Quantifying sheet erosion in agricultural highlands of Sri Lanka by tracking grain-size distributions

Abstract

The reduction of productivity in arable lands of the tropical highlands through intensified soil erosion is a major reason for food scarcity in many developing countries. Identifying soil erosion hot spots in highland agricultural croplands and monitoring the effectiveness of soil conservation are crucial for improving land management practices. This paper develops a low cost and efficient method to quantify the rate of soil loss caused by splash and sheet erosion, in-situ at the plot scale. This method assumes that textural differences between the topsoil and the underlying soil within the plot are due to erosion of the top layer. Grain size analyses conducted in agricultural soils of the Upper Uma Oya Catchment (UUOC) of Sri Lanka provided data to quantify splash or sheet erosion and deposition. Net soil loss from the plot was calculated based on rates of area weighted soil loss and deposition. The net splash and sheet erosion rate in the plot was 20 t ha-1 yr-1 , which is comparable with previous soil erosion results obtained in the area (25 t ha-1 yr-1) at similar temporal and spatial scale and under the same agricultural use. This study suggests that approximately half of the total erosion in the UUOC area results from splash and sheet erosion, whereas the rest is driven by concentrated flow through rill and gully erosion. This method is potentially transferable to other croplands as a robust approach for rapid measurement of splash and sheet erosion.

Investigating spatial contribution of land use types and land slope classes on soil erosion distribution under tropical environment

“…Agricultural land in the form of mixed crops farming and wet rice field covered more than 70% of the watershed area. This condition indicated a high potential for erosion due to farming activities in the watershed as reported in some previous studies (e.g., Merten and Minella 2013;Arnhold et al 2014;Hewawasam and Illangasinghe 2015;Borrelli et al 2016;Guerra and Correia 2016). The high land occupancy for farming was affected by social economic factors of local inhabitants, indicated from the existence of settlements in the study area.…”

“…Heavy rainfall and excessive land cultivation have generally become the main factors which trigger the soil erosion. It causes many deprivations in the tropical regions (Shrestha et al 2014;Andriyanto et al 2015;Hewawasam and Illangasinghe 2015;Pupim et al 2015;Ali and Hagos 2016;Cunha et al 2017;Didonéa et al 2017). In the upstream area, erosion reduces organic matter content in the top soil (Amao et al 2013;An et al 2013;Arnhold et al 2014;Borrelli et al 2016) and reduces water storage capacity, due to the decrease in soil layer.…”

An Overview of Ecosystem Service Studies in a Tropical Biodiversity Hotspot, Sri Lanka: Key Perspectives for Future Research

“…However, research on how soil ecosystems are related to agriculture and food production in Sri Lanka is rare. The few studies we encountered are mostly focused on paddy cultivation [75,76].…”

“…While rice is the staple food in Sri Lanka, we found only a few studies related to rice fields, and these studies were about water quality, nutrient loss, rice production, and soil quality [25,[77][78][79][80][81][82]. Very little research of an interdisciplinary nature was conducted regarding paddies in Sri Lanka [75,83] yet the main income for most rural farmers is rice production.…”

The effect of different crops and slopes on runoff and soil erosion

“…Soil erosion is also a serious and challenging environmental issue related to land management worldwide. It is a complex natural process altered by anthropogenic activities including land clearance, agricultural practices, surface mining, construction and urbanization (Krasa et al 2005;Illangasinghe & Hewawasam 2013;Hewawasam & Illangasinghe 2015). Studies have shown that the key factors controlling soil erosion on hillslopes are erodibility, slope, and land use cover, and that changing these factors can reduce soil erosion (Diyabalanage et al 2017).…”