Saud HAMIDOVIĆ1*, Blažo LALEVIĆ2, Vedrana KOMLEN3, Milan PEŠIĆ4, Vera RAIČEVIĆ2 , Hadi WAISI5 , Amer SUNULAHPAŠIĆ6
1University of Sarajevo, Faculty of Agriculture and Food Sciences, Bosnia and Herzegovina,
2University of Belgrade, Faculty of Agriculture, Belgrade - Zemun, Serbia,
3University "Dzemal Bijedic", Agromediterranean Faculty, Mostar, Bosnia and Herzegovina
4Institute of Soil Science, Belgrade, Serbia
5Institute for Water Management "Jaroslav Cerni", Belgrade, Serbia
6Ministry of Agriculture, Water Management and Forestry of Central Bosnia Canton, Travnik, Bosnia and Herzegovina
*Corresponding author: [email protected]
Abstract
In modern plant production usage of pesticides is necessary in order to obtain good quality of yield. In corn production, Adengo is one of the most used systemic herbicides for control of grasses and broadleaf weeds. Usage of inadequate concentrations of herbicides may have negative consequences for microbial diversity. The aim of this paper was determination of Adengo influence on microbial diversity in soil under corn. Experiment was performed in Ilidža municipality (Sarajevo canton, Bosnia and Herzegovina) by sowing seeds in spring 2016, followed by Adengo application in three various concentrations (0.22; 0.44; and 0.88 l/ha). Control treatment was untreated soil. Sampling for microbiological analyses was performed 15. 30. and 130 days after sowing. Microbial diversity of soil was determined using standard agar plate method. Total number of bacteria was determined on 0.1xTSA, ammonification bacteria on nutrient agar, nitrogen fixation bacteria and Azotobacter sp. on Fyodorov agar, fungi on Rose Bengal streptomycin agar, and actinomycetes on starch-ammonia agar. Microbial activity of soil was expressed as colony forming units per g of dry soil. The highest total bacterial number was detected at the end of experiment. Similar results were obtained for Azotobacter sp. and nitrogen fixation bacteria and fungi while highest abundance of ammonification bacteria was obtained in the start of experiment. Number of actinomycetes was highest after 330 days from sowing. These results may be useful for further application of herbicide Adengo in corn production, as well as other crops planting.
Key words: Herbicide, microbial diversity, corn, Adengo Introduction
Application of agrochemicals are irreplaceable part of traditional agriculture production (Carvalho, 2006). These chemicals have various impacts on soil characteristics (Gaherwal et al., 2015). One of them is pesticide; this term covers a various compounds, such as insecticides, fungicides, rodenticides, herbicides etc. (Aktar et al., 2009). Pesticides are important part of integrated pest management and may have a huge influence in agricultural production (Talebi et al., 2011). Application of pesticides is often linked with high crop productivity and protection from pests (Singh and Datta, 2006). With the increased use of pesticides in agriculture, impact of these agrochemicals on soil processes has received more global attention (Andrea et al., 2000). Every year, about 3x109 kg of pesticides is applied worldwide (Pan-UK, 2003). Unfortunately, long-term dispersion of pesticides has negative
consequences for ecosystem (Castro et al., 2005) and food chain, causing malfunction in living organisms (Arias-Estevez et al., 2008). Also, pesticides affect microbial activity of soil, as well as structure of microbial communities (Cycon et al., 2005), which are important parameters in transformation of organic matter, N and P cycling and crop productivity (Devare et al., 2007). The pesticides are accumulated in surface layer of soil, where microbial activity is highest (Sethi et al., 2015). The influence of pesticides on microbial diversity of soil may be various, depends on various factors (Monkiedje and Spiteller, 2002), such as chemical structure of pesticide, concentration of pesticide, structure of microbial population in soil, different soil characteristics etc. (Digrak and Ozcelik, 1998); in some cases, pesticides stimulate the microbial activity, but other pesticides have deleterious effects on soil microflora (Lo, 2010). Microorganisms play important role in agricultural ecosystem functioning, especially during the corn cultivation, which is one of the most cultivated crops in Bosnia and Herzegovina. Research of microbial activity is considered to be an adequate parameter of estimation of soil disturbance caused by various agricultural practices (Nannipieri et al., 2003). Thus, the aim of this research was determination of soil microbial activity after application of herbicide Adengo.
