Intéractions entre les processus de gestion du carbone et de l'azote lors du développement végetatif du pêcher (Prunus persica (L.) Batsch)

La fertilisation raisonnée est un enjeu important pour l'agriculture durable. L'amélioration de la gestion de la fertilisation azotée des vergers repose sur l'estimation plus mécaniste des besoins en azote de l'arbre au cours de son développement. Cela implique une meilleure compréhension du fonctionnement global de l'arbre., notamment les interactions entre les métabolismes carboné et azoté qui s'exercent au niveau de leur acquisition, leur répartition et leur utilisation lors du développement de l'arbre.. L'objectif de ce travail a e té d'étudier l'influence de la disponibilité en azote et de la taille sur le fonctionnement de l'arbre. Nous avons travaillé à l'échelle de l'arbre entier en utilisant un dispositif expérimental qui a permis la mesure concomitante de l'absorption du nitrate de la photosynthèse sur de jeunes pêchers. Dans un premier temps, nous avons déterminé l'influence de la disponibilité en azote sur les composantes du développement. Dans un second temps , nous avons évalué l'effet de la taille sur l'acquisition, la répartition et l'utilisation du carbone et de l'azote lors du développement.AIX-MARSEILLE3-BU Sc.St Jérô (130552102) / SudocSudocFranceF

Le rôle des prairies temporaires et artificielles dans la gestion des adventices en grandes cultures

Prod 2018-236n GESTAD AGROSUP pole SPE EAInternational audienc

Weed seed rain interception by grass cover depends on seed traits

Weed management requires a better understanding of the dynamics of the weed seedbank, which is a primary source of weeds in a field. Seeds reaching the ground after seed rain replenish the seedbank and therefore contribute to future weed infestations. Our investigation is based on the hypothesis that a permanent vegetation cover, such as a grassland, can prevent weed seeds from reaching the ground. Therefore, we developed an innovative experimental device to simulate in controlled conditions the seed rain of 12 weed species (Capsella bursa-pastoris, Conyza canadensis, Myosotis arvensis, Papaver rhoeas, Poa annua, Polygonum aviculare, Ranunculus sp., Rumex obtusifolius, Sonchus asper, Stellaria media, Taraxacum officinale and Veronica persicaria). We quantified the interception of weed seeds by a grass cover. Grass cover height, seed size and seed appendage (e.g. pappus, wing or awn) increased seed interception, in contrast to seed weight and shape index. From these results, we established a linear model to predict weed seed interception by a grass cover as a function of their seed trait values. The relationship between the predicted interception and weed community dynamics observed in grasslands was negative for some species, indicating that other processes may be involved depending on weed species. The weed seed interception model will be incorporated into an existing model of weed population dynamics to simulate the impact of grassland insertion into arable crop rotations

Modelling crop rotation including temporary grasslands for weed management

Session 3 - Crop modellingEAEcolDurabsen

Parameterizing the "grassland" module in the multispecific model FlorSys

EAEcolDurCT1The multispecies model FlorSys can predict the effects of cropping systems on the dynamics of weed communities in annual crops ; however, it is not configured to predict the fate of weeds in permanent cover such as grasslands. We realized the simulation of a weed seed rain in controlled conditions to estimate the percentage of weed seeds intercepted by a grass cover. Parameters of this linear model will be used to develop a new sub model in FlorSys to be able to simulate weed dynamics in temporary grasslands. We used twelve weed species selected on the basis of specific morphological characteristics and observations made in the experimental set up of SOERE ACBB (Observatory Environmental Research, Agro-ecosystems, Biogeochemical Cycles, and Biodiversity). Weed seeds have a probability to reach the ground which depends on the height of the cover, but also on seed characteristics. So, we determined the favorable traits in the weed seed interception by a grass cover whatever the species considered. The next steps will consist of integrating the interception equation in FlorSys and of analyzing the sensitivity of the modified model. We will compare the model simulations with the observations of weed dynamics in SOERE ACBB, to explain the changes observed in cropping systems with temporary grasslands

Contrasting weed species composition in perennial alfalfas and six annual crops: implications for integrated weed management

International audienceWeed communities are most strongly affected by the characteristics and management of the current crop. Crop rotation may thus be used to prevent the repeated selection of particular weed species. While weed communities are frequently compared among annual crops, little is known about the differences between annual and perennial crops that may be included in the rotations. Moreover, nearly all existing studies (17 articles reviewed) are based on local field experiments rather than commercial fields. We compared the weed composition in perennial alfalfas (Medicago sativa) and six annual crops: winter wheat (Triticum aestivum), oilseed rape (Brassica napus), pea (Pisum sativum), sunflower (Helianthus annuus), maize (Zea mays) and sorghum (Sorghum bicolor) using data from 632 commercial fields in western France. Weed species composition showed the strongest dissimilarities between perennial alfalfas and all annual crops, followed by the well-known differences between autumn- and spring/summer-sown annual crops. Indicator Species Analysis showed that most weed species either preferred perennial alfalfas (including Taraxacum officinale, Veronica persica, Crepis spp., Poa trivialis, Silene latifolia, Capsella bursa-pastoris and Picris spp.) or annual crops (including Mercurialis annua, Galium aparine, Fallopia convolvulus, Chenopodium album and Cirsium arvense). Perennial alfalfas thus suppressed many weeds that are widespread (and sometimes problematic) in annual crops while favouring other species. Shifted weed composition and reduced frequency of several noxious weeds suggest that perennial alfalfas may be used as a valuable part of integrated weed management, reducing the need for herbicides and sustaining plant and animal diversity in agricultural landscapes

