Spring lawn Fertilization

Asked April 24, 2019, 11:36 AM EDT

I live in Cheyenne Wyoming, my lawn is a tuff turf mix of primarily fescue and kentucky bluegrass. I can't find a solid answer if spring fertilization is required, and if so what should the nutrient ratio be? Everything I see says if you do perform a spring fertilizing, then it should be LATE spring application due to the new spring grass focusing on root development. Any guidance would be greatly appreciated.

Laramie County Wyoming

3 Responses

There is a lot of information out there with varying opinions about when and how to fertilize lawns. You're right, it can be confusing.

In terms of nutrients, nitrogen (N) promotes green, vegetative growth. Phosphorus (P) promotes root growth. Potassium (K) can increase cold hardiness in plants. Most lawn fertilizers are high N and low or no P, K. P and K are often found in adequate levels in Wyoming soils, but N levels are often low. Applying P and K to lawns can benefit the lawns but P and K are not always a limiting factor to plant growth. N is the nutrient that will give us the greener, denser lawn.

In terms of timing, quick release/water soluble fertilizers are good options for this time in spring when the grass is greening up but soils are still cool. Make sure you water in the fertilizer after applying to prevent fertilizer burn in the lawn. These quick release fertilizers are usually high in nitrogen and low in phosphorus and potassium. Water soluble nitrogen in quick release fertilizers promote vigorous vegetative growth - the lawn will quickly become greener and more dense. You can expect a 4-6 week fertilizer effect with quick release fertilizers.

Slow release fertilizers and organic fertilizers are good choices for late spring/early summer, and can give a fertilizer effect on the lawn for about 10-12 weeks. Products with additional iron can also increase greening of the lawn and benefit lawns growing in high pH (alkaline) soils.

To encourage root development, set your lawn mower height at 3-4 inches and when you water, water deep and infrequently (1/2 - 1 inch once or twice a week) vs. light and frequent irrigation (<1/2 inch 3-4 days per week). Deeper watering wets the soil profile deeper and encourages deeper rooting. If we water lightly and only wet the soil surface, roots tend to be shallow. Also, the soil surface dries faster and because of the shallow root zone the lawn becomes drought stressed sooner than a lawn with deeper roots. Higher mowing heights also encourage deeper root development.

Thanks for the question.


Thank you for your response. Can I follow up with some additional questions.

I just wanted to narrow in on the time frame for spring fertilization. Should it be early spring or late spring? Based off of what you indicated, it would be totally acceptable to do a nitrogen ONLY based fertilizer in spring? The P and K with Iron should be included into the mix during the summer application?

I've studied the publication regarding lawn care issued by the University of Wyoming. I understand the need for deep and infrequent watering, and have been doing so for the last 2 years. I also aerate every spring to increase the ability of the soil to take in water. I've always wanted to know how to know/measure when you've met that 1/2-1 inch marker. I do not have a sprinkler system installed, so I currently use a strip irrigation system for a majority of the yard since it is narrow and use an impact sprinkler for a square portion I have. I typically leave the water set up in each "zone" for approximately 12-15 minutes, and water every 3 days which equals out to 2x a week.

Lastly, I would just like to know your thoughts about what I can do to reduce the amount of thatch and thatch removal. I know aeration reduces it, and of course there is power raking...which from what I've read should be done infrequently due to the fact that it can damage the lawn root system. I use a bag when I mow, until the last mow of the season, then I typically leave the clippings. This may not be doing anything but I thought I'd add that factor to the conversation.

Thank you again for your time!




Absolutely, nitrogen fertilizer in early spring will give your lawn a green boost. The disadvantage, to me (for what that's worth), with quick release products is the relatively short fertilizer benefit. That means you probably will want to fertilize with a slow release later this year, so you end up fertilizing twice. If you only fertilize once per year, I would do the slow release late spring/early summer. If you don't mind fertilizing twice, do both. For P and K, I would do a winterizer fertilizer application with low or no N and <5% P, K. Iron could be applied spring or summer, but make sure to water it in immediately.

To measure your water output, lay out several plastic containers, cat food cans, Tupperware bowls etc. and turn on the sprinkler. Set a timer to see how long you need to let the water run before an inch of water is collected in the containers. You'll notice differences in the water levels in each container which is an indication of how uniform or not uniform the water distribution is from the sprinkler. This might also help identify dry spots. Once you figure out the time, then run the sprinkler for that long when you irrigate.

As for thatch, aerating annually will help. Keep in mind that water and fertilizer increase growth of the plants and thatch will build up more in a well maintained bluegrass lawn than a lawn that receives less water and fertilizer. So part of the equation is balancing water and nutrients. Aerating more often, like twice a year could help as a preventative measure. Power rakes might be used if the thatch layer has built up to a point where aerating does not seem to help water get to the soil and the lawn always appears dry. Use caution when power raking. You can overdo it and cause damage. Adjust the depth of the power rake to a shallow setting. Settings too deep can rip up too much live plant material. I like to time aeration or power raking with fertilizer applications. Water the lawn the day before. Then aerate or power rake, apply fertilizer, then water again.

If you have a mulching lawn mower, you can forget about bagging if you mow regularly. Letting the grass grow too tall between mowings will leave a mess of clippings behind and contribute to thatch build up. If you mow often enough (once a week) the clippings are smaller and will break down, acting as a slow release fertilizer as it decomposes. If you do continue to bag the clippings, they can be a great addition to the compost pile unless you've applied pesticides to the lawn. If that's the case, bag em and dispose.