Introduction
A fertilizer is a nourishing material of natural or synthetic
origin which mainly provided to soils or tissues of plants. Thus, it enhances
growth of plants (Haq and Mallarino 2005; Mannan 2014). For the purpose to
achieve optimal growth balanced nutrients are required in soil solution to
regulate adequate concentration for growth during plants developmental stages
(Chen 2006). Thus, crops mineral nutrition efficiency can be improved by
applying fertilizer through foliage or in growing medium (Mallarino et al. 2001). By applying fertilizer as
nitrogen, phosphorus, potassium as well as additional nutrients that could
affect many processes of physiological nature could be an opportunity to
influence economical yield (Haq and Mallarino 2005). Though, beneath high and
moderate salinity levels, fertilization affects growth of plants (Haq and
Mallarino 2005; Murtaza et al. 2014).
Hence in interactive studies of nitrogen and salinity, nitrogen supplied form
is important (Murtaza et al. 2000).
According to some studies, increase in nitrate concentration in plants reduce
the uptake of chloride and also retard its accumulation (Murtaza et al. 2000; Bybordi 2010). During salinity stress in plants nitrate has valuable effects that are related to antagonism
between of Na+ and Cl- ions (Munns 2002). The existence of
higher concentration of NO3- enhanced cations translocation such as Ca, K, and Mg, whereas NH4+ has been shown to decrease cations concentration (Nadian et al. 2012; Murtaza et al. 2014). Hence with significant
increase of nitrogen contents, sustain C/N ratio, designated to increase the photosynthesis as well as metabolism activities and ultimately increase biomass of plant (Dubey and Pessarakli 1995; Guan et al. 2011). Therefore, nitrogen additions to the plants showed symptoms of
stress under salinity may improve their tolerance for salt, growth and yield (Jahangir et al. 2009; Nadian et al.
2012).
As soil
salinity is a major abiotic stress with limiting effects on plant growth
worldwide and whole to agriculture produced on salt affected areas.
Approximately, 7% of total world’s soil is affected by salinity and on
approximate basis 20% of world to irrigated land (45 m ha) (Yamaguchi and
Blumwald 2005; FAO 2007). As an abiotic stress, salinity impacts negatively
approximately 20% of 310 million ha lands under irrigation used for crop
production, causing an assessed annual loss of US$ 27 billion. It is cost-effective
to invest in salt‐induced land degradation for sustainable management,
investments for active salt affected lands remediation, should be broader
strategy in arrangement part, or for security of food and be defined as plans
of national action (Qadir et al.
2014). Hence, soil salinity presence is even before of human existence and
farming (Foolad 2004). Thus, more commonly in areas of low rainfall, high
temperature, in arid and due to higher degrees of evapotranspiration in poor
quality irrigated water areas, salty parent material and poor management
practices resulted in net upward salts movement (Neto et al. 2006). In Pakistan, most serious environmental problem is
salinity that is categorized at eighth in terms of extended area (FAO 2006).
Soybean is a leguminous oilseed crop all around the
world by way of with its unique chemical composition and a high-quality digestible
protein source (He and Chen 2013; Vagadia et al. 2017). It contains about 6 % ash, 17–24%
oil, 29% carbohydrates and 37–42% good quality protein (Gibbs et al. 2004). It is a good source
of essential fatty acids including saturated, and polyunsaturated fatty acids,
fibers (USDA 2018), and contains secondary metabolites that are beneficial such
as isoflavones, saponins and phenolic components including minerals, vitamins, and comprises
of energy (Krishnan 2001;
Sakthivelu et al. 2008; Khojely et al.
2018). By management of agronomic production practices for optimized
growth, fertilizer nutrient (Haq and Mallarino 2005; Mannan 2014) and careful
genotypes selection influences soybean yield (Matsuo et al. 2016; Gulluoglu et al.
2017).
Production of
soybean at local level is minor and as importation of it as meal and oil of soya has become prerequisite to meet the demand. The cultivation is on restricted areas with
diminishing trend, need motivation and techniques to raise the cultivation of
soybean to overcome import bill on the edible oil. Therefore, the present study
was conducted to check that either nitrogen has ameliorative role in nutrition
under saline and normal conditions. While the
different sources of nitrogenous fertilizers might be performing better
under saline stress.
Materials and Methods
Plant material and conditions
for growth
Experiment was conducted in wire house, at University of
Agriculture, Faisalabad, Pakistan. Two sets of soybeans (Glycine max L.) genotypes,
No.2429-3130 and No. 3702 (salt tolerant), Lochlon and Ajmari as salt sensitive
were used in the experiment. 12 kg soil was used in pots. Collected soil was
dried in air, sieved in
Determination
of Na+ and K+
Dried
leaves of soybean plants were grounded in grinder. The 0.5 g sample was taken
in digestion flasks and added 7 mL HNO3+3 mL HClO4 and
digested on hot plate of 4 h and raised gradually. After once approximately 3 mL
was left in flask then digestion was stopped. For filtrate Whatman filter paper
(No.42) was used and final volume was obtained by addition of 50 mL by
distilled water. Then sodium and potassium were determined using flame
photometer after standardization (Jones et al. 1990).
