Delta Micro Irrigation Final Report

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INTRODUCTION: Kabocha squash, Cucurbita moschata, is an important cash crop for western Colorado. Over 350 acres of Kabocha squash was planted in Delta and Montrose counties in 1998,1999 and 2000. Virtually all of the Kabocha squash produced in Western Colorado is exported to Japan. Colorado Kabocha producers receive a premium price for their squash due to it's high quality. However, to remain competitive, growers need to utilize methods which can increase production, while maintaining quality and economic viability. The use of plastic mulch and subsurface drip irrigation has been recognized as two areas of agricultural technology which can increase yields and maintain andlor increase quality. At the Rocky Ford Research Station in Southeastern Colorado, Bartolo (1996) found a significant increase in yield of cantaloupes when grown with plastic mulch and subsurface drip irrigation. In Mexico, Kabocha squash is grown using plastic mulch and subsurface drip irrigation, with yields approximating 15-16 tons per acre (E. Hart, pers. communication). In addition, the combination of subsurface drip irrigation and plastic mulch can lead to significant water savings. Water conservation is an important issue in areas such as Western Colorado which depends on limited water supplies for use in urban and agricultural areas. Subsurface drip irrigation also gives growers flexibility with fertilizer applications. Growers can better manage timing of fertilizer applications. Growers can also decrease the amount of fertilizer applied by having the ability to apply fertilizer directly to the root zone. METHODS: This study was conducted over three seasons, 1998-2000, at the Western Colorado Research Center at the Rogers Mesa site, located 20 miles east of Delta, Colorado. The elevation is 5640 feet. The growing season is approximately 150 days. The field was prepared by disking followed by rototilling to a depth of 6 inches. The mulch and drip tape was laid with a Buckeye combination mulch layer, drip tape applicator and bed shaper (See Figure 1, Appendix A). The beds were 42 inches wide. The beds were 8 feet between centers (See Figure 2 for view of field). The drip tube used for irrigation was T_Tape™ TSX-51030-340 (T-Systems International, San Diego, California). The T -Tape was laid 2-3 inches below the surface of the soil in the center of the bed. The beds and T- Tape were laid in mid-May in 1998, 1999 and 2000. In 1998, three different colored plastic mulches were evaluated: 1) clear, 2) black and 3) green. A red plastic mulch was added to the trials in 1999 and 2000. Plots were included which had only T -Tape without plastic mulch. Irrigation water was delivered through a series of ditches and canals. In order to adequately filter the ditch water, the water was first filtered through 4 Amiad ™ 120 mesh filters followed by 2 Spin_Klin™ 140 mesh filters. In addition, squash seeds and transplants were grown in furrow irrigated plots. Soil moisture was monitored with tensiometers placed at depths of 6 inches and 12 inches. The amount of water used was measured with inline flow meters for 1999 only. Flow meters were not available for 1998. Water usage for 1998 was estimated by calculating the amount of water emitted per row (row lengths were the same in 1998, 1999 and 2000. Water line pressure was maintained at 9 PSI for 1998, 1999 and 2000). Fertilizers were injected via a Chern Feed™ C600P pump. In 1998, 1999 and 2000 approximately 15 gallons ofUran (32% nitrogen) and 21 gallons of 5-5-5 (5% nitrogen, 5% phosphate and 5% potash) was applied over the course of the growing season. One half of plots were planted with 4 week old squash transplants. The second half of the plots were directly seeded. In 1998, seeds and transplants were planted on May 28 and May 29. In 1999, the seeds and transplants were planted on June 15 and June 16. In 2000, seeds and transplants were planted on June 12 and June 13 ( See Figure 3, Appendix A, for young squash plant in mulch). The plot size was 200 feet wide x 160 feet long for all three years. In 1999, the squash trial was rotated immediately to the north of the 1998 squash plot. In 2000, the squash trial was rotated back to the site of the 1998 planting. Row orientation was north to south. In row plant spacing was 2 ft. Each treatment was one row, divided into 4 plots. Each plot was 40 feet long. There were 20 plants per plot. The treatments are in Table 1. Harvest was conducted in the first week of September in 1998 and the second week of September for 1999 (See Figure 4, Appendix A, for view of mature squash field). Squash was not harvested in 2000 due to the loss of irrigation water at the end of August. The Fire Mountain Irrigation company was unable to supply water after Paonia Reservoir reached minimum water levels at the end of August. 2