Light interception as an indicator of leaf area index and risk of diseases in sunflower

International audienc

Mise au point de systèmes de culture adaptés à la ressource en eau: enseignements tirés de l'expérimentation SGCI de Toulouse (1995-2002).

National audienceLa recherche d'économies d'eau en grande culture est une préoccupation grandissante dans le Sud-Ouest de la France pour des raisons économiques et environnementales. Pour concrétiser une démarche de conception et d'évaluation de systèmes de culture adaptés à la ressource en eau, le dispositif expérimental "Systèmes de Grandes Cultures Intégrés" a été conduit de 1995 à 2002 par l'INRA à Toulouse (Haute-Garonne). L'expérimentation en grandes parcelles a permis de valider globalement les stratégies agronomiques et les règles de décision proposées ex ante pour chacun des 3 systèmes variant par la disponibilité en eau d'irrigation. En particulier, il a été montré la nécessité d'un rationnement des besoins en eau et en azote pour les systèmes peu ou pas irrigués, avec des conséquences positives sur la réduction des risques phytosanitaires. Dans le contexte actuel de la grande culture (intérêt des conduites à faibles niveaux d'intrants), cette étude apporte des éléments de jugement technico-économiques et agri-environnementaux originaux. Une méthodologie d'évaluation des systèmes de culture à valeur générale est proposée combinant expérimentation systémique, expérimentation factorielle et simulation

Carbon footprint of cropping systems with grain legumes and cover crops: A case-study in SW France

International audienceAgriculture contributes to a significant proportion of global emissions of greenhouse gases (GHG) but can also participate in climate change mitigation. The introduction of legumes in crop rotations reduces the dependence on N fertilizers and may mitigate the carbon (C) footprint of cropping systems. The aim of this study was to quantify the C footprint of six low-input arable cropping systems resulting from the combination of three levels of grain legumes introduction in a 3-yr rotation (GLO: no grain legumes, GL1: 1 grain legume, GL2: 2 grain legumes) and the use of cover crops (CC) or bare fallow (BF) between cash crops, covering two rotation cycles (6 years). The approach considered external emissions, on-site emissions and soil organic carbon (SOC) stock changes, and prioritized (i) field observations and (ii) simulation of non-measured variables with the STICS model, rather than default emission factors. As expected, fertilizers accounted for 80-90% of external emissions, being reduced by 50% and 102% with grain legumes introduction in GL1-BF and GL2-BF, compared to the cereal-based rotation (GLO-BF). Cover crops management increased machinery emissions by 24-35% compared to BF. Soil nitrous oxide (N2O) emissions were low, ranging between 205 and 333 kg CO2 eq. ha(-1) yr(-1) in GL1-BF and GLO-BF, respectively. Nitrate leaching represented the indirect emission of 11.6 to 27.2 kg CO2 eq. ha(-1) yr(-1) in the BF treatments and 8.2 to 10.7 kg CO2 eq. ha(-1) yr(-1) in the CC treatments. Indirect emissions due to ammonia volatilization ranged between 8.4 and 41.8 kg CO2 eq. ha(-1) yr(-1). The introduction of grain legumes strongly influenced SOC changes and, consequently, the C footprint. In the BF systems, grain legumes introduction in the rotations led to a significant increase in the C footprint, because of higher SOC losses. Contrarily, the use of cover crops mitigated SOC losses, and lowered the C footprint. These results indicated the need of CC when increasing the number of grain legumes in cereal-based rotations. Despite the multiple known benefits of introducing grain legumes in cropping systems our research highlights the need to consider soil organic carbon changes in environmental assessments

Grain legume-based rotations managed under conventional tillage need cover crops to mitigate soil organic matter losses

International audienceInserting legumes in low-input innovative cropping systems can represent a good strategy to reduce current N fertilizer dependency while enhancing ecosystem services. However, although the impact of the use of legumes as cover crops has been broadly studied, very little is known about the effects of grain legume-based rotations on soil organic carbon (SOC) and nitrogen (SON). A cropping system experiment with three 3-year rotations with different levels of inclusion of grain legumes: GL0, GL1 and GL2 (none, one, and two grain legumes, respectively), with (CC) or without (BF, bare fallow) cover crops was established in SW France (Auzeville) under temperate climate. Durum wheat was present in all the rotations to act as an indicator of their performance. Soil organic C and SON were quantified before the beginning of the experiment and after 3 and 6 years (i.e., after one and two complete 3-yr rotations). Aboveground C and N inputs to the soil, and C and N harvest indexes and grain yield of the cash crops were also measured. Inserting grain legumes in the rotations significantly affected the amount of C and N inputs and consequently SOC and SON. After two cycles of the 3-yr rotation, the GL1 and GL2 treatments showed a greater decrease in SOC and SON when compared to GL0. However, the inclusion of cover crops in the rotations led to mitigate this loss. Durum wheat produced significantly greater grain yields in GL1 when compared to GL0, while GL2 presented intermediate values. In turn, the incorporation of cover crops did not reduce C and N harvest indexes or the grain yield of the different cash crops. We concluded that, in such conventionally-tilled grain legume-based rotations, the use of cover crops was efficient to mitigate SOC and SON losses and then increase N use efficiency at the cropping system level without reducing productivity

Contribution of cereal-legume intercropping agroecological weed management

International audienc