A rainfall simulation study of soil erosion on rangeland in Swaziland

Soil erosion is one of the main problems in soil degradation nowadays and is widely distributed in many landscapes worldwide. Particularly water erosion is widespread and determined by rain erosivity, soil erodibility, topographic factors and the management carried out to mitigate this phenomenon. Although this process is mostly known as a consequence of human management such as agriculture or forestry, it is a process that also occurs naturally, being one of the factors that regulate the shape of the landscape.One of the main agents that stabilize the soil surface is biota and its activity, either in the form of plants, microorganisms or as an assemblage in the form of a biological soil crust (biocrusts). However, there are limited studies about how and what extent biota drives soil-stabilizing processes. With particular view on the impact of biocrusts on soil erosion, most studies have been carried out in arid and semi-arid regions, so its influence under other climates is largely unknown.This study focuses on the influence of biota on soil erosion in a temperature and rainfall gradient, covering four climate zones (arid, semi-arid, mediterranean and humid) with very limited human intervention. Other variables such as the origin of the geological formation, geographical longitude and glacial influence were kept constant for all study sites. The effect of vegetation (biocrusts) and its abundance, microbiology and terrain parameters are investigated using rainfall simulation experiments under controlled conditions and by a physico-chemical evaluation of the soil, surface runoff, percolation and sediment discharge, in order to determine the different environmental filtering effects that the soil develops under different climatic conditions.It is expected that as vegetation vigor and cover increase, soil erodibility will decrease. The biocrust is the protagonist of this stabilization in conditions of low pedological development and will become secondary as edaphoclimatic conditions favor the colonization of plants.The results of this study will help to achieve a better understanding of the role of biota in soil erosion control and will clarify its influence on soil losses under different climate and slope conditions. Analyses are currently ongoing and first results of our work will be presented at the EGU 2020.

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Management-induced soil water erosion and nutrient losses in different land use in Mediterranean environment

10.5194/egusphere-egu2020-1151 ◽

2020 ◽

Author(s):

Igor Bogunovic ◽

Leon Josip Telak ◽

Paulo Pereira

Keyword(s):

Land Use ◽

Soil Erosion ◽

Soil Properties ◽

Soil Water ◽

Water Erosion ◽

Rainfall Simulation ◽

Soil Tillage ◽

Conservation Strategies ◽

Nutrient Losses ◽

Olive Orchard

Soil erosion by water is one of the most important degradation processes. Land use has important effects on soil properties, therefore it is key to identify the type of management that have more impacts and find solutions to mitigate it. In order to understand the effects of land use management on soil and soil erosion in the Istria region (Croatia), we studied the impacts of different agriculture practices (vineyard, cropland, and olive orchard) on soil properties and runoff. The simulated rainfall was carried out at 58 mm h&#8722;1 in the summer of 2018 (30% soil water content) for 30 min on 0.785 m2 circular plots. The results showed that bulk density was significantly higher in cropland plots than in the vineyard and olive orchard. Soil organic matter, mean weight diameter, and aggregate stability were significantly higher in olive orchard plots than in the vineyard and cropland. Runoff and sediment losses were higher in olive orchard compared to vineyard plots. Carbon, nitrogen, and phosphorus losses were highest in olive orchard plots with 3.9 kg ha-1, 405.2 g ha-1 and 73.6 g ha-1, respectively, while lower values were measured in the vineyard plots, where nutrients losses were lower with 0.9 kg ha-1, 73.8 g ha-1 and 6.5 g ha-1, respectively. No runoff was observed in cropland plots. Even with the highest measured values of runoff and erosion in the herbicide treated olive orchard, results indicate that both herbicide application and tillage represent a threat to the sustainability of Istrian soils. Vegetation cover on cropland reduces the runoff generation indicating the need for adoption of conservation strategies. In current management, vegetation removal should be avoided since it contributes to practice to reduce nutrient losses and increase the sustainability of the soils.&#160;Keywords: Soil water erosion, Soil tillage, Rainfall simulation, Agriculture land management, Mediterranean&#160;Acknowledgements&#160;This work was supported by Croatian Science Foundation through the project "Soil erosion and degradation in Croatia" (UIP-2017-05-7834) (SEDCRO).

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