In many ways, the desert is an ideal place to grow tomatoes because fungal pathogens that decimate tomato crops in wetter regions are less prevalent here. Plenty of warm sunshine and dry air make tomato plants particularly happy. The real challenge is to provide rich, well-drained soil and sufficient moisture. Certain tomato varieties grow better than others in desert conditions, so careful selection is important as well. By choosing the right location and cultivars for your garden, improving the soil and irrigating properly, you can harvest juicy, delicious tomatoes, grown in the desert sun.
Locate your tomato beds away from drying winds and where they will receive about six hours of sun per day. Choose a place that receives morning sun, but is shaded in the late afternoon.
Provide a bed with deep, rich, well-drained soil, which is slightly acid. Work the soil to a depth of 2 to 3 feet. Add up to one-part organic compost to one-part native soil to improve soil structure, especially if your soil is sand or heavy clay. Buy an inexpensive kit from your local garden center and test the pH of your soil. Add sulfur powder, as necessary, to bring the pH level to around 6.5.
Plant tomato starts in the garden in mid February or as soon as nighttime temperatures are dependably above 60 degrees Fahrenheit. Place ¼ cup of soft rock phosphate in the bottom of each planting hole. Remove the bottom leaves of the starts, and plant them deeply, so that a few inches of the stem is buried to produce more roots.
Sculpt the garden soil with your hands to create a 2-inch deep well around each plant to retain water.
Apply a 6-inch layer of organic mulch, such as bark chips or straw, to the entire bed, avoiding a few inches around the base of each tomato plant. Maintain this mulch layer throughout the season to conserve moisture and cool the soil.
Fill each well with water, allow it to drain and repeat this procedure once more at planting time. Water your establishing tomatoes deeply in the early morning, three times a week for the first three weeks. Irrigate established plants deeply, once or twice a week, to encourage deep roots. Increase irrigation in prolonged drought or extremely hot weather.
Apply a balanced foliar plant food with a garden sprayer once a month, in the early morning when the plants are not receiving direct sun. Look for organic formulas that include molasses and kelp.