Alavala Uma Rajshekhar1, R. Subhash Reddy1 and
P. Chandrasekhar Rao2
1Department of Agricultural Microbiology & Bioenergy,
2Department of Soil science and Agricultural chemistry, College of Agriculture, Professor
Jayashankar Telangana State Agricultural university, Rajendranagar, Hyderabad – 500030, India.
ABSTRACT
In this present studied poly bag experiment was conducted following complete randomized block design with 12 treatments and three replications. Polluted Soil with supply of fresh water, Unpolluted soil with supply of fresh water, Unpolluted soil with supply of polluted water. The results of pot culture were reveals that the Influence of microbial cultures on biological quality and microbial population of polluted soil and spinach yield at 30 and 60 DAS was estimated. Significantly highest bacterial population was recorded in treatments T12 (124.21 ×107 CFU g-1 soil) at 30 DAS and treatment T8 (88.68 ×107 CFU g-1 soil) at 60 DAS. The highest molds population was observed in treatment T3 (17.91, 11.32 ×103 CFU g-1 soil) at 30 and 60 DAS respectively. The treatment T6 showed significantly highest rhizobial population at 30 and 60 DAS (29.23, 20.71 ×103CFU g-1 soil) respectively. The VAM population was highest in the treatment T7 (24.13 ×10 g-1 soil) at 30 DAS and T12 (9.0) at 60 DAS. The highest leaf fresh weight was recorded in T8 (41.63 g plant-1) at 30 DAS and (70.03 g plant-1) at 60 DAS and the lowest fresh weight was recorded in T3, T9 at 30, 60 DAS respectively. The highest leaf dry weight was recorded in T8 (6.62 g plant-1), (4.17 g plant-1) at 30 and 60 DAS respectively and the lowest values were found in T3 at 30 and 60 DAS.
Keywords: Spinach, polluted, unpolluted soil, biological activity, microbial population.
Introduction
Soil fertility is a complex concept that involves many interacting parameters. Cultivated plants may suffer nutritional stresses when the amount or availability of soil nutrients is lower than that required for sustaining metabolic processes in each growth stage . Thus, restoring of nutrients and enhancing their availability by improving soil characteristics and efficiency of plants, are the main objectives of the modern agriculture. Due to the increasing sensitivity to environmental and economic issues, researchers and consumers are more and more aware of the impact of agriculture on the environment. Pollutants such as heavy metals and chemicals in the soil, water and air are affected by various physicochemical, biological, and environmental factors. Bioremediation is a biological process by which environmental pollutants are removed or transformed to less toxic substances. Soil amendments including fertilizer and lime, appropriate moisture levels, and periodic tilling can maximize or improve bioremediation (Brigmon et al. 2002). Phytoremediation specifically utilizes plants for contaminant control and has been combined with soil amendments for increasing or reducing metals uptake (Wilde et al. 2005).
Plants tolerant to heavy metals are able to immobilize metals by accumulation in the roots, adsorption in/onto the roots, and/or precipitation in the rhizosphere. Currently, most of what is known about aided phytostabilization of heavy metal-contaminated soils focuses on analysis of physicochemical soil properties, especially concentration of bioavailable forms of metals/metalloids and their accumulation in plant tissues (Wilde et al. 2005).
Bioindicators are the most important criterion of soil quality (Alkorta et al. 2010; Markert et al. 2003). Many definitions of soil quality have been suggested. However, a short and comprehensive definition is given by Doran and Parkin (1994) who have defined soil quality/soil health as “The capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental quality and promote plant and animal health”. Phytoremediation, the use of plants to extract, sequester, and/or detoxify pollutants through physical, chemical, and biological processes (Saxena et al., 1999) has been reported to be an effective, in situ, non-intrusive, low-cost, aesthetically pleasing, ecologically benign, socially accepted technology to remediate polluted soils (Alkorta and Garbisu, 2001; Garbisu et al., 2002; Weber et al., 2001). It also helps prevent landscape destruction and enhances activity and diversity of soil microorganisms to maintain healthy ecosystems, which is consequently considered to be a more attractive alternative than traditional methods to the approaches that are currently in use for dealing with heavy metal contamination.
