Destruction des intercultures courtes: quand et comment?

Le premier octobre arrive à grand pas et avec lui l’autorisation de destruction des intercultures courtes. Pour rappel, une interculture courte est implantée après une culture de légumineuse récoltée avant le 1er août et qui sera suivie d’un froment. Cette période est l’occasion pour Nitrawal de faire le point avec ses partenaires scientifiques sur les techniques de destruction les plus adaptées en fonction du type et du développement des couvertures de sol

A contrast in sea ice drift and deformation between winter and spring of 2019 in the Antarctic marginal ice zone

Two ensembles of buoys, deployed in the marginal ice zone (MIZ) of the north-eastern Weddell Sea region of the Southern Ocean, are analysed to characterise the dynamics driving sea ice drift and deformation during the winter-growth and the spring-retreat seasons of 2019. The results show that although the two buoy arrays were deployed within the same region of ice-covered ocean, their trajectory patterns were vastly different. This indicates a varied response of sea ice in each season to the local winds and currents. Analyses of the winter data showed that the Antarctic Circumpolar Current modulated the drift near the sea ice edge. This led to a highly energetic and mobile ice cover, characterised by free-drift conditions. The resulting drift and deformation were primarily driven by large-scale atmospheric forcing, with negligible contributions due to the wind-forced inertial response. For this highly advective coupled ice–ocean system, ice drift and deformation linearly depended on atmospheric forcing. We also highlight the limits of commercial floating ice velocity profilers in this regime since they may bias the estimates of sea ice drift and the ice type detection. On the other hand, the spring drift was governed by the inertial response as increased air temperatures caused the ice cover to melt and break up, promoting a counterintuitively less wind-driven ice–ocean system that was more dominated by inertial oscillations. In fact, the deformation spectra indicate a strong decoupling to large-scale atmospheric forcing. Further analyses, extended to include the deformation datasets from different regions around Antarctica, indicate that, for similar spatial scales, the magnitude of deformation varies between seasons, regions, and the proximity to the sea ice edge and the coastline. This implies the need to develop rheology descriptions that are aware of the ice types in the different regions and seasons to better represent sea ice dynamics in the MIZ

Do manures spread before the sowing of a catch crop (CIPAN) present an excessive risk of nitrate leaching?

Description of the subject. The implementation of the Nitrates Directives in the Walloon region (in the south of Belgium) allows the summer spreading of any kind of manure on soils in preparation for the sowing of a catch crop. Objectives. This paper aims to assess whether the spreading of a manure before sowing a catch crop is more risky for groundwater quality than planting a cereal followed by another crop without any action being implemented between the harvesting of the cereal and the sowing (winter or spring) of the next crop. Method. This study is based on measurements of the nitrate nitrogen content of soils, at the beginning of the leaching period, performed on reference parcels and on controlled parcels. Results. Three thousand six hundred soil analyses performed in relation to controlled parcels between 2008 and 2013 showed that the presence of a catch crop (information about the possible application of a manure was not known) led to a nitrate nitrogen content (median) lower (with a very highly significant difference) than in a situation where no action was implemented between the two main crops. For the same period, the analysis of 600 results in reference parcels led to the same conclusion. Moreover, no significant difference was found between the two kinds of manure (“fast action”, such as pig slurry or “low action”, such as bovine manure). Conclusions. After the harvesting of a cereal, the spreading of a manure before sowing a catch crop creates no higher risk for water quality than the succession of a cereal by a crop sowed in the autumn