Quantifying the impact of no‐till on sediment yield in southern Brazil at the hillslope and catchment scales
Résumé
No-till (NT) is a soil management system designed to protect soil resources from
water erosion and provide numerous benefits compared to conventional tillage
through the increase of organic matter inputs into the soil. However, NT in isolation
is not sufficient to control erosion processes caused by an excessive production of
surface runoff. This study evaluated soil losses on agricultural hillslopes under no-till
characterized by contrasted water, soil, and crop management conditions. To this
end, water and soil losses were monitored between 2014 and 2018 at two scales,
including four macroplots (0.6 ha; 27 events) and two paired zero-order catchments
(2.4 ha; 63 events). The resulting dataset covered a wide range of rainfall conditions
that occurred in contrasted soil, crop, and runoff management conditions.
Hyetographs, hydrographs, and sedigraphs were constructed, and these data were
used to evaluate the impact of management on sediment yields, including that of terraces,
scarification, and phytomass on sediment yield. The installation of terraces
reduced sediment yield by 58.7%, mainly through surface runoff control. Crop management
including an increased phytomass input efficiently controlled soil losses
(63%), although it did not reduce runoff volume and peak flow. In contrast, scarification
had no impact on runoff and soil losses. The current research demonstrated the
need to combine the installation of terraces and leaving a high amount of phytomass
on the soil to control surface runoff and erosion and reduce sediment yield. The current
research therefore reinforces the relevance of the monitoring strategy conducted
at the scale of macroplots and zero-order catchments to evaluate the impact
of contrasted water, soil, and crop management methods and select the most effective
conservation agriculture practices.
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