ZONE?SUBSOILING RELATIONSHIPS TO BULK DENSITY AND CONE INDEX ON A FURROW?IRRIGATED SOIL

Abstract

Zone subsoiling on irrigated land has been successfully used to improve potato (Solanum tuberosum L.) yield andquality. Zone subsoiling under furrow irrigation may disrupt water flow and influence infiltration and soil erosion. Wehypothesized that zone subsoiling, done appropriately, will maintain integrity of irrigation furrows, improve small grain anddry bean (Phaseolus vulgaris L.) growth and yield, and not adversely affect water flow, infiltration, or erosion onfurrowirrigated soils. The experiment was conducted at the USDAARS Northwest Irrigation and Soils Research Laboratoryin Kimberly, Idaho. The soil is a Portneuf silt loam (coarsesilty, mixed, superactive, mesic Durinodic Xeric Haplocalcids).Tillage treatments were disk, disk + paratill, paratill, and notill.There were no differences in water infiltration, runoff, orsoil erosion among treatments. Bulk density differences among treatments were largest at the 0.15 to 0.20m depth, and bulkdensity was about 16% to 18% greater on disk and notill treatments than on paratill treatments. The highest frequency oflow cone index (CI) values belonged to paratill treatments (65% to 80% frequency of CI values less than 2 MPa); the lowestfrequency of low CI values belonged to notill treatment (20% frequency less than 2 MPa). Cone index versus bulk densityrelationships depended on soil water content with a slope of 5.81 (r 2 = 0.70) in the wetter year of 1997, and 2.90 in the drieryear of 1995 (r 2 = 0.60). Subsoiling can be accomplished on furrowirrigated lands with no adverse effects on runoff,infiltration, and erosion, but under our conditions did not improve crop growth and yield.