It recently came to my attention that the Sierra Club published an article on a new system for reducing watering in lawns. You can read it here. Basically what the company, AquaCents, does is inject a polyacrylamide gel into the landscape and then the gel supposedly collects irrigation and/or rain water and releases it for plants to take up as the landscape dries.
I think it’s a good concept, but I’m highly skeptical that this is a good product for two reasons. The first is that I’ve used polyacrylamide gels to hold water for plants before and have found no benefit. In fact, most papers out there on the topic show either no benefit or marginal benefit from using these gels in terms of increasing the amount of water available to plants – though I must admit that results are variable.
Please note that I didn’t say I was skeptical that the polymer will hold lots of water – I’m not. It will hold lots of water.
Which leads us to an important question. If we know that the gel will hold water, and this company has done testing which shows reduced watering is required in lawns that use this technology, then why am I skeptical?
Based on what I have read and the experiments I’ve done, I think the company’s testing isn’t telling the whole story.
As far as I can tell, what they’re doing to test this product is injecting it into lawns and then allowing a moisture detector in the lawn to trigger sprinklers to go on when soil moisture falls below a certain level. If you test one lawn with the polymer side by side against another lawn without the polymer, then the lawn with the polymer will use less sprinkler water because the gel holds more water than the surrounding soil – meaning that it stays more moist. So at this point it sure seems like the gel is a good idea — right?
No, because this experiment asked the wrong question. It looked at how much water was in the lawn, NOT HOW MUCH WATER WAS GETTING TO THE PLANT. And that’s what we need to know – how much water gathered up in that gel will actually get to the plant. What I’ve found in my work is that having water in the gel is not the same as getting water to the plant. The gel seems to hold the water too tightly for the plant to get it. It’s a little like having an impenetrable safe filled with five million dollars in gold. Sure, the gold is there, but if you can’t get to it, who cares?
So, why does the grass seem to be growing more roots when the gel is used? My best guess is that the lawns were overwatered in the first place and the gel just provided a way for homeowners to decrease their watering. Let’s face the facts, overwatering of lawns is rampant.
But I mentioned that there were two reasons why I didn’t like the gel. I named the first, so what’s the second? It’s something that I saw on one of Linda’s sites a few years ago and then looked into a little further. Polyacrylamide gel, while relatively safe in and of itself, may break down into more toxic substances. See Linda’s article here.
Finally – and this is just a thought — there are plenty of other absorbent materials out there that might be injected into the ground, including some made of starch – I have tried gels made of starch and have found them to be as effective as those made of polyacrylamide (though I know that’s not saying a lot). Or…maybe we should just water more judiciously. Like I said, just a thought.