Soil Water Survey After Corn Harvest in Northwest Kansas

A survey of available soil water after corn harvest was conducted in Thomas and Sherman counties, Kansas, in 1988, 1989, and 1990. Soils in the region are deep, well-drained, silt loams in the Keith (Aridic Argiustolls) or Ulysses (Aridic Haplustolls) series. Eighty-two randomly selected fields were sampled to a depth of 1.5 m (5 ft) in 30-cm (I -ft) increments at two locations within each field. Each field was equipped with either a surface- irrigation or sprinklerirrigation system. Available soil water (ASW) contents were found to be generally high, ranging from 31 mm (1.23 in.) to 287 mm (11.30 in.) and averaging 70% offield capacity. At sampling, some ASW contents were in excess offield capacity of the soil profile which is approximately 250 mm, (10 in.) for the 1.5-m (5-ft) profile. Within-field variation in ASW was higherfor the surface-irrigatedfields than for the sprinkledfields. An analysis of data from a previously developed model to predict ASW in the spring based on available jallfloil water suggested that preseason irrigation of corn should not be a recommended practice for the region.