Irrigation water salinity structures the bacterial communities of date palm (Phoenix dactylifera)-associated bulk soil

Abstract

The irrigation of date palms (Phoenix dactylifera) with saline groundwater is routinely practiced in the agroecosystems of arid environments because of freshwater scarcity. This leads to salts deposition in topsoil layers and increases soil salinization. However, how different irrigation sources affect soil microbiota is poorly understood. Bulk soil samples were collected from date farms receiving non-saline water and saline groundwater to examine bacterial communities using metabarcoding. Overall, bacterial diversity measures (Shannon diversity index, richness, and evenness) did not vary between irrigation sources. Bacterial communities were structured based on irrigation water sources and were significantly associated with their electrical conductivity. Of 5,155 operational taxonomic units (OTUs), 21.3% were unique to soil irrigated with saline groundwater, 31.5% received non-saline water irrigation, and 47.2% were shared. The Proteobacteria abundance was higher in soil under saline groundwater irrigation while Actinobacteriota abundance was lower. A compositional shift at the genera level was also evident; the abundance of Subgroup_10 and Mycobacterium was higher under saline groundwater irrigation. Mycobacterium was a key indicator of OTU under saline groundwater irrigation while Solirubrobacter was an indicator of non-saline water irrigation. Functional gene analyses showed enrichment of fatty acid, cell wall, and starch biosynthesis pathways in soil under saline groundwater irrigation. These findings provide insights into how “salinity filtering” influences bacterial communities, key taxa, and the potential metabolic function in soil under increasing irrigation water salinities, and have broad implications for arid agroecosystems.

Cover cropping reduces the negative effect of salinity on soil microbiomes

“…Furthermore, members of Thermomicrobiales have been known to be responsible for stress‐tolerance in the plant rhizosphere at sites with lower water activity (Shen et al, 2022). Thermomicrobiales is a prominently abundant oligotrophic order in saline and nonsaline groundwater irrigation in oasis ecosystems of UAE (Loganathachetti et al, 2022). The possible role of Chloroflexi in salinity tolerance is underscored by the fact that it forms a prominent cluster in all salinity‐stressed conditions (SS + CC, SS + NC and NS + NC‐which has low‐salinity levels but does not have the cushioning effect of cover crops).…”

Water pH, not soil pH, alters bacterial community structural pattern and nitrogen cycling pathways in date palm (Phoenix dactylifera L.) roots and bulk soil under freshwater irrigation regime

“…In addition, we have also collected irrigation water samples from each site for chemical analyses (pH and EC). Detailed information regarding the chemical analysis (water and soil) has been provided in previous studies (Loganathachetti et al, 2022;Shamim et al, 2022) and briefly included in Table S1. The irrigation water pH (6.96-7.99) and EC (0.32-3.22 dS.m −1 ) of the freshwater varied widely between the sampling sites.…”

Long-term saline water irrigation affected soil carbon and nitrogen cycling functional profiles in the cotton field

“…Previous studies have indicated a strongly correlation between soil microbial functional genes and taxa abundance with soil environmental factors ( Cui et al, 2016 ; Guo et al, 2023 ; Xiang et al, 2023 ). Loganathachetti et al (2022) proposed that soil salinity was an important determinant of bacterial richness and shannon diversity index. Shen et al (2016) discovered that the bacterial taxonomic diversity/structure was strongly influenced by soil pH.…”