Roanoke Times
Copyright (c) 1995, Landmark Communications, Inc.
DATE: THURSDAY, March 15, 1990< TAG: 9104050128
SECTION: LAWN & GARDEN PAGE: 2 EDITION: EVENING
SOURCE: John K. Arbogast / Special To The Roanoke Times & World News
DATELINE: LENGTH: Long
Basically, organic matter is defined as naturally occurring products of plants or animals or their remains. Organic matter is vital to soil because it improves the tilth, or workability, the structure and the water-holding capacity of the soil; makes nutrients available to plants; and may help to control soil-borne plant diseases.
Most organic-matter additions to the soil, such as leaves, dead plant parts or sawdust, are worked into the soil in the fall to allow the substances time to decay into humus by spring planting time. This is important when "fresh" or green materials are used, including materials that could be too rich for growing plants, those that might cause a soil imbalance for a few weeks, or those that just need to break down to become part of the soil system.
Organic materials that have already aged or broken down, such as compost, old manure from barns or processed forms such as peat moss, can be thoroughly worked into garden rows before seeding or into holes before setting transplants.
Just as in the fall, it is possible in the spring to work in too much organic matter at one time. A good suggestion is to spread a 2-inch organic-material layer and mix it into the soil to the root depth with a rototiller or shovel.
The other boost for vegetables in the spring are fertilizers. Gardeners for years have grown food crops through the use of fertilizers and some folks may not think twice about the importance of this simple practice. Now, however, there is increased concern about the nutrients in fertilizers and manures contributing to pollution problems or simply being wasted.
Garden fertilizers are derived from either chemical or organic sources and may be purchased in many different formulations. It doesn't matter to a growing plant whether the nutrients come from an organic source or a synthetic fertilizer. The major difference is that most organic fertilizers contain small amounts of nutrients which are released to the soil over an extended time, not all at once.
Both processed organic fertilizers, such as fish meal, and synthetic fertilizers, such as 5-10-10, are identified by their analysis, which is the three numbers on the bag or container.
Careful consideration of the analysis tells us just how to use that particular product and what results we can expect. The numbers refer to the percentage of nitrogen, phosphorus, and potassium, respectively, in the fertilizer. For example, a 100-pound bag of 10-10-10 contains 10 percent (which is 10 pounds) of actual nitrogen, 10 percent (10 pounds) of actual phosphorus and 10 percent (10 pounds) of actual potassium. The rest is inert material used to hold the product together.
Examples of processed organic fertilizers which should be easily available at garden outlets are Blood Meal, which contains nitrogen only (12-0-0) and Bone Meal, which contains phosphorus only (0-12-0). Examples of easy-to-find synthetic fertilizers are 5-10-5, 5-10-10, and 10-10-10. Some synthetic fertilizers release slowly as organics do. This information should be on the package label. Synthetic fertilizers are produced in two forms: a granular form that is usually sprinkled on the soil and worked in with a tiller or hand tool, and a water-soluble form that can be mixed with water and sprinkled on the plants' leaves or used to water in a transplant.
Let's look at what the "big three" nutrients do and see how we can use them effectively.
Nitrogen is necessary to plants for leaf growth and greener leaves. The amount and timing of the nitrogen application is very important. Too much or application at the wrong time can lead to an overabundance of foliage with delayed flowering and fruiting, such as when tomatoes receive a lot of nitrogen early in their growth and can't make tomatoes until late summer. Also, too much nitrogen can cause plant death due to excess fertilizer salts around the roots, causing leaf and root burn: This occurs readily with nitrogen but is not as common with the other major fertilizer elements.
Nitrogen also has the reputation for being misused or wasted. Research has shown that up to 50 percent of the nitrogen from inorganic fertilizers can be lost to leaching and other breakdown processes. However, much of this lost nitrogen can be retained by the incorporation of organic matter, proper mulching, slow watering and the maintenance of proper soil pH:
Phosphorus is necessary in the plant to increase fruit development and produce a strong root system. Phosphorus does not leach as much as nitrogen does, but phosphorus that is not used by the plant can be lost in soil erosion.
Potassium, the third major element, is also important to the strength of the plant. It is not responsible for growth of one particular plant part but it does contribute to the formation of carbohydrates and proteins.
Before applying fertilizer to any garden, it is best to test the soil at least once every three years. The test results will tell you the level of nutrients in the soil and will also give the pH of that soil plus recommendations for fertilizer and, if needed lime. Usually, if the nutrient level shown is high, addition of more of that particular element is unlikely to show noticeable results.
Right now, it is a little late to take soil tests from vegetable gardens and have recommendations in time for the early spring garden. So, fertilizer suggestions here are in general terms.
Vegetables can be grouped into three categories according to their fertilizer requirements. Heavy feeders are sweet corn, lettuce and broccoli; these require more nutrients in the ground than medium feeders, such as beans and spinach. Light feeders, such as garden peas, have the lowest requirement and may not need supplemental fertilizing in good soil.
The old method for applying fertilizers was to scatter granular fertilizer over the entire garden according to directions on the fertilizer bag and to till it into the top 6 inches of soil. Commonly suggested amounts for this method are 4 pounds (2 quarts) of 5-10-5 or 5-10-10 mixed in per 100 square feet or 2 pounds (1 quart) of 10-10-10 mixed in per 100 square feet. This old method, though still used, can be wasteful if fertilizer is spread in areas where there will not be plants, such as in garden paths.
A better method is to put fertilizer only where it will be needed. This method is called banding and is done prior to planting or seeding by placing dry granular fertilizer in bands near the seed row. Either one band about 2 inches below the seed depth or one or two bands 2 or 3 inches out alongside the seed row location may be dug. Scatter 1 cup of 5-10-5 or 5-10-10 or 1/2 cup of 10-10-10 fertilizer evenly per 25 feet of band.
Scratch this fertilizer in and cover with garden soil before doing normal seeding. Do not allow the seed and fertilizer to touch, and note that where two side bands are used, only half as much fertilizer is sprinkled in each band. Transplanted crops may also have dry fertilizer banded but will generally benefit more from a liquid starter fertilizer solution used to water in transplants with a small amount of granular fertilizer well mixed into the hole.
Then, to provide nutrients later, where long-term, slow-release fertilizers are not being used, side dressing is suggested, especially for heavy-feeding vegetables. This means the application of dry granular fertilizer to the soil surface or mulch on both sides of the row 6 to 8 inches from the plants about six weeks after growth starts. The same rates used for banding fertilizer prior to planting can be used.
Remember, fertilizing can't be expected to make vegetables grow and produce well if other environmental factors are stressful. Fall seems to be the best time to work on the garden soil and prepare for next year's garden. Conduct a soil test then, build a compost pile from plant debris and work in fresh organic matter or hot manures. If the soil test calls for it, apply lime in the fall since it takes several months for lime to raise the pH.
\ John Arbogast is the agriculture extension agent for Roanoke
by CNB