Supplement 3 - Fall Overhaul

Fall is the time of year when the attention you give your lawn will provide the best long-term results. With that in mind, the Sustainability Institute at Molloy College is looking for homeowners who want to put the practices we described in the educational series that we produced this past summer, 12 Steps to an Organically Green Lawn, into effect.

Supplement 3 - Fall OverhaulIf you can devote a weekend day this fall to implementing the Organic Lawncare Fundamentals, we can help guide you through an easy-to-follow program. In this way, you will provide your lawn with a real boost, so that it can better withstand traffic, drought and pests, and look great next year and for years to come.

Some of the tasks that you might be taking on include:

  • Dethatching
  • Core-aeration
  • Adjusting your soil's pH with an application of lime
  • Top dressing with compost
  • Fertilizing
  • Overseeding

The chart below will give you an idea of what each of these measures will take in terms of preparation, equipment, cost and effort, as well as what benefit they will provide for your lawn.

Lawn Restoration Tasks

If you are doing a major lawn renovation, here is the order in which you should tackle these tasks.

  • Mow low. (Prior to dethatching or overseeding are among the few times you should set your mower height to its lowest setting.)
  • Dethatching. (Only if you have more than a half-inch thick thatch layer)
  • Core-aeration. (Only if your soil is compacted)
  • Adjusting your soil's pH with an application of lime. (If a soil test shows that your soil is acidic and has a pH less than 6.0. Lime can be applied at any time, but if you core-aerate, the holes will help get the lime incorporated into the soil faster.)
  • Top dressing with compost. (Adding compost is of the best things you can do for your lawn.)
  • Fertilizing (If you are going to overseed, a light application will help new seed get established.)
  • Overseeding . (Fills in bare and thin spots. Crowds out weeds.)

Any of these tasks can make a major improvement in your lawn, if the conditions they are remedying are present. Top dressing with compost will help any lawn, but is especially helpful for transitioning lawns that have been chemically maintained to organic maintenance. Overseeding helps fill in bare and thin spots, and can start the transition from a high-maintenance Kentucky bluegrass lawn to a low-maintenance, drought resistant fescue lawn.

DethatchDethatch - Thatch is made up of a combination of dead and living parts of the grass plant such as stems, rhizomes and roots, just above the soil surface. A thin layer (less than ½ inch) of thatch is beneficial. If it gets too thick it can suffocate turf and soil, and keep water and nutrients from reaching the soil. A clue that you may have too much that is that your turf feels springy when you walk on it. Cut a small section of turf and measure the yellow or tan layer between the green grass blades and the brown soil, if it is thicker than ½ inch you should dethatch.

Before you dethatch, you should mow low. This will allow you to pull up the thatch without tearing the grass blades. For small areas, you can use a thatching rake, also called a convex rake. For larger lawns, a powered dethatcher, sometimes called 'power rake,' 'vertical mower' or 'verticutter' is fairly inexpensive to rent. Run it over your lawn twice, first in one direction, then again, perpendicular to the first pass. Rake up and remove all the debris brought up by the dethatcher. Often a lawn will look worse right after dethatching, it can take a couple of weeks to recover.

You can prevent excessive thatch by avoiding over-fertilizing and frequent, shallow watering. Organic lawns that have more earthworms and microbes to break down dead plant matter much less likely to have thatch problems. Tall fescue produces less thatch than Kentucy bluegrass.
AerateAerate - Use a 'core' or 'plug' aerator to reduce soil compaction and to allow soil amendments to get past the turf and down into the soil. 'Spike' aerators don't work as well and can increase soil compaction. Fall is the best time to core aerate, because weed seeds brought up from deep in the soil will be less likely to germinate. Aerating is much easier when soil is moist. If there hasn't been significant rainfall and your soil is dry, water a day or two before you aerate. Apply about an inch of water. If you have an irrigation system installed, mark or flag all the sprinkler heads so you don't run them over. Make multiple passes in different directions in very compacted, high traffic areas.

After aerating, break up the cores of soil that are left on the lawn with a metal rake or by mowing. If you use a mower, you will probably have to have the blades sharpened afterwards. Some people prefer to rake up and remove the cores, to keep the weeds seeds that have been deep in the soil from germinating. This is less important in the fall than the spring, and not necessary if you are going to top dress with compost after aerating.

You can rent a walk-behind core aerator from a power equipment rental company for about $50 for two hours or $120 for eight hours.

Lime - The optimum pH for turf grass is from 6.0 to 6.5. If you have Kentucky bluegrass it is more important that your lawn be kept within that range. Tall fescue is more tolerant of a slightly wider span of pH levels, but also grows best in that optimum range. 
If your lawn's soil pH is below 6.0, you should add lime to raise it. Follow the instructions on the bag, based on the result of your pH test. You should target a pH of no higher than 6.5. Always test your soil before applying lime. See Step 4 of our 12 Steps to an Organically Green Lawn. Lime can be added any time, and takes quite a while to balance the soil pH, so it is not necessary to do it at the same time as the other lawn boosting tasks.

CompostCompost - Applying a quarter-inch of compost will boost your lawn all by itself. See Step 7 of our 12 Steps to an Organically Green Lawn. Top dressing with compost when you seed also helps keep seeds moist so they germinate better.

