Abstract
The sandy croplands in the Free State have been identified as one of the main dust sources in South Africa. The aim of this study was to investigate the occurrence and strength of physical soil crusts on cropland soils in the Free State, to identify the rainfall required to form a stable crust, and to test their impact on dust emissions. Crust strength was measured using a fall cone penetrometer and a torvane, while laboratory rainfall simulations were used to form experimental crusts. Dust emissions were measured with a Portable In-Situ Wind Erosion Laboratory (PI-SWERL). The laboratory rainfall simulations showed that stable crusts could be formed by 15 mm of rainfall. The PI-SWERL experiments illustrated that the PM10 emission flux of such crusts is between 0.14% and 0.26% of that of a non-crusted Luvisol and Arenosol, respectively. The presence of abraders on the crust can increase the emissions up to 4% and 8% of the non-crusted dust flux. Overall, our study shows that crusts in the field are potentially strong enough to protect the soil surfaces against wind erosion during a phase of the cropping cycle when the soil surface is not protected by plants.
Highlights
The emission of dust can have offsite effects on the regional and global climate [1,2,3], global geochemical fluxes [4,5], and human health [6,7]
We focus on the possible influence of physical soil crusts as a boundary condition for dust emissions, and on how crust formation is influenced by agricultural practices
This study identifies the potential significance of physical soil crusts on dust emissions from
Summary
The emission of dust can have offsite effects on the regional and global climate [1,2,3], global geochemical fluxes [4,5], and human health [6,7]. Dust emissions can lead to land degradation due to the removal of fine soil particles and organic material, especially in semi-arid and arid environments [8,9,10,11,12]. Due to these impacts, many studies have focused on assessing the sources of dust and the factors controlling dust emission [13,14,15,16]. Eckardt et al [24] showed that 70% of the Meteosat Second
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