Assessment of the effects of cropland soil remediation strategies on the soil microbial community and tomato agrophysiology

Resum

Water and soil are two of the fundamental pillars of agriculture, so their correct management is essential for the development of sustainable agriculture. However, certain agricultural practices cause imbalances in the balance established by microbial communities in the soil and in the physiological state of crops. Some of these practices are related to the application of chemical compounds that can alter the metabolism of soil microorganisms in a general or specific way. The continuous and increasing use of these chemical compounds in soil has increased the concern about soil contamination. Some of the most recent remediation techniques used in recent years are solarization and ozonation. Solarization is a widely used technique in soil to eliminate or reduce pathogen content prior to cultivation. Ozonation, on the other hand, consists of the application of ozone in gas form on the soil. Both strategies are broad-spectrum techniques that are recently obtaining promising results in the reduction of contaminating compounds in soils. The objective of this Doctoral Thesis is to evaluate how different remediation strategies applied to the soil (solarization and ozonation) before and during the cultivation of Solanum lycopersicum L. can alter the chemical, biological and biochemical characteristics of the soil, as well as plant physiology, productivity and fruit quality. To reach this general objective, this PhD Thesis has been articulated in three chapters in which the effects of different remediation strategies on the soil and on the plant have been analyzed. The results obtained indicate that soil remediation strategies can alter the chemical, biological and biochemical characteristics of the soil. Specifically, the soil microbial community was affected by solarization (Chapter III), as it significantly reduced some of the enzymatic activities evaluated (β-glucosidase and alkaline phosphatase) and microbial biomass, especially fungal biomass. However, the joint application of solarization and ozonation (Chapter IV) did not intensify the effects of solarization. In addition, certain microbial populations with the ability to degrade pesticides showed increases in their relative abundance. Finally, the application of ozone in irrigation water (Chapter V), compared to the application of ozone gas on the soil, altered the physicochemical and biological properties of the soil to a lesser extent. Likewise, the diversity, structure and composition of microbial communities are practically unaffected. Finally, the continuous application of ozone in irrigation water significantly reduced stomatal conductance. Nevertheless, this treatment showed a tendency to increase fruit quality. Therefore, it can be concluded that soil remediation techniques can alter the physicochemical and biological properties of the soil, particularly affecting the soil microbial community. It is important to take into account the mode of application of these techniques, since the application of ozone in gas form in the soil affects the soil microbial community to a greater extent than ozone applied in irrigation water. Regarding the effects of ozone application in irrigation water during the cultivation of S. lycopersicum L., it should be noted that some agro-physiological parameters of the tomato plant were also slightly affected. However, the nutrient content did not suffer alterations due to the treatments evaluated. In addition, the quality of the fruits obtained with the continuous application of ozone in irrigation was slightly better than that of the other treatments