Short-term effects of de-inking paper sludge on the dynamics of soil carbon, nitrogen, and phenolic compounds

Applications of deinking paper sludge (DPS) decreased the establishment of some crops, indicating that it may have inhibiting effects. The effects of soil-applied DPS on total carbon (C), nitrogen (N), C:N ratio, and nitrate, ammonium, and phenolic compounds were studied for 2 years. The phytotoxicity of simulated phenolic solutions of raw DPS and DPS-amended soil was investigated. Twelve phenolic compounds were quantified in raw DPS. Vanillin and 3-hydroxy-4-methoxycinnamic acids increased with DPS applications in amended soil for both years. Total soil C and the C:N ratio increased with DPS applications, while nitrate soil content decreased. Germination indices were affected differently by the phenolic compound solution that simulated DPS. This study highlights the lack of availability of nitrate as the main factor involved in the inhibiting effect of DPS. However, other inhibiting effects of phenolic compounds cannot be ruled out since they are known to inhibit nitrification and to trap nitrate into organic N compounds

Isolation of free-living dinitrogen-fixing bacteria and their activity in compost containing de-inking paper sludge

Knowledge of the microbiology of dinitrogen (N2)-fixing bacteria in compost rich in de-inking paper sludge (DPS) is limited. Dinitrogen (N2)-fixing bacteria from DPS composts were isolated and studied for their N2-fixing activity in vitro and in vivo. Two Gram-negative N2-fixing isolates were identified as Pseudomonas. At 20 C, both isolates revealed that N2-fixing activity was higher than that of three arctic Pseudomonas strains. Their N2-fixing activity was found to occur between 18 and 25 C, a pattern that was similar to the reference isolate Azotobacter ATCC 7486. Composts successfully showed N2-fixing activity after carbohydrate amendments both with and without inoculation of a N2-fixing isolate. These results suggest that DPS composts support N2-fixing bacteria and that N2-fixing activity is dependent on a usable carbohydrate source. 2005 Elsevier Ltd. All rights reserved.Keywords: Dinitrogen-fixing bacteria; Compost; Paper sludge; Glucose; Pseudomonas balearica; Pseudomonas putid

Use of bark and combined paper sludge for the re-vegetation of bark-covered land

This study investigated the use of bark and combined paper sludge, poor and rich in nutrients, in order to develop a suitable plant growth substrate and to establish a vegetation cover on bark-covered land. A short-term field experiment was established in Taschereau, Quebec, Canada to: 1- determine a suitable plant growth medium on a bark-covered land; 2- determine which plant mixture should be selected for establishment on this site and 3- determine a fertilization program for one selected plant. By the end of the summer, the best soil cover consisted of 2.5 cm of combined paper sludge on top of 2.5 cm of black bark, which gave good plant appearance, cover, and yield. On this soil cover, the Savoureux mixture (53% perennial grasses and 37% perennial legumes) in combination with birdsfoot trefoil (Lotus corniculatus L.), Lab02 (65% perennial grasses and 35% perennial legumes) in mixture with MR77 (100% perennial grasses), and birdsfoot trefoil in mixture with bromegrass (Bromus inermis L.) gave good vegetation growth and yields. For the birdsfoot trefoil fertilization experiments, and over all soil covers, nitrogen fertilization was not required, but phosphorus and potassium fertilizations should be, respectively, 140 kg P2O5/ha and 160 kg K2O/ha to obtain good plant growth and yield. These first results suggested that combined paper sludge and black bark can be used as topsoil to favor plant establishment on bark-covered land

Symbiotic dinitrogen fixation in forage legumes amended with high rates of de-inking paper sludge

