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EDDIE SEAGLE: Nutrients, fertilizer critical to plant health

GEORGIA CLIPPINGS: A weekly column on gardening, plants and landscaping

It's important to know the quality of your soil before choosing a fertilizer. (Special photo)

It's important to know the quality of your soil before choosing a fertilizer. (Special photo)


Eddie Seagle (Special photo)

All year I dream of the days of May when the sun is warm, the sky is blue, the grass is green, and the garden is all new again!”

May Dreams Gardens

Plants need water and nutrients for survival. Most plants need about an inch of water per week on the average to accommodate their metabolic and system needs. However, it appears that in the last two years, we either experience a very rainy season or a very dry season or a combination. For example, we have received more than five inches of rainfall in less than 24 hours recently. This means that percolation (water moving through soil) and runoff will be at a maximum in good soils. Furthermore, with high percolation, leaching (removal of nutrients with percolation) will be high thus robbing the plant of necessary nutrients. Therefore, fertilizers enter the picture and must be addressed.

Understanding nutrients and fertilizers is most critical in managing the needs of plants in


Using appropriate nutrients and fertilizers is essential for managing a beautiful landscape. (Special photo)

your home landscape. Before any fertilizer application takes place, it is important to soil test to determine the exact nutrient composition of your soil microenvironment. Randomly collect about one to two cups of soil from each zone within your landscape from the lawn to the flower areas to the special plants (roses, azaleas, etc.) to the trees and shrubs. Keep these samples labeled separately and place in a plastic bag which you will then place in a custom soil testing bag available from your county agent office. Have these tested through this public agency for a nominal fee and allow time for the testing results to return to you. From these results, a determination can be made on the needs in each microenvironment. Soil tests should be conducted every one to two years in the home landscape.

An easy statement to remember the nutrients is C HOPKINS CaFe Managed By Mine Close CuZn Mo (anonymous). From this statement you should recognize carbon (C), hydrogen (H), oxygen (O), phosphorus (P), potassium (K), iodine (I), nitrogen (N), sulfur (S), calcium (Ca), iron (Fe), magnesium (Mg), boron (B), manganese (Mn), chlorine (Cl), copper (Cu), zinc (Zn), and molybdenum (Mo).

Carbon, hydrogen and oxygen are readily available and do not need to be supplemented. The macronutrients are the major nutrients (nitrogen, phosphorus and potassium) needed in the largest amounts and the minor nutrients (calcium, magnesium and sulfur) needed in medium amounts, usually expressed in pounds per acre, per thousand square feet or per 100 square feet.


(Special photo)

The micronutrients are iron, manganese, boron, zinc, chlorine, copper, zinc, iodine, and molybdenum. Other micronutrients are needed but are usually present in sufficient amounts. Iron is needed in the largest amounts and is expressed in ounces per acre, per thousand square feet, or per hundred square feet. The others are needed in grams per area or in parts per million (ppm).

Nitrogen is not part of a soil test because of its mobility in the soil and volatilization characteristics. If necessary, tissue tests can be conducted to determine nitrogen levels, otherwise follow recommendations for subject plants. A soil test should be conducted for pH, P, K, Ca, Mg, Fe and other micronutrients. The pH (potential hydrogen) identifies the degree of alkalinity or acidity of the soil. The pH range is from 0 to 16 with 7 being neutral (below 7 is acid and above 7 is alkaline). Most plants in the area grow between pH of 6.0-7.0, excepting acid-loving plants like centipedegrass, azaleas, etc, which prefer 4.5 to 5.5.

If your pH needs adjusting, add lime to increase and sulfur to lower. By maintaining your pH between 6.0 and 7.0 for most plants, calcium and magnesium will be readily available. As pH changes, so does the availability of nutrients. The soil test results will indicate what you need to do with pH.

The soil test results will further indicate the amounts of these nutrients present, and these will be either deficiencies, optimum levels, or toxicities. With the cost of fertilizer and plant health at a premium, you only want to apply what is needed. Ask the testing unit for a recommendation for your particular plants for each sample tested. If you haven’t soil tested, now is a good time to do it. If you soil test regularly, then late summer or early fall would be ideal. If your soil pH needs adjusting (which takes a few months to achieve) you will certainly have time to make the adjustment before spring and new growth.

Complete fertilizers are those that contain amounts of nitrogen, phosphorus and potassium (N, P, and K). These fertilizers may also contain one or more micronutrients (see label on fertilizer bag), as well as an herbicide to kill weeds (a weed and feed formulation). An incomplete fertilizer does not contain all three nutrients (N, P, and K) and may be labeled as nitrogen, phosphorus, potash, or iron fertilizers, as well as sulfur fertilizers and general micronutrient fertilizers. Most of the formulations that may be needed are readily available at your local garden center.

Fertilizer formulations contain active ingredients (the nutrients) and inert ingredients (the filler or the carrier). The analysis is the concentration of nutrient(s) in the bag. For example, in a 16-4-8 fertilizer analysis (16 percent N, 4 percent P and 8 percent K), the percent active ingredient is 28 percent (16 + 4 + 8) with 72 percent (100 percent minus 28 percent) as inert materials. Most fertilizer formulations to the consumer are packaged in 40 lb bags or less (rose fertilizers may be found in 5 lb bags).

Understanding fertilizers is most critical from purchase through handling to application. Only purchase the amounts needed with little to no leftover. Read the label carefully and understand what it indicates to you. Seek advice at all times. Use the right equipment to make your fertilizer applications to achieve correct rates and uniformity in application. Each fertilizer application should be watered-in successfully with approximately 0.5 inches water. Whether you are fertilizing a large area (lawn or flower bed) or an individual plant, be sure to follow recommendations closely and carefully.

Realize that specialty fertilizers exist for special plants like centipedegrass, roses, azaleas, camellias, annuals, perennials, trees and shrubs, lawns, etc. You should make every effort to use these specialty fertilizers on your specific, specialty plants since you will get the best results offering the highest degree of safety to the plant.

This short lesson in nutrients and fertilizers is only a sample of the knowledge to be learned about managing the nutrition of your plants. May this small degree of awareness ignite your desire to learn and ask questions, encourage you to further apply your gained knowledge, and bring you to further realize that environmental stewardship and sustainability are at the foundation of all your home landscape activities.

Many thanks to all who read this column which is an effort to provide each reader with timely and useful information which is a small contribution on my part in “paying it forward” to my readers. We are planning a mission trip to the Amazon Jungle in Peru this summer and accepting donations to assist in its funding. If you would like to donate to this cause, please make a check payable to Heritage Church and mail to Eddie Seagle, Peru Mission Team, 108 Tallokas Circle, Moultrie, GA 31788. We thank you and would appreciate your prayers for a safe journey for our team.

“Make the most of every opportunity. Let your conversation be always full of grace, seasoned with salt, so that you may know how to answer everyone.” Colossians 4: 5-6.

Dr. Eddie Seagle is a sustainability associate, Golf Environment Organization (Scotland); agronomist and horticulturalist, CSI: Seagle (Consulting Services International); professor emeritus and honorary alumnus, Abraham Baldwin Agricultural College, and associate editor of The Golf Course, International Journal of Golf Science. Direct inquiries to