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Cucumber, Pumpkin, Squash - Irrigation

Soil tension values for different soil textures for use in scheduling drip irrigation, based on various percentages of depletion of available water holding capacity (Field capacity).

Soil Texture 0%
Soil Tension Values (centibars)
Sand, loamy sand 5-10 17-22 25-30
Sandy loam 10-20 22-27 33-40
Loam, silt loam 15-25 25-30 40-50
Clay loam, clay 20-40 35-45 55-65

All of the cucurbits require regular, uniform watering during the growing season. Water shortages during establishment can limit seed germination, transplant establishment, and early vine growth. Inconsistent watering around flowering and fruit set can cause misshapen fruits and induce blossom end rot, and affect fruit sizing, flavor, and color development. Overwatering encourages root rots, belly rot on fruits, and can cause edema or fruit cracking. Furrow irrigation is suitable for the cucurbits and some growers use sprinkler irrigation to aid in stand establishment. Growers who plant through plastic mulches commonly use drip irrigation. Later in the growth of the cucurbits, sprinkler irrigation (solid set, wheel lines, and center pivots) can contribute to foliar diseases and may interfere with bee activity thus reducing fruit set, shape, or size.

Soil water status should be monitored regularly to maintain consistent soil water. Soil moisture monitoring is easily done with a resistance block such as the Irrometer® Watermark sensor. Place sensors at various locations in the field and at several depths in the soil profile to get an accurate measure of soil water content. Sensors typically express soil water content as a tension reading (centibars) that defines effort required to access available water. Soil water monitoring helps determine when to irrigate next. Field capacity describes a soil at 100 percent available water holding capacity after excess water has drained away. Start irrigation for the cucurbits at 25-30% depletion when irrigating by drip systems and at 40-50% depletion of available water holding capacity with furrow or sprinkler systems. Note that irrigation depends on your soil type (Soil tension values for different soil textures table). Other low cost tools and methods to monitor soil water can be found at the ATTRA website

Specific irrigation details are available in the USU extension bulletin, “Vegetable Irrigation: Squash and Pumpkins”.