Dynamics of the diazotroph Bacillus polymyxa in the rhizosphere of wheat (Triticum aestivum L.)after inoculation and its effect on uptake of 15 N-labelled fertilizer

International audienc

Dynamics of the diazotroph Bacillus polymyxa in the rhizosphere of wheat (Triticum aestivum L.) after inoculation and its effect on uptake of 15N-labelled fertilizer

International audienceAn experiment under glasshouse conditions with a sandy soil was conducted to evaluate the effect of the inoculation of wheat (Triticum aestivum L.) roots with Bacillus polymyxa on N uptake by plants and to investigate the effect of N fertilization on the dynamics of this strain. Different treatments were considered: (i) amended (l00 kg N ha -I) or not with 15N labelled ammonium nitrate ; (ii) inoculated (2.5 107 spores per seed and 0.5 109 spores kg-I soil) or not with B. polymyxa CF43. No promoting effect on wheat growth (dry yield) or N uptake was observed after inoculation under these experimental conditions; 62 per cent of the N fertilizer was assimilated by plants during the first 33 days. Inoculation had no effect on the quantity of soil adhering to the roots. Soluble organic C and inorganic N concentrations were higher in the soil adhering to the roots than in bulk soil. However, the nitrate concentration in soil adhering to the roots was influenced by inoculation at the beginning of plant growth, nitrate supply to the root system being delayed by its probable retention in the rhizosphere. Furthermore, total bacteria in roots, soil adhering to the roots and bulk soil was not affected by N fertilization. The number of B. polymyxa cells measured by an AB-ELISA method increased first in the bulk soil and later in the soil adhering to the roots after inoculation. Fertilization with N decreased the B. polymyxa population in adhering soil, competitive suppression of diazotrophs by non-fixing bacteria probably being induced by the presence of large amounts of nutrients in the rhizosphere when N was added

Near infrared reflectance spectroscopy : a tool to characterize the composition of different types of exogenous organic matter and their behaviour in soil

In addition to total organic carbon and nitrogen, potential organic carbon mineralization under controlled laboratory conditions and indicators such as the indicator of remaining organic carbon in soil (I-ROC), based on Van Soest biochemical fractionation and short-term carbon mineralization in soil, are used to predict the evolution of exogenous organic matter (EOM) after its application to soils. The purpose of this study was to develop near infrared reflectance spectroscopy (NIRS) calibration models that could predict these characteristics in a large dataset including 300 EOMs representative of the broad range of such materials applied to cultivated soils (plant materials, animal manures, composts, sludges. etc.). The NIRS predictions of total organic matter and total organic carbon were satisfactory (R(2)p = 0.80 and 0.85, ratio of performance to deviation, RPDp = 2.2 and 2.6, respectively), and prediction of the Van Soest soluble, cellulose and holocellulose fractions were acceptable (R(2)p = 0.82, 0.73 and 0.70. RPDp = 2.3, 1.9 and 1.8, respectively) with coefficients of variation close to those of the reference methods. The NIRS prediction of carbon mineralization during incubation was satisfactory and indeed better regarding the short-term results of mineralization (R(2)p = 0.78 and 0.78, and RPDp = 2.1 and 2.0 for 3 and 7 days of incubation, respectively). The I-ROC indicator was predicted with fairly good accuracy (R(2)p = 0.79, RPDp = 2.2). Variables related to the long-term C mineralization of EOM in soil were not predicted accurately, except for I-ROC which was based on analytical and well-identified characteristics, probably because of the increasing interactions and complexity of the factors governing EOM mineralization in soil as a function of incubation time. This study demonstrated the possibility of developing NIRS predictive models for EOM characteristics in heterogeneous datasets of EOMs. However. specific NIRS predictive models still remain necessary for sludges, organo-mineral fertilizers and liquid manures

PSDR4 ProSys - L’adaptation pédoclimatique, les impacts environnementaux et la valeur économique de nouveaux systèmes de culture durables producteurs de protéines en Bourgogne-Franche-Comté