Oil and protein contents
measurement
The oil
content measurement followed the method of Matthäus and Brühl (2001). The
following formula was used to calculate the oil contents from soya seed.
The
Qw (g) is the oil extracted from seed, W (g) is the
weight of ground sample, and moisture % is the moisture percentage of the
ground sample.
The sieved soy flours (0.5 g) were homogenized in a test
tube with 5 mL of phosphate buffer (0.2 M,
pH 7.8) for protein contents measurement. The mixture was stirred and
centrifuged at 3000 rpm for 10 min. The supernatant (1 mL) was added with 5 mL
coomassie brilliant blue G-250 (CBB) and this mixture was analyzed by the
method of Soluble Protein Content Assay according to Bradford (1976).
Statistical analysis
Analysis of variance (ANOVA) was used for data analysis
up to with two-way interaction using software “Statistix 8.1” for the analysis
and presented by as mean of three replicates of ± SE and P < 0.05 value used for checked significance (Steel et al. 1997).
Results
Effect
of salinity on growth and quality of soybean
There was a significant (P < 0.05) difference
in soybean growth under salt stress and normal conditions. The highest shoot
fresh and dry weights, root fresh and dry weights were observed under normal
conditions and significantly decreased at EC 7.5 and 15 dS
m-1. In case of salt stressed conditions, the highest shoot and root
traits were found in accession No.2429-3130 and lowest values for these traits
in Ajmari at EC 15 dS m-1. A significant
difference was also observed in leaf Na+ and K+
concentration among the all these tested genotypes (Table 5–6). The increase in
Na+ was observed under both the salinity levels as compared to
control. The highest Na+ concentration was recorded in tolerant
genotypes No.2429-3130 and No. 3702 rather than Lochlon and Ajmari. While K+
concentration showed a significant reduction at 15 dS
m-1 compared to respective control and 7.5 dS
m-1 in all four soybean genotypes. The tolerant genotypes sustained
relatively high K+ concentration than the salt sensitive genotypes.
Protein and oil% contents (Table 7 and 8), decreased under salt stress
condition compared to their respective control.
Table 1: Shoot fresh weight
(g plant-1) of soybean genotypes to different levels of NaCl and Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
26.3 ± 0.49 |
23.8 ± 0.88 |
18.8 ± 0.58 |
18.2 ± 0.78 |
25 |
34.0 ± 0.44 |
32.0 ± 0.55 |
25.5 ± 0.68 |
23.4 ± 0.76 |
||
25 |
32.4 ± 0.47 |
31.4 ± 0.45 |
23.9 ± 0.87 |
22 ± 0.69 |
||
NO3- kg ha-1 NH4+
kg ha- |
50 |
35.5 ± 0.75 |
34.7 ± 0.75 |
26.1 ± 1.06 |
25.5 ± 0.73 |
|
50 |
36.8 ± 0.61 |
35.1 ± 0.61 |
25.4 ± 0.53 |
23.8 ± 0.91 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
23.3 ± 1.06 |
20.8 ± 0.66 |
14.8 ± 1.09 |
13.2 ± 0.81 |
25 |
26. ± 0.46 |
25.4 ± 0.73 |
17.2 ± 0.87 |
14.9 ± 0.67 |
||
25 |
25.4 ± 0.8 |
24.5 ± 0.7 |
16.5 ± 0.65 |
14.5 ± 0.57 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
29.0 ± 0.73 |
27.0 ± 0.36 |
20.3 ± 0.61 |
18.3 ± 0.25 |
|
50 |
28.8 ± 0.34 |
