Soil turnover of crop residues from the banana (Musa AAA cv. Petite-Naine) mother plant and simultaneous uptake by the daughter plant of released nitrogen
Résumé
Banana (Musa sp.) residues contain two thirds of the plant nitrogen (N) content at harvest which may represent a large N source for the daughter plant and contribute to reducing fertilizer rates. Our aim was to assess the decomposition kinetics of above- and below-ground banana residues, and to determine the uptake of the released N by the daughter plant. Residue decomposition was analyzed under laboratory and field conditions, and plant N uptake was evaluated in the field using 15N-labelled above-ground residues. The decomposition kinetics was interpreted with a simulation model. In the laboratory, residue decomposition showed an immobilization phase followed by remineralization. The immobilization phase was longer and remineralization was smaller for roots due to their higher C:N ratio and lignin content. The model satisfactorily described both phases and the effect of the residue C:N ratio. Experimental and model results indicated that root residues would be a minor N source for the daughter plant. In the field, above-ground residues decomposed according to first order kinetics. Residue half-life was 2 d in the laboratory and 32 d in the field, which was due to poorer soil–residue contact in the field. At the time of harvest of the daughter plant, 39% of residue N was recovered in the plant, 54% in the topsoil, and 3% in the remaining residues. About 4% of residue N was probably lost by leaching. Nitrogen derived from residues represented 19% (14 kg N ha−1) of N in bunches of the daughter plant and 18% (39 kg ha−1) of the whole plant N. Our study showed that above-ground residue N was an effective N source for the daughter plant, with a good overlap between the period of N release and that of greatest plant demand which reduced the risk of N leaching.