Evaluation d'un modèle à réservoirs pour simuler le bilan hydrique d'une vigne enherbée en climat méditerranéen

Des études récentes ont identifié dans l'enherbement du vignoble une réponse possible aux objectifs de durabilité et de qualité que se doit de s'approprier la viticulture de demain. Pourtant, la concurrence hydrique qu'il induit est un frein à son adoption dans les vignobles méditerranéens. Ce travail vise à évaluer une approche à réservoir pour modéliser le bilan hydrique de l'association vigne-culture intercalaire. Il est une première étape vers l'obtention d'un outil d'évaluation de ces pratiques. Le choix s'est porté sur STICS qui a l'avantage d'avoir déjà été paramétré pour une vigne et de proposer un formalisme relativement élaboré de modèle de sol à réservoirs. Ce travail de modélisation s'appuie sur 4 campagnes de mesures réalisées sur des parcelles viticoles du Languedoc. Sur ces parcelles, les teneurs en eau du sol et la densité apparente ont été suivies à différentes profondeurs. D'autres éléments ont été mesurés qui permettent de paramétrer le modèle. L'association vigne-enherbement, présente sur une seule de ces situations, a fait l'objet d'une étude plus complète avec une observation de son système racinaire et des flux hydriques. Outre ces données recueillies, le paramétrage du modèle a fait appel à un précédent paramétrage réalisé sur un vignoble de Côtes-du-Rhône et à des références trouvées dans la bibliographie. L'évaluation du modèle sur la réserve hydrique du sol pour une vigne en sol nu en conditions méditerranéennes s'est avérée globalement satisfaisante. Les formalismes introduits dans STICS permettent une amélioration sensible de la qualité de la simulation par rapport à un modèle plus simple comme celui de Riou et al (1994), notamment pour l'évaporation et le ruissellement. L'étude de l'association culturale semble justifier d'essayer de modéliser l'association culturale en compartimentant le sol en deux réservoirs étanches, un pour chaque culture. L'évaluation de cette hypothèse montre cependant que le réservoir dédié à la vigne ne peut pas être seulement de la largeur du rang. L'analyse des profils racinaires des deux espèces prouve que la vigne peut trouver des ressources en eau soit plus en profondeur, soit dans la zone exploitée par la fétuque. (Résumé d'auteur

Associating wheat crop and undersown forage legumes in organic agriculture: Incidence of forage legumes species

One of the key issues of organic arable systems is to increase use of N2 fixation from legume plants while enhancing autonomy by the limitation of off-farm inputs. Wheat yield in organic agriculture is generally low and variable. Grain yield and protein content are strongly affected by N deficiency and weed competition (Casagrande et al., 2009). Previous research had clearly demonstrated the benefits of forage legumes to improve N balance and preserve weed infestation (den Hollander et al., 2007). Several authors highlighted the interest of crop mixtures combining cereal and legumes to provide higher overall productivity, enhance ecological services and improve economical profitability (Malezieux et al., 2008). Nevertheless, previous research also highlights how important it is to manage whether above- and belowground interactions between species to optimise benefits and limit competition. We propose here to analyse how the insertion of legumes species influences the performance of organic wheat (yield, grain protein content) but also the weeds population during and after crop cycle

Incidence of soil N fertility on the performance of organic forage legume-wheat mixtures.

One of the key issues of organic arable systems is to bring enough nitrogen in the crop rotation to ensure satisfying crop nutrition. Wheat yield in organic agriculture are generally low and variable. Grain yield and grain protein content are strongly affected by N deficiency and weed competition (Casagrande et al., 2009). Nevertheless, the autonomy of the organic cropping systems has to be improved while off-farm inputs have to be limited. The use of N2 fixation from legume plants should then be improved. Previous research had clearly demonstrated the benefits of forage legumes in association to improve N balance and control weed seed bank. However, it is also well known that legume N2 fixation could be limited depending on the soil N fertility. The functioning of such mixtures could then be disturbed by variations of the nitrogen fertility of the environment. The impact of soil N fertility has to be studied in order to manage whether above- and belowground interactions between species and to optimise benefits of the association

Wheat/forage legume intercropping in organic grain system: an answer to both weed and nitrogen deficiency issues

Organic grain system managers have to find solutions to nitrogen deficiency and weed infestation. It is especially true when no animals are present on the farm to justify the use of forage legumes despite their interests in the crop succession. Our study focused on the role of four legume cover crop species inserted in a succession of winter wheat and maize on both problems. This insertion consisted in relay-intercropping the legumes under the canopy of wheat. Cover crops were maintained on the field after the harvest of the cereal until the sowing of the subsequent maize crop. The performance of the three crops of the succession was monitored as well as weed development and nitrogen dynamic in the soil-plant system. On the one hand, our results showed that black medic and red clover, that supported the best the competition of wheat, were likely to decrease its grain protein content at harvest (-0.3 to -0.4 %). On the other hand, the four species did not decrease intercropped wheat grain yield. They were able to control weed infestation during the intercropping period and between the two cash crops. Finally, nitrogen restitution to the subsequent maize crop was efficient and allowed a significant 30 % increase of maize grain yield

