11 Table 2: Taxonomic (trunk and order level) composition of the soil bacterial community between brackish water and brine. 21 Figure 4: Soil bacterial diversity measurements when not saline. irrigation with water and saline groundwater. a) Richness, (b) Shannon diversity index and (c) Pielous evenness index. 27 Figure 8: Thermal representation of the relative abundance of soil bacteria during irrigation with saline water and saline groundwater.
Introduction
- Overview
- Statement of the Problem
- Research Objective
- Relevant Literature
- Importance and adaptation of date palm plantation in
- Plant – Microbe interaction and their contribution in plant
Apart from salinity, the use of saline water also changes soil pH depending on cation (sodium, calcium and magnesium) and anionic (chloride and carbonate) composition (Guo et al., 2020). Similarly, salinity levels of irrigation water decreased (Chen et al., 2019) as well as increased Shannon diversity index (Chen et al., 2017) in arid agroecosystems. 5 while Actinobacteroidota (Guo et al., 2021) Chloroflexi, Acidobacteria and Planctomycetes are reduced in saline soils (Li et al., 2021).
While saline groundwater irrigation reduced the abundance of Actinobacteria, Gemmatimonadetes and Acidobacteria in cotton field soil (Chen et al., 2019). Another study with irrigation water sources with different salinities showed an increase (Proteobacteria and Actinobacteria) and a decrease (Planctomycetes and Bacteroidetes) of certain taxa in cotton field soil (Chen et al., 2017). It is estimated that about 62 million hectares (20%) of the world's flooded land is adversely affected by salinity (Egamberdieva et al., 2019).
Plant-associated microbiomes provide the plant with preferences for well-being, including developmental progress, uptake, stress resilience, and defense against microorganisms (Trivedi et al., 2020). In addition, they improve the well-being and performance of plants under different pressure conditions (Kumar et al., 2020).
Methods
- Study site description and sample collection
- Soil and water chemistry analyses
- Soil DNA isolation and Illumina sequencing
- Statistical analyses
Soil samples were collected from two different types of irrigation water sources, namely non-saline fresh water (hereafter referred to as desalinated water) and saline groundwater. Raw sequencing reads were analyzed using the R package with the Divisive Amplicon 2 denoising algorithm (DADA2_v1.12) (Callahan et al., 2016). Prior to alpha and beta diversity analyses, the OTU table was normalized to the sample with the smallest number of sequences (1770) using the rrarefy function of the vegan R package (Oksanen et al., 2020).
Analyzes of variance (ANOVA) test followed by Tukey's HSD post-hoc test were performed using the agricolae package to test the differences in soil chemistry. pH, EC and OM), water chemistry (pH and EC) and bacterial diversity (bacterial richness, Shannon diversity index and evenness) between irrigation water sources (non-saline water and saline groundwater irrigation). The indicator species analysis was performed using the multiplatt function of the indicspecies R package and indVal (>0.5) with P<0.05 was obtained for the prediction of indicator species in soil during non-saline irrigation water and saline groundwater. To understand the effect of environmental variables on bacterial community structure patterns between irrigation water sources (non-saline water and saline groundwater irrigation), two-dimensional non-metric multidimensional scaling (NMDS) analyzes based on Bray-Curtis differences were performed using the metaMDS- function. of a vegan package (Oksanen et al., 2020).
The vectors respectively for environmental factors (P<0.05) and centroids representing irrigation water sources (non-saline vs saline groundwater irrigation) were fitted to the NMDS ordination plot using envfit function and 95% confidence intervals (CI) of the plots which was generated using ordinal ellipse function from vegan package (Oksanen et al., 2020). To test the differences between bacterial communities of irrigation water sources, permutation analysis of variance (PERMANOVA) was performed using adonis function from vegan package (Oksanen et al., 2020), in which pseudo-F-statistics were performed by 9999 calculate permutations. of inequality matrices.
Results
- Soil and water chemistry analyses
- Sequence data statistics
- Irrigation water influence on soil bacterial diversity and
- Irrigation water effect on soil bacterial composition
Water chemistry (EC and pH) and soil OM were significantly different between irrigation water sources (non-saline vs saline groundwater irrigation) (P<0.05) (Figure 3a & b). Soil bacterial diversity (richness, Shannon diversity index and evenness) parameters were not significantly different, while non-saline water and saline soil water irrigation (Figure 4). 23 Figure 4: The bacterial diversity metrics of soil while non-saline water and saline soil water irrigation. a) Wealth, (b) Shannon Diversity Index and (c) Peaceful Equality Index.
The dilution curves of soil bacteria did not reach a plateau for either type of soil sample during irrigation of non-saline water and saline groundwater (Figure 5a). Soil bacterial communities were significantly different between irrigation water sources (non-saline versus saline groundwater irrigation) based on multivariate (PERMANOVA and NMDS ordering) analyses. Thermombiotics and Rokubacteriales as top taxa in different amounts, while non-saline water and saline groundwater irrigation occur (Figure 7b and Table 2).
Prevalence (%) calculated from total of 35 samples; # Prevalence (%) calculated from total of 19 non-salt samples; $ Prevalence (%) calculated from total of 16 salt samples]. 29 Table 2: Taxonomic (phylum and order level) composition of the soil bacterial community during non-saline and saline soil water irrigation (Continued). Bacillus, Pedomicrobium and Gaiella were the top genera in soil samples while both types of irrigation water sources (non-saline water and saline groundwater irrigation) (Figure 7c & Table 3).