The objective of this work was to use traditional microbiological methods based on culture techniques to evaluate the biological quality of heavy metal-contaminated soil that has been remediated with aided phytostabilization
MATERIAL AND METHODS
Soil Samples and Soil Characteristics
Soil samples of polluted and unpolluted soils were collected before sowing and analysed for the physical(pH, EC, and particle size and chemical characters like N,P,K and organic carbon parameters) and microbiological properties by adopting standard procedures at Department of Agricultural Microbiology and Bio-energy and Department of Soil Science and Agricultural Chemistry, College of Agriculture, Rajendranagar, PJTSAU, Hyderabad.Water samples were also analyzed before sowing of crop in polluted and unpolluted soils. (table 1).
Table 1. Effect of microbial cultures on microbial biomass carbon at harvesting stage (60 DAS) in polluted and unpolluted soils of spinach beet
|
Treatments |
60 DAS |
| Polluted Soil with supply of fresh water | |
| T1– SF Soil + FYM | 83.30 |
| T2– SF Soil + FYM + VAM + Psuedomonas | 98.30 |
| T3– SF Soil + RDF | 89.31 |
| T4– SF Soil + RDF + FYM + VAM + Psuedomonas | 103.16 |
| Unpolluted soil with supply of fresh water | |
| T5– SF Soil + FYM + Psuedomonas | 109.00 |
| T6– SF Soil + FYM+ VAM + Psuedomonas | 120.03 |
| T7– SF Soil + RDF | 95.20 |
| T8– SF Soil + RDF + FYM + VAM + Psuedomonas | 123.68 |
| Unpolluted soil with supply of polluted water | |
| T9– Soil + FYM | 95.67 |
| T10– Soil + FYM + VAM + Psuedomonas | 118.66 |
| T11– Soil + RDF | 103.38 |
| T12– Soil + RDF + FYM + VAM + Psuedomonas | 129.99 |
| SE m± | 2.383 |
| C.D at 5% | 6.955 |
SF soil = Student Farm Soil, RDF = Recommended dose of fertilizers, FYM = Farm Yard Manure
Crop details
The pot culture experiment was conducted at Department of Agricultural Microbiology and Bioenergy during 2014-15. For this investigation leafy vegetable crop, spinach beet, Pusa Jyothi variety was sown in pot experiments followed completely randomized block design with four treatments and three replications. Microbial cultures (Pseudomonas, VAM) collected from our laboratory. The treatments for poly bag experiment were fixed as twelve treatments each treatment with three replications were designed. All three replications were used to record observations on yield, quality parameters of spinach around 30 and 60 days after sowing.
In this context of pot culture experiment having twelve treatments and followed statistical design .in this treatment subdivided into three parts: polluted soil with supply of fresh water, unpolluted soil with supply of fresh water and unpolluted soil with supply of polluted water. Polluted soil with supply of fresh water have T1: SF Soil+FYM@12 t/ha, T2: SF Soil + FYM + VAM + Pseudomonas, T3: SF Soil + RDF, T4: SF Soil + RDF + FYM + VAM + Pseudomonas. Unpolluted soil with supply of fresh water, have T5: Soil + FYM, T6: Soil + FYM + VAM + Pseudomonas, T7: Soil + RDF, T8 : Soil + RDF + FYM + VAM + Pseudomonas. Unpolluted soil with supply of polluted water, have T9: Soil + FYM, T10: Soil+ FYM + VAM + Pseudomonas, T11: Soil + RDF, T12: Soil + RDF + FYM + VAM + Pseudomonas. The cleaned poly bags were filled with 8 kg soil and this soil was mixed with chemical fertilizer (0.14: 0.24: 0.37 g poly bag-1 NPK), farm yard manure (78.75 g poly bag-1) and Vesicular Arbuscular Mycorrhizae (100 to 150 g of infected propagules poly bag-1) according to the treatments which were neatly arranged in the net house.
