OKLA. CITY —
Fertilizers are often needed to correct soil nutrient deficiencies in nitrogen, phosphorous and potassium to improve soil fertility.
Certainly it is advantageous to start with a suitable soil with healthy amounts of organic material and the proper pH. Organic material can be added to the soil in the form of animal manure, composted plant material or peat moss. Organic matter decomposes to form humus which greatly improves soil structure and is extremely important to the successful growth of plants. Adding organic matter to the soil each year is a good flower/vegetable garden practice.
The measure of soil acidity or alkalinity is referred to as the soil pH. This can be obtained from a soil test. A pH value below 7.0 indicates a soil is acidic and above 7.0 indicates a soil is alkaline. In general, the optimum pH range for nutrient uptake and plant/turf vigor is 5.5-6.5. Above or below this range, certain nutrients, although present in the soil, may not be adequately available to the plant. Should soil be too acidic or too alkaline, lime or sulfur respectively can be added to resolve the pH. Contact your county extension office for additional information on soil tests and correcting pH.
For good growth, plants require certain mineral elements from the soil. Those most often deficient are nitrogen, phosphorous and potassium.
• Nitrogen is required for dark, green color in plants and is essential for continuous growth.
• Phosphorous promotes early root formation and hastens maturity.
• Potassium promotes plant health and disease resistance.
A soil test will provide recommendations for fertilizer requirements.
Commercial fertilizers furnish usable amounts of these three primary elements for plant nutrition. The numbers (or analysis) on the tag or front of the fertilizer package represent the percentages of N (nitrogen), P (phosphoric acid) and K (potash). So a fertilizer with the analysis 12-24-12 would contain 12 percent nitrogen and potash (as K2O) and 24 percent phosphorous (as P5O2). A fertilizer containing some of each of the three main elements is referred to as a “complete fertilizer.” At times, a fertilizer with only one or two of the three elements is required and this would be an “incomplete fertilizer.”
Placement of fertilizers depends on the application. If seeding or starting young transplants in hills and rows, the fertilizer should be placed an inch or two below the depth of the seed or transplant and three inches to either side. It should not come in direct contact with the seed or existing root system. In broadcast applications, the fertilizer should be scattered evenly over the entire garden area and then worked into the soil before planting. For really heavy fertilizer applications, work in half the fertilizer during soil preparation and the other half in the hills or rows at planting.
Starter solutions can be used with transplants to provide them with a ready jolt of nutrients to get them off to a fast start. Starter solutions have a high ratio of phosphorous and are available at local nurseries.
For turf bermuda grass, apply a complete water soluble fertilizer in the spring (quickly available to turf) and straight N source slow-release fertilizers in the summer. Fertilizing prior to spring green-up is not as effective as two weeks after green-up. It is best not to fertilize after Sept. 1 to allow bermuda grass to properly winterize. Cool season grasses like tall fescue do not need as much fertilizer as bermuda grass and they need most of their annual fertilizer in the fall/spring with very little in the summer.
The following workshop will be held at the OSU Extension Center, 930 North Portland, OKC, unless otherwise specified. They are free and open to the public.
• Third Thursday Gardening — 'Roses,' 6-7 p.m., Thursday, May 15.
RAY RIDLEN is a horticulture/agriculture educator for the Oklahoma County OSU Extension Service. He may be reached at 713-1125.