The ProSys project aimed to identify agronomically efficient protein-based cropping systems that can adapt to the context of climate change, meet environmental challenges, are economically viable and represent an acceptable alternative for farmers and the industry. The potential of production and environmental constraints encountered by legumes, under current conditions and in the context of climate change, were studied. In addition, an experiment was conducted to study the previous effect of differentlegume species. An innovation tracking has allowed to identify and analyze protein-producing cropping systems that have been tested by farmers in the region who are satisfied with them. The positive environmental impacts and the interest for the global production of proteins of cropping systems with legumes were evaluated through long-term experimental follow-ups. Finally, the modalities of changing farmers' practices towards plant protein producing systems were analyzed. The creation of working groups with agricultural education and professionals from the agricultural world has enabled the development of a set of tools and communication media to promote the results of the program.Le projet PSDR4 ProSys visait à identifier des systèmes de culture à enjeux protéines performants d’un point de vue agronomique, pouvant s’adapter au contexte du changement climatique, répondant aux enjeux environnementaux, économiquement viables et représentant une alternative acceptable pour les exploitants agricoles et les filières. Les potentiels de production et les contraintes environnementales rencontrées par les légumineuses, dans les conditions actuelles et en prospective dans le contexte du changement climatique ont été étudiées. En complément, une expérimentation a été menée afin d’étudier l’effet précédent de différentes espèces de légumineuses. De plus, une traque à l’innovation a permis d’identifier et d’analyser des systèmes de culture producteurs de protéines qui ont été testés par des agriculteurs de la région qui en sont satisfaits. Les impacts environnementaux positifs et l’intérêt pour la production globale de protéines, de systèmes de culture avec légumineuses ont été évalués via des suivisexpérimentaux de longue durée. Enfin, les modalités du changement des pratiques d’agriculteurs vers des systèmes producteurs de protéines végétales ont été analysées. La création de groupes de travail avec l’enseignement agricole et les professionnels du monde agricole a permis l’élaboration d’un ensemble d’outils et de supports de communication valorisant les résultats du programme

Compostage et valorisation par l'agriculture des déchets urbains

Urban composts constitute a valuable source of organic matter that can be used in agriculture, especially in areas where animal breeding has disappeared. Their use in agriculture is regulated through obligatory standards: NFU 44095 for sludge composts and NFU 44 051 for other organic amendments. These standards assure the innocuousness at short/medium term by limiting the concentrations in trace elements, in organic micropollutants, in pathogens and inerts. Some analytical methods of characterisation have been developed to predict their agronomic value. Long term field experiments are useful tools to evaluate the effects of repeated applications. From the results of the Qualiagro field experiment, the indicator ISMO seems valuable to predict the capacity of organic amendments at increasing soil organic matter contents. Repeated applications of composts have improved soil structure stability, stimulated soil microbial activity, and produced yields equivalent to mineral fertilization. The fluxes of trace elements have reached a few percents of initial soil contents before starting the experiment. After 10 years of experiment, no degradation of grain quality has been noticed nor accumulation of organic micropollutants in soil or sanitary degradation of soils.Les composts d'origine urbaine représentent une source de matière organique valorisable en agriculture, d’autant plus dans les zones où l'élevage a disparu. Leur utilisation en agriculture est réglementée par des normes rendues d'application obligatoire : norme NFU 44 095 pour les composts de boue, norme NFU 44051 pour les autres amendements organiques. Ces normes garantissent l'innocuité à court et moyen terme en limitant les concentrations en éléments traces, composés traces organiques, inertes et pathogènes. Des méthodes de caractérisation au laboratoire permettent d'évaluer leur valeur agronomique. Des essais au champ de longue durée permettent de mesurer les effets de leurs apports répétés. Au vu des résultats de l'essai Qualiagro en Ile de France, l'indicateur ISMO semble prometteur pour prédire leur capacité à entretenir la matière organique des sols. Les apports répétés de composts améliorent la stabilité de la structure du sol. Ils stimulent l'activité biologique, permettent d’obtenir des rendements équivalents à ceux obtenus avec une fertilisation minérale classique. Les flux d'éléments traces représentent quelques pourcents des stocks présents dans le sol avant épandage. Après 10 ans d'essai, aucune dégradation de la qualité des grains n'est mesurée. De même aucune accumulation de composés traces organiques n'est observée, ni de dégradation sanitaire des sols