Does fertilization practices increase residual nitrate nitrogen in soil irrigated with treated wastewater? An experimental trial on maize

Treated wastewater has significantly improved DM yield compared to ground water. The form of nitrogen provided by the water was determinant in drawing yields. Irrigation with ground water (where nitrogen is as nitrate) induces a faster migration of nitrogen at depth. In contrast, using treated wastewater (where nitrogen is as ammonium), resulting in a relative distribution of the remaining nitric smaller in the lower profile and therefore higher in the surface, especially after the second year (2010). In addition, the relative distribution of nitrates in the soil surface is even more important in the presence of organic manure. All happens as if a certain amount of ammonium provided by treated wastewater is retained in the organic compounds of manure. Yields were significantly lower in irrigation with treated wastewater in the second year and especially when fertilization was given in additional. If the soil can be used for storage of the nitrogen supplied by the treated wastewater during the first year of irrigation (24 kg N-NO3/ha before irrigation to 115 kg N-NO3/ha after irrigation), to the second year the capacity drops (to 64 N-NO3/ha) and a significant increase in nitrate leaching occurs. Therefore, unlike the contribution of manure that seems enrich the topsoil nitrate nitrogen, at least during the first campaign, mineral fertilization unreasoning causes faster migration of nitrogen at depth

Carbon and nitrogen sources modulate lipase production in the yeast Yarrowia lipolytica

International audienceAIMS: To analyse the influence of nitrogen and carbon sources on extracellular lipase production by Yarrowia lipolytica-overproducing mutant in order to optimize its production in large-scale bioreactors. METHODS AND RESULTS: The level of lipase production and LIP2 induction, measured using an LIP2-LacZ reporter gene, were compared for different carbon and nitrogen sources and for different concentrations. The localization of the enzyme during growth was also determined by Western blotting analysis using a six-histidine-tagged lipase. SIGNIFICANCE AND IMPACT OF THE STUDY: Tryptone N1 and oleic acid are the most suitable nitrogen and carbon sources for the production of the extracellular lipase by the Y. lipolytica mutant. Higher levels of lipase production were obtained as the tryptone concentration increased in the culture medium. Such a positive correlation was not observed with oleic acid media where the highest lipolytic productivities were obtained in the presence of low concentration. We also demonstrate that in the presence of oleic acid, lipase is cell-bound during the growth phase before being released in the media. CONCLUSIONS: This work provides a better understanding of the mechanism controlling LIP2 expression and, thus, extracellular lipase production in the yeast Y. lipolytica

Évaluation du troisième Programme de Gestion Durable de l'Azote en agriculture. Recommandations en matière de règlementations et de recherches scientifiques

In accordance with the Nitrates Directive, the third "Durable Nitrogen Management Plan" (PGDA) will be soon reviewed in Wallonia (Belgium). The second "Nitrate - Water" workshop took place between 28th May and 1st June 2012. The workshop was attended by both Belgian scientists (Université catholique de Louvain - UCL, Walloon Agricultural Research Center CRA-W, Université de Liège - ULg, Gembloux Agro-Bio Tech) and French scientists (National Institute for Agricultural Research - INRA). In the light of the results of experiments presented by scientists at this workshop, modifications to the PGDA are now recommended. These concern organic and mineral nitrogen fertilization for crops and meadows; catch crops; soil nitrate-nitrogen residue limitation in autumn, at the start of the nitrate leaching period; the management of meadow ploughing and a modification of the dairy cow standard for nitrogen production