EDDIE SEAGLE: Nutrient needs and fertilization

Published 8:00 am Wednesday, March 23, 2022

“Spring makes its own statement, so loud and clear that the gardener seems to be only one of his instruments, not the composer.” Geoffrey Charlesworth. “March’s birth flower is the daffodil. It’s all too appropriate that cheerful yellow flowers represent the first month of spring.” FTD. “The first blooms of spring always make my heart sing.” S. Brown. “You are reborn with the roses, in every spring.” Juan Ramón Jiménez.

It’s late March and spring is here! It’s time to think about spring activities in the landscape to improve the health and curb appeal of your plants. At the top of the list is understanding the nutrient needs and fertilizer applications in the landscape. 

All plants should have the opportunity to enjoy favorable temperatures, sufficient air, proper light, enough water and adequate nutrients for survival. Most plants in our area need about an inch of water per week on the average to accommodate their metabolic and systematic needs. However, we cannot depend upon rainfall and nature alone to satisfy these needs. Thus, irrigation and fertilizer programs should be implemented.

Understanding nutrients and fertilizers is very critical in managing the needs of plants in the 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 specific 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 can be conducted annually, biennially, or every three years in the home landscape, depending on plant responses, soil chemistry and precipitation rates.

Plants need certain elements for survival, including 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, both usually expressed in pounds per acre, per thousand square feet or per 100 square feet.

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 14 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, if anything.

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 center for a recommendation for your particular plants for each sample tested. If you haven’t soil tested, now is the time to do it. If you soil test regularly, then late summer or early fall would be ideal because any adjustment in pH takes a few months to achieve. Thus, this strategy allows 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%N, 4%P and 8%K), the percent active ingredient is 28% (16 + 4 + 8) with 72% (100% – 28%) as inert materials. Most fertilizer formulations to the consumer are packaged in 40 lb bags or less (5 lb bags for roses, flowers, etc.).

Understanding fertilizers is most critical from purchase through handling to application. Only purchase the amounts needed with little 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 inch of 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. Using specialty fertilizers on your specific, specialty plants 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 stimulate your desire to learn more and ask questions about the landscape.

“It is by the name of Jesus Christ of Nazareth… Salvation is found in no one else, for there is no other name under heaven given to men by which we must be saved.” Acts 4:10-12. “As God’s chosen people, holy and dearly loved, clothe yourselves with compassion, kindness, humility, gentleness and patience.” Colossians 3:12. “The fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, self-control. Against such things there is no law.” Galatians 5:22-23. “May the God of hope fill you with all joy and peace as you trust in Him, so that you may overflow with hope by the power of the Holy Spirit.” Romans 15:13.

Eddie Seagle is a Sustainability Verifier, Golf Environment Organization (Scotland), Agronomist and Horticulturalist, CSI: Seagle (Consulting Services International) LLC, Professor Emeritus and Honorary Alumnus (Abraham Baldwin Agricultural College), Distinguished Professor for Teaching and Learning (University System of Georgia) and Short Term Missionary (Heritage Church, Moultrie). Direct inquiries to csi_seagle@yahoo.com.