1 Effects of Phosphate-rock Mining Wastewater Fertigation on Chickpea (Cicer arietinum) Cultivation and Soil Microbial Diversity

Abstract

The conventional intensive use of chemical fertilizers poses significant threats to agro-ecosystem sustainability, leading to soil deterioration and environmental pollution. This study explores the potential of utilizing phosphate-rock mining wastewater (MWw) as a sustainable alternative for fertigation in chickpea cultivation. The investigation, conducted under both greenhouse and field conditions, evaluates the impact of raw and diluted MWw on chickpea growth, yield, and soil microbial diversity. In greenhouse experiments, chickpea plants subjected to MWw fertigation exhibited enhanced root and shoot growth, increased seed and pod production, and improved chlorophyll content. The inclusion of the Mesorhizobium mediterraneum strain "C11" further augmented these positive effects. Principal component analysis revealed a clear positive influence of MWw and inoculation on chickpea yield. Field trials conducted in a semi-arid region demonstrated that MWw fertigation significantly increased shoot dry weight, with variations observed between chickpea cultivars. Meta-genomic analysis of soil microbial communities indicated a substantial impact of fertigation on bacterial phyla composition, particularly an increase in Proteobacteria abundance. The induced and inhibited bacterial spectra highlighted the influence of MWw on specific bacterial families, including Rhodanobacteraceae and Dongiaceae. The MWw used in the study exhibited slightly alkaline pH and contained essential micronutrients. The study emphasizes the potential of MWw, combined with microbial inoculation, as a sustainable source of water and nutrients for chickpea cultivation. The positive effects on plant growth and soil microbial diversity suggest that MWw fertigation could contribute to more environmentally friendly agricultural practices. Overall, this research provides valuable insights into utilizing phosphate-rich wastewater for sustainable agriculture, particularly in regions facing water scarcity and environmental challenges.