There are products that claim to be liquid aerators that you spray on your lawn with a hose end sprayer. These include LazyMan Liquid Lawn Aerator, Aerify Plus and Nitron A-35.
But how well does liquid aeration work?
The first bullet point on the Aerify information page states that Aerify "Eliminates the need for mechanical aeration" (in bold) followed by "Reduces soil compaction". The claims for LazyMan Liquid Lawn Aerator are similar. Nitron A-35's makers don't go so far as to say it's a replacement for mechanical aeration.
The makers of Aerify go on to say how their liquid aerating product is better than mechanical aeration.
So what's in these back saving products and do they work?The ingredient that is in all these products is a type of surfactant. In some it's ammonium laureth sulfate or some other anionic surfactant. The use of these products (alkyl sulfates) are common and chances are you come in contact with them (hopefully) every day. Surfactants make "water wetter" by reducing the surface tension of water. At least that's how Mr. Wizard explained it when I was a kid. The surface tension of water is like a little skin that holds a drop of water together like a balloon. These particular substances are also very good at creating foam.
You're basically spreading shampoo on your lawn. Expensive shampoo. The claim is that around 1 oz of product in 1 or more gallons of water spread over 1,000 sq feet, then watering in will reduce soil compaction. Does it seem reasonable that 1 oz of shampoo can do the same or better job than pulling around 20,000 4" deep 1" diameter cores? That doesn't seem likely to me and I'm someone who spreads cornmeal on my lawn!
University Studies on Liquid AerationThe Colorado extension office has a page that agrees that there is no proof and that liquid lawn aeration is not effective. (Emphasis added.)
While it is difficult to ascertain what is contained in these products, a few have been shown to contain liquid humates (essentially liquid organic matter) and soap-like materials like sodium lauryl (or laureth) sulfate. It is simply wishful thinking to believe that a highly diluted solution of either of these applied to a compacted soil will in any affect soil bulk density. There is no indication that ANY of these products has ever been scientifically evaluated for effectiveness.These two other publications from the North Carolina Cooperative Extension Service and Oregon State's Cooperative Extension indicate that surfactants can be effective under certain conditions where the soil is very hydrophobic. Hydrophobic meaning the soil will not absorb water and instead will bead up on the surface like on a freshly waxed car. "Water does not bead up on wettable soil; therefore, unless beading is present, a surfactant or wetting agent would be an unnecessary expense." So unless your soil has a shiny factory finish, surfactants don't seem to do too much.
Simply stated, there is no "chemical" substitute for physical remediation of soil compaction - namely the traditional core cultivation techniques that have been used for years on all types of turf areas. At best, these "wonder products" might provide some minor degree of wetting agent effect - and nothing more. Wetting agents increase spreading and penetration of liquids across surfaces and into or throughout surfaces.
This USGA Turfgrass and Environmental Research Program Study on water retention in golf greens(pdf) included humic acid. The conclusion was that it didn't do anything to aid water retention in the tested greens which is contrary to claims that humic acid will help increase the water retention of sandy soils. Though humic acid may have other benefits to the soil, I can't find any studies indicating that it can be used as an alternative to core aeration.
Just Use Humic Acid?
I actually have some Aerify PLUS which I purchased based on some advice I received but I didn't see any noticeable difference in compaction. I got it before I started looking into the product. Later on, I core aerated with the Turf Hound aerator and that seemed to really help the grass as the holes allowed water and air to get deep into the soil where the roots are.
Aerify Plus is more than just a surfactant, it contains Humic Acid, Kelp and other elements and micronutrients. I plan to use it up after I found out that alkyl sulphates, such as ammonium laureth sulfate, are easily biodegradable and don't cause any harm to water. Once I finish the bottle, I'm just going to get humic acid and use kelp meal (Organica Kelp Booster) instead.
Maybe even a liquid kelp. At 2 tsp/gal/1k sq ft that 35oz bottle can do the 5 suggested applications to 21,000 sq ft. Need to be careful though because it contains a bit of potassium so make sure not to over apply and keep track of the other potassium you're putting in your lawn. Potassium isn't something that leaves your soil quickly, so you don't need to apply too much.
Basically, this is the way I see it. Wetting agents and surfactants are like tapping a stuck jar against the counter or running it under hot water. It will help get a stuck jar open but it's just a waste of time and water if the lid isn't stuck. If your soil isn't hydrophobic, your lid isn't stuck!