Evaluate the relationship between organic and inorganic sources of nutrients on microbial population dynamics and enzyme activities in soil

Introduction

Wheat (Triticum aestivum L.) is an essential cereal crop belonging to the Poaceae family and has emerged as a staple food in various regions across the globe due to its nutritional value and palatability Wheat is one of the oldest cereals widely consumed by human being. Wheat requires a good supply of nutrients for its growth and yield but chemical fertilizers alone are unable to maintain the long-term soil health and crop productivity (Subba Rao and Srivastava 1998) [1] , because they are unable to supply many other minor and trace elements. Improper and imbalanced use of chemical fertilizers coupled with less addition of organic manures has resulted in deterioration of soil health in terms of emerging multinutrient deficiencies and deterioration of physical soil properties. The addition of organic manures not only supplies the nutrients for crop growth but also improves different soil physical, chemical and biological properties. Balanced fertilizers through organic and inorganic sources improve the soil health as well as boost the productivity of wheat. Efficacy of organic sources to meet the nutrient requirement of crop is not as assured as mineral fertilizers, but the joint use of chemical fertilizers along with various organic sources is capable of improving soil quality and higher crop productivity on long-term basis. Majorly poor management of fertilizer has key role to play in obtaining low yield productivity, so in order to achieve optimum crop productivity management of nutrients through judicious application of organic sources, bio-fertilizers and micro-nutrients are required. Besides it has manorial proteins and it has valuable supports soil biological activities besides improving soil structure, water holding capacity and other physicochemical properties of soil. Highest productivity of crops in sustainable manner without deteriorating the soil and other natural resources could be achieved only by applying [3] . Their inputs are in general beneficial for the overall health of the agroenvironment (Jedidi et al. 2004) [4] . Organic sources of nutrients include farmyard manure (FYM) generated from sheep, poultry litter (PL), green manures, sewage sludge, and press mud (Farhad et al. 2011; Iqbal et al. 2014) [5,6] . Bio-fertilizers are inputs containing microorganism which are capable of mobilizing nutritive elements from complex and non-usable form to simple and usable form through biological processes (Cakmakc et al. 2007) [7] . Biofertilizers are the live formulation of microorganisms which have the ability to mobilize plant nutrients in the soil and offer a cheap, low capital intensive, non-bulk and ecofriendly source to boost productivity (Kloepper et. al. 1989) [8] . Biofertilizers due to its renewable, cheap and ecofriendly nature has gained increasing popularity in the past one decade in the field of agriculture and food production. Bio-fertilizers are one of the important components of the sustainable agriculture for increasing the yield and maintain the soil fertility (Narula et al. 2005) [9] . In this context, organic manures (biofertilizers) would be the viable option for farmers to increase productivity per unit area.

Materials and methods 2.1 Experimental location and season

The experiment was conducted at "Students' Instructional Farm", Department of Agronomy, Chandra Shekhar Azad University of Agriculture & Technology, Kanpur, (U.P.) which is situated between 25 0 26' to 26 0 58' North latitude, 79 0 31' to 31 0 34' East longitude and at the 125.9 meters above sea level in the alluvial tract of Indo -Gangatic Plain zone of central part of Uttar Pradesh, India during the Ravi Season 2024-25 to 2025-26.

Soil condition

The soil of experimental field was sandy loam in texture having low soil organic carbon (0.42 %), low available N (180.87 kg ha -1 ), medium available P (12.9 kg ha -1 ) and K (130.10 kg ha -1), bulk density (1.32 Mg M -3 ), particle density (2.68 Mg M -3 ) contents with neutral pH 8.13 (1:2.5 soil: water ratio). The biological properties of the initial soil sample viz. dehydrogenase activity ranging from 21.67 to 22.89 μg TPF g -1 soil day -1 , phosphatase 200.17 to 207.67 g PNP g -1 h -1 soil, soil microbial biomass carbon (SMBC) 212.09 to 215.87 MBC g -1 soil and bacterial, fungal and actinomycetes population 12.87 to 13.18 cfu x 10 5 g -1 soil, 9.87 to 10.08 cfu x 10 5 g -1 soil and 10.23 to 11.87 cfu x 10 5 g -1 soil, respectively, during the 1st and 2nd year of experiments.

