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Fertilize correctly for best plant growth
MISSISSIPPI STATE -- Beautiful lawns and gardens show that experienced gardeners know how to use fertilizer, but the novice often finds the array of options, timing schedules and application rates confusing.
Horticulture specialists with Mississippi State University shared some tips on fertilizer use to take some pressure off gardeners who want to do what is best for their plants.
“The main thing is to get some fertilizer on the plants,” said Norman Winter, Extension horticulturist. “My favorite blend is a 12-6-6 with minor nutrients, but it's not a life-or-death situation if you give your plants something else.”
The numbers on a package of fertilizer indicate, in order, the amount of nitrogen, phosphorus and potassium contained in the mix. Fertilizers with numbers like 13-13-13 or 10-10-10 are referred to as balanced fertilizers because they contain equal amounts of the three major nutrients. Those that are slow-release allow the nutrient to enter the soil over a longer time period.
Winter urged landscapers to add the appropriate fertilizer before planting, usually at a rate of 2 pounds per 100 square feet of bed space. After the plants are growing, most benefit from fertilizer applications every four to six weeks.
“I'm a believer in frequent, light applications of fertilizer,” Winter said. “Try to keep the dry fertilizer off the foliage and sprinkle it on the surface of the ground around the plants. Be sure to water after you fertilize.”
Winter said he is unscientific in his fertilizer application and sprinkles it out generously without measuring. Be sure not to make any piles of fertilizer, and try to keep the granules from touching plants.
Liquid fertilizers work well and tend not to burn plants as easily. Winter said they can be more convenient than dry fertilizers.
“I've been using liquid fertilizers more this summer than I have in the past, and I find my plants are blooming well and longer,” Winter said.
David Nagel, Extension vegetable specialist, said liquid fertilizers can work well for vegetables, too.
“Adding a little bit of fertilizer at a time is actually the most efficient way to fertilize,” Nagel said. “With soluble fertilizers, you're adding this week what the plant is going to use this week.
“Nutrients have to be dissolved in water to be taken up by the roots. In a dry year like this, not only are the plants not getting water, but they're not getting nutrients,” Nagel said. “Putting the fertilizer out with the water gives the plant two things at once.”
These soluble fertilizers, or those that are dissolved in water, are convenient but more expensive than granular fertilizers. It is easy to apply more soluble fertilizer than is needed since it doesn't seem like very much is being applied at any one time.
“The major problem with soluble fertilizer is applying so much that the plants remain vegetative and do not produce flowers or vegetables,” Nagel said.
While liquid fertilizers are good for vegetables, the majority of the fertilizer the crop needs should be added to the soil before the plants are in the ground. All of the phosphorus, most of the potassium and about half the nitrogen should be added to the soil before planting.
Fertilizer added later can be applied in water or as a side-dress, which is when a strip of fertilizer is laid down beside the plants. Work this into the top few inches of the soil for best results, but be sure to avoid damaging the roots while disturbing the soil.
Timing is important for fertilizer applications, and gardeners should apply at the ideal time for the type of plant being grown. Extension Publication 1091 and Information Sheet 411 have guidelines for fertilizing vegetables and ornamental plants. These are available from county Extension offices or online.
Lawns should be fertilized to meet the needs of the grass as well as the desires of the homeowner. Golf greens are some of the most heavily fertilized areas, and those who want a lawn that looks like a golf green will have to apply a lot of fertilizer every month.
Centipede grass lawns generally need very small amounts of fertilizer and may only require one application a year. Slow-release forms of nitrogen are common for lawn fertilizers and will relieve homeowners of the need to apply fertilizer every few weeks. Consult Extension Publication 1322 for fertilizer rates and timing to fit grass varieties and location.