilizer: What Is It And How Does It Work?

The agriculture industry relies heavily on the use of NPK fertilizer. But what makes up NPK fertilizer, and how does it work?

There are numerous building blocks of life that plants need for healthy growth. Soils often lack these elements, either naturally, or as a result of over cultivation, and needs to have these building blocks put back into it.

NPK fertilizer is primarily composed of three main elements: Nitrogen (N), Phosphorus (P), and Potassium (K), each of these being essential in plant nutrition. Among other benefits, Nitrogen helps plants grow quickly, while also increasing the production of seed and fruit, and bettering the quality of leaf and forage crops. Nitrogen is also a component of chlorophyll, the substance that gives plants their green color, and also aids in photosynthesis.

Phosphorus, also a key player in the photosynthesis process, plays a vital role in a variety of the things needed by plants. Phosphorus supports the formation of oils, sugars, and starches. The transformation of solar energy into chemical energy is also aided by phosphorus, as well as is development of the plant, and the ability to withstand stress. Additionally, phosphorus encourages the growth of roots, and promotes blooming.

Potassium, the third essential nutrient plants demand, assists in photosynthesis, fruit quality, the building of protein, and the reduction of disease.

While these three elements only scratch the surface of healthy plant nutrition and growth, they are the main nutrients required in the development of healthy, productive plants. FEECO International has over 60 years of experience providing fertilizer and equipment solutions to the fertilizer industry. FEECO has the ability to process waste materials into fertilizers, and to process various types of nutrient-rich, easy to handle fertilizers.

Understanding N-P-K

Regardless of its type, any fertilizer you buy will come with information about the nutrients it contains. Prominently featured will be the N-P-K ratio, the percentage the product contains by volume of nitrogen (chemical symbol N), phosphorus (P), and potassium (K). A 16-16-16 fertilizer, for example, contains 16% nitrogen, 16% phosphorus, and 16% potassium. A 25-4-2 formulation contains 25% nitrogen, 4% phosphorus, and 2% potassium.

All fertilizers contain at least one of these components; if any is missing, the ratio will show a zero for that nutrient (a 12-0-0 fertilizer contains nitrogen but no phosphorus or potassium, for instance). Boxed, bagged, and bottled products display the N-P-K ratio on the label. For fertilizers sold in bulk from self-serve bins, the ratio is noted on the bin; for future reference, be sure to write the information on the bags you fill and bring home.

COMPLETE AND INCOMPLETE FERTILIZERS

A fertilizer containing all three major nutrients is called a complete fertilizer; a product that supplies only one or two of them is an incomplete fertilizer. Using a complete fertilizer for every garden purpose seems sensible, but in fact it isn't always the best choice. If the soil contains sufficient phosphorus and potassium and is deficient only in nitrogen (as is often the case), you can save money by using an incomplete fertilizer that provides nitrogen alone (ammonium sulfate, for example). In some instances, complete fertilizers can even harm a plant. Exotic, bright-blossomed proteas, for example, will not tolerate excess phosphorus: they "glut" themselves on it and then die.

The inexpensive soil test kits sold at garden centers can give you a rough idea of the nutrients available in various parts of your garden; for a more detailed evaluation, you may want to pay for a professional analysis. By revealing which nutrients may be lacking, such tests can help you choose an appropriate fertilizer.

GENERAL AND SPECIAL-PURPOSE FERTILIZERS

The various products labeled "general-purpose fertilizers" contain either equal amounts of each major nutrient (N-P-K ratio 12-12-12, for example) or a slightly higher percentage of nitrogen than of phosphorus and potassium (such as a 12-8-6 product). Such fertilizers are intended to meet most plants' general requirements throughout the growing season.

Special-purpose fertilizers, on the other hand, are formulated for specific needs. They're aimed at the gardener who wants a particular combination of nitrogen, phosphorus, and potassium for certain plants or garden situations. These fertilizers are of three general types.

One type, used during the period of active growth, contains largely nitrogen. Such products, with N-P-K ratios such as 16-6-4, are often used in spring, when you want to encourage lush growth or green up your lawn.

Another type is meant to stimulate root growth, stem vigor, and flower and fruit production. Fertilizers of this sort contain little nitrogen and higher levels of phosphorus and potassium; the N-P-K ratio may be 3-20-20, for example. These products are applied at different times and in different ways, depending on what you want to achieve. When you prepare a new planting area, for instance, you'll work a dry granular fertilizer of this sort deeply into the soil, putting the phosphorus and potassium where roots can absorb them. The nutrients help strengthen the new plants' developing stems and encourage the growth of a dense network of roots.

To promote flower production and increase the yields of fruit or vegetable crops, you apply the same sort of fertilizer to established plants after they've completed their first flush of growth. You can use either dry granules, scratching them lightly into the soil, or apply a liquid formula with a watering can or a hose-end applicator.

A third group of fertilizers is designed for use on specific plants. These feature the N-P-K ratios determined to elicit the best performance from the particular plant, as well as other elements proven valuable to that plant. Such fertilizers are named according to the plant they're intended to nourish. Especially useful are formulas for citrus trees and acid-loving plants such as camellia and rhododendron.

Recently, other such plant-specific fertilizers have appeared on nursery shelves, each claiming to be the best choice for a certain plant or group of plants; you may see several sorts of "tomato food" or "flower fertilizer," for example. The jury is still out on the benefit of many of these products, and you will often do just as well to use a general-purpose type. The main distinction is often the price: the "special" formulas are usually costlier than general-purpose kinds.