Quantifying the impact of no‐till on runoff in southern Brazil at hillslope and catchment scales

Abstract

No-till (NT) is a conservation system that improves the hydrological regime of agricultural slopes by providing greater surface protection and benefits to the physical and hydrological properties of soils. However, the isolated use of NT is not enough to control runoff and its associated degradation processes. Therefore, this study aimed to evaluate the runoff of agricultural slopes under NT under different runoff control conditions by monitoring 63 rainfall events in two 2.4-ha zero-order catchments and 27 rainfall events in four 0.6-ha macroplots. The catchments are paired and similar in terms of the type of soil and relief, but different regarding the presence of terraces. The macroplots have different soil and crop management systems. By using monitoring techniques, the hyetographs and hydrographs revealed the influence of the different types of management on the catchments and macroplots and allowed rainfall characteristics, runoff volume, runoff coefficients, water infiltration, peak runoff, response times, and curve number to be analysed. The terraces positively affected the NT and controlled runoff and related variables, in addition to infiltration significantly increasing and runoff reducing in the terraced catchment. All the hydrological information assessed pointed to the positive effects provided by the presence of the terraces. The results in the macroplots showed that high amounts of phytomass and/or chiselling do not control runoff and its correlated variables in medium and high magnitude events. The study concludes by underlining the need for additional measures to control runoff (terraces), even in areas under NT and with high phytomass production. Additionally, the study emphasizes the importance of monitoring at the catchment scale to better understand the hydrological behaviour of agricultural areas and provide the necessary parameters to effectively control runoff.

Terracing increases soil available water to plants in no-tillage

“…Benefits arising from the use of the terrace, such as increased infiltration (Barros et al, 2014), less runoff (Menezes et al, 2020;Londero et al, 2021) and sediment and contaminant transport (Barros et al, 2020;Didoné et al, 2021), and extending river baseflow (Didoné et al, 2017;Minella et al, 2017) are well-known effects and indicators that the availability of water in the soil also should increase in terraced areas. However, this benefit had not yet been evaluated and shown with the details and robustness of the data of our study.…”

“…The average annual Penman-Monteith evapotranspiration is around 1170 mm, according to Sistema Irriga ® , a global service for irrigation management. The catchments were delimited in 2014 to study the effect of terracing on reducing runoff, sediment and nutrient loss (Londero et al, 2021). The effect of terracing on the variation of soil water content, which is the focus of this study, was evaluated from November 1, 2016 to February 28, 2018 (729 days).…”

“…However, the increase in water available to plants due to improvements in soil structure and increased organic matter content is still a controversial subject (Minasny and McBratney, 2017). Furthermore, water loss due to runoff is commonly reported in well-managed no-tillage crops (Merten et al, 2015;Didoné et al, 2017;Londero et al, 2021). Whether the water lost as runoff would be a share needed to refill available water to plants up to its capacity is still an issue that needs further examination.…”

“…It emerged as a conservation practice to reduce soil and water loss by erosion in tillage systems (Pruski et al, 1997;Bertol et al, 2007), but its use was discouraged with the introduction of no-tillage system (Levien et al, 2011). However, significant water loss occurs even in crops properly managed under no-tillage (Didoné et al, 2017;Londero et al, 2021). This is drastically reduced with the use of terraces (Londero et al, 2017).…”

Managing runoff in rainfed agriculture under no-till system: potential for improving crop production

“…Nonetheless, water and soil losses caused by runoff have been significant on catchment (Didoné et al, 2014(Didoné et al, , 2015 and hillslope (Deuschle et al, 2019;Londero et al, 2021) scales in southern Brazil, even after approximately 30 years of no-till consolidation. In a stormwater event, runoff will be conveyed according to the spatial variability of the topography (Berry, 2005), leading to erosion and sediment transfer to water bodies (Morgan, 2005).…”