Nitrogen release from eucalypt leaves and legume residues as influenced by their biochemical quality and degree of contact with soil

Corbeels Marc, O'Connell Anthony M., Grove Tim S., Mendham Daniel S., Rance S.J.. 2003. Nitrogen release from eucalypt leaves and legume residues as influenced by their biochemical quality and degree of contact with soil. Plant and Soil, 250 : 15-28.

https://doi.org/10.1023/A:1022899212115

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Résumé : Large areas of short-rotation eucalypt plantations are being established in south-western Australia on land previously used for agriculture. Options for maintaining soil N supply include retention of harvest residues and legume inter-cropping. We evaluated the effects of adding the residues of five legume species and Eucalyptus globulus leaves on inorganic N dynamics in two soils (a Rhodic Ferralsol or red earth and a Haplic Podzol or grey sand) using two modes of residue application in a laboratory incubation experiment (519 days). The time course of net N immobilisation and mineralisation in both soils was strongly influenced by the type and mode of application. Eucalypt leaves caused strong N immobilisation (-7 mg N g-1 residue-C) over the entire 519-day incubation, whereas for the legume species, N that was eventually immobilised at the start of the incubation, remineralised later to different degrees. Amongst the legumes, largest amounts of N were released from lupin residues (18 mg N g-1 residue-C) and lowest amounts from field pea (2 mg N g-1 residue-C). However, initial residue quality parameters were not significantly (P > 0.05) correlated with N release from the residues. Grinding and incorporating of the residues caused a much greater immobilisation of N than when residues were cut and surface applied. When ground residues were incorporated, immobilisation of N was more severe and endured for longer in the finer textured red earth than in the coarse textured grey sand. Where residues were surface applied, N dynamics were similar for both soil types. The results of this study suggest that legumes used as a mulch in eucalypt plantations are a readily available source of N for trees, and that the benefits from retention of harvest residues are more likely in maintaining soil N fertility on the long-term.

Mots-clés Agrovoc : légumineuse, Vicia faba, Pisum sativum, Vicia sativa, Lupinus albus, Lathyrus ochrus, mulch vivant, feuille, Eucalyptus globulus, dégradation, amendement organique, résidu, composition chimique, azote