Fertilizing A Lawn [video]

In this video, field specialist Margaret Hagen, discusses the process of fertilizing a lawn. 

Video Transcript

Hello I'm Margaret Hagen, a field specialist for the University of New Hampshire Cooperative Extension. Today we're going to talk about fertilizing your lawn. When you go to the garden center to purchase lawn fertilizers often the number of choices are overwhelming. So why should you even bother to fertilize your lawn? Fertilizing a lawn will help you keep a good quality lawn that has nice dense turf and no weeds.

In New Hampshire we tend to grow mostly cool season grasses. Most of these grasses will do quite well with a fertilization program that applies one to two pounds of nitrogen fertilizer per 1,000 square feet per year. Because most grasses will go semi-dormant during the summer you can probably get away with applying fertilizer in the spring and fall or even just in the fall. Fall is the best time to fertilize because not only is grass still growing it's storing away nutrients and other essential elements it will need for growth next spring. Cool weather warm soil plenty of rain and lots of sunshine create the perfect environment in fall for grass to develop strong roots. In New Hampshire, it's best to make a fall fertilizer application just before or after Labor Day. Fall lawn fertilizer applications should be complete before September 15th in northern New Hampshire and by October 1st in southern New Hampshire.

How much and how often you fertilize your lawn will depend on what you find aesthetically pleasing. If you want a lawn that looks like a carpet you'll need to spend more time on maintenance practices including fertilizing. Before deciding to go to the store to purchase fertilizer it's a good idea to do a soil test to assess the nutrient status in your soil. For a small fee, the UNH Cooperative Extension soil testing laboratory can analyze your soil and provide lime and fertilizer recommendations based on the results. Adjusting your pH to between 6.0 and 6.5 will increase the ability of turf to effectively utilize the nutrients that are in soil from your fertilizers.

When you look at a bag of lawn fertilizer you'll see three numbers prominently displayed these numbers represent the percent by weight of each of the three major nutrients in the bag. These nutrients are nitrogen, phosphorus, and potassium. Nitrogen promotes rapid growth and gives grass its lush green color. Phosphorus is needed for the healthy development of roots. Potassium helps regulate water movement within the plant as well as increasing the plants ability to stand both drought and cold. Starter fertilizers like this one will generally have a relatively high percentage of phosphorus to promote good root development.

As you can see the analysis on this bag is 24-25-1. The bag contains twenty five percent phosphorus, necessary when feeding a new lawn. In contrast this, bag has an analysis of 18-0-3 and contains no phosphorus. Established lawns do not have a high phosphorus requirement. Simply leaving grass clippings on the lawn will supply sufficient phosphorus. Most lawn fertilizers for sale now contain little or no phosphorus because phosphorus runoff into New Hampshire's lakes, streams, and ponds has had negative impact on water quality. In addition, most of New Hampshire soils provide all the phosphorus that a home lawn needs. A new state law that went into effect in 2014 requires that phosphorus in lawns and fertilizers sold by retail stores should be used only on newly established or repaired lawns or on lawns testing deficient in phosphorus. Annual applications may not exceed a rate of one pound per 1,000 square feet per year.

Lawn fertilizers for use in the spring have a relatively high amount of nitrogen to promote rapid growth in a green. On this bag of Agway Greenlawn 3003 has 30% nitrogen much of it available to the plant in a relatively short period of time. Most summer fertilizers have a lower amount of nitrogen like this Jonathan green summer survival with an analysis of 1-30-3. The nitrogen in summer fertilizers tends to be in a form that is slowly available over time to avoid stressing the grass or causing fertilizer burn. Fertilizers designed for use in the fall tend to have less nitrogen and more potassium, or potash, for cold tolerance. Fall fertilizers also tend to have 25% to 50% of their nitrogen in a form that is slowly available over time. If you have problems with dandelions, violets, or other broadleaf weeds you may want to buy a fall fertilizer that also contains a broadleaf weed killer.

Organic lawn fertilizers promote the growth of a dense green lawn naturally they can be purchased or created at home. You can leave grass clippings and/or most leaves on the lawn.
As they break down they release nutrients back into the soil. Organic granular fertilizers are often made up of grain such as ground corn cottonseed as well as blood or feather meal.
Organic fertilizers become available slowly as they are broken down by beneficial bacteria and fungi in the soil. Located on the back of the fertilizer bag will be information about the types of spreaders that can be used and the number at which they need to be set. Lastly, try to schedule fertilizer applications when a long steady rain is forecast. If that's not possible be sure to water in your fertilizer with the sprinkler.

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