Wheat yield
In order to determine the effects of grain and straw yield of wheat, inoculating Amycolatopsis strains alone and together with WS was performed. The obtained results are summarized in Table 1. According to the results, significant increases in wheat straw and grain yield after applying only 5% WS to the soil (P < 0.001) were observed relative to the control. Regarding the control without any amendment, an increase of 24% in straw yield and 49% in grain yield were determined (Table 1). Similar to studies carried out by Brock et al. (2011) and Zhao et al. (2016), significant increases were noted in plant crop yield as a result of the application of organic compounds to the soil. Two main reasons could explain these increases in crop yield. First, the nutrient content of the soil increases after the amendment as plant nutrients are full of organic compounds in the structure, and thus, contributing to an increase in crop yield (Espe et al., 2015). Secondly, there is an increase in plant crop yield due to organic compounds applied to soils. It could improve soil properties such as aggregate stability, water retention capacity, and cation exchange capacity (Murphy, 2015).
It was determined that Amycolatopsis strains inoculated into the soil significantly increased grain and straw yield of the wheat compared to control (Table 1). The increase was mostly observed for the inoculation of A.azurea. In this case, grain yield and straw yield were increased by 274% and 74%, respectively, compared to the control. The associated reasons for the increase in plant production in microbial inoculation to soils could be due to i) fixation of atmospheric N by microorganisms (Kızılkaya, 2009), ii) increase in the solubility of organic and inorganic P in the soil by microorganisms (Ogut and Er, 2016), and iii) hormones that increase plant development such as auxins (Egamberdiyeva, 2005), cytokinins (Garcia de Salamone et al., 2001), gibberellins (Gutiérrez-Mañero et al., 2001) by microorganisms such as the production of microbial metabolites and hydrolytic enzymes, and vitamins (Ahmad et al., 2018). In addition to those, it could be due to creating a better plant growth environment by increasing the aggregation by microorganisms or indirect effects such as antibiotic production. There is no scientific evidence that Amycolatopsis strains would carry out N fixation, increases the solubility of organic and inorganic P in soil, or directly affect the yield of plant crops by synthesizing hormones such as gibberellins, auxin. However, Amycolatopsis strains could synthesize antibiotics such as balhimycin, vancomycin, rifamycin (Nigam et al., 2014; Xu et al., 2014; Frasch et al., 2015; Kumari et al., 2016), vanillin (Fleige and Steinbüchel, 2014; Fleige et al., 2016) and therefore, causing polycyclic aromatic hydrocarbons to degrade (Ortega-González et al., 2015). In this study, the fact that A.magusensis, A.orientalis, and A.azurea increased the grain and straw yield of the wheat, could be attributed to the antibiotic synthesis properties of Amycolatopsis strains.
Table 1
The effects of inoculating Amycolatopsis strains alone and together with WS on grain and wheat yield
Treatments
|
Weight (gr/pot)
|
Change (%)
|
Straw
|
Grain
|
Straw
|
Grain
|
Control
|
10.26 ± 0.32 d
|
2.44 ± 0.10 e
|
--
|
--
|
WS (50 g kg− 1)
|
12.74 ± 1.43 c
|
3.64 ± 0.21 d
|
24.20 ± 13.91 d
|
49.04 ± 8.53 d
|
A. magusensis
|
15.53 ± 0.56 b
|
7.54 ± 0.21 c
|
51.36 ± 5.42 c
|
208.88 ± 8.62 c
|
A. orientalis
|
16.16 ± 0.61 b
|
8.67 ± 0.20 b
|
57.47 ± 5.94 b
|
255.46 ± 8.20 b
|
A. azurea
|
17.92 ± 1.01 a
|
9.14 ± 0.15 a
|
74.63 ± 9.84 a
|
274.45 ± 5.97 a
|
A. magusensis + 50g WS kg− 1
|
2.15 ± 0.16 e
|
1.21 ± 0.03 f
|
-79.01 ± 1.58 e
|
-50.55 ± 1.25 e
|
A. orientalis + 50g WS kg− 1
|
2.86 ± 1.50 e
|
0.98 ± 0.03 f
|
-72.12 ± 1.57 e
|
-59.97 ± 1.03 f
|
A. azurea + 50g WS kg− 1
|
2.54 ± 0.06 e
|
1.20 ± 0.02 f
|
-75.21 ± 0.54 e
|
-50.96 ± 0.63 e
|
F-value
|
172.346***
|
1862.946***
|
1982.910***
|
175.361***
|
***P < 0.001 |
As given in Table 1, Amycolatopsis strains applied to the soil together with WS decreased the grain and straw yield dramatically (P < 0.001). Compared to the control, the reduction in the grain yield by Amycolatopsis strains varied between 50–60%. Moreover, the straw yield was found to be between 72–79%. The wheat yield increased when WS and Amycolatopsis strains alone were applied to the soil. It is interesting to note that wheat yields drop significantly after the application of these together. Amycolatopsis strains inoculated with WS affected more significantly by the soil microbiological properties. It was found that Cmic and SBR were more available in pots with these combinations (Table 3). This may be due to heterotrophic Amycolatopsis strains, which supply the C from the organic C compound of WS. Thus, they were the dominant microflora in the environment. In this context, the growing population could synthesize more antibiotics, and this may result from the lack of positive effects of microflora on wheat yield by suppressing other microflora. Especially, bacteria populations such as nitrifier bacteria involved in N transformation might disappear from the environment due to the synthesized antibiotics. Eventually, this might prevent the formation of nutrients that can be taken as mineral N, and plant yield may have decreased.
