Does intercropping of legumes with oilseeds modify mycorrhizal colonisation?

Abstract

Abstract Background and Aims Legume-oilseed intercrops are increasingly grown in mechanised agricultural systems for their improved nutrient use efficiency. However, the mechanisms that underpin this advantage are not well known. This study aimed to investigate the effect of intercropping and species mixture on the arbuscular mycorrhizal fungi (AMF) colonisation of oilseed and legume crops, and subsequent effects on crop phosphorus nutrition. Methods We sampled legume-oilseed intercrops in field experiments and measured the level of AMF root colonisation and shoot phosphorus. Additionally, we grew legume-oilseed intercrops in the glasshouse using AMF-inoculated ( Rhizophagus irregularis ) and mock-inoculated treatments. Measurements included mycorrhizal colonisation, root and shoot biomass, and shoot phosphorus. Results Mycorrhizal colonisation and the subsequent effect on phosphorus nutrition was host plant dependent. Lentil was the most mycorrhizal plant, followed by linseed, chickpea, and then canola. Only in lentil in the glasshouse was there a correlation between mycorrhizal colonisation and shoot phosphorus (R = 0.79, p<0.001). Intercropping reduced mycorrhizal colonisation of lentil in the glasshouse but not in the field; intercropping did not affect AMF colonisation in any other species. The interaction between intercropping and AMF had a limited effect on crop growth and shoot phosphorus, while intercropping alone increased canola shoot phosphorus. Conclusion The role of AMF in the growth and phosphorus nutrition of legume-oilseed intercropping systems appears host specific, and lacks a “one size fits all” solution. Research should be directed towards host plant-AMF specificity, and field studies using diverse soil P profiles.