Healthy, happy lawns
April 17, 2018
It's mid-April and lawns are starting to green up. I forgot to do my fall fertilization in October and the grass really needs a boost. There are weeds, especially clover, invading thinner areas of the lawn. Weed invasion indicates a weak turf, which can result not only from inadequate nutrients, but also from poor watering practices or compacted soil. In Northern Nevada, we fertilize no more than three times a year, or less if we use a slow-release fertilizer. The cool-season grasses in our area stop growing when temperatures are high, so we don't fertilize in the heat of summer.
Nitrogen is the most important element in developing a healthy, attractive lawn, followed by potassium and then phosphorus. The fertilizer label indicates–besides the amount of nitrogen–whether it is water-soluble or water-insoluble. The water-soluble form is more rapidly available to the plant. Water-insoluble nitrogen is more slowly available. The latter form may be more convenient as a single application that will supply the needs of the grass for a longer time.
Be aware that fertilizers can contribute to water pollution through runoff if applied too frequently or improperly. It's important to use the right application equipment. Water deeply the day before you fertilize. After fertilizing, but before watering the fertilizer in, sweep any fertilizer on sidewalks, walkways, or driveways back onto lawns—not into street gutters and storm drains. After fertilizing, irrigate just enough to wash the fertilizer off the leaves and into the soil. Apply fertilizer only to planted areas where plant roots can take it up, and only when grass is actively growing; use no more than the recommended rates. Use slow-release fertilizers to minimize leaching (University of California, Davis IPM).
It's not too early to fertilize lightly, about half the strength recommended on your fertilizer and spreader equipment. In six weeks, fertilize using the full amount. A slow-release fertilizer works well for this second fertilizer application in mid-May, particularly if the soil is sandy. Wait until September or October for the last fertilization of the season to provide quick green-up in spring. If you only fertilize once a year, do it in the fall after your last mowing of the year.
Leave your grass clippings on your lawn. This does not cause excess thatch, if you are mowing your lawn properly. Grass clippings contain up to five percent nitrogen. Returning the clippings back to the lawn reduces the amount of fertilizer needed to keep the lawn green.
JoAnne Skelly is Associate Professor & Extension Educator, Emerita, University of Nevada Cooperative Extension. She can be reached at firstname.lastname@example.org.