Table 2. Effect of microbial cultures on fresh weight at 30 and 60 DAS in polluted and unpolluted soils of spinach beet
| Treatments | Fresh weight of leaf/plant | |
| 30DAS | 30DAS | |
| Polluted Soil with supply of fresh water | ||
| T1– SF Soil + FYM | 30.48 | 46.48 |
| T2– SF Soil + FYM + VAM + Psuedomonas | 34.02 | 54.05 |
| T3– SF Soil + RDF | 23.02 | 38.65 |
| T4– SF Soil + RDF + FYM + VAM + Psuedomonas | 39.40 | 60.54 |
| Unpolluted soil with supply of fresh water | ||
| T5– SF Soil + FYM + Psuedomonas | 31.30 | 52.30 |
| T6– SF Soil + FYM+ VAM + Psuedomonas | 39.89 | 64.87 |
| T7– SF Soil + RDF | 26.61 | 40.32 |
| T8– SF Soil + RDF + FYM + VAM + Psuedomonas | 41.63 | 70.03 |
| Unpolluted soil with supply of polluted water | ||
| T9– Soil + FYM | 26.40 | 38.12 |
| T10– Soil + FYM + VAM + Psuedomonas | 34.71 | 61.03 |
| T11– Soil + RDF | 28.82 | 50.37 |
| T12– Soil + RDF + FYM + VAM + Psuedomonas | 41.36 | 68.10 |
| SE m± | 0.176 | 0.167 |
| C.D at 5% | 0.513 | 0.488 |
Chemical fertilizers
Phosphorus and potassium @ 0.24 g poly bag-1 P2O5 and 0.37 g poly bag-1 K2O were applied through Di Ammonium Phosphate and Muriate of Potash respectively as basal application. Nitrogen was applied in the form of Urea @ 0.24 g poly bag-1 after germination and after 30 and 60 days after sowing. Farmyard manure was applied @ 78.75 g poly bag-1 which was mixed with soil according to the treatments requirement. EC and pH of FYM were 0.95 dS/m and 7.59 respectively and Ni, Co, Cd content in FYM was 0.91, 0.20, 0.01-0.02 respectively.
Table 3 Effect of microbial cultures on dry weight at 30 and 60 DAS in polluted and unpolluted soils of spinach beet
| Treatments | Dry weight of leaf /plant | |
| 30DAS | 30DAS | |
| Polluted Soil with supply of fresh water | ||
| T1– SF Soil + FYM | 4.05 | 2.84 |
| T2– SF Soil + FYM + VAM + Psuedomonas | 4.73 | 3.24 |
| T3– SF Soil + RDF | 3.16 | 2.22 |
| T4– SF Soil + RDF + FYM + VAM + Psuedomonas | 5.55 | 3.58 |
| Unpolluted soil with supply of fresh water | ||
| T5– SF Soil + FYM + Psuedomonas | 4.62 | 2.93 |
| T6– SF Soil + FYM + VAM + Psuedomonas | 5.82 | 3.80 |
| T7– SF Soil + RDF | 3.55 | 2.52 |
| T8– SF Soil + RDF + FYM + VAM + Psuedomonas | 6.62 | 4.17 |
| Unpolluted soil with supply of polluted water | ||
| T9– Soil + FYM | 3.47 | 2.55 |
| T10– Soil + FYM + VAM + Psuedomonas | 5.45 | 3.38 |
| T11– Soil + RDF | 4.55 | 2.86 |
| T12– Soil + RDF + FYM + VAM + Psuedomonas | 5.97 | 3.95 |
| SE m± | 0.046 | 0.03 |
| C.D at 5% | 0.133 | 0.103 |
Seed Sowing and maintenance
The poly bags were sown with Pusa Jyothi variety of spinach beet at the rate of 20 seeds per poly bag. After germination, thinning was done and routine care was taken to protect the plants from pest and diseases.
