The fate of nitrogen from winter-frozen rapeseed leaves: mineralization, fluxes to the environment and uptake by rapeseed crop in spring.

摘要: For environmental purposes, very early sowing of winter rapeseed may reduce nitrate leaching thanks to the high N uptake capacities in autumn. However, freezing could lead losses leaf nitrogen, amounting more than 100 kg ha-1 (Dejoux et al., 1999). Here we investigated agronomic and consequences decomposition fallen leaves, based on field laboratory studies with 15N labeled leaves (C:N=9). The potential kinetics were measured by incubation laboratory. In field, all removed at beginning replaced artificially frozen −15°C , which laid soil surface. Compared a thermal time basis, proceeded as quickly incubations was complete after 116 normalized days 15 °C. proportion derived from absorbed again rape plants, 28% flowering 24% harvest. This recovery is assumed result synchronization active absorption spring. Leaf mineralization did not increase mineral content or harvest, but observed 40% loss 15N. As no simulated, this supposed be gaseous. Such percentage explained fact that decomposing lay surface, climatic conditions conducive such emissions. quantity nature these gaseous emissions have studied for other types leaves. reabsorbed, fertilizer application rates reduced accordingly.