Assessing nutrient safety net and crop yield in a Mediterranean agroforestry using 15N labelling experiment

2024

Article référencé dans le Web of Science WOS:001244723900002

Mahmud M., Bertrand I., Bazot S., Delpierre N., Leadley P., Ngao J., Marsden C., Dugué Rémi, Morfin A., Marmagne A., Barthes L.

Journal of Soil Science and Plant Nutrition, 2024, [Early access], p. [12 p.] ISSN 0718-9508

This study aimed to assess crop yield and soil nitrogen removal by trees from a potential nitrogen leaching pool in Mediterranean agroforestry, in a N-15-labeled fertilizer field experiment. We hypothesized that the applied N-15 would be taken up by the trees, understorey vegetation strip (UVS), and soil microbial biomass, and that crop yield would be reduced in agroforestry systems. In a two-block agroforestry design, N-15-labeled urea was applied to the crop-soil surface in agroforestry and monocrop plots. We analyzed the N-15, nitrogen, and carbon contents of the aboveground and belowground compartments of the trees, crops, and UVS, as well as that of the soil microbial biomass. No labelled N-15 was found in the trees, UVS and microbial biomass. Additionally, agroforestry-crop yielded a -20% lower yield compared to monocrop. The absence of N-15 uptake by trees was attributed to the tree age and rooting pattern, which resulted in the lack of tree roots in contact with the labelled fertilizer. The absence of labelled N-15 in the microbial biomass indicated a preference for pre-existing organic matter over newly generated N-15 from urea mineralization. The capacity of agroforestry systems on crop yield and potentially leachable nitrate may be influenced by the age of trees and prevailing environmental and management practices. Further investigations after several years of tree growth are necessary to better understand the long-term effects of tree age on crop yield and the nutrient retention capacity, including the response pattern of nitrogen-fixing trees.

Biologie du sol [074] ; Sciences du monde végétal [076] ; Biotechnologies [084]

Fonds IRD [F B010090765]

fdi:010090765