Fingerprinting sediment sources in a large agricultural catchment under no‐tillage in Southern Brazil (Conceição River)

Abstract

Brazil is a leader in the adoption of conservation agriculture practices and technologies. However, the impact of these practices on sediment sources at the catchment scale has not been quantified yet, particularly in grain growing regions, where a conservationist no‐tillage system is implemented to protect soils. To address this knowledge gap, a sediment fingerprinting study based on elemental geochemistry was carried out in a large agricultural catchment (804 km2) of Southern Brazil where no‐tillage practices dominate. A total of 156 soil samples were taken to characterize the three main potential sediment sources: cropland (n = 79), unpaved roads (n = 41), and channel banks (n = 36). Sediment sampling was performed using a time‐integrated sampler (n = 33) and by collecting fine‐bed material (n = 34) at five locations across the catchment. Sediment was also sampled during flood events at the catchment outlet (n = 20). Sediment source contributions were calculated using an optimal suite of geochemical properties and a mixing model. Results showed that although the catchment is not particularly sensitive to soil erosion (i.e., deep clayey soils with gentle slopes), the amount of sediment supplied by cropland to the river network remains very high (up to 1.63 Mg·ha−1·year−1). Sediment fingerprinting results showed that even when no‐tillage is implemented, cropland remains an important source of sediment, supplying up to 70% of the material transiting the Conceição River. Accordingly, the current conservation farming system in this catchment needs to be improved to further reduce soil erosion and sediment yield.

Presence of Anthropogenic Markers in Water: A Case Study of the Guaporé River Watershed, Brazil

“…Agriculture and livestock rearing are the main economic activities, while urban areas occupy only 0.6% of the area. [32] The presence of anthropogenic markers was monitored in four sub-watersheds of the Guapor e River watershed named Capingui, Marau, Lajeado Carazinho, and Carazinho (Figure 1).…”

Tracing Sediment Sources in a Subtropical Agricultural Catchment of Southern Brazil Cultivated With Conventional and Conservation Farming Practices

“…In the Guaporé catchment, overbank sediment deposition may be observed in the vicinity of the river system in the upper catchment area. Previous findings indicated that cropland (88 ± 19%) was the main source of outlet sediment, compared with very low channel bank contributions (10 ± 18%) (Tiecher, ). As the sediment supply from channel banks is negligible in this catchment, the discussion will focus on the variations of cropland contributions to sediment transport in this catchment.…”

“…In this current study, sediment sources are investigated in the agricultural Guaporé catchment (Rio Grande do Sul, Brazil) where croplands were modelled to dominate the sediment supply (88 ± 19%) (Tiecher, ). Contrasting farming practices (e.g.…”

Fingerprinting the sources of water-mobilized sediment threatening agricultural and water resource sustainability: Progress, challenges and prospects in China

“…Sediment fingerprinting approach has attracted expanding interest driven by increasing recognition of the environmental significance of fine-grained sediment and the urgent need to target management measures, and this is reflected by a rapid growth in the number of scientific publications (Koiter et al, 2013;Walling, 2013). The growing body of literature focuses on either methodological assessment and refinement by testing critical assumptions (e.g., source classification, fingerprint property behavior, uncertainty, mixing model optimization), or reports case study applications in various environments for scientific and management (e.g., identifying critical source for targeting control measures, re-evaluating managed sites and assessing conservation efficacy) purposes (Tiecher et al, 2018).…”