Horticulture Risk Management Series
Rainfall Capture and Drip Irrigation - techniques to consider in developing drought management strategies for vegetable production.
Dr. Frank J. Dainello, Extension Horticulturist-Commercial Vegetable Crops
Department of Horticultural Sciences, Texas A&M University, College Station
As drought conditions continue to persist across the state, the greater is the need for techniques that reduce the risk of crop failure associated with water shortages for irrigation purposes. The urgency to find ways to reduce agricultural water use will increase as the state=s population continues to climb and create a greater demand on its limited water supply. Since drought conditions usually occur in most areas of Texas growers should strive to incorporate as many water saving techniques into their standard management practices for vegetable production whenever possible.
In response to the need for reducing crop production water use, a team of Specialists from the Texas Agricultural Extension Service conducted a series of field tests in the Wintergarden to demonstrate the latest techniques for reducing crop water use; drip irrigation, plasticulture and Rainfall Capture (RFC). Results obtained from these tests are described in this publication.
The initial demonstration was established in cooperation with McFaddin Farms of Uvalde, Texas. Water use efficiency of drip-irrigation + plasticulture and RFC were compared with that achievable with conventional furrow irrigation of cantaloupe. Drip irrigation was scheduled based on soil moisture tension at a 12 inches depth as indicated by tensiometers. When 45 centibars of tension were reached, one-acre inch of water was applied. No supplemental water was given to the RFC capture plots. The cooperator scheduled the water applications for the furrow treatment. In order to capture and store moisture received throughout the fall and winter months prior to spring planting, the RFC treatment was established October 26, 1993. The RFC technique consists of establishing two polyethylene-lined mini catchment basins, 22 inches apart, on an 80-inch wide raised bed. Each basin was approximately 10 inches wide across the top, 4 inches deep, and 3 inches wide across the bottom. Holes spaced 3 feet apart were punched in the bottom of the lined catchment basins and covered with soil to allow moisture to enter the bed for storage in the soil profile. The drip irrigation + plasticulture and the furrow-irrigated blocks were established the following spring on April 4, 1994. The cantaloupe crop was then planted on April 12. All treatment plots were approximately 5 acres in size. 14.04 inches of rainfall were received in the RFC block prior to the establishment of the other treatments. An additional 13.12 inches of rain was received by all treatments during the cropping season.
A second demonstration was established in 1995 in conjunction with Cargil Farms of Uvalde. In this demonstration comparisons were made between drip irrigation, RFC, and, plastic mulched furrow irrigated beds. Due to weather conditions and scheduling problems the RFC treatment was established at the same time as the other treatments, April 6. The crop was planted on April 15 in 10 acre blocks per treatment. Approximately 9.6 inches of rainfall was received during the cropping season at this location.
Drip irrigation greatly increased yields, as compared to furrow irrigation, (25,812 and 25,621 lbs/A, compared to 13,3676 lbs/A and 16,988 lbs/A respectively) for the drip and the furrow techniques respectively at the McFaddin and Cargil Farms. In addition, applied water was reduced 16-20 inches in the drip treatments, respectively, at the Cargil and McFaddin Farms. Under the conditions of these demonstrations, the RFC technique resulted in greater marketable yields than achieved with furrow irrigation.
By comparison, approximately 24 inches of water was applied to the furrow plots at the McFaddin Farm and 28 inches at the Cargil farm. However, a cantaloupe crop exceeding 25,000 lbs/A was produced with 4 inches of water drip applied at the McFaddin Farm and 8 inches at the Cargil Farm. A good measure of applied water-use efficiency is the ratio of total gallons of water applied to pounds of fruit produced. Ratios of 4.3:1 and 50:1 were obtained at the McFaddin location from drip and furrow irrigated treatments respectively, whereas, 7.4:1 and 33.4:1 were obtained at the Cargil location. A ratio of 0:1 was achieved with the RFC treatment since no supplemental water was applied to this treatment. Fruit size was noted to be slightly reduced s in this treatment suggesting that RFC should be used in conjunction with supplemental irrigation and not as a stand alone technique. When comparing non mulched beds with mulched beds, a reduction of 8.4 inches(28.5%) was achieved by the use of plastic mulch combination with furrow irrigation, and, 2.9 (35.8%) with drip irrigation.
Research is currently underway in which the value of using RFC in combination with drip, sprinkler and furrow irrigation system to improve water use efficiency of these systems.
Based on the results of these demonstrations and results from other locations, the use of Drip irrigation, plasticulture and RFC are all effective water management tools for use in coping with drought conditions and/or limited water supplies. Unfortunately, these systems can also significantly increase production costs. However, the use of such techniques may be required in order to sustain production under drought conditions and/or water shortages as a result of increasing population.