Experimental design and treatments details

The experiment was arranged in a Factorial Randomized Block Design with 54 treatment combinations involving three levels of organic sources (control, FYM @ 5 t ha -1 , vermicompost @ 2.5 t ha -1 ), two levels of inorganic sources (control, ZnSO4 @ 5 kg ha -1 + boron @ 2 kg ha -1 ) and three levels of bio-inoculants (control, Azotobactor, PSB, replicated thrice. Wheat var. K-1317 was taken as a test crop to observe direct effect of the treatments. The 100% NPK recommended dose of fertilizer for wheat was 120 kg N, 60 kg P2O5 and 60 kg K2O ha -1 , respectively. Half dose of N and full dose of P and K were applied as basal in the form of urea, di ammonium phosphate and muriate of potash manually by placement method into open furrows, respectively. The remaining N was applied in two equal splits at tillering and flower initiation stages, respectively during both the years. Soil samples were collected after harvesting of the crop and analysed by the standard procedure.

Results and discussion

Biological properties

The data pertaining to biological properties under different treatments are presented in Table 1 andfigure 1. The activity of dehydrogenase and phosphatase enzymes differed significantly amongst all the treatments. The data showed significant variation of soil dehydrogenase and phosphatase enzymes due to organic, inorganic source of nutrients and bioinoculants practices at amongst all the treatments during both years and on pooled basis also. Pooled analysis data of both year that, dehydrogenase activity of soil and phosphatase enzymes was recorded significantly maximum (25.43 µg TPF g -1 soil day -1 ) and (229.66 g PNP g -1 hr -1 soil) under the organic source at FYM @ 5 t ha -1 (O1) followed by vermicompost @ 2.5 t ha -1 (O2) (24.93 µg TPF g -1 soil day -1 ) and (225.11 g PNP g -1 hr -1 soil) and minimum dehydrogenase activity of soil and phosphatase enzymes (22.61 µg TPF g -1 soil day -1 ), (204.15 g PNP g -1 hr -1 soil) were recorded under the treatment of control (00). Among the inorganic source of nutrients practices significantly maximum dehydrogenase activity of soil and phosphatase enzymes (25.33 µg TPF g -1 soil day -1 ) and (228.76 g PNP g -1 hr -1 soil) during both years were recorded under ZnSO4 @ 5 kg ha -1 + boron @ 2 kg ha -1 (I1) as compared to without inorganic source (23.31 µg TPF g -1 soil day -1 ) and (210.53 g PNP g -1 hr -1 soil) treatment (I0). Bioinoculants practices also significantly influenced by application of Azotobactor (B1) recorded significantly highest dehydrogenase activity of soil and phosphatase enzymes (25.63 µg TPF g -1 soil day -1 ) and (231.49 g PNP g -1 hr -1 soil) followed by PSB (B2) (24.63 µg TPF g -1 soil day -1 ), (222.38 g PNP g -1 hr -1 soil) and lowest dehydrogenase activity of soil and phosphatase enzymes (22.71 µg TPF g -1 soil day -1 ) and (205.06 g PNP g -1 hr -1 soil) was recorded under the treatment of control (B0).This increased might be due to manure promote biological and microbial activities and accelerated the breakdown of organic substances in the added manure, which is known to stimulate the dehydrogenase activity (Pedrazzini and Mckee, 1984) [10] . The increased activity by increasing