Benefits

Applying mulch to your garden is a wonderful way to add organic matter to your soil. Plus, adding mulch has several other very useful benefits.

Adding Organic Matter

Although it doesn’t typically contribute nearly the volume of organic matter that cured compost adds to your garden, regularly applying mulch still adds significantly to your soil’s organic matter. Plus, mulch has such a profoundly positive effect on every other aspect of your garden that its relatively small typical contribution of organic matter is still well worth it. In short, at least it’s contributing some organic matter while providing all of those other benefits. Notice, for example, the clumps of mulch sticking up at the tops of earthworm burrows throughout your garden, as if these auspicious annelids have overstuffed their little tunnels’ mouths in their attempts to hoard every bit of surrounding mulch. Think about the richness of their castings bleeding out of their burrows into the soil, and you’ll get a sense of just one such benefit of mulch.

Besides, one can add huge volumes of mulch, adding a significant amount of organic matter to one’s garden. In How to Grow Vegetables and Fruits by the Organic Method, J.I. Rodale describes a gardener and farmer, for example, who harvests the hay from half of his field to be used on mulch on the other half. His soil on the mulched half is rich and spongy, teeming with microbial life, and his garden plants are the epitome of health, vibrance, and production. Most of us don’t contribute nearly this level of mulch to our soil each year, probably swayed by the bare-soiled paradigms of gardening and farming we’re most used to seeing, but there’s no reason we can’t. We, and our soil, would benefit greatly from it.

At first, before we’ve created an extra nitrogen storehouse in our soil, if we apply volumes of dry mulch like straw, some of the nitrogen needed by our plants will be taken from the soil by the mulch as it breaks down. One way to offset this is to simply sprinkle a little extra nitrogen over the top of the mulch after you apply it. Fish emulsion works perfectly for this. One can also counteract this by applying mulches that are still filled with their own inherent nitrogen—fresh, green, herbicide-and-weed-free hay and grass clippings, for example.

Other Benefits

Beyond adding organic matter, mulch has many other benefits in the garden. It, for example, is your biggest ally for thwarting weeds and soil erosion, moderating soil temperatures, holding in soil moisture, and providing your plants with their ideal microclimates.

Bare soil exists in only a few places in nature, and, where it does, it’s a sign of extremely poor fertility, sparse organic matter, and rank erosion. In most places in nature, especially the healthy ones we’d like to emulate, the soil is, instead, covered and protected by layers of dead vegetation from previous years and the current years’ foliage that rises above it. These layers of protection provide a warming blanket against winter cold and a cooling buffer against summer heat. And they are the first hit by the pounding force of raindrops, absorbing their compacting, erosive energy and gently dripping their moisture to the soil.

Thwarting Erosion

In the same way, an applied layer of mulch allows you to protect your garden soil from the compaction and erosion caused by the direct hits of rain. The force of falling raindrops is actually much more significant than most people tend to appreciate. Bare soil can be dramatically compacted and eroded over the course of a single large rainfall. Over an entire growing season, the effects can easily compound to nullify much of the hard work you’ve done to loosen the soil and wash away loads of your precious topsoil and added organic matter. Applying a layer of mulch—even possibly a very thin layer, depending on the plants being grown (explained in more detail below)—amazingly protects your precious garden soil from all of the deleterious effects of rain, leaving it to absorb only the beneficial ones.

Stymieing Weeds

Bare soil rarely exists in the natural world because many plants have specifically adapted to grow in it, finding their niche in areas that have less competition. Their seeds have, likewise, adapted to sprout with the increased light and/or heat of bare soil. As such, they thrive in the bare soil of your garden. However, because mulch shades and cools the soil, even the lightest coverings of it greatly lessen the prevalence of most of these weeds.

Moderating Soil Temperature

Besides thwarting erosion and stymieing weeds, mulch also moderates the temperature of the soil, keeping it cooler during the summer and warmer over the winter. Both of these moderations aren’t just for the benefit of our plants but also for our worms and microbial life. Just take a gander at soil left to bake in the sun, and you can make several conclusions about the health of the microbial life there. Likewise, soil left uncovered in the winter experiences huge temperature swings and deep freezing, both of which either drive our earthworms away or kill those that haven’t already left.

Holding in Soil Moisture

Mulch, likewise, holds in soil moisture to an amazing degree. Bare soil dries out relatively quickly during windy, dry weather. Even a thin layer of mulch, by contrast, even one that covers only one-third of the soil’s surface area, retains soil moisture much longer in these conditions, showing the darker color of dampened soil on the surface for days or weeks after the bare soil’s surface looks bone dry. Correspondingly, thickly mulched soil will retain its moisture for almost miraculous periods of time in these conditions.

What’s the Best Mulch

Some of you may be wondering, “So what’s the best mulch?” In short, it tends to be straw, but check out the above link for more information.