Oh, interesting! That’s a very good tip I’ve never heard before. Thank you, Joseph!
Wood chips work great ON TOP OF garden soil. Not so much when mixed in.
I generally discourage their use, cause people love to till. Relatives till. Helpful neighbors till. People forget then till. Weeds creep in, so they till.
Ha ha ha, that makes sense! So they’re only a good idea in a no-till situation.
What I’m trying right now is when I get weeds coming through my mulch, I smother them in more mulch. Sometimes that’s a little scattering of wood chips and sometimes it’s setting an entire hay-bale, or even a flag-stone on top of a thistle.
Like most things wood chips work great, but everything comes down to context. For example I’m in a hot humid climate with lots of rain and clay soil that retains moisture. My lot also collects the water from the surrounding properties. I mainly use wood chips for soil improvement and weed suppression, but also to keep my topsoil in place and absorb moisture.
In a dry desert climate I would think the deeper wood chips the better. They should help retain a ton of moisture, but I would make sure to apply them right after a rain. The addition of Biochar is also extremely helpful for holding pockets of water in the soil.
Also just because the soil feels dry does not mean there is no water. Research has found that clay dry enough to blow in the wind still contains as much as 70% water by weight. The issue is that plant roots can’t access it, so only mycorrhizal fungi can make it available. This is why over time wood chip mulch combined with a no till system allows huge amounts of water and nutrients available to the plant that would typically be inaccessible.
So in my opinion even if you need to irrigate a thickly mulched wood chip garden in a desert climate temporarily, long-term it would be worth it assuming you don’t mind spreading wood chips on regular basis.
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I’ve never heard any details about how native groups used rock mulches, though I think they were mostly for perennial plants. As @UnicornEmily said below, the problem for annual gardens is that the rocks tend to sink in too much, and then they become a real pain.
Larger cobbles or flagstones might work well, since they would be easy to remove and replace, and wouldn’t sink as fast. But I’ve never tried this.
A friendly reminder to use present tense for Indigenous people’s agricultural practices
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Rocks do help in fall and spring. They keep the soil temperature more even, basically acting as thermal mass. In early spring they keep the soil from warming up as fast, as it’s not exposed to the sun.
If I use rock mulch I much prefer large permanent rocks that I use as edge or to keep weeds back around trees.
Rocks can also form a water barrier or help to direct water so your water goes where you want it. Conversely, the area under and immediately around large rocks often retains water better than bare soil.
In the past, rocks have been used to condense water out of the air. They also act as nutrient traps, holding dead grasses and debris as it breaks down.
The advantages and drawbacks depend on your situation and what you’re trying to accomplish. The drawbacks can become strengths depending on how they’re used.
Labor: As mentioned before, small rocks tend to sink into the soil so you end up sifting to find them all. All rocks have to be moved, and if you’re using them around annuals they have to be removed at the end of the season. I prefer to use rock as a permanent part of the landscape so I don’t have to move it all the time.
Water: small rocks, pebbles, gravel, will not absorb water but pass it through. Large rocks create edge, and depending on the size there can be a spot underneath that is much drier but the soil around the edge will be wetter right after a rain event. However, large rocks will also prevent evaporation so the area under the rock tends to stay wet longer. Rocks can be used to divert or direct water to where you want it. I like to plant around large rocks so that water can be used.
Heat: Rock tends to both heat up and cool down quickly. It can warm your soil early in the year but can also insulate and keep soil cooler. The differences depend on the kind of rock, your soil, air temps, cloud cover, etc.
Rock is also hard, and I have a tendency to trip on things that roll, so if I need to use rock I prefer large and flat.
It makes a great “top layer” for water catchment areas in the ground. Good boundaries and markers.
If you test out the use of rock mulch in your garden, let us know how it works.
As far as row cropping, it was and is used to minimize work. It makes garden chores easier, allows for low impact irrigation as well as tilling. Planting and harvesting in straight rows is more efficient in a lot of ways.
I was raised on row cropping, tillage, and all the rest. It simply wasn’t feasible in my desert climate–we were spending way too much water for too little return. So I had to look for alternatives.
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