Organic Fertilizers Columbia SC
Columbia , SC
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Organic soil amendments surround organic compost. Clockwise from 1 clock: azomite, sul-po-mag, black rock phosphate, seaweed meal, greensand, soybean meal, gypsum pellets, lime and an organic blend.
ynthetic fertilizers are, as the name implies, manufactured. Because they are derived from natural sources, a portion of the nutrients in organic fertilizers may be temporarily locked up, unavailable to plants until it's unleashed by a combination of warmth and moisture that stimulates microbial activity. This has its advantages. Because warmth and moisture also coax plants to grow, nutrients from organic fertilizers are doled out in sync with plants' needs.
A single application may be sufficient to last the whole growing season, and nutrients are less likely to be washed out of the soil by rainfall before plants get a chance to use them. But if you spread a season's worth of synthetic fertilizer beneath your plants, you're likely to "burn," or damage, plant roots and/or lose nutrients through leaching. You also might choose to use an organic fertilizer for philosophical reasons rather than its effects on the soil and plants. The manufacture of synthetic fertilizers uses fossil fuels - nonrenewable resources.
Organic fertilizers offer opportunities to recycle all sorts of waste materials, from feedlot manure to sewage sludge to brewery wastes, into nutritious plant food. However, be careful of the contents of certain fertilizers when you are using them on edible plants. For example, sewage sludge and leather meal may contain heavy metals and should not be used on vegetable or edible-flower gardens. Why Fertilize at All? Soil loses nutrients naturally as rainfall percolates through or skims particles off the surface. And when you harvest vegetables, fruits and flowers, you are removing the nutrients within those plant parts from the site. All told, plants require 16 nutrient elements - three from the air and 13 from the soil (see the chart on page 20). But the three primary nutrients - nitrogen (N), phosphorous (P) and potassium (K) - are needed in the largest amounts. Most soils contain sufficient reserves of the other nutrients.
The other nutrients might also hitchhike along when you fertilize for the big three, or when you apply limestone to counteract acidity. Another plus for organic fertilizers is that they are not pure chemicals, and their impurities include many of the other required nutrients. The Menu In the world of organic fertilizers, there are many different sources for each of the three major nutrients plants need. Let's begin with nitrogen, because this is the nutrient that is needed in the largest amount and the one most readily lost from the soil.
Nitrogen: Nitrogen in organic fertilizers is derived from manures, animal by-products and plant parts. Actual nitrogen concentrations of manures vary not only with the kind of animal, but also with the bedding used, the age of the manure and how it was stored. Animal by-products (such as blood meal) and plant parts (such as soybean meal) are generally more concentrated and more consistent in their nitrogen concentration. Animal by-products rich in nitrogen include blood meal, fish extracts, hoof and horn meal, dried whey, and leather dust; plant parts include soybean meal, cottonseed meal, alfalfa pellets or meal, corn gluten (also a natural herbicide), and beet pulp. Phosphorus: Manures are also fairly rich in phosphorus. Other relatively rich sources for these nutrients are certain animal by-products, as well as certain rocks. Animal by-products rich in phosphorus include bone meal and dried whey. Phosphorus-rich rocks, such as the appropriately named rock phosphate, are ground up into fine particles that release their phosphorous slowly, over many years, when applied to the soil. Alfalfa pellets and alfalfa meal are also rich in phosphorus. Note: In general, manure should be well-composted before it is applied to a garden with plants or before planting takes place. Raw manure can burn plants, especially if they are young. Potassium: Manures also contain some potassium, but richer sources include natural minerals and certain plant derivatives. Greensand and granite are two potassium-rich rocks; both release potassium slowly and over a long period of time. Potassium derived from wood ash, seaweed, and alfalfa pellet or meal are more quickly available to plants.
Complete, or mixed, fertilizers: Many commercially available organic fertilizers are blends of two or more of the above ingredients. One advantage of blends is that they provide a spectrum of nutrients - if that's what you need. Depending on the particular blend, the total amount of nutrients and how quickly they are available to your plants can also vary. The label will state, in bold numbers, the concentrations of nitrogen, phosphorus and potassium. For example, a 10-5-10 fertilizer contains 10 percent nitrogen, 5 percent phosphorus and 10 percent potassium by weight. The fine print tells you the various other ingredients that make up the mix. Incomplete fertilizers: This is the alternative to mixed fertilizers. Incomplete simply means that the fertilizer contains only one essential nutrient, such as nitrogen in a 7-0-0 fertilizer, or potassium in a 0-0-10 fertilizer. Getting Started The way to know just how much N, P, K or any other nutrient your soil needs is with a soil test. Soil tests are especially useful in new gardens. Once you have gardened in the same spot for a few years and amended the soil with the appropriate fertilizers and pH treatments, then your garden will only need enough nutrients to make up for natural losses and what you harvest.
