Geotextiles vs. Organic Mulch
As weed barriers, geotextiles are popular solutions for home gardeners, landscapers, and farmers alike. There are other options, of course, which offer certain advantages of their own. Inorganic mulches include gravel, pebbles and river rocks, although shredded rubber mulch is more popular for playgrounds, given its natural shock absorbency and resistance to weather effects. In these examples, it’s always best to lay a geotextile barrier above the soil and below the mulch to prevent rocks or bits of rubber from disappearing into the soil and encouraging weeds to sprout.
Organic mulches continue to be very popular. In some cases, they’re available at no cost, are environmentally friendly, and can enrich the soil as they decompose. Options like wood chips and bark mulches, or shredded leaves and compost offer some protection from erosion and can add nitrogen to the soil. Pine needles decompose slowly and can acidify the soil, if that’s one of your goals. Newspaper and cardboard are simple to apply and it’s easy to get even coverage, but no one would describe the look as attractive.
On the other hand, mulches themselves can carry weed seeds which are happy to sprout directly from that nutritious layer of damp compost. They can also bring in pests, fungus and some plant diseases, especially if you opt for the free type. Dry mulches can also be a fire risk, which is a huge concern in dry western regions of the US.
Geotextile ground covers do an excellent job at limiting weed growth. When light is unable to penetrate the soil, seeds simply do not germinate or develop. Of course, if soil accumulates on top of the ground cover or an organic mulch is added to cover the geotextile, weeds are happy to establish themselves even if the organic layer is very shallow.
Geotextile fabric is widely used in construction and erosion control projects because it stabilizes the soil and protects it from the erosive effect of wind and flowing water. Most types of geotextiles allow at least some water to permeate the soil, but the penetration is slow and lacks the destructive energy of heavy rainfall. If you’re choosing gravel or river rock as your mulch of choice, an underlayment of landscape fabric keeps your gravel from sinking into the ground and less is needed to achieve your goal.
Ground Covers for Organic Farmers
Organic farmers must amend their soil periodically to maintain a healthy level of organic material and nutrients. Obviously, chemical fertilizers are not an option, and neither are herbicides for weed control, but some also assume that geotextiles are also prohibited.
In fact, USDA studies have indicated that organic farmers can still control weeds by using fabric ground covers, even after adding compost to the soil This treatment simplifies the process of preparing the soil and reduces the possibility that rainfall will create nutrient-rich runoff that can severely damage ecosystems in local waterways
Weed Barrier and Water Control
Geotextile barriers used as weed barriers not only block out light to keep weed seeds from germinating, but they create a barrier that prevents weeds on the surface from taking root. Geotextile fabrics also allow water and air to pass through and nourish crops, but you can choose from a wide variety of products and make your selection based on stats like permeability. If your crop is thirsty and water is scarce, geotextiles can allow water from rainfall or irrigation to pass through, while preventing the moisture from evaporating. If your crop prefers dry feet and you’re subject to occasional deluges, a fabric with low permeability can allow a limited amount of moisture through while directing most of the water into drainage ditches, while avoiding a flood emergency and weeks of soggy roots.
Erosion control
Geotextile ground cover provides a unique advantage that some other mulches don’t offer. While a generous layer of gravel can mitigate soil erosion resulting from a strong rainstorm, gravel can also be lifted and carried away if the flow of water is strong enough, especially in areas prone to washouts. Soil disturbed in this way will also tend to subsume the gravel unless a layer of geotextile is installed as a barrier over the soil.
Organic mulch, especially lightweight bark nuggets are easily carried off by flowing water and provides little stability to the soil beneath it.
Other Benefits
Weed suppression, moisture retention, and erosion control are excellent benefits from using geotextile ground covers, but there are a few additional benefits that aren’t often mentioned. Dark geotextile fabric helps soil retain heat and absorb thermal energy during cold weather. Lighter fabric shades the soil and helps roots remain cooler in hot weather.
Another surprising benefit is cleaner produce. When the soil is covered and protected with geotextile fabric, soil and organic mulch materials aren’t splashed onto low lying produce, saving time and effort in post-harvest preparation.
