Background to Land Susceptibility to Wind Erosion Modelling
Wind erosion is a natural phenomenon that takes place when soil surface is exposed to the erosive force of the wind when soil particles are loose enough to be detached and transported by the wind. Terrestrial vegetation including crops depends on appropriate top soil with nutrients as a substrate on which vegetation/crops grows in addition to other climatic factor requirements.
Generally, soil plays two major functions;
Anchor the plant and to
Provide certain vital nutrients for the plant’s growth.
Removal of any amount/component of the soil layer, especially topsoil, renders the soil less capable of supporting vegetation or crop growth and hence environmental surface is considered degraded. Wind erosion is therefore of great concern to the agricultural production because of its adverse effects on soil, a subtrate to plant growth. The scientific studies such as this, is geared towards gannering information that will inform on the sustainable use and management of narual resources such as soil.
The literature on wind erosion, especially in agricultural soils, is categorized into three major areas:
Studies on basic process and mechanisms of wind erosion e.g. Lyles (1977, 1988).
Documentation of wind erosion in different environments e.g. Borelli et al. (2014, 2015a); Fenta et al. (2020).
Modelling approaches to wind erosion e.g. Hagen (2010); Jarrah et al.
(2020); Fryrear et al. (1998, 2001); Tatarko and Wagner (2007); Borelli et al. (2015b, 2017).
In some cases, the same literature may deal with more than one aspect as shown above.
Understanding the concepts of Soil Abrasion
Soil particles abrasion is dependent on external forces, that combines with various soil particle characteristics to cause motion in the direction of either the wind or water forces. The external forces i.e. wind and water requires that the following:
Minimum threshold force be attained, in order to initiate particle movement.
Soil particle has to be light enough, devoid of air spaces, that causes floating tube effect, and
The particles location be devoid of barriers such as vegetation, artificial blockages among others (D.W. Fryrear et al., 1994), to allow for smooth
particle transportation withoiut barriers.
On the other hand, Soil particles properties are as a result of soil forming processes including weathering and tectonic movements, majorly natural processes, with recent anthropogenic factors beginning to shape the processes. Anthropogenic factors influence the properties of soil over time, and as a result, influence soil particle strength to resist motion and infiltration (Soil Erosion, 2013).
Over time, soil particle losses its resilience and coping mechanism to resist abrasion by the agents of erosion. For instance, The East African Mountains represent the most arable areas of the continent with approximately 40% of the arable land between the tropics located on the mountainous regions. These areas are prone to high amounts of rainfall characterized by bimodal rainfall patterns or better still, rainfall throughout the year.
The rainfall patterns experienced in these areas practice advance and intensive agricultural activities with little or no soil care practices. Instead, the agricultural areas are characterized by high levels of fertilization, increasing the acidity of the soil leading to loss of organic carbon content in the soil. This increases the carbon emission to the atmosphere, becoming one of the major contributors to climate change. These farming practices, have since increased soil erosion and leaching in the mountaineous areas than in undulating terrains (Kadomura and Yamamoto, 1978). There is however, an alarming concern for soil conservation in highland areas due to its dwindling ability in high yield production. On the other side, the arid and semi-arid regions, which are characterized with pastoralist activities, plain lands and patchy vegetation, are continuously losing their ability for vegetation sprouting during the rainy season. This is caused by the continuous formation of the soil crust layer, that hinders germination. The soil crust formation is also interpreted as the lack of organic content in the soil that influences plant growth. Normally, the erosion of the fine soil particle with organic content is contributed by huge cattle herds, coupled with natural aspects of strong winds that lacks any barrier that dissipates wind force.
Understanding the impacts of Soil Abrasion
The loss of soil fertility affects crop productivity over time with the world glaring at a possible global food shortage by 2050, as soil productivity and arable lands continues to shrink (ELD and UNEP, 2015; Kirui and Mirzabaev, 2014). Developing countries are reported to lack deliberate focus for assessing the degradation extent, and putting in place conservation measures that will exponentially reduce the adverse effects and reverse long term soil leaching (Haregeweyn et al., 2015; Hurni et al., 2015). Generally, forces that propagate the soil erosion are influenced by different factors including climatic conditions, and in the case of the Eastern Africa Mountains, the amount of runoff water as well as the steep slope and terrain greatly influence erosion. Other factors such as temperature, soil type as those endowed with organic matter are easily eroded downstream (Fenta et al., 2020). Other factors may include the availability of opposing forces such as vegetation cover, artificial barriers, and the soil crusting effect believed to be the coping mechanism of the soil particles to resist erosion, which majorly affects the arid and semi-arid areas, among others (D.W. Fryrear et al., 1994)