Wildflower plantings, trees and shrubs may not need any fertilizer, especially if you keep the ground beneath such plantings blanketed with a permanent mulch of leaves, straw or some other organic material, all of which release nutrients into the soil as they decompose. Fruit trees and bushes, and more formal flower gardens need moderate fertilization. The hungriest part of the garden is the vegetable patch, because here is where you push growth and (hopefully) carry off an abundance of nutrients with your harvest. The actual amount of fertilizer to apply depends on the nutrient concentration of the fertilizer. Try to find a fertilizer close to the ratio of N, P and K that your soil test recommends. Since this can be difficult to do exactly, base your application rate on the nitrogen element. If you are still unsure as to the exact amount you should apply to your soil, talk to someone in your local nursery, garden center or agricultural extension. Before fertilizing, include a pH test in your soil profile.
Inadequate soil pH may inhibit the plants in your garden from retrieving the nutrients from the soil. Most vegetables are comfortable at a pH of 6.0 to 7.0. Add lime to bring the pH up (more alkaline) and sulfur to bring it down (more acidic). Do-it-yourself nutrient and pH tests are generally available at garden stores. For more sophisticated (and more expensive) testing, contact your local agricultural extension. Applying Organic Fertilizers Keep in mind how plants feed and how organic fertilizers act in the soil when using them. Most feeder roots - of all plants, from strawberries to oaks - lie just beneath the surface, so generally there is no need to work organic (or synthetic) fertilizer deep into the soil. Besides, the low oxygen levels there would retard microbial growth, in turn slowing nutrient release from organic fertilizers. Make exception to that no-dig rule when phosphorous levels are low. This nutrient moves very slowly in the soil, so the only way to spread it quickly through the root zone is to mix it into the top 6 to 12 inches of soil. Once your soil is up to snuff with respect to phosphorous, periodic applications at the surface will trickle down through the soil profile rapidly enough to maintain adequate levels throughout the root zone.
Remember that the nutrients in most organic fertilizers are initially insoluble and come in forms that plants cannot use immediately. Account for the time lag between application and nutrient release by spreading organic fertilizers a few weeks before planting - or even a few months! Fertilizer applied in fall will be in place, ready to release its goodness just as plants start to grow in spring. Because soil microorganisms need time, warmth and moisture to release nutrients from organic fertilizers, dry soils may need special consideration.
Fertilizers applied to the soil surface cannot feed plants as long as the surface remains dry. In this case, watering not only quenches a plant's thirst; it also provides it with food. Occasionally, you may have to tailor your fertilizer to special conditions. For instance, an especially long spell of unseasonably cool weather in spring slows microbial activity. If you need to spur plant growth, apply a light application of some soluble organic fertilizer whose nutrients are available immediately - blood meal or fish emulsion, for example. A quick-acting fertilizer might also be needed when a plant is so hungry that it actually shows symptoms of starvation - yellowing, older leaves, for example - and needs some fast food. Leaves can absorb nutrients directly, and for a really quick effect, you can even spray solutions of fertilizers, such as seaweed extract or fish emulsion, right on leaves. Avoid plant injury by reading label directions and following specified rates carefully.
Note: Be sure to use this topical application after watering or forecast rain, because the water will wash the fertilizer off the leaves. Consider use of quick-acting fertilizers as quick fixes only. If you build up good reserves of nutrients in your soil, such applications are rarely, if ever, needed. Bulk in the Diet Much of the benefit in feeding plants organically comes not from the nutrients they contain, but from the organic matter - the bulk - associated with those nutrients. Among other benefits, organic matter helps soils hold water and air, makes nutrients already in the soil more available, and helps prevent diseases. Keep in mind that the more concentrated a fertilizer, the less organic matter it contains. If you use concentrated fertilizers, make sure also to apply plenty of bulky organic matter. Dig materials such as straw, peat, compost and leaves into the soil; or lay them on as mulch. There's no substitute for a pitchfork in good gardening. Lee Reich is a garden writer and consultant based in New Paltz, N.Y. His most recent book is Weedless Gardening (Workman Publishing).