Intercropping is a sustainable agroecological tool known to provide multiple benefits to farmers. Several studies have shown that arbuscular mycorrhizal fungi (AMF) play a key role for the improved grain yields in intercropping systems through facilitative nutrient and water uptake via the common mycorrhizal network (CMN), yet little is known on the rate of hyphal spread. Here we hypothesized that AMF species differ in the rate of extraradical hyphae to spread from one plant to another, thereby affecting the growth of the intercropped plants. To test our hypothesis, we established experimental microcosms in the greenhouse, in which one pigeon pea (Cajanus cajan) and two finger millet (Eleusine coracana) plantlets were kept in separate pots, connected by soil bridges of 5 or 12 cm length, inaccessible to roots but accessible to fungal hyphae. The pigeon pea plants were pre-inoculated with Claroideoglomus etunicatum, Rhizophagus fasciculatus or Rhizophagus irregularis. All three AMF species led to a strong growth promotion compared to uninoculated control of the short microcosms and more than doubled the biomass of pigeon pea. The biomass as well the phosphorus content of finger millets connected by AMF to the pigeon pea differed with the length of the soil bridge and the species of AMF. By applying ¹⁵N isotopes to the soil of pigeon pea pots we revealed that in both lengths of the microcosms R. fasciculatus and C. etunicatum transported nitrogen from pigeon pea to finger millet across distances of up to 12 cm but R. irregularis did not. Furthermore, by destructive sampling, we estimated a hyphal spread of 4.1 mm d⁻¹ by C. etunicatum across a 12 cm soil bridge. We conclude that the row distance between the crops and the choice of AMF species play a crucial role for the application of AMF as biofertilizer.

间作是一种可持续的农业生态工具，已知可为农民提供多种利益。多项研究表明，丛枝菌根真菌 (AMF) 通过共同菌根网络 (CMN) 促进养分和水分吸收，在间作系统中提高谷物产量方面发挥关键作用，但对菌丝传播的速度知之甚少。在这里，我们假设 AMF 物种的根外菌丝从一种植物传播到另一种植物的速度不同，从而影响间作植物的生长。为了验证我们的假设，我们在温室中建立了实验缩影，其中一只木豆 ( Cajanus cajan ) 和两只手指小米 ( Eleusine coracana) 小植物被保存在单独的盆中，由 5 或 12 厘米长的土桥连接，根无法进入但真菌菌丝可以进入。将木豆植株预先接种有黑穗病菌( Claroideoglomus etunicatum)、Rhizophagus fasciculatus或Rhizophagusinformalis。与未接种的短缩微世界相比，所有三种 AMF 物种都导致了强烈的生长促进，并使木豆的生物量增加了一倍以上。AMF与木豆连接的指黍的生物量和磷含量随土桥长度和AMF种类的不同而不同。通过将¹⁵ N 同位素应用到木豆盆的土壤中，我们发现在微观世界R 的两个长度中。束状和C . etunicatum将氮从木豆运输到指小米，距离可达 12 厘米，但R . 不规则的人没有。此外，通过破坏性取样，我们估计4.1毫米d的菌丝蔓延^-1通过Ç。etunicatum跨越 12 厘米的土桥。我们得出结论，作物之间的行距和 AMF 物种的选择对于 AMF 作为生物肥料的应用起着至关重要的作用。