farming irrigation

Winter vegetable fields in the Gila Valley are a study in three types of irrigation – sprinkler (near the top), drip (middle) and flood (near the bottom) – as seen Friday afternoon.

Time seems to have flown! How wonderful to have 70 degree mornings and on some nights, turning off the air conditioning and opening the windows and let all the stale summer air out. It hasn’t rained for months, to some it’s a blessing and others see it as a curse. To the non-farming community, a shower for a day to wash off all the trees and plants, clean the air and make the desert smell wonderful would be a blessing. With our miserly three inches per year rainfall, if we are lucky, we long for the cloudy skies. To the agricultural community, rain can be a curse because it interrupts the delicate balance of land preparation, planting, irrigation, cultivation, fertilization and a dozen other critical operations in the production of the 175 different winter crops that we grow and harvest.

Growers in Yuma use irrigation to provide the life-giving water to the crops they grow. There are three basic types of irrigation that are used. Most common by far is flood irrigation, where the water is turned on to the fields through large, high flow turnouts on to perfectly flat or furrowed rows. The irrigation districts provide water through their canals, distributing it to farm ditches that carry the water to the individual fields. The flood systems are constantly being improved so that the on-farm irrigation efficiency exceeds 75 percent. This level of efficiency means the crops are receiving exactly the amount of water that is needed for the stage of growth the plant is in. Our surface systems are among the most efficient in the world.

When the seed is first planted or the seedling cauliflower or broccoli is transplanted, the farmers use sprinkler irrigation to get the seed germinated or the baby plants started. Using the sprinklers has many advantages including reducing the ambient air temperature from over 100 degrees to 70 to 80 degrees, a much better situation for the plants. Sprinklers also push any potential salts below the root zone of the seedlings, encouraging uniform growth of the little plants and reducing plant loss. Another plus is that if there are insects, such as whitefly or aphids, the bugs are washed off the plants before they can do any damage. Cauliflower, broccoli, head lettuce and romaine lettuce all take 2 to 3 months to get to a harvestable size, so after being sprinkled and getting a healthy start, the growers switch the fields to flood irrigation to prevent wetting the developing produce. With our warm temperatures and winds, water spots can develop on the leaves reducing the quality of the lettuce.

A third system used by some growers, are surface or underground drip systems. Drip systems require a higher level of maintenance and management. Concerns with drip on our soils are the salts left on the soil surface that can affect the plant growth if washed into the plant root zone, blockage of the emitter so the plants are not getting watered properly and pressure variations, again not watering all the plants evenly. One of the keys to our successful vegetable crop production is that all of the plants being harvested from a field be of the same quality and quantity. With drip systems, there can be irregular plant growth in our climate. Without our amazing irrigation, there is no farming.

Bobbi Stevenson-McDermott is a retired soil and water conservationist. She can be reached at rjsm09@msn.com.

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