The paper de-inking process produces a waste by-product, de-inking paper sludge (DPS), which contains paper fibers, clay particles, and inks and has high C and Ca and low N and P concentrations. Use of high rates of DPS to increase the soil organic matter thus requires provision of high rates of N for adequate plant growth. Using dinitrogen (N2)-fixing forage legumes is an alternative to the N fertilization under such circumstances. In a 2-yr field study (1995 and 1996), the effect of different rates of DPS (0, 50, or 100 Mg dry matter ha−1), applied once in October 1994, were evaluated on symbiotic N2 fixation of forage legumes established on two soil types in Eastern Quebec, Canada. Symbiotic N2 fixation was measured in alfalfa (Medicago sativa L.), birdsfoot trefoil (Lotus corniculatus L.), red clover (Trifolium pratense L.), and sweetclover (Melilotus officinalis L.); bromegrass (Bromus inermis L.) was used as the reference (non N2–fixing) crop. Dinitrogen fixation was estimated by the 15N natural abundance method. The percentages of N derived from the atmosphere increased significantly with DPS in the year of establishment (1995). In the first production year (1996), the effects of DPS on N2 fixation were mainly observed at the first cut. Our results show that DPS used as an organic amendment generally led to similar or greater forage legume productivity and greater N2 fixation compared with unamended controls in the first production year and is compatible with sustainable agricultural practices

Root colonization of faba bean (Vicia faba L.) and pea (Pisum sativum L.) by Rhizobium leguminosarum bv. viciae in the presence of nitrate–nitrogen

There is a lack of knowledge concerning the effect of nitrate–nitrogen (NO3– –N) at levels known to inhibit nodule formation and functioning on root colonization of dinitrogen-fixing legumes. Firstly, this study investigated potential differences between Rhizobium leguminosarum bv. viciae 175F9 and its bioluminescent-labeled strain 175F9.lux on root colonization of faba bean (Vicia faba L.) and pea (Pisum sativum L.). These two strains similarly colonized the roots of both hosts. Secondly, this study evaluated the effects of 0 and 10 mol·m–3 NO3– –N on root colonization of faba bean and pea by strain 175F9.lux, over time. Averaged over both hosts and harvest dates, the presence of NO3– –N increased the rhizobial population and the root length colonized. In addition, our results showed that bioluminescence activity increased from 7 to 14 days after sowing and was not correlated to rhizobial population. Finally, to demonstrate that an increase in bioluminescence activity was not an indirect effect of nitrate on R. leguminosarum bv. viciae 175F9.lux, this study investigated the effects of increasing carbon (mannitol) and nitrogen (NO3– –N) concentrations on the rhizobial population and bioluminescence activity. The carbon source was more important than the nitrogen source to increase the rhizobial population and bioluminescence activity, which increased with increasing mannitol concentration, but not with increasing nitrate concentration. Results from this study demonstrated that NO3– –N increased rhizobial population, especially for faba bean, and the length of root colonized.Il manque de connaissances concernant les effets de l’azote sous forme de nitrate (NO3– –N), à des concentrations connues pour inhiber la formation de nodosités, sur la colonisation des racines des légumineuses fixatrices d’azote. Dans un premier temps, les différences potentielles entre la souche mère, 175F9, de Rhizobium leguminosarum bv. viciae et la souche 175F9.lux porteuse d’un marqueur de bioluminescence ont été étudiées sur la colonisation des racines de la féverole (Vicia faba L.) et du pois (Pisum sativum L.). Les deux souches ont colonisé les racines de ces deux plantes hôtes de façon similaire. Dans un deuxième temps, cette étude a évalué l’effet de 0 et 10 mol·m–3 de NO3– –N sur la colonisation de la féverole et du pois par la souche 175F9.lux. Selon la moyenne des deux souches aux deux dates de récolte, la présence de NO3– –N a augmenté la population des rhizobia et la longueur des racines colonisées. Les résultats ont aussi révélé que l’activité de la bioluminescence a augmenté de 7 à 14 jours après les semis, mais il n’y a pas eu de corrélation avec la population des rhizobia. Finalement, pour démontrer que l’augmentation de l’activité de la bioluminescence n’était pas une conséquence indirecte de l’effet de l’azote sur le R. leguminosarum bv. viciae, 175F9.lux, les effets d’une augmentation du carbone (mannitol) et de l’azote (NO3– –N) sur la population des rhizobia et de l’activité de la bioluminescence ont été mesurés. La source de carbone s’est révélée plus importante que la source d’azote pour augmenter la population des rhizobia et l’activité de la bioluminescence, qui a augmenté avec l’accroissement des concentrations de mannitol mais non avec celles de l’azote. Les résultats de cette étude ont démontré que le NO3– –N a favorisé la population des rhizobiums ainsi que la longueur des racines colonisées, particulièrement chez la féverole