26.2 ± 0.66 |
19.6 ± 1.24 |
16.8 ± 0.6 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
19.9 ± 0.8 |
14.5 ± 0.4 |
14.5 ± 1.2 |
13.19 ± 0.9 |
25 |
23.1 ± 0.80 |
22.1 ± 1.0 |
17.2 ± 0.9 |
15.6 ± 0.8 |
||
25 |
23.1 ± 0.5 |
21.8 ± 1.1 |
18.8 ± 0.2 |
14.8 ± 1.1 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
25.5 ± 0.8 |
23.5 ± 1.2 |
18.8 ± 0.2 |
18.2 ± 0.5 |
|
50 |
23.9 ± 0.7 |
22.9 ± 0.9 |
16.2 ± 0.4 |
15.5 ± 0.7 |
(Each value is an
average of three replicates± S.E)
Table 2: Shoot dry weight
(g plant-1) of soybean genotypes to different levels of NaCl and Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
5.6 ± 0.8 |
4.6 ± 0.1 |
2.8 ± 0.5 |
2.6 ± 0.2 |
25 |
5.7 ± 0.2 |
5.6 ± 0.6 |
2.8 ± 0.3 |
2.47 ± 0.10 |
||
25 |
5.7 ± 0.1 |
4.6 ± 0.2 |
2.8 ± 0.1 |
2.7 ± 0.1 |
||
NO3- kg ha-1 NH4±
kg ha- |
50 |
5.7 ± 0.3 |
4.7 ± 0.1 |
2.9 ± 0.3 |
2.7 ± 0.3 |
|
50 |
5 .7 ± 0.2 |
4.6 ± 0.2 |
2.8 ± 0.10 |
2.7 ± 0.1 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha- |
0 |
4.5 ± 0.1 |
3.5 ± 0.1 |
1.9 ± 0.1 |
2.1 ± 0.1 |
25 |
4.6± 0.4 |
3.5 ± 0. |
2.0 ± 0.2 |
2.1 ± 0.2 |
||
25 |
4.6 ± 0.2 |
3.5 ± 0.2 |
1.9 ± 0.1 |
2.1 ± 0.6 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
4.8 ± 0.1 |
3.6 ± 0.2 |
2.2 ± 0.2 |
2.1 ± 0.1 |
|
50 |
4.6 ± 0.2 |
3.5 ± 0.2 |
2.1 ± 0.2 |
2.1 ± 0.6 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
3.3 ± 0.1 |
2.7 ± 0.1 |
1.4 ± 0.10 |
1.2 ± 0.01 |
25 |
3.3 ± 0.5 |
2.8 ± 0.4 |
1.5 ± 0.10 |
2.1 ± 0.05 |
||
25 |
3.3 ± 0.2 |
2.8 ± 0.2 |
1.4 ± 0.1 |
1.2 ± 0.17 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
3.4 ± 0.1 |
2.8 ± 0.7 |
1.5 ± 0.2 |
1.3 ± 0.1 |
|
50 |
3.4 ± 0.8 |
2.8 ± 0.4 |
1.5 ± 0.4 |
1.3 ± 0.3 |
(Each value is an
average of three replicates± S.E.)
Effect of nitrogenous nutrition on soybean growth and quality
The application of N increased the shoot fresh and dry
weights, root fresh and dry weights under both saline and normal condition
however there was a significant (P < 0.05) difference between the
soybean genotypes under salt stressed conditions (Table 1–4). Plant leaf ionic
contents very significantly affected by treatments and with high significant
difference between the genotypes. The interactive effect of nitrogen treatment
was highly significant. The application of both nitrate and ammonium form
significantly reduced concentration of leaf Na+ and increased the
leaf K+ concentration, and consequently the growth. Increased
nitrogen supply led towards increased ratio of leaf K: Na in salinity stress
condition (Table 9). The salt-tolerant genotypes responded more efficiently to
nitrogen application at significant values than salt-sensitive genotypes. The
effect of nitrate application was more as compared to ammonium and in the same way more to salt
tolerant than to sensitive. Application of nitrogen at both sources (NO3-
and NH4+) and levels (25 and 50 kg ha-1) had significant
differences and increased the protein and oil content of soybean. However,
response was pronounced in tolerant genotypes as compared to sensitive (Lochlon and Ajmari) ones.
