When plants do not grow well and the reason why isn’t obvious; gardeners may blame the soil and look for a quick fix.
We all know marketing can make a product sound like the next best thing to sliced bread or a quick fix; fortunately most of us know it pays to learn a little more when something sounds too good to be true.
The role of Nebraska Extension is to extend research-based information. Here’s some information related to a few soil amendment products that may sound better than they actually are.
A soil amendment is something incorporated into soil to improve soil structure. The goal is to make the soil easier to work, increase moisture and nutrient holding capacity and improve aeration and drainage. Fertilizer is not a soil amendment. It adds nutrients but it does not improve structure.
A few soil amendment products that have not lived up to their hype are hydrogels, also known as water crystals and water retention granules, gypsum and soil microbes.
Hydrogels are polyacrylamide gels. These gels or crystals absorb water and swell to several times their original size. The gels then slowly release water over time into the soil.
They might work for a while, once they begin releasing water to plants. However, within two to five years, these gels degrade into substances such as acrylamide. Acrylamide is a neurotoxin and potential carcinogen and it can be absorbed through the skin or inhaled.
Even in its intact state, polyacrylamide can cause skin irritation and mucus membrane inflammation. The use of these gels, crystals or granules is not recommended in home gardens and landscapes.
Gypsum is marketed as softening clay soils, loosening compacted soils and treating soil salinity. In very specific soil situations, gypsum can be a helpful amendment. But rarely are these soil conditions found in home gardens and landscapes.
Gypsum is hydrated calcium sulfate. It is effective in treating sodic soils, which are soils high in exchangeable sodium. Although gypsum can improve structure in sodic soils that are well-drained, it will not soften clay soil or loosen compacted soil.
Products sold as soil microbes do not work well either; with the exception of inoculating legume crops with rhizobia. In most other cases, little or no improvement in soil health and microbial populations are observed.
Soil microbes are an extremely important component of soil ecosystems. Most occur naturally and do not need to be added. Even poor-quality soils contain some soil microbes. If soil is managed correctly, such as adding organic matter, not overwatering, not working the soil when wet and more, existing microbial populations increase.
Organic matter is the most important soil amendment. It improves soil structure in sandy and clay soil. As a rule, we recommend incorporating organic matter, like compost, on a regular basis. Organic matter is the next best thing to sliced bread and it can be made at home or found for free.
And by the way, sand may be free, but it is not recommended for adding to clay soil. If not added in the right proportions, sand can make clay soil issues even worse. The best way to improve the structure of clay soil is to thoroughly incorporate organic matter.