Clay soils can create problems in lawns. They are dense and compacted and have poor drainage. They stay soggy when wet, and turn rock hard when they dry out in the summer. When soils are this "tight", necessary air, water and nutrients can not move through them. Roots are stunted and the grass is stressed, weakened, and more prone to disease, insects and even weeds.
Most experienced gardeners know that the best way to improve clay conditions in garden beds is to till or mix in lots of organic matter –such as compost, peat moss, leaves, etc... This process can immediately improve soil aeration and drainage, and will increase the beneficial soil microbes that break down the organic matter and turn it into humus. With humus you end up with an improved and more granulated soil structure. *
But how do you improve clay soil that already has a lawn growing in it? There is no way to till in organic matter down deep into and below the root zone without tilling
up the lawn. The standard advice is to " top dress "the lawn with
compost, leave the clippings, fertilize organically and wait... and
wait... and wait for all of that organic matter to eventually decompose and improve the soil. But the denser the
clay, the longer it will take for this to occur – often many years.
The reason it takes so long for clays to improve when top dressed as above is that the soil microbes necessary for decomposing organic matter are "Aerobic" - meaning they need air/oxygen to survive. Clay, which is made up of microscopic-sized particles tightly bonded together, has a very little air space in it- most of it near the soil surface.
A Faster Solution
If you could increase the amount of air in the clay by just a small amount, you can encourage the beneficial soi-building microbes to generate and grow in numbers. One way to do this is by creating temporary pores and channels in the clay with a soil penentrant called Aerify PLUS –Liquid Soil Aerator and Bioactivator. (Yes, we are promoting our product, but frankly, it is a real difference maker)
Aerify PLUS breaks apart clay bonds to create microscopic air space deep into the clay. Each application can work deeper. It also adds liquid organic matter to help generate and feed beneficial soil microbes of all types (including mycorrhizae) at the same time. It helps improve drainage in your lawn clay, encourages deeper rooting, frees up nutrients and water in the root zone and helps move organic matter deeper into the soil. By improving clay conditions you can create a much healthier lawn in a more bioactive soil.
Additionally, once your lawn clay begins to open up, the soil becomes healthier and earthworms will start to appear in your soil in greater numbers. Earthworms will enhance and speed up the soil improvement process because they aerate the soil as the tunnel up and down. They also digest thatch and other organic matter in the soil and convert it into humus and rich, fertile castings.
If your lawn is growing in a poor clay soil, it will always be prone to the problems that come with clay - compaction, poor drainage, fungus, moss, weeds, poor nutrient availability and color, root-stress and a host of other undesirable conditions. Improve the clay and you will improve the lawn. It is as simple as that.
FYI, I treated my own lawn organically for many years and top dressed with compost as well. Though the top 4-5 inches eventually got pretty good, the clay underneath remained gray and sticky. After a few seasons of treating with Aerify PLUS, it was as if all the organics that I had put in the soil finally became were able to be utilized down deep where I wanted it to go. My lawn clay soil became dark and crumbly more than 1½ feet deep- and earthworms abound.
* Also See Working With Wet Clay Soils in the Garden
Stuart Franklin is President of Nature’s Lawn & Garden, Inc. (http://www.natureslawn.com), located in the Buffalo, NY area.
He is also the author of Building A Healthy Lawn- A Safe and Natural Approach (Storey Publishing 1988) which is now out of print, but some copies are still available. Write to firstname.lastname@example.org
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