Microvirga, Ammoniphilus, Nitrospira and Lysinibacillus were highly abundant in soil under non-saline groundwater irrigation (Figure 7c and Table 3).
Discussion
Soil and water chemistry changes between irrigation sources
Water chemistry (EC and pH) and soil organic matter (SOM) were significantly different between irrigation water sources. A higher EC of saline groundwater can be attributed to increased sodium and chloride concentrations in groundwater used for irrigation, as previous studies reported sodium and chloride as the major ions of saline groundwater (Egamberdieva et al., 2010; Khan et al., 2019 ). Although the pH values of the irrigation water samples used in this study were neutral to slightly alkaline, a previous study from a nearby region reported an acidic to neutral pH for saline groundwater (Khan et al., 2019).
The reason for the slightly alkaline properties of irrigation water samples may be due to the interaction of water with soil and the potential release of calcium from dissolving lime during irrigation. Soil OM in agricultural land consists of both partially and fully decomposed organic material from litter (leaf and root). In this study, soil size was significantly lower with saline water irrigation compared to non-saline water irrigation.
This finding is similar to a previous study, which showed a decrease in soil organic carbon with increasing soil salinity (Wong et al., 2008). The percolation of saline water through soil layers would reduce aggregate formation in the soil, resulting in loss of soil organic carbon (Ju et al., 2019; Trivedi et al., 2017; Yu et al., 2021).
Soil does not alter bacterial diversity but unique OTUs
Our results showed that soil bacterial communities were indeed structured according to irrigation water sources (non-saline water and saline groundwater irrigation) into distinct clusters and irrigation water EC (salinity) was the main structuring factor. Our results are consistent with previous studies on natural saline soils (Guo et al., 2021; Li et al., 2021; Nan et al., 2022) and soil while irrigating saline groundwater (Chen et al., 2017; Chen et al., 2019). However, studies focused on the source of irrigation water (secondary salinity) covered only a narrow range of salinities dS m-1) from a single site. Surprisingly, a study in soil from a spinach field showed no effect on bacterial communities in the salinity range of 0.85-15 dS m-1 (Mark et al., 2017).
Consistent structuring of the bacterial community according to irrigation water sources (non-saline water and saline groundwater) as found despite the coverage of multiple geographic locations and a wide range of salinity (ds m-1), resulting from non-uniformity in bacterial communities due to spatial variability. Soils are proposed to temporarily select bacterial communities through a deterministic process of 'salinity filtering', whereby sol–. In addition, soil samples from saline groundwater irrigation were heterogeneously clustered compared to soil, whereas saline irrigation showed greater variation in soil sample bacterial communities during saline groundwater irrigation than saline irrigation, possibly selecting a subgroup bacterial communities between soils, while irrigation with saline groundwater.
Taxa compositional variations according to irrigation sources
Proteobacteria consist of rapidly proliferating bacteria capable of growing under extreme temperature and nutrient-limited conditions (Chen et al., 2019; Zhang et al., 2019). At the genus level, saline irrigation enriched Microvirga, a free-living nitrogen fixer belonging to Alphaproteobacteria isolated previously from desert soil (Amin et al., 2016), indicating their role in the nitrogen cycle. Mycobacterium, an indicator taxon for saline irrigation in this study, was previously isolated from the rhizosphere of plants known to be actively involved in plant growth promotion (Karmakar et al., 2021) and also able to withstand salinity stress (Asmar et al. , 2016).
Genus abundance of subgroup_10 (Acidobacteriota) increased in soil under saline irrigation, whose members were reported to accumulate starch indicating its potential role as an osmoprotectant against salt stress (Kristensen et al., 2021). Irrigation with non-saline water increased Actinobacteria phylum, which has shown sensitivity to salinity in a previous study (Li et al., 2021). Bacillus is known to produce endospores under hot and saline conditions, secrete EPS, form biofilm and improve soil compaction (Marvasi et al., 2010).
The other Bacillales members (Bacillus, Lysinibacillus, Domibacillus, Oceanibacillus) detected in this study are also known to play a similar role (Marvasi et al., 2010). Plant growth promoting rhizobacteria (PGPR) members detected while non-saline water (Bacillus, Lysinibacillus, Domibacillus, Oceanibacillus and Marmoricola) and saline groundwater (Novibacillus) (Mandic-Mulec et al., 2015; Martínez et al., 2018; Mukhtar et al., 2018; al., 2021) irrigation indicates that soil can serve as a base for bacterial recruitment in the rhizosphere of date palms.
Conclusion
I showed that soil selectively allows colonization of specific sets of bacterial communities between irrigation water sources (non-saline water vs saline water) at wider geographical distribution and salinity intervals due to In summary, the results of this study show that soil selects for specific bacterial taxa and communities under different irrigation water sources ( non-saline water and saline water) in the soil, which is essential for sustainable land use, crop production and rehabilitation. Shifts in soil microbial metabolic activities and community structures along an irrigation water salinity gradient in a typical arid region of China.
Identification of key taxonomic categories characterizing microbial community diversity using comprehensive classification: a case study of microbial communities in Hangzhou Bay sediments. Long-term saline irrigation reduces soil nutrients, bacterial community diversity, and cotton yield in a gray desert soil in China. Soil salinity and pH influence soil bacterial community composition and diversity along a laterite slope at the Avon River Critical Zone Observatory, Western Australia.
Short communication Proline accumulation is a general response to abiotic stress in date palm (Phoenix dactylifera L.). Effect of saline drip irrigation water on microbial diversity and fertility of Aeolian sandy soils.
