There is no evidence yet that polyacrylamides are toxic.
In fact, we have been using them in diapers and many other applications for some time, so safety does not appear to be the issue.
How to make more moisture and nutrients available in the soil
The real question is, though they are terrific water absorbers, do they work in releasing moisture back into the soil?
Studies are somewhat inconclusive but at the very least, it has been proven that lacing sandy soil with polyacrylamides reduces water leaching through the sand when these particles expand due to water absorption.
- Basically, they slow down leaching by filling the airspace between the sand particles.
- For an in-depth discussion, see the conclusions in this study (here) on Cross-Linked Polyacrylamides in sandy soil for crop production.
The real issue here is how to make more moisture available in the soil while also making nutrients available. Sandy soils tend to have a big increase in nutrient leaching and Florida has a long history of ground water contaminated by fertilizers.
The study noted above stated that though there was greater water retention and less leaching, that was only after a period of approximately 2 hours where moisture ran through the particles.
It takes about 2 hours before the polymers begin to absorb the moisture and swell sufficiently. That's two hours where fertilizers are washing through the soil with the water and therefore eventually reaching groundwater.
Making nutrients available
Why not spend a little extra money and build up the organic content of the soil? Build some soil culture? implement a composting program?
Plenty of sandy soils have successfully grown turf through these means and kept nutrients up in the top eight inches of the soil well away from groundwater.
Subirrigate the lawn with drip pipe for real irrigation savings.
- Our friends at Enviroscape in sunny california have an installation video up (here) that will give you the basic concept.
- The EPA Greenscapes program studies show that subirrigation will save the homeowner as much as 75% in costs in its lifetime over a sprayhead system (detailshere) so regardless of what soil choices you make, consider a sub irrigation before you spend money on spray heads.
For more information:
Read "How do I design garden irrigation? What software can I use for it?" a Q&A answered by Cassy Aoyagi.