Material and methods
The experiment was performed at Butmir location (Ilidža municipality, Sarajevo canton, Bosnia and Herzegovina). In May 2016, sowing a corn seeds (Pioneer hybrid PR37NO1) was performed. After seeds sowing, treatment of soil by herbicides Adengo (Bayer AG, Germany) obtained from local distributor was conducted in order to prevent the growth of broad-leaved weeds and grasses. This herbicide was applied in three concentrations: 0.22; 0.44; and 0.88 l/ha. In control treatment, herbicide was not applied.
Soil sampling was performed 15; 30; and 130 days after sowing. Samples were taken from the depth 0 to 30 cm at several points in the field. In second and third sampling, samples were taken from the nearness of plants at several points. After preparation of composite sample, microbiological analyses were performed.
Total number of bacteria was determined using 0,1xTSA, ammonification bacteria on nutrient agar, nitrogen fixation bacteria and Azotobacter sp. on Fyodorov agar, fungi on rose bengal streptomycin agar (Peper et al., 1995), and actinomycetes on starch-ammonia agar. Incubation for fungi was performed at 25°C for 5 days, while for Azotobacter sp., and other bacteria at 28°C for 2, and 6 days, respectively. After incubation, microbial activity of samples was expressed in colony forming units (CFU) per gram of absolutely dry samples.
Results and discussion
Usage of pesticides and other agrochemicals affects the crucial functions and activity of soil microorganisms (Milošević and Govedarica, 2002). Enzyme systems of microorganisms comprise up to 90% of soil metabolic activity (Lee, 1994), and its number and activity may serve a good indicator of soil quality after pesticides application (Konstantinović et al., 1999).
In our study, microbial activity depends on type of microorganisms, time of sampling and herbicide concentrations.
Total number of bacteria may be used as an important parameter of soil fertility (Jarak and Čolo, 2007). In all treatments, at the end of experiment highest total number of bacteria was recorded. Similar trend was noticed in Azotobacter sp. number in most of treatments (tab. 2) In most of treatments, in first sampling higher number of bacteria was noticed compared with second sampling (tab. 1), while abundance of Azotobacter sp. was higher in second sampling.
Highest number of bacteria and Azotobacter sp. was noticed in treatment with 0.44 l/ha of herbicide after 130 days of sowing (122.3x105, and 103.7x102 CFU/g, respectively).
Table 1. Total number of bacteria in soil under corn (CFU x 105/g) Treatments
Time of sampling
15 days 30 days 130 days
Control 26.6 25.7 100.6
Adengo 0,22 l/ha 48.6 12.8 78.4
Adengo 0,44 l/ha 19.4 24.2 122.3
Adengo 0,88 l/ha 46.3 13.2 82.9
Nitrogen fixation bacteria are diverse and play important role in reduction of atmospheric nitrogen to ammonia (Orr et al., 2011). In all treatments (except of control), the number of nitrogen fixation bacteria was lowest at the end of experiment. Increase of herbicide concentration was followed by increase of bacterial activity (tab. 3). In first sampling, highest activity of nitrogen fixation bacteria was noticed in treatment with highest herbicide concentration (276.9x102 CFU/g), in second sampling in treatment with 0.44 l/ha (166.7x102 CFU/g) and in third in control treatment (122.5x102 CFU/g).
Table 2. Azotobacter sp. in soil under corn (CFU x 102/g) Treatments
Time of sampling
15 days 30 days 130 days
Control 87.7 67.0 94.3
Adengo 0,22 l/ha 53.8 54.1 46.3
Adengo 0,44 l/ha 45.1 49.0 103.7
Adengo 0,88 l/ha 37.3 40.4 54.4
Table 3. Nitrogen fixation bacteria in soil under corn (CFU x 102/g)
Ammonification bacteria use proteins as an energy material (Miletić et al., 2012) and its presence is one of the indicators of soil fertility (Sargsyan et al., 2013). Abundance of ammonifiers is highest in soil with high level of nutrients (Marinković et al., 2008). In all treatments (except of control) highest number of ammonifiers was recorded in first sampling.