Improving salt stress responses of the symbiosis in alfalfa using salt-tolerant cultivar and rhizobial strain

Salt stress can affect alfalfa growth directly by adversely affecting metabolism, or indirectly by its effect on Rhizobium capacity for symbiotic N2 fixation. Growth and carbohydrate metabolism in leaves, roots and nodules of two alfalfa cultivars (Medicago sativa cv Apica and salt-tolerant cv Halo) in association with two rhizobial strains (A2 and salt-tolerant Rm1521) exposed to different levels of NaCl (0, 20, 40, 80 or 160 mM NaCl) were assessed under controlled conditions. For both cultivars, shoot and root biomasses and shoot to root ratio significantly declined with increasing NaCl concentrations. Under 80 mM NaCl, Halo plants yielded 20% more fresh shoot biomass than Apica while plants inoculated with Rm1521 allocated more biomass to the roots than to the shoots compared to A2. Halo plants maintained a steady shoot water content (about 80%) under the entire range of NaCl concentrations. Shoot water content was more variable in Apica. Apica in association with salt-tolerant strain Rm1521 maintained a better water status than with strain A2, as indicated by the higher shoot water content at 80 mM NaCl. Under salt stress, two major compatible sugars involved in plant osmoregulation, sucrose and pinitol, increased in leaves while a large accumulation of starch was observed in roots. In nodules, pinitol, sucrose and starch increased under salt stress and were much more abundant with strain Rm1521 than with A2. This suggests that there could be an active transport from the shoot to the nodules to help maintain nodule activity under NaCl stress and that strain Rm1521 increases the sink strength toward nodules. Our results show that combining cultivars and rhizobial strains with superior salt tolerance is an effective strategy to improve alfalfa productivity in salinity affected areasKeywords: Medicago sativa L. Salt stress Osmoregulation Pinitol Nodule Salt-tolerant cultiva

Selection of rhizobial strains differing in their nodulation kinetics under low temperature in four temperate legume species

Abstract Background Winter climate change including frequent freeze‐thaw episodes and shallow snow cover will have major impacts on the spring regrowth of perennial crops. Non‐bloating perennial forage legume species including sainfoin, birdsfoot trefoil, red clover, and alsike clover have been bred for their adaptation to harsh winter conditions. In parallel, the selection of cold‐tolerant rhizobial strains could allow earlier symbiotic nitrogen (N) fixation to hasten spring regrowth of legumes. Methods To identify strains forming nodules rapidly and showing high N‐fixing potential, 60 rhizobial strains in association with four temperate legume species were evaluated over 11 weeks under spring soil temperatures for kinetics of nodule formation, nitrogenase activity, and host yield. Results Strains differed in their capacity to form efficient nodules on legume hosts over time. Strains showing higher nitrogenase activity were arctic strain N10 with sainfoin and strain L2 with birdsfoot trefoil. For clovers, nitrogenase activity was similar for control and inoculated plants, likely due to formation of effective nodules in controls by endophyte rhizobia present in seeds. Conclusions Selection based on nodulation kinetics at low temperature, nitrogenase activity, and yield was effective to identify performant rhizobial strains for legume crops. The use of cold‐tolerant strains could help mitigate winter climatic changes

Selection of parameters for seagrass management: Towards the development of integrated indicators for French Antilles

Este artículo contiene 15 páginas, 6 figuras, 3 tablas.Seagrass beds are increasingly impacted by human activities in coastal areas, particularly in tropical regions. The objective of this research program was to study seagrass beds characteristics under various environmental conditions in the French Antilles (FA, Caribbean Sea). A total of 61 parameters, from plant physiology to seagrass ecosystem, were tested along a gradient of anthropogenic conditions, distributed across 11 sites and 3 islands of the FA. A selection of 7 parameters was identified as relevant for the monitoring of seagrass meadows in the framework of public policies. They combined “early warning indicators” (e.g. nutrients and some trace metals) and long-term responding parameters (e.g. shoot density) adapted to management time scales. The ecological status of seagrass meadows was evaluated using a PCA. This work is a first step towards monitoring and management of seagrass meadows in the FA.This study was funded by the French Ministry for the Ecological Transition within the framework of the French Coral Reef Initiative and the French Biodiversity Office.Peer reviewe