Dry aggregate stability of soils influenced by crop rotation, soil amendment, and tillage in the Columbia Plateau

Abstract

Abstract Dry aggregate stability (DAS) is an important factor that influences soil erodibility. The purpose of this study was to measure DAS of soil, as well as assess the effect of crop rotation, soil amendment, and tillage on DAS in the main wind erosion area across the inland Pacific Northwest United States (iPNW). The stability of dry aggregates was measured using a commercial penetrometer and was found to be lower for soils in the iPNW than previously reported in other regions. Significant differences in DAS were found between tillage treatments at all locations. Dry aggregate stability was 24 to 114% higher for no-tillage summer fallow than tillage-based summer fallow treatments. Although not significant, DAS for a winter wheat-summer fallow (WW-SF) rotation was consistently higher than winter wheat-camelina-summer fallow (WW-C-SF) or winter wheat-safflower-summer fallow (WW-S-SF) rotations at two sites in central Washington. In contrast, when green manure or biosolids were applied as an amendment, there was no difference in DAS. Dry aggregate stability was more closely related to clay content than other soil properties (i.e. sand content and surface area of primary particles). Clay content, in the range 9 to 14%, can therefore be used to estimate DAS of soils in the iPNW. No-tillage management practices was beneficial to maintain greater DAS, thereby making soil aggregates more resistant to erosion and degradation.