Table 3: Root fresh weight (g plant-1) of soybean genotypes to
different levels of NaCl and Nitrogen after 110 days
of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
5.2 ± 0.09 |
4.1 ± 0.06 |
3.9 ± 0.19 |
2.8 ± 0.02 |
25 |
6.5 ± 0.26 |
5.2 ± 0.13 |
4.3 ± 0.31 |
3.4 ± 0.20 |
||
25 |
5.6 ± 0.30 |
4.9 ± 0.16 |
4.1 ± 0.45 |
3.1 ± 0.05 |
||
NO3- kg ha-1 NH4+
kg ha- |
50 |
7.8 ± 0.28 |
6.6 ± 0.35 |
5.1 ± 0.19 |
5.1 ± 0.15 |
|
50 |
7.7 ± 0.26 |
6.1 ± 0.32 |
4.8 ± 0.20 |
3.9 ± 0.22 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha- |
0 |
5.3 ± 0.55 |
4.5 ± 0.29 |
2.2 ± 0.16 |
2.2 ± 0.18 |
25 |
6.7 ± 0.21 |
5.3 ± 0.15 |
2.6 ± 0.25 |
2.3 ± 0.26 |
||
25 |
5.4 ± 0.17 |
5.0 ± 0.09 |
2.2 ± 0.20 |
2.0 ± 0.5 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
6.2 ± 0.05 |
5.6 ± 0.24 |
3.5 ± 0.13 |
3.6 ± 0.22 |
|
50 |
5.9 ± 0.16 |
5.2 ± 0.03 |
3.4 ± 0.17 |
3.1 ± 0.36 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
3.9 ± 0.36 |
3.5 ± 0.36 |
2.2 ± 0.20 |
1.6 ± 0.28 |
25 |
4.5 ± 0.24 |
4.0 ± 0.09 |
2.2 ± 0.20 |
2.1 ± 0.07 |
||
25 |
4.2 ± 0.10 |
3.9 ± 0.03 |
2.4 ± 0.07 |
1.9 ± 0.07 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
5.0 ± 0.34 |
5.0 ± 0.34 |
2.5 ± 0.19 |
2.2 ± 0.29 |
|
50 |
4.4 ± 0.06 |
4.3 ± 0.29 |
2.5 ± 0.19 |
2.0 ± 0.06 |
(Each value is an average of three replicates± S.E)
Table 4: Root dry weight (g
plant-1) of soybean genotypes to different levels of NaCl and Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
0.88 ± 0.04 |
0.70 ± 0.06 |
0.35 ± 0.07 |
0.26 ± 0.03 |
25 |
1.05 ± 0.06 |
0.90 ± 0.01 |
0.56 ± 0.03 |
0.40 ± 0.04 |
||
25 |
0.91 ± 0.09 |
0.84 ± 0.06 |
0.49 ± 0.03 |
0.37 ± 0.04 |
||
NO3- kg ha-1 NH4+
kg ha- |
50 |
1.31 ± 0.15 |
1.55 ± 0.12 |
0.81 ± 0.06 |
0.63 ± 0.03 |
|
50 |
1.18 ± 0.09 |
1.40 ± 0.04 |
0.75 ± 0.04 |
0.49 ± 0.04 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha- |
0 |
0.75 ± 0.07 |
0.79 ± 0.04 |
0.45 ± 0.03 |
0.36 ± 0.03 |
25 |
0.92 ± 0.10 |
0.84 ± 0.07 |
0.49 ± 0.03 |
0.42 ± 0.01 |
||
25 |
0.87 ± 0.07 |
0..82 ± 0.01 |
0.43 ± 0.05 |
0.39 ± 0.04 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
1.05 ± 0.05 |
0.96 ± 0.02 |
0.63 ± 0.06 |
0.49 ± 0.04 |
|
50 |
0.98 ± 0.10 |
0.80 ± 0.05 |
0.42 ± 0.05 |
0.45 ± 0.03 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
0.34 ± 0.01 |
0.36 ± 0.03 |
0.42 ± 0.05 |
0.16 ± 0.01 |
25 |
0.38 ± 0.01 |
0.37. ± 0.01 |
0.21 ± 0.03 |
0.18 ± 0.03 |
||
25 |
0.33 ± 0.02 |
0.28 ± 0.00 |
0.24 ± 0.04 |
0.14 ± 0.01 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
0.41 ± 0.04 |
0.37 ± 0.01 |
0.20 ± 0.01 |
0.23 ± 0.03 |
|
50 |
0.35 ± 0.01 |
0.32 ± 0.01 |
0.19 ± 0.01 |
0.17 ± 0.01 |
(Each value is an average of three replicates± S.E)
Table 5: Leaf Na+
(mg/g DW) content of soybean genotypes to different levels of NaCl and Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
4.9 ± 0.4 |
4.7 ± 0.4 |
2.3 ± 0.1 |
2.8 ± 0.4 |
25 |
4.1 ± 0.2 |
3.4 ± 0.1 |
1.8 ± 0.4 |
2.10 ± 0.2 |
||
25 |
5.4 ± 0.3 |
4.2 ± 0.6 |
2.1 ± 0.1 |
7.4 ± 0.6 |
||