Inhibitory effect of herbicides was noticed 30 days after sowing, followed with increase of ammonifiers number in third sampling compared to second (tab. 4). Lowest number of ammonifiers was recorded in treatment with 0.22 l/ha of herbicides after 30 and 130 days of sowing (4.1; and 10.3x105 CFU/g, respectively), while highest activity was noticed in first sampling of 0.88 l/ha treatment (30.5x105 CFU/g).
Treatments
Time of sampling
15 days 30 days 130 days
Control 92.0 150.4 122.5
Adengo 0,22 l/ha 250.0 79.0 40.3
Adengo 0,44 l/ha 73.7 166.7 53.1
Adengo 0,88 l/ha 276.9 146.9 55.7
Table 4. Ammonification bacteria in soil under corn (CFU x 105/g)
Treatments
Time of sampling
15 days 30 days 130 days
Control 12.2 21.6 25.1
Adengo 0,22 l/ha 21.4 4.1 10.3
Adengo 0,44 l/ha 16.8 12.1 15.2
Adengo 0,88 l/ha 30.5 10.6 14.8
Fungi are important systematic group of microorganisms which play a crucial role in decomposition of organic matter (Vieira and Nahas, 2005). They are more acid tolerant organisms compared to bacteria, thus, fungi are dominant microorganisms in acid soils (Rousk et al., 2009). Actinomycetes are also involved in significant processes in soil (Ghorbani-Nasrabadi et al., 2013); they may survive under various soil conditions and stimulate the plant development (Hamdali et al., 2008). As can be seen from table 5, in most of samples, higher number of actinomycetes compared to fungi was recorded. In treatments with herbicide, highest number of fungi was noticed in first sampling, while abundance of actinomycetes was highest in second sampling. In control treatment fungal and actinomycetes activity was highest in second sampling.
Table 5. Fungi and actinomycetes in soil under corn (CFU x 103/ g)
Results of previous researches showed the various impact of herbicides on soil microflora. In general, its application can cause decrease of beneficial microorganisms number (Aktar et al., 2009). For example, application of triclopyr inhibits activity of several bacterial populations (Pell et al., 1998), glyphosate has negative influence on nitrogen-fixing bacteria (Santos and Flores, 1995), while 2,4-D reduces the growth of cyanobacteria (Singh and Singh, 1989).
These results are similar with our observation (tab. 3), where inhibitory activity of herbicide can be seen after 130 days from sowing. On the other side, some researchers suggest that some herbicides have stimulatory effects on microbial activity. Jena et al. (1987) found that butachlor had stimulatory effect on growth of anaerobic nitrogen fixation bacteria. Glyphosate applied at high concentration produces a short-term stimulation of bacterial growth (Ratcliff et al., 2006).
Treatments
Fungi Actinomycetes
Time of sampling
15 days 30 days 130 days 15 days 30 days 130 days
Control 9.5 26.6 13.7 105.9 274.0 108.0
Adengo 0,22 l/ha 66.8 9.4 15.4 51.3 87.7 18.0
Adengo 0,44l/ha 57.3 11.1 24.8 85.9 135.7 104.5
Adengo 0,88l/ha 70.3 19.0 7.8 54.6 159.0 48.0
Conclusion
These results confirms that herbicide Adengo has various effects on soil microbial activity. Its impact depends on applied concentrations and microbial populations. Our results may be useful for further application of herbicide Adengo in corn production.
Acknowledgements
This research is partially supported by Ministry of Education, Science and Technological Development of the Republic of Serbia, Grant No. TR 31080.
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MICROBIOLOGICAL PROPERTIES OF SOIL UNDER CORN AFTER