Turf Fertilization

Many lawns are looking a bit pale. This happens regularly this time of year but this year, with the extra rain makes it worse.

Bermuda grass needs an extra bump in nutrition. It can be accomplished two different ways. One cures the problem and one masks it. The problem causing the grass to be dull or light in color is iron deficiency.

Adding a light application of iron not exceeding one half pound per 1000 square feet will cure it. Adding extra nitrogen fertilizer temporarily greens the lawn up but only masks the problem. Additionally, the nitrogen will cause a large flush of growth.

If the grass needs lots of vigor to repair damage from dogs digging, kids playing or golfers divoting then the extra nitrogen is needed. Most lawns do fine with normal nitrogen and the iron to green them up without having all the growth. For plants other than grass is is important to use a chelated form of iron for best results. Lawns sport such shallow roots an inexpensive form works just as well because the roots get it before it gets bound up chemically. The reason iron is needed this time of year lies with the grass' vigor in the heat. The demand increases with the vigor and iron is not easy for plants to absorb. Curiously iron becomes less available for uptake if the grass or plants are kept too moist. In addition to the wet soil conditions our high pH soils exaserbate the problem. For a root to absorb iron a coupl factors must be in harmony. The iron must be in a chemical form the roots can take in. If its in the right form then the soil's oxygen levels must be high. There is a tricky oxygen transfer that must take place to get the iron in. Wet soils contain lower levels of oxygen. When applying iron another consideration needs attention. Iron fertilizers are notorious for being a great cement, rock, stucco or cool-decking stain. Many a sidesalk or cool-deck has been permantly stained And heaven forbid you should ever get any in the pool. Use caution when applying it near the hardscape. Use a drop speader as opposed to a throw spreader to control where it goes. If some granules get on the sidewalk or rock sweep or brush it back onto the grass. Do not wash it off or the stains will appear and stay. So if your lawn is pale green or dull put out some iron and grass will green up quickly. Make the applicaion as uniform as possible. Only the grass getting the iron will turn green. Missed stips in the lawn will look bad compared to the areas getting the iron.

Written by Terry Mikel, College of Agriculture and Life Sciences, the University of Arizona, 602-470-8086.
Material originally appeared in Arizona Republic
Return to index