ISSN:
1573-5036
Keywords:
biochemical quality
;
Brassica napus L.
;
decomposition
;
incubation
;
leaf fall
;
N recovery
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract For environmental purposes, very early sowing of winter rapeseed may reduce winter nitrate leaching thanks to the high N uptake capacities of rapeseed in autumn. However, freezing could lead to high losses of leaf nitrogen, amounting to more than 100 kg N ha-1 (Dejoux et al., 1999). Here we investigated the agronomic and environmental consequences of the decomposition of fallen leaves, based on field and laboratory studies with 15N labeled leaves (C:N=9). The potential kinetics of decomposition of leaves were measured by incubation in the laboratory. In the field, all leaves were removed at beginning of winter and replaced by labeled leaves, artificially frozen at −15°C , which were laid on the soil surface. Compared on a thermal time basis, decomposition proceeded as quickly in the field as in the incubations and was complete after 116 normalized days at 15 °C. The proportion of 15N derived from labeled leaves, absorbed again by the rape plants, was 28% at flowering and 24% at harvest. This high N recovery is assumed to result from the synchronization of leaves decomposition and active N absorption by rape in spring. Leaf N mineralization did not increase soil N mineral content at flowering or at harvest, but we observed a 40% loss of 15N. As no leaching was simulated, this loss was supposed to be gaseous. Such a high percentage could be explained by the fact that the decomposing leaves lay on the soil surface, and by climatic conditions conducive to such emissions. For environmental purposes, the quantity and nature of these gaseous N emissions have to be studied for other climatic conditions and types of leaves. As a proportion of N is reabsorbed, N fertilizer application rates could be reduced accordingly.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1014934924819