Nutrient contents of wheat
The application of Amycolatopsis strains alone and together with WS was studied to understand the effects of grain and straw of wheat within different scopes. The obtained results within the scope of N and P are given in Table 2. The corresponding results within the scope of K and Ca are presented in Table 3. It was found that the nutrient content of the wheat increased in general as a result of the application of WS and Amycolatopsis strains alone and together. It was observed that the application led to increases in the N and P content in the grain and straw of the wheat compared to the control. When WS applied with Amycolatopsis strains (Table 2), this application also increased the content of grain K and stem Ca content of the plant (Table 3). Jones et al. (1991) reported that the nutrient adequacy levels of the leaves of the wheat plant should be 1.75–3% N, 0.2–0.5% P, 1.5-3% K, and 0.2-1% Ca. According to these values, it was found that in the control application, the N content of the plant samples at harvest was insufficient. However, P, K, and Ca contents were found to be sufficient.
Similarly, Orhan et al. (2006), Çakmakçı et al. (2001), Kızılkaya (2008), Esitken et al. (2010) found that the product yield and nutrient content of the plant such as N, P, and K significantly increase with the inoculation of different microorganisms to the soil, in raspberry, sugar beet and barley, spring wheat, strawberry, respectively. In this study, the main reason why P, K, Ca contents of the plant in the control application without any fertilizer application are determined at a sufficient level is, without a doubt, due to the fact that the test soil contains sufficient levels of P (23.52 mg kg− 1), K (1.12 cmol(+)kg− 1) and Ca (23.08 cmol(+)kg− 1) to meet the plant’s need. It is thought that the N (0.18%), which was initially found in the soil at an average level, did not fully meet the requirements of the plant during the vegetation period. With microbial inoculations in the soil, increased nutrient content in the plant is related to promotes the mineral uptake of plants, and microorganisms promote mineral uptake with different mechanisms (Gouda et al., 2018; Backer et al., 2018). However, it may not be due to the normal ion uptake of mineral uptake by plants but due to volume increase of root system that is made of root amount, thickness, and length. Increased number of lateral roots by bacteria and widening of the root tips increases root surface area and it causes the plant to absorb more water and nutrients (Pinton et al., 2007). In inoculation with Amycolatopsis strains, including antibiotics secreted by the bacterial species, secretions do not only protect the plant root system against pathogenic organisms but also increases plant root development and eventually increases mineral intake by plants so that more nutrients may be absorbed by grain and straw of wheat.
