Bacterial community structural analysis of saline and sodic water irrigated soils and its effect on wheat growth
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Date
2014
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CCSHAU
Abstract
The problem of the salinity or sodicity existed long before the start of agricultural practices. It has now become a very serious problem for crop production, particularly in arid and semi-arid regions, which constitute about one third of the world’s land surface. Irrigation water always includes some amount of dissolved substances, collectively called salts. Due to inadequate and unassured supplies of good quality water in many arid and semi-arid regions of the world, farmers use saline or sodic ground water for irrigation of crops. Long-term and indiscriminate use of such water causes accumulation of salts, particularly Na, which not only adversely affects the physical and chemical properties of soil, but also modifies the quality of soil organic carbon and its biotic components. Saline water is categorized as water with an EC > 4.00 deciSiemens / meter (dS/m) while sodic water is categorized as water with an RSC > 2.5me/l. The effects of salinity or sodicity on soil chemical and physical properties are well known and their effects on the soil microbial community and microbiological processes remain relatively unstudied. Thus keeping in view the above facts, a total of 15 saline water irrigated rhizospheric soil along
with their respective water samples were collected from Hisar, Jind, Sirsa and Rewari districts. The pH
and ECiw of these water samples varied from 6.00 - 8.20 and 2.48 - 17.14 dS/m respectively. Their
respective soil samples were analyzed for pH, ECe, organic C, total N and total P, which varied from 6.04
- 8.10, 4.10 - 21.00 dS/m, 0.13 - 0.45%, 0.012 - 0.044 % and 587 - 703 mg P/kg soil, respectively.
Similarly, a total of 20 sodic water irrigated rhizospheric soil and their respective water samples were
also collected from Hisar, Mahendergarh, Karnal and Kaithal districts. The water samples were analyzed
for the RSC, pH and ECiw, which was above 2.50 me/l, 8.50 - 10.90 and 1.01 - 1.50 dS/m, respectively.
The pH, ECe, organic C, total N and total P of soil samples ranged from 8.30 - 10.50, 1.00 - 2.40 dS/m,
0.09 - 0.46%, 0.002 - 0.040% and 625 - 701 mg P/kg soil, respectively. The viable counts of bacteria for
the above soil samples collected from saline and sodic soils were taken on Jensen’s, malate, Pikovaskaya,
King’s B media and soil extract agar. It was observed that with the increase in EC, there was decrease in
viable counts. A total of 215 morphotypes were obtained from the above 35 different soil samples, out of
which 91 and 124 morphotypes belonged to saline and sodic soils, respectively. Most of these
morphotypes were identified as gram -ve rods, cocci and small rods in addition to some fraction of gram
+ve small rods and cocci. All these morphotypes were characterized for agriculturally useful traits such
as P-solublization, siderophore production, IAA production and ammonia excretion. Out of 91
morphotypes obtained from saline and 124 morphotypes from sodic soils, only 15 and 18 morphotypes,
respectively, were found to have all the above four characteristics. In saline soil, more numbers of
morphotypes were ammonia excreters while in sodic soil, IAA producers were present more in numbers.The genomic DNA of the morphotypes obtained on soil extract, Jensen’s and malate media was isolated
by the CTAB method and was amplified for nifH gene by using degenerative primers, nifH for and nifH
rev. Out of 57 morphotypes obtained from saline soil and 86 morphotypes obtained from sodic soil, 28
and 42 morphotypes, respectively, showed nifH gene amplification, indicating that these morphotypss
can fix nitrogen. The efficiency of six promising bacterial morphotypes isolated each from saline (JK246,
JJ355, SK543, JS 509, RS 502 and JP323) and sodic soils (KtJ571, KtK569, KrK564, KrS530, KrS546
andKtP390) were checked in wheat variety KRL 210 at different levels of induced salinity having an EC
of 0, 4, 8 and 12 dS/m and sodicity with RSC 0, 10 and 15 me/l, respectively. The bacterial counts were
less in uninoculated plants as compared to inoculated one. Moreover, in all the treatments, the total
bacterial counts were higher at 45th day of sowing then the counts recorded before sowing and as the crop
reached to maturity, the viable counts start decreasing. Best results were observed at EC 4 dS/m and RSC
10 me/l in terms of plant height, no. of tillers, plant dry weight and mean grain weight. The significant
difference with respect to these parameters was observed in all the induced EC or RSC levels. The
inoculation of different morphotypes isolated from saline or sodic soils resulted in a significant increase
in plant growth parameters as compared to control or uninoculated plants. In all the treatments with
different EC or RSC levels, the consortia performed better as compared to individual morphotypes and
the reference strains i.e. Mac 27 and P-36 in terms of plant growth parameters both in saline (SK543+ JS
509+ RS 502+ JP323) as well as sodic (KrK564+ KrS530+ KrS546+ KtP390) soils.
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Keywords
biomass, tropical zones, area, productivity, biological phenomena, land resources, vegetative propagation, nutrients, storage, remote sensing