IRRIGATION EFFECTS ON ROOT AND STARCH PRODUCTION AND WATER USE OF THE POTENTIAL DOMESTICATE, COYOTE GOURD

The coyote gourd (Cucurbita digitata Gray) is one of several xerophytic plants under investigation as crops for arid or semiarid lands. This study evaluated the effects of irrigation on root and starch production and consumptive water use of coyote gourd cultivated as an annual. Three irrigation treatments were tested in 1986 at a 360-m elevation site near Maricopa, AZ on Casa Grande sandy loam using stands of 65 to 75 plants per m2. Irrigation treatments had no significant effect on fresh root yield, but irrigating when available soil water was 75% depleted (I2) gave higher starch yields than irrigating when soil water was 50% depleted (Ii). Starch content was highest in roots of plants that were subjected to prolonged periods of water stress. Consumptive water use ranged from 410 mm in a dry treatment to 580 mm in a wet treatment. Although 45% of water used seasonally was obtained from the top 0.4 m of soil, water was extracted to a depth of at least 2.6 m. The highest water-use efficiency, 4.4 kg fresh roots per m3 of water, was in the I2 treatment. This research indicates that the coyote gourd has attributes advantageous for cultivation in arid or semiarid regions, but further studies are needed to determine its potential as a starch crop.