Table 2
The effects of inoculating Amycolatopsis strains alone and together with WS on N and P contents of wheat
Treatments
|
N (%)
|
P (%)
|
Straw
|
Grain
|
Straw
|
Grain
|
Control
|
0.68 ± 0.04 g
|
1.72 ± 0.08 e
|
0.35 ± 0.01 c
|
0.46 ± 0.01 b
|
WS (50 g kg− 1)
|
0.82 ± 0.03 f
|
2.65 ± 0.06 c
|
0.45 ± 0.02 b
|
0.44 ± 0.01 c
|
A. magusensis
|
1.28 ± 0.09 b
|
3.38 ± 0.07 a
|
0.56 ± 0.02 a
|
0.51 ± 0.02 a
|
A. orientalis
|
1.23 ± 0.05 bc
|
3.19 ± 0.06 b
|
0.54 ± 0.01 a
|
0.52 ± 0.01 a
|
A. azurea
|
1.39 ± 0.06 a
|
2.27 ± 0.10 d
|
0.55 ± 0.01 a
|
0.52 ± 0.01 a
|
A. magusensis + 50g WS kg− 1
|
1.00 ± 0.06 e
|
2.25 ± 0.10 d
|
0.33 ± 0.01 c
|
0.31 ± 0.01 d
|
A. orientalis + 50g WS kg− 1
|
1.08 ± 0.03 de
|
2.37 ± 0.14 d
|
0.34 ± 0.02 c
|
0.33 ± 0.02 d
|
A. azurea + 50g WS kg− 1
|
1.16 ± 0.07 cd
|
2.24 ± 0.09 d
|
0.34 ± 0.01 c
|
0.34 ± 0.02 d
|
F-value
|
59.463***
|
116.798***
|
138.806***
|
105.018***
|
***P < 0.001 |
Table 3
The effects of inoculating Amycolatopsis strains alone and together with WS on K and Ca contents of wheat
Treatments
|
K (%)
|
Ca (%)
|
Straw
|
Grain
|
Straw
|
Grain
|
Control
|
1.75 ± 0.06 a
|
4.46 ± 0.13 ab
|
0.31 ± 0.01 bc
|
0.35 ± 0.01
|
WS (50 g kg− 1)
|
1.55 ± 0.11 b
|
4.48 ± 0.10 a
|
0.30 ± 0.02 c
|
0.33 ± 0.02
|
A. magusensis
|
1.45 ± 0.02 cd
|
4.47 ± 0.06 a
|
0.41 ± 0.01 a
|
0.33 ± 0.01
|
A. orientalis
|
1.46 ± 0.01 cd
|
4.52 ± 0.05 a
|
0.42 ± 0.01 a
|
0.37 ± 0.01
|
A. azurea
|
1.47 ± 0.02 bc
|
4.26 ± 0.12 b
|
0.42 ± 0.01 a
|
0.36 ± 0.01
|
A. magusensis + 50g WS kg− 1
|
1.37 ± 0.02 de
|
3.52 ± 0.12 c
|
0.32 ± 0.01 b
|
0.33 ± 0.01
|
A. orientalis + 50g WS kg− 1
|
1.36 ± 0.01 e
|
3.23 ± 0.19 d
|
0.32 ± 0.01 b
|
0.33 ± 0.01
|
A. azurea + 50g WS kg− 1
|
1.34 ± 0.04 e
|
3.05 ± 0.09 d
|
0.32 ± 0.01 b
|
0.33 ± 0.02
|
F-value
|
20.579***
|
86.854***
|
107.357***
|
3.887ns
|
***P < 0.001 |
Soil microbiological properties
As a result of the inoculation with Amycolatopsis strains alone and together with WS, and its effects on Corg and some microbiological properties are given in Table 4. It is determined that inoculating Amycolatopsis strains alone to soil and the change in Corg content is not statistically significant, but as a result of infusing Amycolatopsis strains with WS, the most increase in Corg content occurs (P < 0.001). Similarly, it was found that WS application added to the soil at the level of 5% significantly increased the Corg content (P < 0.001). This is a clear indication that there will be more increases in Corg content with microbial inoculation when there is an adequate source of organic matter in the soil. When compared to the control and application of WS only, the main reason for the increase in Corg content is related to the microbial excretions are more common in this environment and contributions of capillary roots to Corg content with an increase in root secretions of better growing plant roots contribute (Powlson et al., 2001; Pinton et al., 2007). However, obtained results are limited to the 124-day greenhouse trial. Without a doubt, organic compounds in the soil will be used as a C source by the growing microorganism population after the experiment, and Corg content will also decrease (Li et al., 2018).
