All About Fertilizers
Fertilizer Basics Well-fed plants are healthier, more productive and more beautiful. This guide will walk you through the basics of why and how to fertilize your plant. Plant Nutrients 101 Plants need to be fertilized because most soil does not provide the essential nutrients required for optimum growth. Even if you are lucky enough to start with great garden soil or pot mix, as your plants grow, they absorb nutrients and leave the soil less fertile. By fertilizing your garden, you replenish lost nutrients and ensure that plants have the nutrients they need to flourish. Six Primary Nutrients There are six primary nutrients that plants require in fairly large quantities. 1. Carbon from CO2 in the air 2. Hydrogen from water 3. Oxygen from water and air 4. Nitrogen helps plants make the proteins they need to produce new tissues. In nature, nitrogen is often in short supply so plants have evolved to take up as much nitrogen as possible, even if it means not taking up other necessary elements. If too much nitrogen is available, the plant may grow abundant foliage but not produce fruit or flowers. Growth may actually be stunted because the plant isn't absorbing enough of the other elements it needs. 5. Phosphorus stimulates root growth, helps the plant set buds and flowers, improves vitality and increases seed size. It does this by helping transfer energy from one part of the plant to another. To absorb phosphorus, most plants require a soil pH of 6.5 to 6.8. Organic matter and the activity of soil organisms also increase the availability of phosphorus. 6. Potassium improves the overall vigor of the plant. It helps the plants make carbohydrates and provides disease resistance. It also helps regulate metabolic activities. Three Additional Nutrients That Matter Plants also need these three nutrients, but in much smaller amounts: 1. Calcium is used by plants in cell membranes, at their growing points and to neutralize toxic materials. In addition, calcium improves soil structure and helps bind organic and inorganic particles together. 2. Magnesium is the only metallic component of chlorophyll. Without it, plants can't process sunlight. 3. Sulfur is a component of many proteins. Micronutrients Finally, there are seven elements that plants need in tiny amounts. Healthy soil that is high in organic matter usually contains adequate amounts of each of these micronutrients: boron copper iron molybdenum zinc chlorine manganese Organic vs. Synthetic Do plants really care where they get their nutrients? Yes, because organic and synthetic fertilizers provide nutrients in different ways. Organic fertilizers are made from naturally occurring mineral deposits and organic material, such as bone or plant meal or composted manure. Synthetic fertilizers are made by chemically processing raw materials. In general, the nutrients in organic fertilizers are not water-soluble and are released to the plants slowly over a period of months or even years. For this reason, organic fertilizers are best applied in much earlier stages of growth. These organic fertilizers stimulate beneficial soil microorganisms and improve the structure of the soil. Soil microbes play an important role in converting organic fertilizers into soluble nutrients that can be absorbed by your plants. In most cases, organic fertilizers and compost will provide all the secondary and micronutrients your plants need. Synthetic fertilizers are water-soluble and can be taken up by the plant almost immediately. They are best to provide immediate plant nutrients requirement in a controlled manner. But applying too much synthetic fertilizer can "burn" foliage and damage your plants. For the long-term health of your garden, building the soil with organic compost and applying synthetic fertilizers when necessary is the best way to go. This will give. Foliar Feeding? Plants can absorb nutrients eight to 20 times more efficiently through their leaf surfaces than through their roots. As a result, spraying foliage with liquid nutrients can produce remarkable yields. For best results, spray plants during their critical growth stages such as transplanting time, blooming time and just after fruit sets. What About pH? Even if proper nutrients are present in the soil, some nutrients cannot be absorbed by plants if the soil pH is too high or too low. For most plants, soil pH should be between 6.0 and 7.0. A soil test will measure the pH of your soil. You can buy a simple pH tester on Amazon and do it yourself. Lime or wood ash can be used to raise pH; sulfur or aluminum sulfate can lower pH. Keep in mind that it's best to raise or lower soil pH slowly over the course of a year or two. Dramatic adjustments can result in the opposite extreme, which may be worse than what you started with. How to Choose a Fertilizer In most cases, an all-purpose, 5-5-5 fertilizer will provide the nutrients all plants need for healthy growth. If a soil test reveals certain nutrient deficiencies, or if you want to tailor your fertilizer to the needs of particular plants (tomatoes vs. flowers), you can select a special formulation. What you choose will depend on your soil and what you are growing. The three numbers that you see on a fertilizer label, such as 5-5-5, tell you what proportion of each macronutrient the fertilizer contains. The first number is always nitrogen (N), the second is phosphorus (P) and the third is potassium (K). This "N-P-K" ratio reflects the available nutrients (by weight) contained in that fertilizer. For example, if a 100-pound bag of fertilizer has an N-P-K ratio of 5-7-4, it contains 5 pounds of nitrate, 7 pounds of phosphate (which contains phosphorus), 4 pounds of potash (which contains potassium) and 84 pounds of filler. Note that the N-P-K ratio of organic fertilizers is typically lower than that of a synthetic fertilizer. This is because by law, the ratio can only express nutrients that are immediately available. Most organic fertilizers contain slow-release nutrients that will become available over time. They also contain many trace elements that might not be supplied by synthetic fertilizers.