Proper lawn nutrition
Amy Jordan, Special to the Gazette
Thursday, September 22, 2011
Lawns are important for many reasons, such as their ability to absorb carbon dioxide from the environment and release oxygen, control pollution and reduce erosion, and the cooling effect lawns provide. In my last column, I discussed the process to plant new grass in lawns that died out over the hot, dry summer.
Now that we have had some rain and are able to see what might have survived we will focus on fertilization. This was briefly covered earlier, but because of the importance I decided to delve into the process a little more deeply.
If you overseeded or planted a new lawn within the last few weeks and fertilized at the time of planting, you will not need to fertilize again until about the time of the final mowing. September is the most important time to fertilize cool season grasses because it helps to thicken the turf, encourage new plants, and improve the root system. Nitrogen is the nutrient needed in greatest quantity by turfgrass. Nitrogen fertilizer will give green color and a moderate rate of top growth during the fall. The September application will be used up during the fall growth period, and another will be needed before winter (applied at about the time of the last mowing).
Nitrogen carriers are of two types: slow release and quick release. Many turf fertilizers are mixtures of both, in varying proportions; these are best for this time of year. Bags of fertilizer should indicate the release rate of its contents.
One pound of actual nitrogen per 1,000 square feet of lawn should be applied in September. Most lawn fertilizers sold in consumer product lines will deliver about one pound of actual nitrogen per 1,000 square feet, if the directions on the bag are followed. To confirm that, you can calculate the amount of actual element being applied by checking the analysis for yourself. The analysis is the 3 number sequence listed on the bag, representing nitrogen, phosphorus, and potassium (N-P-K). These numbers are the percentages of each element contained in the bag. For instance, an analysis of 25-5-5 would contain 25 percent actual nitrogen, 5 percent actual phosphorus, and 5 percent actual potassium. To apply one pound of actual nitrogen using fertilizer with this analysis, 4 pounds of fertilizer would need to be applied per 1,000 square feet because there is one-fourth pound of actual N per pound of fertilizer.
Planning to apply 1 pound of actual N per 1,000 square feet is one thing, actually doing it is another. Spreaders need to be properly calibrated to put down the correct amount of fertilizer, taking into account the walking speed of the operator. An alternative calibration method would be to measure the area of your lawn, weigh the amount of fertilizer required by your lawn and pour it into the spreader, then set the spreader on a low setting and keep going over the lawn (varying your direction) until the fertilizer is gone. Avoid the temptation to set the spreader on a higher setting. The low setting, combined with several trips across the lawn, helps ensure uniform application of the fertilizer.
Always fill your spreader on pavement, never on the lawn. Be sure to sweep up all fertilizer granules from sidewalks, driveways, and streets. Granules left to wash down storm drains will eventually end up in streams and rivers. After they have been swept up, they can be reapplied to the lawn.
Need a visual? The “how-to” gardening videos done by K-State Research and Extension are a great resource. You can find them at the KSRE website www.ksre.ksu.edu, or a link on the lawn and garden page at www.lyon.ksu.edu.
ZaneRokklyn (anonymous) says...
Thanks, Amy! But all the benefits you list for lawns are done much more effectively by trees or bushes or pretty much any perennial plants larger than grass. When you say lawns have these benefits, what are you comparing them to -- concrete? gravel?
If you do have a lawn, a polyculture (a mixture of multiple types of groundcover) will outperform a monoculture in all but the most perfect weather conditions. Look up and down your street and see who has the greenest lawn after this summer's brutal drought -- if your street is like mine, it will be the lawn full of crabgrass and clover that's green and healthy, while the zoysia and bluegrass are dead and brown.
If you do grow just grass, there are organic alternatives to the nitrogen fertilizer you recommend -- notably compost -- that don't have the downside of polluting our streams and rivers if you overshoot. I can't speak to the quantity of compost one would need to equal the nitrogen content of chemical fertilizer, but I know that you have given advice on that topic in the past. It's a shame it didn't make the cut for this column, but I hope you'll address it in a future column!
September 22, 2011 at 1:38 p.m. ( permalink | suggest removal )