Codesigning biodiversity-based agrosystems promotes alternatives to mycorrhizal inoculants

Abstract

Facing the challenge of the ecological transition of agriculture, biodiversity opens new avenues to enhance ecological interactions and reduce chemical input dependency. Designing biodiversity-based agrosystems requires an agroecological approach that combines key principles: exploring a wide range of concepts and solutions, adopting systemic reasoning, implementing a sitespecific approach, developing an action-oriented process, and maintaining a continuous improvement dynamic. This type of approach has never been developed to harness mycorrhizal fungi, which are key components of soil biodiversity, because their beneficial action on crops depends on complex and underexploited ecological interactions. At present, mycorrhizae are mainly used through industrial inoculants that fit within the productionist paradigm. To shift toward agroecological approaches, we implemented a methodological framework conceived to better address the design of mycorrhiza-friendly cropping systems by sharing knowledge with farmers in four different study areas (Provence, French Guiana, Guadeloupe, and Martinique). This framework includes participative workshops, a board game, and prospective exercises to collect farmers' proposals and the factors that prevent from implementing mycorrhiza-friendly cropping systems. We showed that 90% of the farmers proposed alternatives to industrial inoculants, 50% of them adopted systemic reasoning by combining these alternative proposals. Most farmers understood that they were all potential "mycorrhizae producers". We showed, for the first time through on-farm experiments that valorization of indigenous mycorrhizal fungi strains using a donor plant is an effective practice to increase root colonization before planting (up to a frequency of 95% and an intensity of 32%). Considering the increasing supply of mycorrhizal inoculants and despite the uncertainty of related knowledge, we codesigned innovative practices. Learning communities (technical advisors, high school teachers, etc.) assumed responsibility for continuous improvement in knowledge and practices. Finally, beyond the issue of mycorrhizae, we showed that an agroecological approach could bring stakeholders one step further into the design of biodiversity-based agrosystems.

Does Commercial Inoculation Promote Arbuscular Mycorrhizal Fungi Invasion?

“…In undisturbed soil, i.e., no-till cropping, cover crops or crop rotation could benefit succeeding main crops by supplying AMF communities [47,52,53]. Thus, designing a mycorrhizafriendly cropping system using a diverse rotational sequence, utilizing cover crops, and adopting no-till agriculture [57] and an agroecological approach, such as a donor crop, where the donor crop is intercropped with the target crop, could help harness the functional diversity of indigenous AMF communities [58]. Moreover, inoculation via donor crop is a more convenient and effective inoculation approach in large-field or woody crops where inoculation could be labor intensive or technically difficult [36].…”

Flint maize root mycorrhization and organic acid exudates under phosphorus deficiency: Trends in breeding lines and doubled haploid lines from landraces

“…Although conventional agricultural management can exert adverse effects on AM fungal communities ( Helgason et al, 1998; Oehl et al, 2003), a high diversity of AMF can still be found in agricultural fields ( Hijri et al., 2006; Sasvári and Posta , 2010). Thus, the use of the native AMF community to enhance mycorrhizal benefit for crops might be an alternative to the inoculation of non‐native mycorrhizal strains ( Chave et al, 2019). However, a better understanding of the effects of the native AMF community on the performance of the various crop species and crop varieties under field conditions is necessary.…”

Field performance of different maize varieties in growth cores at natural and reduced mycorrhizal colonization: yield gains and possible fertilizer savings in relation to phosphorus application

“…Although conventional agricultural management can exert adverse effects on AM fungal communities (Helgason et al 1998;Oehl et al 2003), high diversity of AMF can still be found in agricultural fields (Hijri et al 2006;Sasvari et al 2011). Thus, using the native AMF community to enhance mycorrhizal benefit for crops could be an alternative besides inoculating non-native mycorrhizal strains (Chave et al 2019). But it is a prerequisite to understand how the native AMF community affects the performance of different crop species and varieties under field conditions.…”