Soil Quality and Water Intake in Traditional‐Till vs. No‐Till Paired Farms in Washington's Palouse Region

Abstract

Many farmers in the steeply sloped Palouse region of eastern Washington and northern Idaho practice no‐till (NT) farming. Soil quality and water intake parameters were assessed in standing wheat (Triticum aestivum L.) stubble along summit, side, and toe‐slope positions in a 2‐yr study at three paired‐farm sites using traditional tillage (TT) vs. NT management. Paired sites had similar south‐facing aspect, slopes ranged from 29 to 45%, and NT fields had not been tilled from 2 to 20 yr. Soil aggregates >1000 μm were 5.4 to 9.8% higher in NT compared with TT. Soil organic carbon (SOC) in NT was 30% greater than in TT at the toe‐slope position. Dehydrogenase enzyme activity (DEA) was higher in TT, mainly due to the exposed CaCO3 layer at the side‐slope position and higher pH of TT. Phospholipid fatty acid methyl ester (PLFA) analysis showed that fungal biomarkers were higher and Gram positive and Gram negative biomarkers were lower in NT compared with TT. There were no differences in over‐winter soil water storage or ponded water infiltration rate in undisturbed standing wheat stubble between TT and NT, indicating soils that produce high wheat grain yield of 6 Mg ha−1 or more have similar water intake regardless of tillage history as long as the stubble is left standing over winter. Results show long‐term cumulative benefits of NT vs. TT on soil quality, but no differences in soil water intake when stubble is left standing over winter, possibly due to the high quantity of wheat root channels produced in both systems.