Spring Lawn Care - Fertilizer and Lime

In the spring the thoughts of many homeowners turn to the lawn and spring lawn care. Where to begin? A good place to start is with a soil test, especially if you haven't had your soil tested in three years or more. Call the URI Gardening Hotline for information on how to take soil samples and where to send them.

Your soil test results will likely indicate that the soil needs lime in order to support a healthy lawn. Most Rhode Island soils are very acidic, often with a pH of less than 6.0. Grasses prefer to grow in soil with a pH of 6.0 - 7.0: the higher pH makes the nutrients in the soil more readily available to grass.

While a soil test will provide a specific recommendation as to the amount of lime to apply, most RI soils will benefit from an application of about 40 lbs of lime/1,000 square feet of lawn. Lime is available in two forms: pelletized and dust. Pelletized is slightly more expensive but easier and neater to apply. Dust lime is cheaper but messy.

The next important step for most lawns is an application of fertilizer. Proper fertilization can keep your grass thick and healthy. This helps the lawn resist insects and disease and makes it harder for weeds to grow. Of course, you don't want to overdo it, especially in a drought year. Too much fertilizer can make the grass grow too quickly. You will have to cut it more often and the grass will be weaker and more vulnerable to insects and disease.

URI generally recommends fertilizing your lawn 2 - 3 times per year. Use major holidays as reminders: fertilize in the spring around Mother's Day or a little earlier, put down a second application around Labor Day and a third between Halloween and Thanksgiving. If you leave your grass clippings on the lawn, you can skip the Labor Day feeding.

There is a bewildering array of fertilizer products on the market. Most bags display three numbers: N (nitrogen), P (phosphorus), and K (postassium). Nitrogen promotes grass growth and green color. Phosphorus helps develop roots and potassium helps plants resist drought and disease. For established lawns, URI recommends a fertilizer with a 3-1-2 or a 4-1-2 ratio of N/P/K. Always read the label carefully to make sure that you are purchasing the right material for your situation.

Some people prefer to use an organic fertilizer. An advantage of the organic products is that they typically contain nitrogen in a "slow release" form. This means that the nutrients will be released slowly over time so that the grass can be absorb them efficiently. Most (not all) synthetic fertilizers contain predominately water soluble or "quick-release" nitrogen. This will provide quicker green-up but may overstimulate the grass.

Organic fertilizers are bulkier: you usually have to apply more pounds of an organic versus a synthetic fertilizer to deliver the same amount of nitrogen to the lawn. However, organic fertilizers often contain other materials (organic matter for example), that provide additional benefits to the lawn beyond the nutrients. Organic fertilizers also tend to be more expensive.

Fertilizers are applied with either a drop or a rotary spreader. A drop spreader allows more controlled application and will keep fertilizer off the driveway and out of flower beds. On the other hand, it is easier to miss spots with a drop spreader and this may result in stripping. A rotary spreader is quicker and there is more overlap so less chance of stripping.

No matter which type of spreader you use, sweep up any fertilizer that lands on the sidewalk or driveway. If not cleaned up, this material may wash directly into the storm drains and from there, to our rivers and streams.

For more information on lawn care, visit the URI GreenShare Fact Sheet Web Site: www.uri.edu/ce/ceec