The low down on desert dirt and soil conditions
Desert soil generally falls into one of these categories: rocks, sand, or clay. Or a horrible combination of these. High pH (alkalinity) is the norm. Oh yes, I almost forgot to mention high salt content and the fact that desert dirt starves plants of micronutrients like iron and sulpher, too. Deep loamy soil with neutral pH, the kind of nutritious soil, rich in organic material that gives plants all they need, is simply not found in hot, dry climates.
So your first step when you are planting a garden should be to improve the soil. In fact, if you plan to spend $100 on your garden, the first $80 should go into soil amendments! Plants grown in soil rich in organic materials are more likely to remain healthy and resist pests and diseases.
Amend. Amend. Amend the soil
So how do you improve the soil? By clearing out any rocks, then digging in compost or soil amendments available at nurseries or home improvement stores. These organic materials will help bring the soil–whether it is sand or clay–closer to the neutral pH and give it that high-nutrient, loamy texture plants love. You probably will also want to add fertilizer that has been especially prepared to combat our high pH. Ask about this at the plant nursery.
And how often should you amend? Unfortunately, adding organic materials is not a one-time event. You should do it at least once a year to maintain plant-friendly dirt. Enthusiastic gardeners amend twice annually. Good soil needs about 5% to 7% composted organic material. Be sure that all amendments you add have been composted. Digging in green leaves or fresh grass clippings without composting can do more harm than good.
Small rocks in the soil are not a problem In fact, they will help loosen the dirt and allow for better drainage. Big rocks, obviously, can block root growth.
Beware: if you have heavy clay soil, whatever you do, do NOT add sand in an attempt to make it lighter or drain better. What you will end up with is adobe brick! Lots of compost, dug into the clay, will make it lighter and the plants happier.
Now about caliche
Caliche is a white or ivory-colored calcium carbonate substance that occurs in cement-like layers throughout our desert. The layers, which can be from a few inches to many feet thick, may appear near the surface or deep below. Caliche near the surface can block root growth causing plants to be stunted or die. And it takes a pick axe to break through a caliche layer! If you are planning to put in a pool it pays to have a soils engineer dig test holes to see if the site has caliche. Removing caliche to make room for a pool can be very expensive.
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