Microbial ecology in sustainable fruit growing: genetic, functional and metabolic responses

Soil microorganisms play a key role in several functions of orchards, such as soil organic matter decomposition and control of its cycle, regulation of mineral nutrient availability, atmospheric nitrogen fixation, formation of mycorrhiza, production of substances able to stimulate plant growth, etc. Well-structured, biodiverse and biologically-active soil microbial communities ameliorate soil physical and chemical conditions and, consequently, soil habitability for fruit trees. Particularly, sustainable, conservative, high-C input soil practices, such as minimum tillage, and endogenous organic matter inputs from spontaneous cover crops and pruning material increase the genetic, functional and metabolic soil microbial biodiversity. This, in turn, make fruit orchards more resilient to natural and anthropogenic stressors. On the contrary, an intensive agricultural management of agro-ecosystems, with a massive input of fertilizers and pesticides and not-well planned irrigation, causes decreases in soil quality and fertility, both in terms of physico-chemical and microbiological properties. Especially under semi-arid climates, a sustainable soil management aimed at increasing soil organic carbon and microbiological fertility, is of key importance. In this chapter, we present a survey on the researches carried out in several experimental fruit groves in the last two decades by our research group. We here discuss the changes in the structure, dynamics and complexity of soil microbial communities and their relationships with soil health status and soil fertility.