NO3- kg ha-1 NH4+
kg ha- |
50 |
3.5 ± 0.2 |
2.7 ± 0.1 |
1.5. ± 0.7 |
2.4 ± 0.3 |
|
50 |
3.9 ± 0.1 |
3.2 ± 0.5 |
1.6 ± 0.1 |
1.7 ± 0.1 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha- |
0 |
7.4 ± 0.2 |
6.3 ± 0.2 |
4.5 ± 0.5 |
4.2 ± 0.1 |
25 |
6.1 ± 0.2 |
5.8 ± 0.2 |
3.9 ± 0.1 |
3.8 ± 0.3 |
||
25 |
6.6 ± 0.2 |
6.0 ± 0.2 |
4.2 ± 0.4 |
4.0 ± 0.5 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
4.7 ± 0.3 |
4.7 ± 0.8 |
3.2 ± 0.1 |
3.0 ± 0.2 |
|
50 |
5.9 ± 0.2 |
5.6 ± 0.2 |
3.8 ± 0.3 |
3.6 ± 0.7 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
8.3 ± 0.3 |
7.6 ± 0.3 |
6.1 ± 0.20 |
5.6 ± 0.6 |
25 |
8.0 ± 0.3 |
7.3 ± 0.2 |
5.5 ± 0.20 |
5.2 ± 0.1 |
||
25 |
8.2± 0.3 |
7.4 ± 0.7 |
5.9 ± 0.2 |
5.4 ± 0.5 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
6.1 ± 0.2 |
4.5 ± 0.2 |
4.1 ± 0.2 |
3.6 ± 0.5 |
|
50 |
7.8 ± 0.3 |
7.1 ± 0.3 |
5.4 ± 0.9 |
5.0 ± 0.3 |
(Each value is an average of three replicates± S.E)
Discussion
Salinity is worldwide
problem causing threat to agricultural food production and sustainability. It
also encourages other stresses that negatively impacts crop growth
like osmotic, nutrient deficiency and specific ion toxicity, through upsetting
growth of plant and development by varying physiological and biochemical mechanisms associated
(Sairam et al. 2002; Chen 2006; Hanin et
al. 2016; Shu et al. 2017). The
increase in concentrations of NaCl decreased the development of plants of soybean in both types of genotypes tolerant and sensitive; it could be due to osmotic stress and specific ion
toxicity of Na+ as well as Cl- in the root which also
hinders the uptake of other ions and nutrients (Parveen et al. 2016).
Table 6: Leaf K+
(mg/g DW) content of soybean genotypes to different levels of NaCl and Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+ kg ha-1 |
0 |
40.6 ± 1.7 |
37.5 ± 1.1 |
21.0 ± 1.6 |
20.20 ± 1.0 |
25 |
45.8 ± 1.3 |
42.8 ± 1.1 |
24.4 ± 0.9 |
23.50 ± 0.5 |
||
25 |
44.2 ± 1.2 |
41.2 ± 2.1 |
23.1 ± 1..2 |
21.90 ± 1.1 |
||
NO3- kg ha-1 NH4+
kg ha- |
50 |
51.3 ± 2..7 |
47 ± 1.7 |
28.3 ± 0.8 |
27.20 ± 0.9 |
|
50 |
48.0 ± 1.8 |
45.4 ± 2.0 |
26.4 ± 0.9 |
25.50 ± 0.7 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+
kg ha- |
0 |
34.3 ± 0.9 |
30.1 ± 1.0 |
14.5 ± 0.5 |
13.20 ± 0.9 |
25 |
38.9 ± 1.4 |
34.8 ± 1.4 |
16.2 ± 0.5 |
16.40 ± 0.3 |
||
25 |
37.0 ± 1.4 |
33.3 ± 1.4 |
15.2 ± 0.6 |
14.8 ± 0.5 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
45.1 ± 1.0 |
41.4 ± 0.9 |
17.9 ± 0.8 |
18.8 ± 0.7 |
|
50 |
41.8 ± 1.7 |
38.3 ± 1.1 |
16.1 ± 1.0 |
16.4 ± 0.8 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+
kg ha-1 |
0 |
25.1 ± 0.70 |
23,3 ± 1.2 |
9.2 ± 0.00 |
8.6 ± 0.2 |
25 |
29.3 ± 1.03 |
27.1 ± 0.9 |
12.0 ± 0.70 |
11.8 ± 0.3 |
||
25 |
27.2 ± 1.0 |
25.0 ± 0.6 |
11.2 ± 0.6 |
10.6 ± 0.3 |
||
NO3- kg ha-1 NH4+
kg ha-1 |
50 |
34.3 ± 1.1 |
32.2 ± 1.1 |
13.9 ± 0.2 |
14.1 ± 0.4 |
|
50 |
31.8 ± 1.7 |
29.2 ± 0.7 |
12.6 ± 0.3 |
12.4 ± 0.9 |
(Each value is an average of three replicates± S.E)
