Mycorrhizas in South American Anthropic Environments

The agricultural expansion has leaded to increase the irrigated cropland area and the use of fertilizers, resulting in water degradation, increased energy use, and common pollution. Of particular concern is the increased interest to reduce the environmental impacts of high quantities of water dedicated to irrigation by agricultural activities We are now truly recognizing the importance of sustainable measures in agriculture such as conservation of the vegetation cover and management approach to understand surface and deep soil responses to global change. The agroecology management based on key processes from natural ecosystems can help to solve some agricultural difficulties. Increasing studies on the Arbuscular mycorrhizal fungi (AMF) has showed their importance for soil ecology and studies on their biodiversity have spread in some agro-ecosystems such as corn and soybean monocultures. Therefore, it is needed to deeply study the mycorrhizal functions under global change. In this chapter, we examine the major developments and advances on mycorrhizal fungi based on recent research from South American countries. New reports on the occurrence of mycorrhizas in Amazonian dark earth, as well as the inoculum production of arbuscular mycorrhizal fungi native of soils under native forest covers, have resulted in a more detailed understanding of the soil biology from South America. Reports from Amazonian dark earth or “Terra preta do índio” soil has stimulated the use of biochar worldwide as a soil conditioner that can add value to non-harvested agricultural products and promote plant growth. Few reports from Brazil showed that the addition of inorganic fertilizer, compost and chicken manure resulted in increases in plant cover and plant species richness. In this sense, the biochar/mycorrhizae interactions also can be prioritized for sequestration of carbon in soils to contribute to climate change mitigation

Root–soil–microbe interactions mediating nutrient fluxes in the rhizosphere

Plant roots have both direct and indirect effects on nutrient availabilities and fluxes in rhizosphere soil. Direct effects include impacts that are a consequence of root growth, water/nutrient uptake and secretion of compounds that promote solubility of poorly available elements such as phosphorus and iron. Indirect effects are largely a consequence of plant–microbe interactions, mediated by the release of organic compounds from roots that both shape rhizosphere microbial community structure and promote microbial nutrient cycling activity. In recent years, significant advances have been made in the quantification of root-mediated impacts on soil biogeochemical processes, demonstrating the importance of these interactions for nutrient cycling to support plant productivity and as a critical control point for the response of soils to environmental change. This is now supplemented with an appreciation that there is a strong element of regulation, both plant and microbial, in how the underlying interactions are established and maintained. This raises the exciting possibility that management of root–microbiota interactions could be a realistic means of improving plant health and productivity, while potentially also mitigating environmental impacts. This chapter discusses progress in quantifying root impacts on soil processes and parallel advances in characterising the specificity of the plant-driven selection of associated microbiota. A clear opportunity for future research is to combine these approaches, functional -omics technologies and bioinformatics to guide next-generation crop breeding that targets both the plant and its associated microbiota (i.e. the holobiont), for productivity and resilience in sustainable agricultural systems