Safe Lawn Fertilizer


While a lovely lawn beckons for a picnic basket and a blanket, the carpet beneath your feet will feel less wholesome if not tended appropriately. Proper cultural practices, with sustainability and health as top priorities, will keep your lawn the envy of your neighbors and still provide you with a suitable place to get a breath of fresh air.


Application of fertilizer should occur when turfgrass is actively growing. Cool-season grasses grow during the spring and fall and should receive the majority of their fertilizer at these times. The growing times for warm-season grasses are almost the opposite of cool-season. Fertilizing for warm-season grasses should occur when grass has become fully green during the spring and about six to eight weeks before the predicted date of first frost. Fertilizer should be applied in an even distribution to prevent stripes. Spread half the fertilizer in one direction; finish the other half in a perpendicular direction works well.

Package Information

The fertilizer label has numbers that indicate the percentage of nitrogen, phosphate and potash that the package contains. When the soil is deficient in phosphorus or potassium, a complete fertilizer containing all three elements should be used. When soils contain high levels of phosphorus or potassium, an application of nitrogen will suffice. In general, lawns that are established require only nitrogen on a regular basis. Nitrogen fertilization should be used with care; excessive growth can occur from the overuse of nitrogen.

Water Solubililty

The source of nitrogen in a fertilizer will determine how quickly it is made available to the lawn. Water-soluble sources are immediately usable. Slow-release fertilizers act slowly, releasing nutrients over time. These fertilizers need less frequent application and can be applied at a higher rate. Water-soluble materials generally last four weeks, while slow-release fertilizers last eight to 10 weeks. Water-insoluble nitrogen, listed as WIN, is shown as a percentage of the total nitrogen. Often, the package contains water-soluble and water-insoluble nitrogen.

Thatch and Aeration

Thatch is a tight layer of turf material that lies between the blades of grass and soil. Removing thatch on an older lawn may be necessary to provide the soil suitable access to nutrients. Layers of dead and living material can interfere with nutrient uptake. Microorganisms in the thatch sometimes utilize the nitrogen, making it unavailable to the lawn. Thatch develops when organic matter builds up on the soil faster than decomposition can occur. Excess nitrogen can encourage thatch. Aeration is of benefit to compacted, thatch-ridden lawns. Best done by an aeration machine, small plugs of soil are pulled to allow for better oxygenation of the soil. Nutrients, in turn, are better absorbed when roots have better access to oxygen and water.


Despite the beauty of a freshly mowed, raked and trim lawn, the process of mowing can weaken turf and use vital nutrients, which requires more frequent application of fertilizers. Raising the height of the lawn allows the lawn more leaf surface. Photosynthesis, the process of acquiring energy from the sun, necessitates leaf area. Cut no more than one-third of existing foliage with each mowing. Leaving grass clippings on the lawn provides needed nutrients after each mowing.

Keywords: lawn fertilizer, lawn mowing, thatch on lawn, aeration of lawn, water-soluble fertilizer, water-insoluble fertilizer

About this Author

Andrea Peck has been writing since 2006. Her work has appeared in "The Rogue Voice," "Information Press" and "The Tribune." Her writing focuses on topics about gardening and the environment. Peck holds a Bachelor of Arts in mathematics and a minor in biology from San Diego State University.