Table 7: Protein content
(%) of soybean seed to different levels of NaCl and
Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+ kg ha-1 |
0 |
43.43 ± 0.57 |
42.11 ± 0.77 |
41.76 ± 0.35 |
40.24 ± 0.43 |
25 |
45.76 ± 1.46. |
44.93 ± 1.24 |
43.52 ± 2.63 |
43.90 ± 1.10 |
||
25 |
45.10 ± 0.86 |
44.60 ± 0.73 |
45.10 ± 0.57 |
43.60 ± 1.04 |
||
NO3- kg ha-1 NH4+ kg ha-1 |
50 |
49.60 ± 0.89 |
47.26 ± 0.72 |
46.10 ± 1.55 |
45.60 ± 1.03 |
|
50 |
49.21 ± 0.89 |
47.06 ± 0.80 |
45.96 ± 1.09 |
44.13 ± 1.93 |
||
7.5 dS m-1 |
NO3- kg ha-1 NH4+ kg ha-1 |
0 |
41.86 ± 0.34 |
41.60 ± 0.41 |
42.10 ± 0.68 |
39.36 ± 0.95 |
25 |
46.76 ± .74 |
44.26 ± 0.43 |
43.80 ± 2.99 |
41.89 ± 2.30 |
||
25 |
45.76 ± 0.87 |
46.93 ± 0.73 |
44.10 ± 1.84 |
43.26 ± 0.73 |
||
NO3- kg ha-1 NH4+ kg ha-1 |
50 |
47.76 ± 0.50 |
48 06 ± 0.66 |
45.76 ± 2.00 |
44.33 ± 1.02 |
|
50 |
46.10 ± 1.84 |
45.26 ± 1.00 |
45.10 ± 1.62 |
41.93 ± 0.90 |
||
15 dS m-1 |
NO3- kg ha-1 NH4+ kg ha-1 |
0 |
42.10 ± 0.68 |
41.70 ± 0.85 |
39.43 ± 0.87 |
36.26 ± 1.05 |
25 |
45.20 ± 0.50 |
43.66 ± 0.60 |
42.76 ± 0.50 |
39.26 ± 0.56 |
||
25 |
44.80 ± 1.17 |
43.26 ± 1.41 |
43.76 ± 0.46 |
37.60 ± 1.20 |
||
NO3- kg ha-1 NH4+ kg ha-1 |
50 |
46.43 ± 1.54 |
44.60 ± 0.62 |
45.76 ± 0.65 |
41.60 ± 1.61 |
|
50 |
45.10 ± 0.88 |
42.60 ± 0.75 |
44.43 ± 0.65 |
39.96 ± 1.31 |
(Each value is an average of three replicates± S.E)
Table 8: Oil (% DM) of
soybean genotypes to different levels of NaCl and
Nitrogen after 110 days of stress
Salinity |
Nitrogen |
|
No. 2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3- kg ha-1 NH4+ kg ha-1 |
0 |
18.89 ± 0.29 |
18.19 ± 0.39 |
17.67 ± 0.52 |
16.68 ± 0.15 |
25 |
19.56 ± 0.59 |
18.86 ± 0.34 |
18.34 ± 0.75 |
17.00 ± 0.53 |
||
25 |
19.22 ± 0.23 |
18.52 ± 0.61 |
18.01 ± 1.23 |
17.00 ± 0.67 |
||
NO3- kg ha-1
NH4+ kg ha-1 |
50 |
20.22 ± 0.91 |
19.52 ± 0.34 |
19.01 ± 1.76 |
18.00 ± 1.73 |
|
50 |
19.89 ± 0.30 |
19.19 ± 0.51 |
18.68 ± 0.89 |
17.33 ± 1.00 |
||
7.5 dS m-1 |
NO3- kg ha-1
NH4+ kg ha-1 |
0 |
18.22 ± 0.78 |
17.52 ± 0.51 |
17.01 ± 0.89 |
16.02 ± 1.00 |
25 |
19.47 ± 0.40 |
18.52 ± 0.66 |
18.01 ± 0.73 |
17.22 ± 0.67 |
||
25 |
18.89 ± 0.59 |
18.19 ± 0.65 |
17.68 ± 1.45 |
16.67 ± 0.44 |
||
NO3- kg ha-1
NH4+ kg ha-1 |
50 |
20.22 ± 0.67 |
19 66 ± 0.44 |
19.38 ± 0.74 |
17.23 ± 1.00 |
|
50 |
19.89 ± 0.38 |
19.19 ± 0.63 |
18.86 ± 0.66 |
17.14 ± 1.12 |
||
15 dS m-1 |
NO3- kg ha-1
NH4+ kg ha-1 |
0 |
16.89 ± 0.62 |
16.52 ± 1.06 |
15.01 ± 0.65 |
13.33 ± 0.36 |
25 |
17.22 ± 0.93 |
16.86 ± 0.59 |
16.34 ± 0.23 |
14.67 ± 0.78 |
||
25 |
17.16 ± 0.36 |
16.69 ± 0.18 |
16.21 ± 0.37 |
14.40 ± 0.45 |
||
NO3- kg ha-1 NH4+ kg ha-1 |
50 |
17.56 ± 0.58 |
17.19 ± 0.88 |
16.74 ± 0.95 |
15.17 ± 0.27 |
|
50 |
17.39 ± 0.35 |
17.02 ± 0.84 |
16.54 ± 0.42 |
14.83 ± 0.60 |
(Each value is an average of three replicates± S.E)
Table 9: K+/Na+
ratio of soybean genotypes to different levels of NaCl
and Nitrogen after 110 days of stress
Salinity |
Nitrogen form |
Level |
No.2429-3130 |
No. 3702 |