levels of fertilizer application might be attributed to the fact that inorganic source of nutrient stimulated the activity of microorganisms to utilize the native pool of organic carbon as a source of carbon, which acts as substrate for these enzymes. Masto et al., (2006) [18] reported that dehydrogenase activity was dependent on addition of number and amount of nutrient. The significant increase of enzyme activity was also found by the use of bioinoculants as compared to no inoculation control. Increased the enzyme activity of soil significantly over no inoculation, may possibly be due to the improvement in the porosity and more availability of nutrients (especially P) to the plant (Shinde and Bangar, 2003) [19] . It is evident from data presented in Table 1, that the contents of soil microbial biomass carbon (SMBC) varied significantly under different treatments during both years and on pooled basis also. On the basis of pooled analysis data, it is clear that organic source significantly affected soil microbial biomass carbon and application of FYM @ 5 t ha - 1 (O1) recorded significantly highest soil microbial biomass carbon (255.75 µg MBC g -1 soil) fallowed by vermicompost @ 2.5 t ha -1 (250.60 µg MBC g -1 soil) and lowest soil microbial biomass carbon (213.36 µg MBC g -1 soil) was recorded under the treatment of control (O0). Under the inorganic source of nutrients practices soil microbial biomass carbon significantly affected by application of ZnSO4 @ 5 kg ha -1 + boron @ 2 kg ha -1 (I1) recorded significantly highest soil microbial biomass carbon (243.24 µg MBC g -1 soil) over to without inorganic source (I0) treatment (236.57 µg MBC g -1 soil). Bioinoculants practices also significantly influenced soil microbial biomass carbon and application of Azotobactor (B1) recorded significantly highest soil microbial biomass carbon (252.92 µg MBC g -1 soil) and followed by PSB (B2) (248.48 µg MBC g -1 soil) and lowest soil microbial biomass carbon (218.31 µg MBC g -1 soil) was recorded under the treatment of control (B0).The higher microbial biomass in FYM might be due to higher below ground plant residues as well as added FYM (Grego et al., 1998) [16] . Microbial biomass carbon increased with increase in doses of inorganic fertilizers may be due firstly to increase in microbial population (Hasebe et al., 1985) [17] and secondly to the formation of root exudates, mucigel soughed off cells and underground roots of previous cut crops, which also play an important role in increasing biomass carbon (Goyal et al., 1992) [15] . The SMBC increased with fertilizer level were also reported by Gogoi et al., (2010) [14] . Moreover, the use of bioinoculants in an integrated manner enhanced the microbial biomass carbon during both the years. The increase might be due to integrated use of fertilizer, FYM and bioinoculants add more organic matter, which provide carbon and energy to the soil microbes resulting into multiplication of microbial population and increase in soil microbial biomass carbon during both the years. The results of the present investigation are in accordance with the finding of Datt et al., (2013) [12] . The data pertaining to biological properties under different treatments are presented in