Comparison of the occurence of BNI activity of ribwort plantain (Plantago lanceolata L.) and a common cover crop mixture (phacelia and white mustard) to a bare soil

Abstract

Nitrogen (N) management in agriculture plays a critical role in addressing environmental challenges such as nitrate leaching and greenhouse gas emissions. Sustainable practices, including the use of cover crops, and Biological Nitrification Inhibition (BNI) offer a promising approach to mitigate these issues. This study investigated the potential of three cover crops—plantain (Plantago lanceolata) and white mustard (Sinapis alba) + phacelia (Phacelia tanacetifolia), a common cover crop mixture—to influence soil nitrogen dynamics and emissions across a crop rotation cycle. The objective is to assess whether these crops could reduce nitrification rates and contribute to more sustainable nitrogen management. Field experiments were conducted in a randomized block design, with cover crops sown as intercultures according to two main comparisons: late ploughing (Lp) versus early ploughing (Ep) and control (C) versus cover crops (M). Soil samples were collected periodically to measure nitrate (NO₃⁻), nitrite (NO₂⁻), and ammonium (NH₄⁺) concentrations, while gaseous emissions of nitrous oxide (N₂O) were monitored using static chamber techniques. Laboratory analyses were performed to determine potential nitrification rates. Statistical analyses included a univariate analysis of variance (ANOVA) and multivariate approaches to explore the influence of treatments on nitrogen dynamics. The results showed that white mustard had a highest biomass production, which was linked to more pronounced interactions with soil nitrogen dynamics compared to phacelia. Nitrate concentrations were significantly reduced by cover crop mixture. N₂O emissions were principally influenced by soil moisture levels, with wetter conditions leading to increased denitrification. The study highlighted variability in nitrogen dynamics impacted by weather conditions, emphasizing the complexity of predicting the impact of the type cover crop on nitrogen dynamics. The termination treatment also showed effects on nitrogen dynamics. In conclusion, the results partially met the initial objectives by demonstrating the influence of cover crops on nitrogen management. White mustard emerged as the most effective in reducing nitrate leaching risks. For producers, the findings underscore the importance of selecting cover crops adapted to local conditions to optimize their environmental benefits. Future research should focus on long-term studies to confirm the cumulative effects of BNI-capable crops and explore their interactions with other management practices, such as timing of sowing and incorporation into the soil.