RESULTS AND DISCUSSION
Microbial population (CFU g-1 of Soil)
Influence of microbial cultures on biological quality of polluted soil and spinach yield at 30 DAS and 60 DAS on the microbial population in soil was estimated viz., bacteria, Rhizobium, Azospirillum, Azotobacter, actinomycetes, Pseudomonas, molds and VAM show the data presented in the Table .
Table 4. Influence of different treatments on microbial population in polluted and unpolluted soils of spinach beet at 30DAS
Bacterial population (× 107 CFU g-1 of Soil)
Bacterial population in soil differed significantly on application of microbial cultures on biological quality of polluted soil and spinach yield .Initial bacterial population in the polluted soil was 30×107 CFU g-1 of soil and in unpolluted soil was 40×107 CFU g-1 of soil. At 30 DAS, treatment T12 recorded significantly higher bacterial population (124.21) as compared to all other treatments but was on par with treatment T2 (117.85) and T8 (123.85). The significantly lowest (82.98) bacterial population was found with the treatment T7. At 60 DAS, treatment T8 recorded significantly higher (88.68) bacterial population than all other treatments and treatment T5 (83.38) and T12 (84.21) was on par with T8. The significantly lowest (46.46) bacterial population recorded in the treatment T9.
Rhizobium population (× 103 CFU g-1 of Soil)
Rhizobial population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield. Initial rhizobial population in polluted soil was 12.4×103 CFU g-1 of soil and in unpolluted soil was 18.4×103 CFU g-1 of soil. At 30 DAS, treatment T6 recorded significantly higher (29.23) rhizobial population as compared to all other treatments and was on par with treatment T5 (26.23), T7 (26.58), T8 (28.00) and T11 (27.20). The significantly lowest (16.32) rhizobial population recorded in the treatment T4. At 60 DAS, treatment T6 recorded significantly higher (20.71) rhizobial population as compared to all other treatments and was on par with the treatment T5 (18.66), T7 (17.90) and T9 (17.00). The significantly lowest rhizobial population (10.7) recorded in the treatment T4.
Azotobacter population (× 103 CFU g-1 of Soil)
Azotobacter population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield. Initial Azotobacter population in polluted soil was 3.1×103 CFU g-1 of soil and in unpolluted soil was 4.9×103 CFU g-1 of soil. At 30 DAS, treatment T7 recorded significantly higher (15.13) Azotobacter population among all other treatments and was on par with T6 (12.7), T9 (14.26) and T11 (15.00). The significantly lowest (9.7) Azotobacter population found in the treatment T4. At 60 DAS, treatment T5 recorded significantly higher (12.46) Azotobacter population as compared to all other treatments. The significantly lowest Azotobacter population recorded in the treatment T3 (2.43).
Azospirillum population (× 103 CFU g-1 of Soil)
The population of Azospirillum differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield (Table & ) Initial Azospirillum population in polluted soil was 4.2×103 CFU g-1 of soil and in unpolluted soil was 6.5×103 CFU g-1 of soil. At 30 DAS, treatment T12 recorded significantly higher (12.1) Azospirillum population among all other treatments and was on par with T8 (10.5), T9 (10.9), T10 (11.4) and T11 (12.00). The significantly lowest (8.36) Azospirillum population found in the treatment T1 and T5. At 60 DAS, treatment T12 recorded significantly higher (9.4) Azospirillum population as compared to all other treatments and was on par with treatment T4 (8.53). The significantly lowest Azospirillum population recorded in the treatment T11 (4.26).
Actinomycetes population (× 104 CFU g-1 of Soil)
Actinomycetes population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield (Table &). Initial Actinomycetes population in polluted soil was 8.2×104 CFU g-1 of soil and in unpolluted soil was 6.2×103 CFU g-1 of soil. At 30 DAS, treatment T7 recorded significantly higher (41.77) actinomycetes population among all other treatments. The significantly lowest (21.48) Actinomycetes population found in the treatment T9. At 60 DAS, treatment T7 recorded significantly higher (34.73) actinomycetes population as compared to all other treatments and was on par with treatment T5 (34.27). The significantly lowest actinomycetes population recorded in the treatment T9 (15.67).
