Published 8 December 2009.
Sandy loam soils exist throughout Australia. Sandy loams are a good growing medium in that they are light and arable, they can hold and release nutrients so that plants are well nourished and if there is a reasonable amount of organic matter, Sandy loam soils can hold and release enough moisture to adequately meet the needs of the plants growing in it. But these same Sandy loam soils have a split personality, much the same as Dr Jekyll and Mr Hyde; whilst Sandy loams can be good, beneficial and productive… they can also turn against the very plants they are supposed to nurture. Mr Hyde soils are water-resistant or hydrophobic.
Hydrophobic soils are not restricted to sandy soils alone, peat moss and soils with high organic matter can also become hydrophobic. When Sandy loam soils dry out the soil particles develop a waxy coating and no matter how much water is applied, the soil will not absorb the water and, the plants living in it will die from drought.
Thus, it is imperative that hydrophobic soils are treated regularly with an appropriate soil-wetting agent. Wetting agents are detergent-like products that reduce the surface tension of the water enabling water to penetrate the waxy coating on the soil which allows water to re-wet the soil; so the soil returns to its normal water holding capacity.
Without boring you with the science of EO/PO Copolymers, poly-oxyalkylene glycols, granular surfactants, humectants, and their relative phytotoxicity, a general rule; the long-lasting soil rewetters are highly likely to be harmful to aquatics, amphibians, earth-worms and micro-organisms. The wetters with a short activity such as the yucca-based wetting agents are more eco-friendly but need to be applied regularly.
To protect the natural ecosystem remember to be very cautious about using long lasting soil wetters and always read these product labels carefully to ensure they are indeed "aquatics friendly".
Today there are many soil-wetting agents on the market. A few of the more commonly available products are:
In the old days, my grandmother would mix 1/2 cup of pure soap flakes and 1/2 cup or raw Blackstrap Molasses with 1 litre of boiling water till they were dissolved then add that to 50 litres of cold water and then water the everything in her garden. This method is probably just as effective, and equally likely to be just as ecologically damaging as some of the commercial re-wetting products.
If you care about the environment we live in please ensure you do some research first before purchasing just any soil re-wetting product.