Table 2 and figure 2. The microbial population showed higher bacterial population as compared to actinomycetes and fungi in wheat rhizosphere after harvest of the wheat in both the years. The data showed significant variation of soil bacteria, actinomycetes and fungi due to organic, inorganic source of nutrients and bioinoculants practices at amongst all the treatments during both years and on pooled basis also. Pooled analysis data of both year that, soil bacteria, actinomycetes and fungi was recorded significantly maximum (19.68 ×10 5 cfu g -1 soil), (18.27 ×10 5 cfu g -1 soil) and (18.06 ×10 5 cfu g -1 soil) under the organic source at FYM @ 5 t ha -1 (O1) and minimum soil bacteria, actinomycetes and fungi (18.97 ×10 5 cfu g -1 soil), (16.35 ×10 5 cfu g -1 soil), (16.35 ×10 5 cfu g -1 soil) and (13.73 ×10 5 cfu g -1 soil), (12.92 ×10 5 cfu g -1 soil), (12.52 ×10 5 cfu g -1 soil) were recorded under the vermicompost @ 2.5 t ha -1 (O2) and control (00). Among the inorganic source of nutrients practices significantly maximum soil bacteria, actinomycetes and fungi (17.96 ×10 5 cfu g -1 soil), (16.75 ×10 5 cfu g -1 soil) and (16.35 ×10 5 cfu g -1 soil) during both years were recorded under ZnSO4 @ 5 kg ha -1 + boron @ 2 kg ha -1 (I1) as compared to without inorganic source (16.96 ×10 5 cfu g -1 soil), (14.94 ×10 5 cfu g -1 soil) and (14.94 ×10 5 cfu g -1 soil) treatment (I0). Bioinoculants practices also significantly influenced by application of Azotobactor (B1) recorded significantly highest soil bacteria, actinomycetes and fungi (19.48 ×10 5 cfu g -1 soil), (17.76 ×10 5 cfu g -1 soil) and (17.56 ×10 5 cfu g -1 soil) followed by PSB (B2) (17.96 ×10 5 cfu g -1 soil), (16.75 ×10 5 cfu g -1 soil), (16.55 ×10 5 cfu g - 1 soil) and lowest soil bacteria, actinomycetes and fungi (14.94 ×10 5 cfu g -1 soil), (13.02 ×10 5 cfu g -1 soil) and (12.82 ×10 5 cfu g -1 soil) was recorded under the treatment of control (B0).The increased microbial population might be due to application of organic manures in turn provides adequate biomass as a feed for the microbes and helps in increasing microbial population in soil (Singh et al., 2012) [20] . The increase in microbial population might be due to increasing levels of N, P and K which increases the biomass, root exudates and ultimately provides carbon and energy to the soil microbes resulting into multiplication of microbial population (Geetha kumari and Shivashankar, 1991). The results are harmony with the finding of Chand et al., (2010) [11] . The bioinoculants Azotobactor, PSB either singly or in combination significantly increased the population of microbes viz., bacteria, actinomycetes and fungi in rhizosphere soil after harvest of wheat over no inoculation during both the years. The bioinoculants trigger the microbial population might be possibly due to the improvement in the porosity and more availability of nutrients (especially P) to the plant by the bioinoculants (Shinde and Bangar, 2003) [19] . Sushila and Giri (2000) [21] also reported increase in microbial population in rhizosphere of wheat with Azospirillum and Azotobacter inoculations biomass as a feed for the microbes and helps in increasing microbial population in soil (Singh et al., 2012) [20] .