Lochlon |
Ajmari |
Control |
NO3-
kg ha-1 NH4+
kg ha-1 |
0 |
8.28
± 0.7 |
7.97
± 0.1 |
9.13
± 1.6 |
7.21
± 1.0 |
25 |
11.17
± 0.3 |
12.60
± 0.1 |
13.55
± 0.9 |
11.19
± 0.5 |
||
25 |
8.18
± 0.2 |
9.81
± 1.1 |
10.95
± 1..2 |
7.25
± 0.5 |
||
NO3 kg
ha-1 NH4+
kg ha-1 |
50 |
14.65
± 0..7 |
17.40
± 1.7 |
18.86
± 0.8 |
11.33
± 0.7 |
|
50 |
12.30 ± 0.8 |
14.20
± 2.0 |
16.50
± 0.9 |
15.00
± 0.7 |
||
7.5 dS m-1 |
NO3-
kg ha-1 NH4+
kg ha-1 |
0 |
4.64
± 0.9 |
4.77
± 0.0 |
3.22
± 0.5 |
3.14
± 0.9 |
25 |
6.38
± 0.14 |
5.52
± 0.4 |
4.15
± 0.5 |
4.32
± 0.3 |
||
25 |
5.6
± 0.4 |
5.55
± 1.4 |
3.62
± 0.6 |
3.70
± 0.5 |
||
NO3 kg
ha-1 NH4+
kg ha-1 |
50 |
9.59
± 1.0 |
8.80
± 0.9 |
5.59
± 0.8 |
6.27
± 0.7 |
|
50 |
7.08
± 0.7 |
6.83
± 1.1 |
4.20
± 1.0 |
4.55
± 0.8 |
||
15 dS m-1 |
NO3-
kg ha-1 NH4+
kg ha-1 |
0 |
3.02 ± 0.70 |
3.06
± .08. |
1.51
± 0.00 |
1.54
± 0.2 |
25 |
3.66
± 0.03 |
3.71
± 0.9 |
2.19
± 0.70 |
2.27
± 0.3 |
||
25 |
3.32
± 0.0 |
3.37
± 0.6 |
1.90
± 0.6 |
1.96
± 0.3 |
||
NO3 kg
ha-1 NH4+
kg ha-1 |
50 |
5.62 ± 0.9 |
7.10
± 1.1 |
3.39
± 0.2 |
3.92
± 0.4 |
|
50 |
4.0
± 0.27 |
4.11
± 0.7 |
2.33
± 0.3 |
2.48
± 0.9 |
(Each value is an
average of three replicates± S.E)
Additionally,
soybean plants have a large harvest index for nitrogen as compared to other
legumes. The soybean cultivars exposed to nitrogen application had an
optimistic effect on yield of soya seed (Jahangir et al. 2009; Maw et al.
2011). This study results are similar to Maw et al. (2011) that application of nitrate to soybean cultivars
increased the yield and this increase were mainly attributed to accumulation of
dry matter in leaves at fifth stage of vegetative growth. Tshivhandekano and Lewis (1993) revealed that maize and wheat fed within NH4+
more sensitive to salinity than plants fed with NO3- when grown in solution culture.
The dry matter of cotton and corn decreases by increase in salinity but by application of nitrogen increases
(Homaee et al. 2002) the growth. The
salt tolerant genotypes-maintained K+ higher levels and enhanced
growth than salt sensitive genotypes. The previously this has been reported in various crops including wheat, rice (Murtaza et al. 2014), tomato (Amjad et al. 2014), spinach, strawberry (Kaya et al. 2001, 2003) and soybean (Jahangir et al. 2009; Parveen et al. 2016). Parveen et al. (2016) reported that salinity
severely reduced the growth of soybean plants and yield by upsetting
morphological, physiological processes in all soybean genotypes yet more
pronounced effect was on sensitive plant as compare to tolerant. Nadian et al. (2012) found that by increasing
salinity noticeably decreased root and shoot growth. The high Na inhibitory
effect on K uptake concentrations and also on growth of plant improved with
increased nitrogen supply and this led to increase in ratio K: Na in leaf under
conditions of stress. In fact, nitrogen applications more than recommended rate
compensate the detrimental effects under salinity stress.