Agronomical techniques to improve technological and sanitary quality

In spite of variable grain protein contents, baking quality of organic wheat was found to be acceptable to good. Mycotoxin (DON) infestation was generally low on tested grain samples. Choice of wheat cultivar was the most efficient way to obtain higher grain quality. Fertilization with readily available nitrogen and, to a lower extent, association with legumes and green manures with mixtures containing fodder legumes also improved grain quality. Reduced tillage affected soil quality and wheat yield but had little effects on grain quality

New challenges to improve organic bread wheat production in Europe

The total organic area in the EU-27 had an annual average growth rate of nearly 15% from 1998 to 2006 with winter wheat being the most important cereal crop. Wheat yield in organic farming is around 30% to 70% of yield of conventional farming but higher premia for organic wheat may to some extent compensate for this. Bread wheat is grown in a variety of crop rotations and farming systems and four basic organic crop production systems have been defined. Nitrogen deficiency and weed infestation are considered to be the most serious threat in organic wheat production. Organic wheat producers will have to fulfil the technological needs of bakers although the requirements differ widely from small artisan bakers to large enterprises handling the organic bread processing. To maintain and expand organic wheat production, there is a need to control weed population, manage nitrogen nutrition and maintain crop diversity in the cropping system. In order to obtain a share in the premium price of organic wheat products, farmers may involve in further processing and marketing

Techniques to improve technological and sanitary quality

Agronomical ways for better quality and safety Choice of cultivar is an efficient way to obtain higher grain quality. Intercropping legumes (grain or forage) improves weed competition and N availability for wheat crop or succeeding crop. Green manure can be an effective alternative to farmyard manure. Fertilization with readily available nitrogen improves yield and quality when water is available. Reduced tillage affects soil fertility and wheat yield but has little effects on grain quality. Technological ways for better quality and safety Milling process strongly influences flour characteristics. Stone milling improves nutritive value; characteristics remain very stable independent of the milling yield. Flour characteristics from roller milling appear very susceptible to the milling yield. Increasing the milling yield in the aim of enriching nutritional quality has a detrimental effect either on safety (DON) or on bread-making quality (bread volume)

Technological quality of organic wheat in Europe

The demand for high quality organic bread wheat is increasing. The quality level of organic wheat harvested in EU is mainly dependant on variety, environmental conditions and agronomic practices. In some countries, protein content and composition, influencing technological value, are equivalent to those produced under conventional practices. Beside agronomical techniques, technological processes can help to maintain a good quality. Pre-treatments before milling such as debranning were found to be efficient in reducing DON contamination. The project highlighted the necessity to redefine the methods to assess the quality of organic wheat

Process outcomes from a randomized controlled trial comparing tailored mammography interventions delivered via telephone versus DVD

Objective Tailored, interactive mammography-promotion interventions can increase adherence if women are exposed to and find them usable. We compare exposure to and usability of interventions delivered via telephone vs. DVD. Methods Process evaluation measures from 926 women randomly assigned to telephone or DVD intervention and completing post-intervention surveys. Results ∼83% of each group reported exposure to all content. Partial exposure was higher for DVD (9% vs. 0.4%; p < .01); no exposure was higher for phone (15% vs. 8%; p < .01). There were no differences in exposure by age or race. Full phone exposure was less likely for women who already made mammography appointments. Usability rating was higher for DVD (p < .05), driven by ratings of understandability and length. Usability of both interventions was correlated with lower baseline barriers, and higher fear, benefits, and self efficacy. Higher ratings for phone were associated with lower knowledge and contemplating mammography. Non-whites rated DVD better than whites. Conclusion Both tailored interactive interventions had wide reach and favorable ratings, but DVD recipients had greatest exposure to at least partial content and more favorable ratings, especially among non-white women. Practice implications This first evaluation of a tailored, interactive DVD provides promise for its use in mammography promotion

PLANT BASED-DIVERSITY PRACTICES IN CONVENTIONAL AND ORGANIC FARMING: A FARMERS’ SURVEY IN FRANCE

Enhancing plant-based diversity within agroecosystems may be an efficient way to achieve the objective of designing more resilient and low-input agricultural systems. The objectives of this study were (i) to describe the plant-based diversity practices implemented in organic or conventional agriculture in France and (ii) to identify the motivations of the farmers to apply such practices. It was also to compare the integration of such practices in organic or conventional farming systems. The survey was carried out in five French regions with 196 farmers that apply at least one plant-based diversification practice. Five diversification practices were studied: diversified crop rotations, use of catch crops, simultaneous intercropping, agroforestry and semi-natural landscape elements. Simultaneous intercropping and agroforestry are less applied compared to catch crops and semi-natural landscape elements because they imply a deeper change in the cropping system. Nevertheless, organic farmers apply more often such practices (simultaneous intercropping and agroforestry) and 40% of them applied more than 4 of these practices at the same time (compared to less than 20% of the conventional farmers). Organic farmers seem thus to be a step further than conventional farmers with regard to the transition towards agroecological systems