Storage efficiency of preplant irrigation

Drainage and water storage efficiency of preplant irrigation in the deep silt loam soils of western Kansas were evaluated. Drainage from the soil profiles was significant, even when soil water contents were less than the “field capacity” value, if extended drainage times were involved. The Ulysses (fine-silty, mixed, mesic Aridic Haplustoll), Richfield (fine, montmorillonitic, mesic Aridic Argiustoll), and Keith (fine-silty, mixed, mesic Aridic Argiustoll) soils drained 89, 61, and 69 mm (3.5, 2.4, and 2.7 in), respectively, from day 3 to day 33 following thorough wetting of the soil profiles (covered soil surfaces). From day 33 to day 63, the Richfield drained 18 mm (0.7 in) and the Keith drained 23 mm (0.9 in). For a given soil and precipitation pattern, storage efficiency of preplant irrigation was influenced largely by soil water content immediately prior to irrigation and by irrigation amount, with storage efficiency decreasing as either or both factors increased. Irrigation management during the growing season influenced soil water content after harvest and thus water storage efficiency during the off-season. If preplant irrigation is not necessary to establish a crop, irrigation water should be reserved for seasonal application.