By Scott Calhoun,
In much of the desert, it’s generous to call the stuff we plant in “soil.” The dirt in our gardens typically has high mineral content (e.g., rocks) and very low organic matter. That makes it difficult to dig. Also, sand can drain lightning fast; compacted clay can take days. Here are two common desert soil types and how to deal with them.
In low-lying areas -- near washes, arroyos, dry riverbeds, or dried up seabed areas -- you are likely to have sandy soil. Consider yourself lucky if you do, because in many ways it is the easiest soil type to deal with. This is because sandy soil drains quickly, and most desert-adapted plants require fast drainage. You also can dig holes with a shovel. What sand lacks is moisture-holding capacity. This means you need to water more frequently. You can increase sandy soil’s water-holding capacity by adding organic matter such as compost.
Clay and Caliche
Hardpan clay and caliche are tough to work with. Caliche is a white calcium carbonate soil layer that is so hard that gardeners new to the area often mistake it for cement. Hardpan clay and caliche soils share a common problem: poor drainage. You might need a pickaxe or digging bar to break them up.
Even though digging is tough, don’t get discouraged. Your desert plants have evolved to live in tough conditions. You’ll be surprised at how well they grow with just a little work breaking up the soil before you plant.
For really stubborn hardpan and caliche, use a digging bar (see photo) to make additional drainage slots at the base of the planting hole to drain water. You also can mound the soil to increase root depth. When irrigating in heavy soil, make sure you irrigate slowly and for a longer duration than you would in sand.
Growing Edibles: Amending Soils
Unlike the desert-adapted landscape planting methods mentioned above, planting veggies and other edibles requires good, rich soil that drains well. In the desert that often means using raised beds. You can make raised beds out of anything from reclaimed bricks to cement blocks. Then fill them with a rich, heavily amended soil.
And how do you create that rich, heavily amended soil? Start with some quality bagged topsoil and add lots of soil amendments, such as compost made from your own garden debris (see photo). As the old adage goes: There is nothing you can do after you plant your vegetables that has as much effect on how they grow as what you do to the soil before you plant.