Proper Soil Composition for a Phoenix Garden

Understanding what makes good soil is essential to successful gardening in the harsh Phoenix climate (Zone 9B - Low Desert). Express Vegetable Gardens will not only provide you with the perfect soil type for your specific needs, but also develop a fertilizing program for you to be successful year in and year out.

Call us to schedule a free consultation where we can help you craft a soil strategy for your specific gardening needs. We'll do the hard work of delivering the soil and setting up your beds so you can enjoy endless bounties of fresh fruits and vegetables year round. For those who enjoy digging a bit deeper into the soil, please continue reading.


Soil Texture

Successful gardening in Phoenix starts with proper soil composition. There are three main ingredients that make up your soils mineral particles: sand, silt, and clay. It is rare to find a soil that is 100% composed of any one soil type. The texture of a soil is the percentage of each of these three types of soil that is in a garden bed and it influences the amount of water the soil can hold, the rate of water movement through the soil, and how workable and how fertile the soil is. 

  • Sandy soil is made up of large, rough particles. Soil that contains too much sand will lead to water draining away too quickly and is considered nutrient-poor soil.
  • Clay soil is nearly the opposite of sand. Clay soil particles are very small and absorb water and nutrients extremely well. However, too much clay in the soil leads to root-rot.
  • Silt particles are in between sand and clay particles and feel similar to flour when dry. 

A well balanced soil is considered ideal for most vegetables and is considered a loam with 40% sand, 40% silt, and 20% clay.   

Organic Matter

Organic matter in the soil includes plants (or animals) that are alive, dead, or in a state of decomposition. When we add organic material to our gardens such as leaves, manure, or other plant parts we think we're doing our plants a huge favor, however, this organic material should not be confused for the organic matter or humus that our gardens actually want. Humus is organic material that is fully decomposed and is ready to be consumed by the beneficial microbes in the soil. Although soil looks dead from afar, it is actually teeming with life. One teaspoon of topsoil contains around one billion individual microscopic cells. These tiny cells feed on the humus or organic matter in the soil. This is important because these microorganisms are working day and night converting the minerals in the soil into food that are plants can digest. To provide our gardens with organic humus we should consider using a compost bin to break down larger material first before adding to our gardens or simply purchasing ready to use humus bags. An ideal garden has somewhere around 10% humus in the make up of the soil's composition. 

Soil Acidity (pH)

Once a healthy composition of soil particles is achieved the next thing to consider is the pH of the soil in your garden bed. Testing your soil using a common testing kit will yield a number between 0 and 14. The lower the number, the more acidic or "sour" the soil is, while a higher number is more alkaline or "basic." If the pH number is too high or too low the minerals in the soil become unavailable for your vegetables' roots to absorb. Most crops like a fairly neutral level of acidity with a pH around 6-7. Overly acidic soils are neutralized by adding powdered or pelleted agricultural limestone. Do not overdo the limestone as it it much easier to raise the pH of a soil than to lower it. To lower a soils pH, elemental sulfur or iron sulfate can be used. These products can be purchased at most nurseries and are mixed into the garden beds accordingly. Wait at least one month after amending your soil's pH before planting as root burn can occur.  Organic matter can be used to lower your soils pH, however, this process will take longer to achieve results.

Fertilizing and Replenishment

Even after taking the time to perfect your soil's texture, and pH, your garden soil plan is not complete until you have developed a healthy fertilizing and replenishment program. Some gardeners swear by, and have tremendous success using the pure organic humus method of fertilizing which entails adding compost around the plants multiple times per growing season, however, they miss the fun of studying the soil. A tree in the forest feeds itself, every leaf blossom, fruit, and branch is returned to the soil. A cultivated fruit tree is not so fortunate. Each year its produce is removed, never to be returned to the soil. Somehow this continual taking-away must be balanced. This is where fertilization becomes important. There are 16 chemical elements known to be important to a plants growth and survival. They are divided into two groups: non-mineral and mineral. The non-mineral elements are hydrogen, oxygen, and carbon and are provided by the air and water. The 13 mineral elements which come from the soil are divided into two categories; primary and secondary. The primary nutrients are nitrogen, phosphorous and potassium. On the back of standard fertilizer bags you will see an N-P-K ratio. These letters represent their chemical symbols. These three nutrients are used in large amounts by the plants and often times have to be replenished via a fertilizer. A common recommendation for vegetables is to apply 1 pound of a 10-10-10 fertilizer or 2 pounds of a 5-10-5 (or 5-10-10) fertilizer per 100 feet of row per season. The secondary nutrients used in much smaller quantities can be obtained by the addition of organic matter in the garden or any all purpose fertilizer. If you have one pesky spot in your yard or a bed that just isn't producing like it used to a soil test can be performed to determine which nutrient is lacking. 


Express Vegetable Gardens recommends setting up separate beds for similar fruits, vegetables, and herbs so that the soil, watering, and fertilizing patterns can be conditioned appropriately. For example, you could have one bed for all your leafy greens, another bed for root crops, and pots for your bushy herbs. For those who enjoy homemade salsa, a salsa garden can be created by putting an array of peppers in one bed. The possibilities of proper vegetable gardening are endless and with some basic knowledge anybody can be on their way to successful backyard gardening!

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