Treatments

Total microbial count (cfu g soil -1 ) Bacteria (a×10 5 cfu g -1 )

Fungi (b×10 5 cfu g -1 ) Actinomycetes (c×10

Conclusion

The overall results demonstrated that enzyme activity, soil microbial biomass carbon and microbial properties of soil were improved by combined application of organic source of nutrients, inorganic source of nutrients and bioinoculants over control. Hence, it can be concluded that integration of all the treatment in balance form improve the physico chemical and biological properties of the soil. Finally, the goal is to integrate the use of all natural and manmade sources of plant nutrients, so that crop productivity increases in an efficient and environmentally benign manner, without sacrificing soil productivity of future generations.

References

1. Subba Rao A, Srivastava S. Role of plant nutrients in increasing crop productivity. Fertil News. 1998;43(4):65-75.
2. Chandrashekara CP, Harlapur SI, Murlikrishna S, Girijesh GK. Response of maize (Zea mays L.) to organic manures with inorganic fertilizers. Karnataka J Agric Sci. 2020;13:144-146.
3. Jones SK, Rees RM, Skiba UM, Ball BC. Influence of organic and mineral N fertilizer on N₂ from temperate grassland. Agric Ecosyst Environ. 2007;121:74-83.
4. Jedidi N, Hassen A, Cleemput OV, Hiri MA. Microbial biomass in a soil amended with different types of organic wastes. Waste Manag Res. 2004;22:93-99.
5. Farhad W, Cheema MA, Saleem MF, Hammad HM, Bilal MF. Response of maize hybrids to composted and non-composted poultry manure under different irrigation regimes. Int J Agric Biol. 2011;6:923-928.
6. Iqbal Z, Khalid M, Soleman N, Jones DL. Differential utilization of dissolved organic and inorganic nitrogen by wheat (Triticum aestivum L.). J Plant Nutr. 2014;37:2094-2107.
7. Cakmakc R, Donmez MF, Erdogan U. The effect of plant growth promoting rhizobacteria on barley seedling growth, nutrient uptake, some soil properties, and bacterial counts. Turk J Agric For. 2007;31:189199.
8. Kloepper JW, Lifshitz R, Zablotowicz RM. Free-living bacterial inoculant for enhancing crop productivity. Trends Biotechnol. 1989;7(2):39-44.
9. Narula N, Kumar V, Singh B, Bhatia B, Lakshminarayana K. Impact of biofertilizers on grain yield in spring wheat under varying fertility conditions and wheat-cotton rotation. Arch Agron Soil Sci. 2005;51(1):79-89.
10. Pedrazzini FR, McKee KL. Effect of flooding on activities of soil dehydrogenases in rice (Oryza sativa L.) roots. Soil Sci Plant Nutr. 1984;30:359-366.
11. Chand S, Somani LL, Bhandari SC. Effect of fertilizer, farmyard manure (FYM) and biofertilizer on the population of Azotobacter and phosphate solubilising bacteria (PSB) in the soil. J Indian Soc Soil Sci. 2010;58(4):460-463.
12. Datt N, Dubey YP, Chaudhary R. Studies on impact of organic, inorganic and integrated use of nutrients on symbiotic parameters, yield, quality of French-bean (Phaseolus vulgaris L.) vis-à-vis soil properties of an acid Alfisol. Afr J Agric Res. 2013;8(22):2645-2654.
13. Geethakumari VL, Shivashankar K. Studies on organic amendment and CO₂ enrichment in ragi/soybean intercropping systems. Indian J Agron. 1991;36:202206.
14. Gogoi B, Barua NG, Baruah TC. Effect of integrated supply of nutrients on soil microbial biomass carbon in an Inceptisol of Assam. J Indian Soc Soil Sci. 2010;58(2):241-244.
15. Goyal S, Mishra MM, Hooda IS, Singh R, Beri V, Choudhary MR, et al. Build-up of microbial biomass with continuous use of inorganic fertilizers and organic amendments. In: Proceedings of the International Symposium on Nutrient Management for Sustained Productivity. 1992;2:149-151.
16. Grego S, Marinari S, Moscatelli MC, Badalucco L. Effect of ammonium nitrate and stabilized farmyard manure on microbial biomass and metabolic quotient of soil under Zea mays. Soil Biol Biochem. 1998;128:132137.
17. Hasebe A, Kanazawa S, Takai Y. Microbial biomass in paddy soil II: microbial biomass C measured by Jenkinson's fumigation method. Soil Sci Plant Nutr. 1985;34:349-359.
18. Masto RE, Chhonkar PK, Singh D, Patra AK. Changes in soil biological and biochemical characteristics in a long-term field trial on a sub-tropical Inceptisol. Soil Biol Biochem. 2006;38:1577-1582.
19. Shinde DB, Bangar ND. Studies on dual inoculation of nitrogenous and phosphatic bacterial cultures in sugarcane. J Maharashtra Agric Univ. 2003;28:190192.
20. Singh A, Singh VK, Chandra R, Srivastava PC. Effect of integrated nutrient management on pigeon pea-based intercropping system and soil properties in Mollisols of the Tarai region. J Indian Soc Soil Sci. 2012;60(1):3844.
21. Sushila R, Giri G. Influence of farmyard manure, nitrogen and biofertilizers on growth, yield attributes and yield of wheat (Triticum aestivum) under limited water supply. Indian J Agron. 2000;45(3):590-595.