by Blake Herzog
There may not be a lot going on in your garden at the start of the new year, but this can make it a good time to concentrate on soil health and adding beneficial organic matter to it, according to the University of Arizona Cooperative Extension for Pinal County.
Southern Arizona soil has a way of collapsing into hard layers that make it difficult to impossible to get enough nutrients to your plants, even if it’s been well-prepped beforehand. A good way to counter this is to frequently add compost, decomposed manure, forest mulch or other types of well-rotted plant or animal matter, UA Extension Agent Richard Gibson wrote in its January 2018 newsletter.
When soil particles are crunched together with little space in between, it’s difficult for water, air and nutrients to penetrate, and plants can be starved of them. When organic matter is added and continues to decompose in the soil, it provides the space necessary for the good stuff to be absorbed, while creating channels which will aid the process in the future. This can also helps improve other soil problems like pH, low nitrogen fertility, poor microorganism activity and even caliche.
Desert soils tend to be low on organic matter simply because there isn’t enough rainfall to support many trees, shrubs or grasses to provide it naturally, so if you’re not sure whether your garden needs more you might as well go ahead and add some.
Gibson said flower and vegetable beds should be given a good helping of well-rotted matter every two to three years, at least 2 or 3 inches mixed into the top 6 to 9 inches of soil. Since this can be an ordeal to accomplish, he suggests integrating organic matter throughout the gardening process.
Some gardeners work compost into the soil, under the plant, and after the new plants have emerged, then come back in and lay a mulch of organic matter on the beds and furrows to cool the soil and prevent evaporation. At the end of the growing cycle, the plants and any remaining mulch can be tilled into the soil, then they reseed and lay down a new mulch layer.
So what kind of materials work best, especially for the desert?
The experts at www.wateruseitwisely.com posted an article a year ago pointing out mulching is essential for water conservation as it reduces evaporation by providing a buffer between the soil and the bone-dry atmosphere. It also insulates the earth from low temperatures in winter, as well as high ones in summer.
Wood chips are a popular organic mulch around trees and shrubs in Arizona, because it’s relatively heavy and not as easily dispersed by wind or landscaping activity.
For vegetable and fruit gardens, composted mulch is a good option, having gone partway through the decomposition process so it can jump-start it when added to soil. Fully finished compost is richer in nutrients and can act as a mulch as well as a soil additive. Both are more likely to get blown away than wood chips, however.
You don’t necessarily have to go to the store to get this type of organic matter, the website says; leftover leaves, grass clippings or straw from the yard works fine, as long as it’s free of pesticides and chemicals if you’re sticking to an organic regimen. Alfalfa is also an excellent mulch and adds nitrogen to the soil.
Most any type of material can also be purchased at garden or home improvement stores. Remember, however, that manure usually isn’t a good option if you’re living in an urban or suburban-type neighborhood.