When applying compost, you'll need a shovel, wheelbarrow and a rake. To spread the compost 'sling' it over your turf with the shovel, then rake it in so it doesn't cover the grass blades. Some people like to use the back of a metal 'bow' rake to work the compost into the turf. Others prefer to use a flexible leaf rake to rake the compost in. It takes a bit of sustained work, but will bring about great improvements in your lawn.

Unless you are top dressing a very small patch of grass, having compost delivered in bulk will be easier and less expensive then buying by the bag. To apply a quarter-inch of compost, you will need three-quarters (.75) of a yard of compost per 1,000 square feet of lawn. Long Island Compost is a wholesaler and will not deliver less then 20 yards. But if you call them at 516-334-6600, they can give you a number of a company in your area that they supply, who will be able to deliver to you.

Fertilization - Fertilizer is not the most important part of maintaining an organic lawn, and many lawns will do fine without added nitrogen. See Step 5 [add link] of our 12 Steps to an Organically Green Lawn. However a light application can help new grass to grow and get established. As part of overseeding for this fall lawn restoration, we recommend applying half a pound  (.5 lbs) of nitrogen per 1,000 square feet, if you haven't applied fertilizer yet this year. (In general, you shouldn't add more than 3 lbs per 1,000 square feet in one year, or more than 1 lb / 1,000 sq ft. in one application.) It is better if you make two applications, .25 lbs per 1,000 sq. ft. before seeding, then another .25 lbs per 1,000 sq. ft. a couple of weeks after the grass has germinated and started to grow.

So how much fertilizer do you need to buy to get .5 lbs of nitrogen per 1,000 of lawn?

Every bag of fertilizer has an N-P-K number on it. The first number is the 'N'. It tells you the percentage of nitrogen in the fertilizer. The second is 'P' for phosphorus, and the third is 'K' for potassium. New York law prohibits the application of phosphorus, except in the case of establishing a new lawn or unless a soil test indicates a need for phosphorus. So you should find a fertilizer with 0 for the P number. It can be a bit harder to find an organic fertilizer with no phosphorus. Ringer Lawn Restore has a 0 phosphorus product.

FertilizationThere are also New York state and Nassau and Suffolk county laws prohibiting the application of fertilizer in the winter. In general, you should not be applying fertilizer after October 31.

The N number is what we will be focusing on here. To find out how many pounds of nitrogen are in a bag of fertilizer, multiply the N number, as a percentage, by the total pounds of fertilizer that the bag contains.
If you want to put down one-half pound (.5 lbs) of nitrogen per 1,000 square feet, on a 2,500 sq ft lawn, first divide your lawn area by 1,000 [2,500 ÷ 1000 = 2.5]. Then multiply by the number of lbs per 1000 sq ft you want to apply to find the total amount of nitrogen you'll need [2.5 x .5 = 1.25]. You'll want 1.25 lbs of nitrogen.

Since the 8-0-1 fertilizer is 8% nitrogen, divide the number of pounds of nitrogen you want to apply to your lawn by .08 to find the amount of fertilizer you need to apply. [1.25 ÷ .08 = 15.625] You can round that up to 16 pounds.

Purdue University has an online calculator that can do the math for you.  Click on Calculate Fertilizer, then Granular, then Nitrogen. After that enter the N-P-K number of your fertilizer, the rate you want to apply it at (we recommend no more than .5 lbs per 1,000 square feet), and the area of your lawn. You can also enter the size and cost of the bag. The calculator will tell you how much fertilizer you should apply per 1,000 square feet and the total amount you will need for the whole lawn. If you entered the size and cost per bag, it can also tell you how many bags of fertilizer to buy and what the overall cost will be.

OverseedingOverseeding - Overseeding will thicken up your turf, helping it outcompete weeds. Choosing the correct seed is important. See Step 2 of our 12 Steps to an Organically Green Lawn.

A note about Kentucky bluegrass: Fescues require less maintenance, less water and less nitrogen, and are preferable to Kentucky bluegrass for an organic lawn. Many people prefer the look and feel of bluegrass however. If you are going to use bluegrass seed, recognize that it will take longer to germinate, and you will have to have the seed spread by the 18 or 19 of September (more likely the weekend of the 13 or 14 if you can only do significant yard work on weekends) in order to ensure enough time for it to germinate and grow so you can make a final fertilizer application on the weekend before the October 31 deadline.

Mow low and rake away clippings and thatch before overseeding. After you spread your grass seed, rake to make sure it is in good contact with the soil.

It is important to keep grass seed moist until all the seed germinates. This can take a few weeks of very light watering one or more times a day when there is no rain. Wait until the new grass is one third higher than the height you are going to mow at before you mow. If you are cutting at 3.5 inches, wait until the new blades are a bit more than 4.5 inches tall.

Long Island Organic Landscapers
Although it's easy for the average homeowner to maintain their lawn organically, some may too busy and wish to hire a professional. In that case there are thousands of landscapers on Long Island to choose from, but only a small but growing number of experts who can maintain your lawn and landscape without the use of chemical pesticides. They can be found here.

To see all the previous steps in the series, please visit 12 Steps to an Organic Lawn

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The Sustainability Institute
7180 Republic Airport Farmingdale, New York 11735