Pseudomonas population (× 104 CFU g-1 of Soil)
Pseudomonas population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield.
Initial Pseudomonas population in polluted soil was 18.2×104 CFU g-1 of soil and in unpolluted soil was 28×104 CFU g-1 of soil. At 30 DAS, treatment T10 recorded significantly higher (96.10) Pseudomonas population as compared to all other treatments and was on par with treatment T12 (96.00). The significantly lowest Pseudomonas population recorded in the treatment T1 (29.16). At 60 DAS, treatment T12 recorded significantly higher (60.25) Pseudomonas population as compared to all other treatments and was on par with T7 (58.68).The significantly lowest (30.89) Pseudomonas population was recorded in the treatment T11.
Molds population (× 104 CFU g-1 of Soil)
Molds population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield . Initial molds population in the polluted soil was 15×104 CFU g-1 of soil and in unpolluted soil was 29×104 CFU g-1 of soil. At 30 DAS, treatment T3 recorded significantly higher (17.91) molds population as compared to all other treatments. The significantly lowest (4.33) molds population was recorded in the treatment T10. At 60 DAS, higher molds population (11.32) was observed with the treatment T3 as compared to all other treatments and was on par with treatment T1 (10.04). The significantly lowest (1.95) fungal population recorded in the treatment with T8.
VAM population (× 103 CFU g-1 of Soil)
VAM population differed significantly as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield (Table 4.1& 4.2, Fig 4.8). Initial VAM population in polluted soil was 4.8×100 CFU g-1 of soil and in unpolluted soil was 7.2×103 CFU g-1 of soil. At 30 DAS, treatment T7 recorded significantly higher (24.13) VAM population among all other treatments and was on par with T6 (20.80). The significantly lowest (7.49) VAM population found in the treatment T3. At 60 DAS, treatment T12 recorded significantly higher (9.00) VAM population as compared to all other treatments and was on par with treatment T2 (8.04), T6 (8.99), T9 (8.34), T10 (7.88). The significantly lowest VAM population recorded in the treatment T7 (4.14).
Microbial population recorded in the rhizosphere soil at flowering stage and harvesting stage indicated significant increase due to application of microbial cultures. Population was significantly higher under the treatment T8: SF Soil + RDF + FYM + VAM + Psuedomonas and T12 = Soil + RDF + FYM + VAM + Psuedomonas. This is due to application of VAM and Pseudomonas along with FYM will enhance high number of cells in the rhizosphere which will compete with the nature genera.
Microbial Biomass Carbon
Microbial biomass carbon differed significantly at harvesting stage (60 DAS) as influenced by application of microbial cultures on biological quality of polluted soil and spinach yield. At 60 DAS, treatment T12 recorded significantly higher (129.99) microbial biomass carbon as compared to all other treatments and treatment T8 (123.68) was on par withT12. The significantly lowest microbial biomass carbon recorded in the treatment T1 (83.3). The MBC was higher in unpolluted soil compared to polluted soil individually that the microbial activity and mass is reduced in polluted soil due to the accumulated pollutants.
Leaf fresh weight (g plant-1)
The data presented revealed that the leaf fresh weight was significantly affected by different treatments with RDF, combination of inorganic, organic manures (FYM, and biofertilizer ) at 30 DAS and 60 DAS of crop. The highest leaf fresh weight plant-1 was recorded in treatment T8 (41.63 g plant-1) than the rest of treatments at 30 DAS in unpolluted soils. The lowest leaf fresh weight per plant was showed in T3 (23.02 g plant-1) at 30 DAS in polluted soils. The highest leaf fresh weight was observed in T8 (70.03 g plant-1) and the lowest value observed in T9 (38.12 g plant-1) at 60 DAS in unpolluted soil. It was observed that the treatment T8 (70.03 g plant-1) comprising RDF + FYM + VAM and Pseudomonas showed highest values at 30 DAS, 60 DAS in unpolluted soils over other treatments.
