Home & Garden: Fertilizing your lawn for best results | PostIndependent.com

Home & Garden: Fertilizing your lawn for best results

Curt Swift
Free Press Gardening Columnist

Fertilizing a lawn before (or during) a period of hot weather can increase stress on the grass, increasing chances of disease problems and grass burning.

If your grass needs fertilizer during hot weather, apply only a small portion of what is normally recommended. I find that one-quarter to one-half of the normal fertilizer application rate during the heat reduces the chances of disease and “burning.”

Fertilizer is best applied when the soil is moist. Fertilizers are salts, and when applied to dry soil the roots can be damaged by reverse osmosis. The same thing happens to you when swimming in salt water. Moisture is pulled out of your skin.

In the case of your lawn, moisture pulls from the roots, resulting in less water and nutrient absorption. Applying the fertilizer to moist soil dilutes the salt concentration and reduces the potential for root damage.

Fertilizer, whether in the liquid or granular form, can burn leaves. A property owner recently contacted me about damage to his lawn from a liquid fertilizer application. The amount of nitrogen was appropriate at 1 pound of nitrogen per one-thousand square foot area of turf, but the lawn was still injured.

The applicator added a herbicide to the fertilizer, requiring the lawn not be watered for 24 hours to enhance the herbicide’s effectiveness. In this case, delaying watering was the appropriate recommendation (and avoiding the application during the heat of the day) would have avoided the problem.

Watering a lawn, field or other weed-infested area prior to an herbicide application helps increase the uptake of the chemical by the weeds. Applying an herbicide to water-stressed weeds is one of the common reasons for the lack of weed control. It is also recommended to fertilize the weed-infested area prior to applying an herbicide. The more succulent the weed, the more effective the herbicide will be in killing the weed.

If you have sprayed a weed with an herbicide designed to kill its roots and the spray was not successful, the problem may have been due to the weed being stressed from a water or nutrient deficiency. Weeds in that condition have a thicker cuticle on their leaves and stems which inhibits the uptake of herbicide. Weeds that are stressed also have limited fluid movement from the leaves to the roots; thus inadequate amounts of the herbicide move into the roots. Watering and fertilizing several days prior to applying an herbicide helps correct these uptake and translocation problems, resulting in a better kill.

GJ Free Press columnist Dr. Curtis E. Swift is a retired horticulture agent with the Colorado State University Extension. Reach him at Curtis.Swift@alumni.colostate.edu, 970-778-7866 or check out his blog at http://SwiftsGardeningBlog.blogspot.com. He owns Swift Horticultural Consulting and High Altitude Lavender.

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