Thus, beneath salinity stress conditions nitrate valuable effects are related to antagonism between of Na+ and Cl-
ions (Munns 2002). The existence of higher
concentration of NO3- enhanced cations
translocation such as Ca, K, and Mg, whereas NH4+ has been shown to decreased cations
concentration (Nadian et al. 2012; Murtaza et al. 2014). Hence with significant increase of nitrogen content, C/N ratio decreased, designated by increased the photosynthesis as well as with metabolism activity and ultimately increase in biomass of plant (Dubey and Pessarakli 1995; Guan et al. 2011). Therefore,
nitrogen additions to the plants show symptoms of stress under salinity improved their tolerance
to salt, growth and finally yield (Jahangir et al. 2009; Nadian et al.
2012).
As form of nitrogen application effect, the growth, with mixed addition of NO3-/NH4+
produced highest yields under saline and normal conditions of soil (Cox and
Reisenauer 1973; Botella et al. 1997;
Drihem and Pilbeam 2002). Also, stromal contents
and proteins of thylakoid increased by improved nitrogen supply in the chloroplast of leaf and finally enhanced leaves photosynthetic capacity (Homaee et al. 2002). Accumulation of solutes takes place under the
sufficient nitrogen supply, important role of these in osmoticum adjustments as glycinebetaine, glutamate,
proline, carnitine, sorbitol, fructans, polyols, trehalose, sucrose and
oligosaccharides also increased by potassium and phosphorus added nutrition (Nadian et al.
2012). As osmolytes precisely produced by plants
and counter the salinity osmotic deficit efficiently through solutes accumulation in cytoplasm and in vacuole by seizing the toxic ions (Knight et al. 2000; Munns and Tester 2008). Fertilizer application at optimum rates to
soils under salinity moderately lighten the adversial salinity effects on
photosynthesis and also on photosynthesis-related parameters and yield
components by full filling the nutritional demands of salt effected plants
(Albassam 2001; Sultana et al. 2001).
The appropriate and suitable use of nitrogen fertilizer in all types of soil is
vital, but mostly in saline soils, where nitrogen use may minimize the damaging
effects of salinity on growth of plant and yield (Shen et al. 1994; Flores et al.
2001; Abdelgadir et al. 2005).
Thus addition of NH4+ in
place of NO3- in structures can reduces the uptake of
other cations, like Mg2+, Ca2+ and K+, that could be described by antagonism between cations and NH4+ The proportion
of these effect differ according to factors between regulations made in the ionic balance of
nutrients and growing conditions.
Consequently, a vigilant use of NH4+ is suggested
for crops which are sensitive to Ca deficiency including sweet pepper and tomato (Sonneveld and Voogt 2009).
As it is
recognizable, that salt stress affected the soybean plants physiology significantly
that resulted to decreased growth; nevertheless, better growth maintained in
salt tolerant genotypes. Nitrogen application decreased the NaCl toxic effects
which result in low levels of Na+ to tissue and activities of
antioxidant enzymes in favorable conditions, enhanced photosynthetic features
and consequently enhanced growth of plants. Thus, highest levels of nitrogen
addition and nitrate form can be used as a good amendment facilitator against
salt stress and also as a remedy for sensitive species/varieties for production
of crop in stressed environment. Reduced crop productivity at high salinity
generally triggered by an ionic imbalance causing toxicity, due to osmotic
stress and ROS production in soybean plants (Akhtar et al. 2010; Jahangir et al.
2009; You and Chan 2015; Parveen et al.
2016). Salinity stress delayed the flowering and pod maturity enhanced in
soybean ultimately effect grain development, causing it to shrivel (Jahangir et al. 2009; Parveen et al. 2016). Thus, this response was
steady for salt tolerant and genotypes in flowering, reproductive and
grain-filling stages, with significantly fewer pods per plant and leading
towards lower grain yield (grain plant-1) (Mannan et al. 2013). The salinity stress
negatively affect yield and quality mainly due to short duration for protein
and accumulation of oil by reducing seed yield per plant (Krasensky
and Jonak 2012; Sabagh et al. 2015a, b).
Conclusion
Salinity
stress adversely reduced the growth of all genotypes while the application of N
increased the plant growth under both saline and non-saline conditions. The
application of N was more beneficial for accession tolerant soybean genotype
which produced drier biomass production, protein content and oil percent and K
content through N application rather than sensitive genotypes under both saline
and non-saline conditions. Application of nitrate form increased the plant
growth and improved the protein and oil percent and K+ content as compared
to ammonium form. Hence, it was concluded that the application of N fertilizers
in the nitrate form is more beneficial for soybean crop under saline conditions
rather than NH4.
Acknowledgement
The support of the Higher Education Commission (HEC) of
Pakistan and the University of Agriculture Faisalabad are gratefully
acknowledged.
Author Contributions
Azhar S and MAU Haq designed the
experiment; Azhar S conducted experiment, collected data and analyze the
samples with the coordination of MAU Haq; MAU Haq wrote the manuscript; Azhar S
and J.Akhtar drafted the manuscript and EAWariach review it before submission.
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