In the Garden:
Southwestern Deserts
October, 2013
Regional Report

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Healthy soil promotes healthy, attractive plants.

Improving Garden Soil

Cool-season flower and vegetable planting is here at last, and it's time to improve the soil in garden beds. Desert soils look boring beige in comparison to those rich, black soils found in other parts of the country. The difference is due to the limited amount of organic matter found in desert soil: less than 1 percent.

Desert plant life doesn't drop much litter to decompose over time and build up in the soil. Envision a New England sugar maple leaf the size of a man's outstretched hand versus a palo verde leaf the size of a baby's fingernail, and you'll understand why we desert gardeners need to supplement the organic matter in our vegetable beds!

Adding Organic Matter
Dig in and loosen the soil to a depth of 12 to 18 inches. Most annual vegetable, flower, and herb roots grow about 12 inches deep, so loosening allows the roots to easily penetrate through the soil. If your soil is too hard or rocky to dig, raised beds are a good option. They work best if they are at least 18 to 24 inches deep.

Next, layer 4 to 6 inches of compost on top of the soil. Compost is often referred to as "gardener's gold" because of all the benefits it provides. In clay soil it improves drainage so roots don't rot. In sandy soil it improves water and nutrient retention so you don't have to water or fertilize as much. Regardless of soil type, compost improves fertility and attracts earthworms, which are great soil-builders.

Don't Forget Fertilizer
The next step is to add nitrogen and phosphorus fertilizer. Nitrogen promotes lush, green foliage growth, and phosphorus promotes flowering and fruiting. Desert soil typically contains plentiful potassium, so it isn't necessary to add it. If your soil is heavy clay, add gypsum or soil sulfur. Either of these soil amendments works to improve water penetration through the soil and reduce sodium buildup.

Thoroughly incorporate all of these amendments, rake smooth, and you're ready to dig in to fall gardens!


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