Reducing herbicide use and leaching in agronomically performant maize-based cropping systems: An 8-year study

摘要

Irrigated maize-based Cropping Systems (CS) are questioned because of the high risk of herbicide transfer to water. An 8-year systemic experiment was conducted to ⅰ) compute a multi-performance comparison between a Conventional Maize Monoculture (MM_(Conv)) and four CS that aimed to reduce irrigation and herbicide leaching: MM_(LI), a low-input MM using cover crop and Integrated Weed Management (IWM) techniques; MM_(Still), a Strip-tillage MM using cover crop; MM_(CT), a Conservation Tillage MM with cover crop; Maize-MSW, an IWM Maize ro-tated with Soybean and Wheat and ⅱ) determine the main drivers and evaluate the influence of CS on herbicide leaching in maize. Drainage water was collected through 1 -m depth lysimeter plates and analysed for 6 herbicide molecules and 1 degradation metabolite. MM_(LI) yielded 10.7 t ha~(-1) close to MM_(Conv) (11.5 t ha~(-1)) despite a lower herbicide use (-57%) and irrigation (-21%). MM_(LI) and Maize-MSW had less drainage events compared to MM_(Conv). MM_(CT) and MM_(Still) both yielded less (respectively 7.6 t ha~(-1) and 6.2 t ha~(-1)) while their herbicide use increased (both +24%). Mean annual her-bicide losses were 0.5 ± 1.0 g ha~(-1) for MM_(LI),0.7 ± 1.2 g ha~(-1) for Maize-MSW, 1.3 ± 2.1 g ha~(-1) for MM_(Still), 2.0 ± 4.8 g ha~(-1) MM_(Conv) and 3.0 ± 9.6 g ha~(-1) for MM_(CT). Herbicide leaching remained variable but was consistently and mostly influenced by drainage volume. According to the CS, only 1.5 to 6.0 drainage events were responsible for 90% of the herbicide losses. High leaching peaks were identified for mesotrione and glyphosate and may indicate that preferential flows occurred, especially under MM_(CT). Quantity applied had limited influence on herbicide leaching. To reduce the herbicide leaching risk, CS must concomitantly manage water quality and quantity through a combination of agroecological practices, as in MM_(LI), a CS able to reach other technical objectives. Present study recommends assessing CS through a diversity of performance indicators.