How effective are undersown crops and strip-tillage at mitigating soil erosion and pesticide transfer in maize crops? Results and insights from field trials

Clement, Timothée;et.al.
(2023) Adaptation strategies for soil and water conservation in a changing world. 5th WASWAC World Conference. — Location: Olomouc, Czech Republic (19.June.2023)

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  • Clement, Timothéeorcid-logoUCLouvain
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Abstract
Silt loam soils of the European loess belt are vulnerable to erosion and intensively cropped with a large share of spring crops in rotation. Besides the soil conservation issue, the transfer of runoff, sediment and associated pollutants from cropland cause acute off-site impacts such as muddy floods and pollution of surface water bodies. There is thus increasing pressure on the farming sector to implement alternative cropping practices to alleviate environmental externalities. To this end, as part of the Intell’eau project, we assessed the efficiency of two soil conservation practices at mitigating water, sediment, and pesticide flows in forage maize by means of erosion plots under natural rainfall during the 2021 and 2022 cropping seasons. A control treatment, representing conventional maize farming practices, was compared to 1) red fescue or white clover sown in the inter-row at the same time as the maize and 2) strip-tillage, which consists in preparing the seedbed by tine-tilling the maize row only, leaving the inter-row surface undisturbed. All treatments were implemented in triplicate. Results from the undersown plots showed no statistically significant difference in seasonal runoff, soil and pesticide (sulcotrione) losses compared to the control practice (bare inter-row), both in 2021 and 2022. Most soil and pesticide losses occurred in the spring (May-June), when the undersown crops and maize were still poorly developed (< 5% total vegetation cover). Both treatments combined, the average soil loss rate reaches 12.9 ± 6.2 t/ha in 2021 and 4.7 ± 1.6 t/ha in 2022. After two years, we observed severe weed pressure in the undersown maize plots, strongly affecting maize yields (-28% compared to conventional maize). This was caused by the limited spectrum of action of sulcotrione, which was selected to control weeds without killing the undersown crops. When strip tillage was performed after a well-developed winter cover crop (mustard in 2021, or oats-phacelia in 2022), a statistically significant difference (p<0.1) between strip-tillage and the conventional practice (rotary harrow) was observed regarding seasonal runoff (mean mitigation effect in 2021 and 2022 of -69%), soil (-85%) and sulcotrione (-66%) losses. In contrast, when strip-tillage was performed on soil left bare during winter or after a poorly-developed winter cover crop (0.55 t dry matter/ha), no significant differences were observed in terms of runoff, soil and pesticide losses. Considering all trial sites and years, yield losses in strip-tillage compared to conventional farming ranged from -8% to -28 %. Further investigations (additional years and locations) are needed to better assess the effectiveness of these two techniques. Quantifying the relationship between the amount of winter cover crop residues and the surface flows mitigation effect thanks to strip-tillage is of particular interest. Further investigation of the benefits of undersown crops in pluri-annual experiments must also be considered, since benefits are expected on the one hand from a well-established cover during the winter period, and on the other hand from the supply of organic matter to the soil upon destruction in late winter – early spring, with likely benefits in terms of improved soil structure.
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Clement, T., & et al. (2023). How effective are undersown crops and strip-tillage at mitigating soil erosion and pesticide transfer in maize crops? Results and insights from field trials. Adaptation strategies for soil and water conservation in a changing world. 5th WASWAC World Conference., Olomouc, Czech Republic. https://hdl.handle.net/2078.5/241007