Leaf dry weight (g plant-1)
The data presented revealed that the leaf dry weight was significantly influenced by recommended dose of fertilizers, combination of inorganic, organic manures (FYM) and biofertilizers (VAM and Pseudomonas ) at 30DAS and 60 DAS. The highest leaf dry weight plant-1 was observed in T8 (6.62 g plant-1) and lowest value in T3 (3.16 g plant-1) was observed at 30 DAS . The highest leaf dry weight was observed in T8 (4.17 g plant-1) and the lowest in T3 (2.22 g plant-1) at 60 DAS. Among all the treatments, T8 comprising RDF, FYM, VAM and Pseudomonas was showed highest dry weight of leaf per plant at 30 DAS & 60 DAS in unpolluted soils. In same way, the lowest dry weight of leaf was found in T3 at 30 and 60 DAS in polluted soils. Similar results were reported by Madhvi et al. (2014). It was reported that increased leaf area and leaf dry weight in spinach was due to application of chemical fertilizers along with organic manures and biofertilizers.
CONCLUSIONS
Taken together the results obtained in the present study clearly indicate that use of the polluted soil or polluted water for raising spinach beet crop gave reduced yield in terms of leaf fresh weight and dry weight. The yield was significantly highest in the treatment (T8) with FYM, RDF and microbial cultures VAM & Pseudomonas in a normal soil irrigated with fresh water. The microbial populations viz. bacteria, molds were more influenced by the application of FYM and chemical fertilizers irrespective of the soil or water pollution.
REFERENCES
- Wilde, E., R.L. Brigmon, D. Dunn, M. Heitkamp, D. Dagnan. 2005. Use of vetiver grass for phytoextraction of lead from firing range soil. Chemosphere 61: 1451-1457.
- Brigmon, R.L., D. Camper, F. Stutzenberger. 2002. Bioremediation of compounds hazardous to health and the environment – an overview. In: Biotransformations: Bioremediation Technology for Health and Environmental Protection (ed. V.P. Singh), pp. 1-28. Elsevier Science Publishers, The Netherlands.
- Alkorta, I., J.M. Becerri, C. Garbisu. 2010. Recovery of soil health: The ultimate goal of soil remediation processes. In: Trends in Bioremediation and Phytoremediation (ed. G. Płaza), pp. 1-9. Research Signpost, India
- Markert, B.A., A.M. Breure, H.G. Zechmeister. 2003. Bioindicators and Biomonitors. Principles, Concepts and Applications. 997p. Elsevier Science Ltd.
- Doran, J.W., T.B. Parkin. 1994. Defining and assessing soil quality. In: Defining Soil Quality for a Sustainable Environment (ed. J.W. Doran, D.C. Coleman, D.F. Bezdicek, B.A. Stewart), pp. 3-12. Soil Science Society of America, Inc., Madison, US.
- Garbisu, C., Alkorta, I., 2001. Phytoextraction: a cost-effective plant-based technology for the removal of metals from the environment. Technol., 77(3):229-236.
- Garbisu, C., Hernandez-Allica, J., Barrutia, O., Alkorta, I., Becerril, J.M., 2002. Phytoremediation: a technology using green plants to remove contaminants from polluted areas. Environ. Health, 17(3):173-188.
- Weber, O., Scholz, R.W., Bvhlmann, R., Grasmuck, D., 2001. Risk perception of heavy metal soil contamination and attitudes toward decontamination strategies. Risk Anal., 21(5):967-977.
- Madhavi, Y., Goud, P .V., Reddy, K. M and Saidulu, A. 2014. Effect of different levels of vermicompost, castor cake, poultry manure and biofertilizers on growth and yield of Indian spinach (Beta vulgaris bengalensis). Crop Research. 37(1/3): 148-151.