Contribution à l'évaluation multicritère des systèmes de culture en protection intégrée contre les adventices : cas des émissions de protoxyde d'azote

In the context of the multicriteria evaluation of Integrated Weed Management (IWM) cropping systems, our study highlights the impacts of the combination of alternative agricultural practices to herbicide reliance on N2O emissions from soils. The study was located at the INRA experimental site of Dijon-Epoisses (47 ° 20'N, 5 ° 2'E) and considered 4 cropping systems, a reference system designed to maximize financial returns (S1) and three IWM systems (S2, S3, S5). The setup of high resolution measuring devices, combining the non-steady state chamber method with infrared gas analysis, allowed to estimate the intensity of N2O emissions from the calcareous clay soil, which is specific of Dijon plain, with average fluxes laying between -6 and 257 g N2O-N ha-1 day-1. The intensity of fluxes was closely related to environmental parameters (temperature, water filled pore space, inorganic N amount) and particular agricultural practices, leading to significant differences between systems. N2O emissions were notably affected by soil management and nature of crops. The conversion of S2 system to no-till in 2008 increased the N2O emissions, fluxes being at least 6 times more important than those emitted by the other cropping systems, during the year 2012. Moreover, these emissions, equivalent to 0.7 ha-1 C-CO2 ha-1, could have offset the soil additional carbon sequestration induced by reduced tillage during the studying period. Similarly, the degradation of legume crop residues in the S3 and S5 systems respectively enhanced N2O emissions in 2011 and 2012, by comparison with the S1 reference system. Elsewhere, the monthly monitoring of the soil microbial communities sizes has also helped to highlight temporal variability induced by the agricultural practices (tillage, harvest) as well as the seasonal variability. However, in this study the fluctuations of nitrifying and denitrifying communities sizes observed did not explain the variability of N2O emissions, whatever the considered cropping system. Finally, the modeling of N2O emitted from the 4 cropping systems, using NOE and DNDC models, allowed to identify the mains factors regulating the emissions. In addition, the NOE model accurately identified the S2 system, without tillage, as the most N2O emitter, in accordance with field observations. Thus, our study reinforces the relevance of modeling to estimate and explain N2O emissions in different cropping systems.Dans le cadre de l’évaluation multicritère des systèmes en protection intégrée contre les adventices (PIC-Adventices), cette étude a eu pour objectif d’étudier l’impact de la combinaison de pratiques alternatives à l’usage d’herbicides sur les émissions de N2O par les sols. L’étude a été conduite sur quatre systèmes de culture, un système de référence en agriculture raisonnée (S1) et trois systèmes PIC-Adventices (S2, S3, S5), sur le site expérimental Dijon-Epoisses (47°20'N, 5°2'E). La mise en place de dispositifs de mesure à haute résolution, alliant la méthode des chambres d’accumulation de gaz en surface du sol aux analyses de gaz par infrarouge, a permis d’estimer l’intensité des émissions de N2O pour les sols argilo-calcaires caractéristiques de la plaine dijonnaise, avec des flux moyens compris entre -6 et 257 g N-N2O ha-1 jour-1. Cette intensité s’est avérée étroitement liée à certains paramètres environnementaux (température, part de porosité occupée par l’eau, teneur en azote), et certaines pratiques agricoles, induisant des différences significatives entre les systèmes. Les émissions de N2O ont notamment été affectées par le mode de gestion des sols et la nature des cultures constituant la succession de chaque système. L’absence de travail du sol depuis 2008 dans le système S2 s’est traduite par une amplification des émissions de N2O d’un facteur multiplicatif d’au moins six par rapport aux autres systèmes pour l’année 2012. Par ailleurs, ces émissions équivalentes à 0.7 t C-CO2 ha-1 pourraient avoir compensé la séquestration de carbone additionnelle induite par le travail réduit du sol pendant la période de mesure. De la même manière, la dégradation des résidus de culture légumineuse, dans les systèmes S3 et S5 ont respectivement stimulé les émissions de N2O en 2011 et en 2012, en comparaison avec le système de référence S1. Par ailleurs, le suivi mensuel de la taille des communautés microbiennes du sol a également permis de mettre en évidence une variabilité temporelle liée aux pratiques culturales (travail du sol, récolte), en plus de la variabilité saisonnière. En revanche, dans cette étude les variations de taille des communautés microbiennes nitrifiantes et dénitrifiantes ne sont pas apparues comme un facteur d’explication de la variabilité des émissions de N2O, quel que soit le système. Enfin, l’approche par la modélisation des émissions de N2O sur les quatre systèmes, à l’aide des modèles NOE et DNDC, a permis d’identifier les principaux facteurs de régulation de ces émissions. De surcroît, le modèle NOE a bien identifié le système de culture S2, sans travail du sol, comme étant le système le plus émetteur de N2O, conformément aux observations de terrain. Cette étude renforce donc la pertinence de la modélisation pour estimer et analyser les émissions de N2O dans différents systèmes de culture