Table 4
The effects of inoculating Amycolatopsis strains alone and together with WS on Corg and soil microbiological properties
Treatments
|
Corg
|
SBR
|
Cmic
|
Cmic/Corg
|
qCO2
|
Control
|
0.42 ± 0.10d
|
13.04 ± 1.64e
|
121.37 ± 5.28f
|
1.23 ± 0.27b
|
2.58 ± 0.36c
|
WS (50 g kg− 1)
|
3.01 ± 0.03c
|
22.22 ± 0.27d
|
182.91 ± 2.94e
|
0.25 ± 0.01c
|
2.92 ± 0.04c
|
A.magusensis
|
0.34 ± 0.12d
|
55.74 ± 3.19c
|
230.03 ± 9.46d
|
3.06 ± 0.98a
|
5.82 ± 0.44b
|
A.orientalis
|
0.31 ± 0.05d
|
57.74 ± 0.66c
|
244.22 ± 9.53c
|
3.31 ± 0.36a
|
5.67 ± 0.27b
|
A.azurea
|
0.35 ± 0.16d
|
59.12 ± 2.39c
|
247.22 ± 11.30c
|
2.95 ± 0.01a
|
5.75 ± 0.37b
|
A.magusensis + 50g WS kg− 1
|
3.66 ± 0.16a
|
75.73 ± 2.39b
|
283.75 ± 11.33b
|
0.32 ± 0.01c
|
6.41 ± 0.37a
|
A.orientalis + 50g WS kg− 1
|
3.76 ± 0.18a
|
81.26 ± 3.00a
|
321.82 ± 9.19a
|
0.36 ± 0.03c
|
6.06 ± 0.20ab
|
A.azurea + 50g WS kg− 1
|
3.29 ± 0.07b
|
80.14 ± 4.14ab
|
318.63 ± 8.01a
|
0.40 ± 0.02c
|
6.04 ± 0.44ab
|
F-value
|
702.180***
|
299.638***
|
221.191***
|
28.778***
|
66.318***
|
***P < 0.001; |
Corg : total organic carbon (%); BSR: basal soil respiration (mgCO2-C gr− 1.24 h); Cmic : microbial biomass C (mg C g− 1 24 h); Cmic/Corg: %; qCO2: the microbial metabolic quotient (µg CO2-C mg− 1 Cmic h− 1) |
Soil Basal Respiration (SBR) is defined as a constant respiration rate in the soil caused by the mineralization of organic matter, and it is estimated based on CO2 evolution or O2 uptake (Dilly and Zyakun, 2008). The determination of SBR measurement is a widely used indicator in the assessment of both microbial respiration in the soil and mineralization of organic matter (Creamer et al., 2014). In this study, the most SBR among applications was obtained by inoculation with Amycolatopsis strains with WS (Table 4). This is followed by inoculation with Amycolatopsis strains alone and WS, respectively (P<0.001). This reveals that organic matter mineralization and microbial CO2 production in soils are mostly obtained in inoculation with Amycolatopsis strains. Similarly, studies carried out by Rui et al. (2016) and Mierzwa-Hersztek et al. (2018), it has been determined that SBR has significant increases by adding organic matter to the soil or by microbial inoculation.
In this study, Substrate Induced Respiration (SIR) method was used to evaluate microbial biomass (Cmic). Microbial population in soil produces CO2 from an easily degradable substrate in a simple structure added to soils. As a result of this, maximal respiration occurred at the beginning is determined, and this is widely used in Cmic estimation (Anderson and Domsch, 1978; Nakamoto and Wakahara, 2004). In this study, it was determined that all applications significantly increased Cmic in soil (P<0.001) when compared to the control application. Just like in SBR, the most Cmic is obtained in infusion with Amycolatopsis strains with WS. The obtained results show that microbial inoculation to soil and the addition of WS increases microbial biomass (Table 4). Similarly, with the studies carried out by Beare et al. (1990) and Rui et al. (2016), it has been determined that microbial inoculations and organic waste applications to soil significantly increases Cmic. Besides, it is known that antibiotics synthesized by Amycolatopsis strains reduce populations by suppressing other microflora in the soil and rhizosphere region (Thomashow et al., 2008). Therefore, it can be said that Amycolatopsis strains inoculated with increased microbial activity in the experiment are dominant microorganisms in the soil environment.
The ratios of Cmic in Corg were calculated based on Corg and Cmic data of soils. According to the results obtained, the highest Cmic/Corg ratios were obtained in applications where Amycolatopsis strains were inoculated (2.95–3.31). The lowest Cmic/Corg rates were found in applications where WS and WS with Amycolatopsis strains were applied (Table 4). Although the ideal Cmic/Corg ratio varies between 1–4% in agricultural soils, the ideal rate is intended to be around 5%, and the Cmic/Corg ratio alone provides a more sensitive assessment opportunity compared to the evaluation of Corg and Cmic alone (Sparling, 1992). This case reveals that the most appropriate application in terms of balance and approach to ideal conditions that will occur at the end of Corg and infusion in soils can only be obtained in applications where Amycolatopsis strains are inoculated.
The microbial metabolic quotient or qCO2 is a microbial respiration rate for one Cmic unit and it represents the capacity of microorganisms in the soil to use Corg (Chao et al., 2019). According to the results obtained from the study, the highest qCO2 values were obtained in applications where Amycolatopsis strains were inoculated with WS (6.04–6.41). This is followed by Amycolatopsis strains inoculations and WS application, respectively (Table 4). This case is a clear indication that the inoculation of Amycolatopsis strains in the soil also uses WS which is added to the soil. Because in these applications, not only qCO2 was determined high but also Cmic and SBR of the soils were found high (Table 3).