Can legume companion plants control weeds without decreasing crop yield? A meta-analysis

Companion plant intercropping involves growing a cash crop with another plant that is not harvested, to confer a set of benefits on the crop and the environment. Weed control and herbicide use reduction are one of the principal reasons for adopting this approach. Companion plants should compete with weeds for light, nutrients and water, but they may also compete with the crop. The species grown must therefore be carefully chosen and managed so as to outcompete weeds but limit competition with the crop and yield loss. In this meta-analysis, we aimed to quantify the effects of companion plants on weed regulation and cash crop yields, and to analyze their sources of variability. We reviewed different intercropping systems involving an annual cash crop and a legume companion plant from around the world. We report data from 34 scientific articles, corresponding to 476 experimental units (i.e. combinations of site × year × cash crop × legume companion plant species × agricultural practices), and we explore whether intercropping with legume companion plants can control weeds while maintaining crop yield. Yield and weed biomass ratios were analyzed as response variables. We used the type of cash crop (straw cereals, maize or other crops), the methods used to establish the companion plants (living mulch, synchronized sowing or relay intercropping) and the overlap between the growth periods of the companion plants and the cash crop as explanatory variables.Intercropping with a companion plant resulted in a lower weed biomass and a higher yield (win-win situation) than non-weeded or weeded control treatments, in 52% and 36%, respectively, of the experimental units considered. A higher weed biomass associated with a lower yield (lose-lose) was observed in only 13% and 26% of the experimental units, in comparisons with non-weeded and weeded control treatments, respectively. Considering all the experimental units together, the companion plants had no significant effect on cash crop yield, but significantly decreased weed biomass, by 56% relatively to a non-weeded control treatment, and 42% relative to a weeded control treatment. The greatest benefits from companion plant intercropping were reported for maize, with yields 37% higher than those for non-weeded control treatments. The other explanatory variables tested had no significant effect on yield or weed control. Thus, the use of legume companion plants generally seems to enhance weed control without reducing crop yield, but the conditions giving rise to win-win situations should be explored further, to encourage the spread of this technique among farmers

Weed response and crop growth in winter wheat-lucerne intercropping: a comparison of conventional and reduced soil-tillage conditions in northern France

International audienceChanging agricultural practices from conventional to conservation tillage generally leads to increased weed populations and herbicide use. To gain information about the possible use of lucerne (Medicago sativa L.) cover crop as an alternative and sustainable weed-control strategy for winter wheat (Triticum aestivum L.), an experiment was performed at Thiverval-Grignon, France, from 2008 to 2010. We compared conventional and reduced tillage as well as the presence 5 and absence of living mulch (i.e. lucerne) on weeds and wheat production. Percentage soil coverage and aboveground biomass of wheat, lucerne and weeds were measured at the end of grain filling. Weed communities were analysed in terms of composition and diversity. During both seasons, wheat biomass did not significantly decrease in reduced-till trials compared with conventional ones (7.0 and 7.2 t ha –1 , respectively, in 2008–09; 6.9 and 7.1 t ha –1 in 2009–10). Regardless of soil management, the percentage soil coverage by wheat significantly decreased when it was intercropped, although 10 wheat biomass was not significantly reduced compared with the sole crop. To minimise cash-crop losses, we studied the competition between wheat, lucerne and weeds, testing various herbicide strategies. Early control of lucerne allowed better balance between weed control and wheat development. In addition, weed communities varied among treatments in terms of abundance and composition, being reduced but more varied in plots associated with lucerne. A functional group analysis showed that grasses benefited from reduced-till conditions, whereas problematic weeds such as annuals with 15 creeping and climbing morphologies were substantially reduced. In addition, annual and perennial broad-leaf species with rosette morphology were also significantly decreased when lucerne was used as living mulch. Wheat production in reduced-till conditions intercropped with lucerne living mulch may be useful for integrated weed management, reducing the need for herbicides. Additional keywords: cover crop, plant biomass, reduced inputs, weed biocontrol, weed diversity

The influence of severe shoot pruning on growth, carbon and nitrogen status in young peach trees (Prunus Persica)

International audienceOne-year-old peach trees (Prunus persica (L.) Batsch) were severely pruned in July by removing 60% of the shoots. Tree responses were analyzed in terms of architecture and nutritional status. Tree growth was recorded from July to September by nondestructive (leaf production, thickening and branching of the remaining secondary axes) and destructive measurements (biomass partitioning and concentrations of total nitrogen (N) and nonstructural carbohydrates (NC) in specific tissues). The dry weights of pruned trees were lower than those of control trees at the end of the growing season (i.e., 2.5 months after pruning), whereas shoot:root ratios were restored to the initial values. Tree response occurred in two stages. During the first 24 days following pruning, the growth components of the remaining secondary axes were similar to the control, and new secondary axes were produced. During the next 17 days, increases in both diameter and branching of secondary axes contributed to the maintenance of pruned tree growth rate (similar to that of control trees) and restoration of initial shoot:root ratios. No significant effect of pruning was observed on NC concentrations, whereas N concentrations increased in several organs of the pruned trees during the first growth period. The transient increase in internal N availability contributed to the initiation of new axes and the restoration of a more functional biomass partitioning between shoots and roots

Mélanges variétaux et mélanges plurispécifiques : atouts et contraintes

National audienc