Diversification improves the performance of cereals in European cropping systems

In the face of climate change, cropping systems need to achieve a high performance, providing food and feed and adapting to variable environmental conditions. Diversification of cropping systems can support ecosystem services and associated biodiversity, but there is little evidence on which temporal field arrangement affects the performance of crop yields (productivity and stability), partly due to a lack of long-term data and appropriate indicators. The objectives of this study were to quantify the effect of cropping system diversification on yield stability, environmental adaptability, and the probability of diversified systems to outperform less diverse cereal-based systems in Europe. Spring and winter cereal yields were analyzed from long-term field experiments from Sweden, Scotland, and France. We investigated diversification through (i) introduction of perennial leys, (ii) increasing the proportion of ley in the rotation, (iii) varying the order in which crops are positioned in the rotation, (iv) introduction of grain legumes, and (v) introduction of cover crops. The results showed that cereal crops within cropping systems incorporating perennial leys outperformed systems without leys in 60–94% of the comparisons with higher probabilities at low fertilizer intensities. The yield stability of oat did not differ, but mean yields were 33% higher, when grown directly after the ley compared to oat grown two years later in the crop sequence under similar management. Durum wheat grown in a cropping system with grain legumes had higher yields in lower-yielding environmental conditions compared to rotations without legumes. Diversification with cover crops did not significantly affect yield stability. We conclude that diverse cropping systems can increase cereal productivity and environmental adaptability and are more likely to outperform less diverse systems especially when introducing perennial forage legumes into arable systems. Effects of diversification on cereal yield stability were inconsistent indicating that higher productivity is achievable without reducing yield variability. These novel findings can support the design of more diverse and high-performing cropping systems

Diversification improves the performance of cereals in European cropping systems

International audienceAbstract In the face of climate change, cropping systems need to achieve a high performance, providing food and feed and adapting to variable environmental conditions. Diversification of cropping systems can support ecosystem services and associated biodiversity, but there is little evidence on which temporal field arrangement affects the performance of crop yields (productivity and stability), partly due to a lack of long-term data and appropriate indicators. The objectives of this study were to quantify the effect of cropping system diversification on yield stability, environmental adaptability, and the probability of diversified systems to outperform less diverse cereal-based systems in Europe. Spring and winter cereal yields were analyzed from long-term field experiments from Sweden, Scotland, and France. We investigated diversification through (i) introduction of perennial leys, (ii) increasing the proportion of ley in the rotation, (iii) varying the order in which crops are positioned in the rotation, (iv) introduction of grain legumes, and (v) introduction of cover crops. The results showed that cereal crops within cropping systems incorporating perennial leys outperformed systems without leys in 60–94% of the comparisons with higher probabilities at low fertilizer intensities. The yield stability of oat did not differ, but mean yields were 33% higher, when grown directly after the ley compared to oat grown two years later in the crop sequence under similar management. Durum wheat grown in a cropping system with grain legumes had higher yields in lower-yielding environmental conditions compared to rotations without legumes. Diversification with cover crops did not significantly affect yield stability. We conclude that diverse cropping systems can increase cereal productivity and environmental adaptability and are more likely to outperform less diverse systems especially when introducing perennial forage legumes into arable systems. Effects of diversification on cereal yield stability were inconsistent indicating that higher productivity is achievable without reducing yield variability. These novel findings can support the design of more diverse and high-performing cropping systems

