Determination of the wind-erodible fraction of soils using different methodologies

The wind-erodible fraction of the soil (EF) (percentage of aggregates < 0.84 mm in diameter) is a key parameter to estimate the soil susceptibility to wind erosion. The standard method for EF determination is the dry sieving by means of a rotary sieve. Flat sieving with a set of sieves and the use of the equation EF = (29.09 + 0.31 sand + 0.17 silt + 0.33 sand/clay - 2.59 organic matter - 0.95 CaCO3) / 100, R2 = 0.67, [Fryrear, D.W., Krammes, C.A., Williamson, D.L., Zobeck, T.M., 1994. Computing the wind erodible fraction of soils. J. Soil Water Conserv. 49: 183-188] are two alternative ways of determining EF. As the flat sieving has still not been contrasted against the standard rotary sieve method nor the Fryrear et al. equation tested for soils other than US soils, we estimated EF with both dry sieving methods and tested the equation for soils of semiarid regions of Central Aragon (NE Spain) and the Semiarid Pampas (centre of Argentina), two regions prone to wind erosion. Results showed that EF values obtained with the flat sieve were comparable with those obtained using the standard rotary sieve, indicating that the flat sieving technique is suitable for EF determinations. The estimation of EF with the model proposed by Fryrear et al. [Fryrear, D.W., Krammes, C.A., Williamson, D.L., Zobeck, T.M., 1994. Computing the wind erodible fraction of soils. J. Soil Water Conserv. 49: 183-188] did not fit with the measured EF values, indicating that this model is not useful for predicting EF in Spanish and Argentinian soils. This was attributed to the high CaCO3 contents of Spanish soils and the low sand/clay ratios and high organic matter contents of some Argentinean soils. The equation EF = 9.98 + 6.91 sand/clay + 14.1/organic matter (r = 0.933; P < 0.001) was proposed to predict EF in the studied soils.