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<p>Introducing legumes into cropping systems holds significant potential to reduce reliance on nitrogen (N) fertilizers due to their ability to fix atmospheric N₂. In Réunion Island, intercropping the grain legume <i>Canavalia ensiformis</i> with sugarcane has been promoted primarily for weed control; however, its impact on sugarcane and soil N fertility remains underexplored. This study aims to assess whether, under the currently recommended management practices, the introduction of <i>C. ensiformis</i> effectively contributes to N enrichment of the sugarcane-soil system. Using a <sup>15</sup>N isotope tracing approach, we analyzed (i) the N accumulation by <i>C. ensiformis</i>, (ii) the sources of N uptake (biological fixation, fertilizer, soil), and (iii) the fate of N from <i>C. ensiformis</i> residues in the soil–plant system. Our results show that <i>C. ensiformis</i> accumulated an average of 38&#xa0;kg N ha<sup>−1</sup>, with 41% derived from biological N fixation, 16% from fertilizers, and 43% from soil. Around 24% was immobilized in sugarcane mulch during the first 5&#xa0;months of decomposition. Only 3% of sugarcane N originated directly from <i>C. ensiformis</i> residues. Nearly 40% of <i>C.ensiformis</i> <sup>15</sup>N was unrecovered within the mulch-soil–plant system after 1&#xa0;month of decomposition. The N balance remained nearly neutral, with 17&#xa0;kg N ha<sup>−1</sup> fixed and 15&#xa0;kg N ha<sup>−1</sup> lost over the cropping season. Therefore, while intercropping provided a modest contribution to soil fertility, significant N losses constrained its agronomic and environmental benefits. Future studies should focus on optimizing surface-mulched residue management to reduce N losses and enhance soil fertility while sustaining crop nutrition.</p>

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Sources and fate of nitrogen from legume in sugarcane intercropping system

  • 期刊论文

  • 发表日期：

    2025年10月31日

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  • Pauline Viaud,
  • Mathias Christina,
  • Krishna Naudin,
  • Antoine Versini

摘要

Introducing legumes into cropping systems holds significant potential to reduce reliance on nitrogen (N) fertilizers due to their ability to fix atmospheric N₂. In Réunion Island, intercropping the grain legume Canavalia ensiformis with sugarcane has been promoted primarily for weed control; however, its impact on sugarcane and soil N fertility remains underexplored. This study aims to assess whether, under the currently recommended management practices, the introduction of C. ensiformis effectively contributes to N enrichment of the sugarcane-soil system. Using a 15N isotope tracing approach, we analyzed (i) the N accumulation by C. ensiformis, (ii) the sources of N uptake (biological fixation, fertilizer, soil), and (iii) the fate of N from C. ensiformis residues in the soil–plant system. Our results show that C. ensiformis accumulated an average of 38 kg N ha−1, with 41% derived from biological N fixation, 16% from fertilizers, and 43% from soil. Around 24% was immobilized in sugarcane mulch during the first 5 months of decomposition. Only 3% of sugarcane N originated directly from C. ensiformis residues. Nearly 40% of C.ensiformis 15N was unrecovered within the mulch-soil–plant system after 1 month of decomposition. The N balance remained nearly neutral, with 17 kg N ha−1 fixed and 15 kg N ha−1 lost over the cropping season. Therefore, while intercropping provided a modest contribution to soil fertility, significant N losses constrained its agronomic and environmental benefits. Future studies should focus on optimizing surface-mulched residue management to reduce N losses and enhance soil fertility while sustaining crop nutrition.