Contribution to the multi-criteria performance assessment of integrated weed management cropping systems : case of nitrous oxide emissions

Dans le cadre de l’évaluation multicritère des systèmes en protection intégrée contre les adventices (PIC-Adventices), cette étude a eu pour objectif d’étudier l’impact de la combinaison de pratiques alternatives à l’usage d’herbicides sur les émissions de N2O par les sols. L’étude a été conduite sur quatre systèmes de culture, un système de référence en agriculture raisonnée (S1) et trois systèmes PIC-Adventices (S2, S3, S5), sur le site expérimental Dijon-Epoisses (47°20'N, 5°2'E). La mise en place de dispositifs de mesure à haute résolution, alliant la méthode des chambres d’accumulation de gaz en surface du sol aux analyses de gaz par infrarouge, a permis d’estimer l’intensité des émissions de N2O pour les sols argilo-calcaires caractéristiques de la plaine dijonnaise, avec des flux moyens compris entre -6 et 257 g N-N2O ha-1 jour-1. Cette intensité s’est avérée étroitement liée à certains paramètres environnementaux (température, part de porosité occupée par l’eau, teneur en azote), et certaines pratiques agricoles, induisant des différences significatives entre les systèmes. Les émissions de N2O ont notamment été affectées par le mode de gestion des sols et la nature des cultures constituant la succession de chaque système. L’absence de travail du sol depuis 2008 dans le système S2 s’est traduite par une amplification des émissions de N2O d’un facteur multiplicatif d’au moins six par rapport aux autres systèmes pour l’année 2012. Par ailleurs, ces émissions équivalentes à 0.7 t C-CO2 ha-1 pourraient avoir compensé la séquestration de carbone additionnelle induite par le travail réduit du sol pendant la période de mesure. De la même manière, la dégradation des résidus de culture légumineuse, dans les systèmes S3 et S5 ont respectivement stimulé les émissions de N2O en 2011 et en 2012, en comparaison avec le système de référence S1. Par ailleurs, le suivi mensuel de la taille des communautés microbiennes du sol a également permis de mettre en évidence une variabilité temporelle liée aux pratiques culturales (travail du sol, récolte), en plus de la variabilité saisonnière. En revanche, dans cette étude les variations de taille des communautés microbiennes nitrifiantes et dénitrifiantes ne sont pas apparues comme un facteur d’explication de la variabilité des émissions de N2O, quel que soit le système. Enfin, l’approche par la modélisation des émissions de N2O sur les quatre systèmes, à l’aide des modèles NOE et DNDC, a permis d’identifier les principaux facteurs de régulation de ces émissions. De surcroît, le modèle NOE a bien identifié le système de culture S2, sans travail du sol, comme étant le système le plus émetteur de N2O, conformément aux observations de terrain. Cette étude renforce donc la pertinence de la modélisation pour estimer et analyser les émissions de N2O dans différents systèmes de culture.In the context of the multicriteria evaluation of Integrated Weed Management (IWM) cropping systems, our study highlights the impacts of the combination of alternative agricultural practices to herbicide reliance on N2O emissions from soils. The study was located at the INRA experimental site of Dijon-Epoisses (47 ° 20'N, 5 ° 2'E) and considered 4 cropping systems, a reference system designed to maximize financial returns (S1) and three IWM systems (S2, S3, S5). The setup of high resolution measuring devices, combining the non-steady state chamber method with infrared gas analysis, allowed to estimate the intensity of N2O emissions from the calcareous clay soil, which is specific of Dijon plain, with average fluxes laying between -6 and 257 g N2O-N ha-1 day-1. The intensity of fluxes was closely related to environmental parameters (temperature, water filled pore space, inorganic N amount) and particular agricultural practices, leading to significant differences between systems. N2O emissions were notably affected by soil management and nature of crops. The conversion of S2 system to no-till in 2008 increased the N2O emissions, fluxes being at least 6 times more important than those emitted by the other cropping systems, during the year 2012. Moreover, these emissions, equivalent to 0.7 ha-1 C-CO2 ha-1, could have offset the soil additional carbon sequestration induced by reduced tillage during the studying period. Similarly, the degradation of legume crop residues in the S3 and S5 systems respectively enhanced N2O emissions in 2011 and 2012, by comparison with the S1 reference system. Elsewhere, the monthly monitoring of the soil microbial communities sizes has also helped to highlight temporal variability induced by the agricultural practices (tillage, harvest) as well as the seasonal variability. However, in this study the fluctuations of nitrifying and denitrifying communities sizes observed did not explain the variability of N2O emissions, whatever the considered cropping system. Finally, the modeling of N2O emitted from the 4 cropping systems, using NOE and DNDC models, allowed to identify the mains factors regulating the emissions. In addition, the NOE model accurately identified the S2 system, without tillage, as the most N2O emitter, in accordance with field observations. Thus, our study reinforces the relevance of modeling to estimate and explain N2O emissions in different cropping systems

