Title : Effects of treated acid mine drainage (AMD) irrigation on the physiological parameters and biochemical performance of potato cultivars (Solanum tuberosum L.) and soil bacterial diversity
In water-stressed regions such as arid and semi-arid lands, the use of treated acid mine drainage (AMD) water for irrigated agriculture has been suggested as an alternative to address the shortage of fresh water sources. However, the short and long-term impact of using such (un)treated AMD water on crop physiology, and soil health, particularly the microbiome structure and functional capacity, is not known. In this study, we used a combination of physicochemical analyses, physiological parameters, high-throughput Illumina MiSeq 16S rDNA sequencing, and PICRUSt2 predictive functional profiling to characterize the influence of quicklime and fly ash-treated AMD irrigation water on physiological parameters, metabolome and soil bacterial microbiome structure, functions and network profile under greenhouse conditions. A randomized complete block design experiment was conducted with five water treatments levels replicated four times for each of the treatments namely TW1 to TW5. The results showed that the quicklime treatment increased the level of pH in the AMD water, reduced the concentration of electrical conductivity, NO3-, SO42- and ameliorate heavy metals. The treatments with high concentration levels of heavy metals were recorded on soil (ST2 and ST3), water (TW2 and TW3), and potato tubers (TT2 and TT2). However, unsafe levels of heavy metals above the maximum permissible WHO/ FAO levels for water (TW4 and TW5) reported were Pb, Mg and Mo, and As, Cd and Cr for soils (ST4 and ST5) respectively. For potato tuber (TT4 and TT5) for both Marykies and Royal the reported concentrations of As, Cd, Cr, and Pb were found to be above the maximum levels allowed. The irrigation treatments used exhibited that potato crop height, phenodays, chlorophyll content, stomatal conductance, number of tubers, fresh tuber weight, and dry tuber weight of the Marykies and Royal cultivars were improved when irrigated with quicklime treated AMD water. The bacterial domain comprises 46 phyla, 152 classes, 276 orders, 539 families, and 1189 genera. The dominant phyla were Proteobacteria (37.08% - 96.30%), Actinobacteria (0.64% - 20.21%), Firmicutes (0.90% - 58.80%), Bacteroidetes (0.27% - 13.94%), Acidobacteria (0.00% - 6.02%), and Chloroflexi (0.00% - 4.41%). Changes in bacterial diversity were also observed in the soil irrigated with treated AMD with Acidobacteria and Chloroflexi as the dominant phyla. Overall, these findings suggest that EC, pH, Cu, and Pb are important environmental variables that influence the structure and composition of the bacterial community in the soil. To further understand the interaction networks of the microbiome, the top 50 most abundant genera in each group were examined to explore the impact of (un)treated AMD water irrigation on soil microbial community assembly.