Comparison of different methods to determine wind-erodible fraction of soil with rock fragments under different tillage/management

- The wind-erodible fraction of soil determining from rotary sieve (EF-r) are lower than that obtaining from flat sieve (EF-f).
- The relationships between EF-r and soil intrinsic properties depend on soil tillage/management.
- The EF-r is significantly associated with surface soil rock fragments content.
- The EF-r estimation equation in the RWEQ cannot be used to predict the measured EF-r.

Rock fragments (the coarse fraction >2 mm in soil) widely exist in the surface soils of the agro-pastoral ecotone of northern China (APEC region) where is suffering severe soil degradation induced by wind erosion. The wind-erodible fraction of soil aggregate (<0.84 mm dry soil aggregate) (EF) is an important parameter to evaluate soil management systems and estimate wind erosion. Rotary sieve is considered to be a standard device to determine EF. Flat sieves and EF estimation equation used in the Revised Wind Erosion Equation (RWEQ) are two alternatively methods to obtain EF. In this study, 74 soil samples for different soil management/tillage in a typical region of the APEC region were collected to compare rotary sieve, flat sieve and the EF estimation equation for determining EF. The results showed that (1) the EF determining from rotary sieve (EF-r) is closely related to the EF obtaining from flat sieve (EF-f) but the EF-r are generally lower than the EF-f, (2) the EF-r is significantly associated with surface soil rock fragments content for all soil management, (3) the EF-r is not related to soil textural fractions, organic matter and CaCO3 content for tree windbreak, conservation and conventional tillage farmland but is related to that for grassland, (4) the EF estimation equation in the Revised Wind Erosion Equation (RWEQ) cannot be used to predict the measured EF in the APEC region.