Impact des systèmes de culture en protection intégrée contre les adventices sur l'intensité des émissions de N2O par les sols

National audienc

High N2O variations induced by agricultural practices in integrated weed management systems

International audienceAbstractIntegrated weed management aims to decrease the dependence of cropping systems on herbicides by using a combination of several agricultural practices. Environmental impacts of individual practices under various conditions are already known. However, there is scarce knowledge on the impact of combining several practices. Therefore, we studied N2O emissions of weed management cropping systems that use differing practices such as crop diversity, tillage, and herbicide pressure, during about 1 year. Data were compared with a conventionally managed cropping system. Results were also simulated using the NOE model. Results show a large variation of N2O emissions, ranging from 177 g N2O-N/ha for intensive tillage integrated weed management to 362 g N2O-N/ha for the conventional cropping system, 777 g N2O-N/ha for the no herbicide cropping system and 5226 g N2O-N/ha for no-till integrated weed management. Most N2O emissions occurred in spring, despite the absence of fertilizing related N2O peaks. The lowest emissions occurred in autumn and winter. Emissions are explained by interactions between specific soil potential denitrification rate, soil bulk density, temperature, soil water, and inorganic N contents. N2O emissions are accurately predicted by the model NOE, with a global Nash-Sutcliffe coefficient of efficiency equal to 0.80

Impacts of Integrated Weed management in cropping systems on N2O emissions from soils

International audienc

N2O emissions from cropping systems with integrated weed management. The nitrogen challenge: building a blue print for nitrogen use efficiency and food security

International audienceIntegrated weed management (IWM) in cropping systems aims to lower the reliance on herbicides of the crops, by introducing new combinations of agricultural practices in the system development (Munier-Jolain et al, 2009). These combinations may greatly change from a system to another and include a large variety of practices, such as false seed beds, late sowing, mechanical weeding, reduced tillage, specific crop rotations that alternate spring and winter crops, the choice of crop varieties and the use of pesticides with low ecotoxic impacts. Several implemented agricultural practices are likely to alter soil biogeochemical cycles and different components of the greenhouse gas budget (balance between the carbon sequestration and the greenhouse gas emission) of the system: e.g. crop rotation, dates and level of nitrogen fertilization and tillage. The main objectives of our study were to evaluate i) the N2O fluxes emitted from soil during one year for 4 cropping systems (i.e. 3 IWM systems and a local reference of conventional system), and ii) to investigate the relationship between the measured fluxes and soil parameters and the agricultural practices of each system