Chiseling Influences on Soil Hydraulic Properties

Chiseling is now more frequently used for primary tillage in the drylands of eastern Oregon and Washington. Improved measures of chiseling effects on soil water relations are needed to evaluate water intake and infiltration benefits, especially as related to depth of chiseling. Hydraulic conductivity (K)and soil water desorption characteristic (SWDC) were field measured in the 120‐cm soil profile of a Walla Walla (mesic typic Haploxeroll) silt loam before and after chiseling 43‐cm deep. The test Walla Walla soil is layered. Cation exchange capacity, exchangeable Ca2+, clay content, and organic matter all changed at the 30‐cm depth; dry bulk density decreased with depth above 45 cm and was constant below 45 cm; Kwas 10 to 1,000‐fold lower in depths above 30 cm; water contents in the SWDC (−50 to −200 mbar range) were lower in upper 30‐cm layer. Chiseling affected both the SWDC and Kin the upper 30 cm, especially at 10 and 20‐cm depths, but had no influence on these measurements at 40 cm. Both water potential at constant water content in the SWDC and Kwere increased especially in the −50 to −300 mbar range. Failure of chiseling to improve water relations in the mild duripan extending from 30 to 45 cm suggests the need for addition of plant residue or chemical amendments into the chisel slots. Water contents and hydraulic heads during drainage showed that chiseling could reduce evaporation by reducing water content and diffusivity. Overall soil profile hydraulic resistances showed relative average Kup to 15 times greater as a result of chiseling 43 cm deep, but nearly similar accelerated internal drainages were projected for simulated chiseling to 25‐cm depth vs. chiseling to 43 cm.