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<p>Plant diversity is reported to increase the diversity and activity of belowground organisms. Sowing pigeon pea (<i>Cajanus cajan</i> (CC), Fabaceae), a woody legume, into fallow land invaded by mycotrophic siam weed (<i>Chromolaena odorata</i> (CO), Asteraceae), may thus boost soil biology and fertility. To test this prediction, we assessed in an on-farm survey whether root colonization by arbuscular mycorrhizal fungi (AMF) and P availability were higher in bi-species fallow fields with siam weed and pigeon pea (COCC) than in the two single-species fallow fields, in the second year of fallow. The study was conducted in central Côte d’Ivoire and considered four sites with three types of fallow field, each, namely fallows (i) spontaneously invaded by siam weed (CO), (ii) sown to pigeon pea (CC) and kept free from weeds, and (iii) invaded by siam weed, but additionally sown at a quarter strength to the normal seed density to pigeon pea (COCC). Soil and root samples were collected from 0 to 20&#xa0;cm soil depth for chemical analyses and determination of root colonization intensity (rCI) and AMF taxon richness in soil by 18S ribosomal DNA metabarcoding. In the bi-species fallow fields, rCI was assessed in both siam weed and pigeon pea to compare the observed and expected rCI in an effort to detect mixture advantages, namely greater than expected rCI. The fallow types COCC and CO both hosted 28 AMF virtual taxa, while the fallow CC hosted 30. The AMF community composition in the bi-species fallow fields was close to that of the CO single-species fallow fields (Complementarity index C: 13.3%) and somewhat distinct from that of the CC single-species fields (<i>C</i> = 34.3%). The Shannon–Weaver diversity was similar across all types of fallow field. However, rCI in the bi-species fallow was ⁓ 20% higher than expected, suggesting that the AMF infection potential was boosted by the bi-species mixture. Soil pH and available soil P were also higher in COCC (6.5 and 71&#xa0;mg&#xa0;kg<sup>−1</sup>) than CO (6.4 and 61.2&#xa0;mg&#xa0;kg<sup>−1</sup>) and CC (6.1 and 59.1&#xa0;mg&#xa0;kg<sup>−1</sup>). Therefore, sowing the legume shrub, pigeon pea, into siam weed-invaded fallow land has the potential to promote the P uptake by mycotrophic staple crops, such as yam or cassava, in the sub-humid pre-forest areas of West Africa.</p>

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A biological basis for sustainable agriculture in West Africa: enhancing mycorrhiza formation and nutrient availability by seeding pigeon pea (Cajanus cajan, Fabaceae) on siam weed (Chromolaena odorata, Asteraceae)-invaded fallow fields

  • 期刊论文

  • 发表日期：

    2026年6月2日

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  • Guy-Pacome T. Touré,
  • Armand W. Koné,
  • Jacob Nandjui,
  • Anicet E. T. Ebou

摘要

Plant diversity is reported to increase the diversity and activity of belowground organisms. Sowing pigeon pea (Cajanus cajan (CC), Fabaceae), a woody legume, into fallow land invaded by mycotrophic siam weed (Chromolaena odorata (CO), Asteraceae), may thus boost soil biology and fertility. To test this prediction, we assessed in an on-farm survey whether root colonization by arbuscular mycorrhizal fungi (AMF) and P availability were higher in bi-species fallow fields with siam weed and pigeon pea (COCC) than in the two single-species fallow fields, in the second year of fallow. The study was conducted in central Côte d’Ivoire and considered four sites with three types of fallow field, each, namely fallows (i) spontaneously invaded by siam weed (CO), (ii) sown to pigeon pea (CC) and kept free from weeds, and (iii) invaded by siam weed, but additionally sown at a quarter strength to the normal seed density to pigeon pea (COCC). Soil and root samples were collected from 0 to 20 cm soil depth for chemical analyses and determination of root colonization intensity (rCI) and AMF taxon richness in soil by 18S ribosomal DNA metabarcoding. In the bi-species fallow fields, rCI was assessed in both siam weed and pigeon pea to compare the observed and expected rCI in an effort to detect mixture advantages, namely greater than expected rCI. The fallow types COCC and CO both hosted 28 AMF virtual taxa, while the fallow CC hosted 30. The AMF community composition in the bi-species fallow fields was close to that of the CO single-species fallow fields (Complementarity index C: 13.3%) and somewhat distinct from that of the CC single-species fields (C = 34.3%). The Shannon–Weaver diversity was similar across all types of fallow field. However, rCI in the bi-species fallow was ⁓ 20% higher than expected, suggesting that the AMF infection potential was boosted by the bi-species mixture. Soil pH and available soil P were also higher in COCC (6.5 and 71 mg kg−1) than CO (6.4 and 61.2 mg kg−1) and CC (6.1 and 59.1 mg kg−1). Therefore, sowing the legume shrub, pigeon pea, into siam weed-invaded fallow land has the potential to promote the P uptake by mycotrophic staple crops, such as yam or cassava, in the sub-humid pre-forest areas of West Africa.