Dynamics of soil biological fertility as influenced by organic and inorganic inputs under soybean in vertisol

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1 An Asian Journal of Soil Science Volume 7 Issue 1 June, 2012 Research Article Dynamics of soil biological fertility as influenced by organic and inorganic inputs under soybean in vertisol RITU THAKARE AND SANJAY BHOYAR MEMBERS OF RESEARCH FORUM : Corresponding author : RITU THAKARE, Department of Soil Science and Agricultural Chemistry, College of Agriculture, DHULE (M.S.) INDIA ritu.thakre@gmail.com Co-authors : SANJAY BHOYAR, Department of Soil Science and Agricultural Chemistry, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, AKOLA (M.S.) INDIA smbhoyar@gmail.com Received : ; Revised : ; Accepted : Summary The integrated use of crop residues, biofertilizer and inorganic fertilizers in vertisol improved fertilizer use efficiency and nutrient turnover through augmentation of biological activity specially enzyme activity which is a step toward sustainable agricultural production. Highest soil microbial biomass C ( µg Cg -1 soil) and biomass N (30.15 µg N g -1 soil) were recorded in Bradyrhizobium + 100% RDF i.e. 30 kg N + 75 kg P 2 ha -1 treatment followed by incorporation of wheat 4 t ha % RDF. Incorporation of wheat straw and sugarcane trash along with chemical fertilizer significantly increased SMBC and SMBN content over their alone application. There was significant influence of crop residues and biofertilizer on soil enzyme activity i.e. dehydrogenase activity over control. Incorporation of wheat 4 t ha % RDF significantly increased soil dehydrogenase activity as compared to all other treatments. Bacterial and actinomycetes population were found maximum i.e CFU g -1 x 10 7 and 25.0 CFU g -1 x 10 6, respectively in seed treatment with Bradyrhizobium + 100% RDF, whereas, fungal population was found to increase ( CFU g -1 x 10 4 ) with the incorporation of wheat 4 t ha % RDF followed by sugarcane trash with 100% RDF. Seed inoculation with Bradyrhizobium with 100% RDF recorded highest grain yield (24.59 ha -1 ) and was followed by wheat straw + 100% RDF. SMBC, SMBN, dehydrogenase activity and soil biota were significantly correlated with soybean yield. Key words : Soil microbial biomass carbon and nitrogen, Soil microbial population, Dehydrogenase activity, Integrated nutrient management,vertisol How to cite this article : Thakare, Ritu and Bhoyar, Sanjay (2012). Dynamics of soil biological fertility as influenced by organic and inorganic inputs under soybean in vertisol. Asian J. Soil Sci., 7(1):. Introduction The living soil is a central part of soil fertility because the activity of soil organisms rendered available the elements in plant residues and organic debris entering the soil. Part of this material, however, remains in the soil and contributes to its stabilization by humus build up. The productivity and stability of soil as a medium for plant growth depends greatly on the balance between living and non-living components. Energy from the sun and nutrients essential for growth stored in the fabric of crop plants, are recovered for reuse through decomposition activities of microorganisms in soil. The soil organic matter formed during this process serves both as a continuous nutrient supply and a factor stabilizing the soil physical environment (Howard, 1972). To maintain productivity, soluble nutrients removed from soil through plant growth and harvest must be replaced, either as fertilizers or through biological decomposition of organics. Soil microorganisms play a vital role in soil health but are often forgotten in farming systems. There is a growing interest in their beneficial effects, their role as soil health indicators and factors that influence their abundance and diversity. As soil microorganisms decompose the organic matter, they also assimilate a portion of the nutrients in soil to build up their body. The nutrients in soil microbial biomass are mineralized from the dead microorganisms. Therefore, soil microbial biomass is considered as a source and sinks for nutrients and is an active pool of organic matter in soils. Because of its important role in various ecological systems, nitrogen and carbon contained in soil microbial biomass (i.e. SMBN and HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE

2 RITU THAKARE AND SANJAY BHOYAR SMBC) has received much attention in recent years. Contribution of organic matter to soil from manure plant residues or root secretion usually increases the levels of SMBN, SMBC and enzyme activities. Besides this biofertilizer application seems to enhance the soil microbial activity and nutrient availability. Studies of biological activities in soils are important as they indicate the potential of soil to support biochemical processes which are essential for the maintenance of soil fertility (Dkhar and Mishra, 1983). Considering the paramount significance of soil microbial processes, as a main driving force in the decomposition of organic materials and also as an early indicators of changes in soil properties resulting from soil management and environment stresses in agricultural ecosystems, this study was designed to assess the effects of organic and inorganic inputs on soil biological fertility under soybean in vertisol. Resources and Research Methods Field experiment was conducted at Central Research Station, Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola (M.S.) during Kharif on soybean crop. Twelve treatments was replicated thrice in a Randomized Block Design. The treatments consisted of 75% RDF (22.5kg N kg P 2 ha -1 ), 100% RDF (30 kg N + 75 kg P 2 ha -1 ), and incorporation of wheat straw and sugarcane 4 t ha -1 and seed inoculation with Bradyrhizobium. The surface soil samples (0-30 cm) from each plot were collected and dried in shade, ground and sieved through 2 mm sieve. The soil of the experimental plot was clay in texture, alkaline in nature (7.68), medium in available N ( kg N ha -1 ), and low in available P (16.10 kg P 2 ha -1 ) and rich in potash ( kg K 2 O ha -1 ). The organic C content and total N content of soil were 3.4 g kg -1 and %, respectively. Fresh soil samples were used for biological studies. Soil microbial biomass C and N was estimated by using chloroform fumigation- incubation method (Jenkinson and Powlson, 1976). Fungal, bacterial and actinomycetes population were determined by using serial dilution method as described by Dhingra and Sinclair (1993). The dehydrogenase activity was examined by TPF method as described by Klein et al. (1971). Research Findings and Discussion Results pertaining to soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN) and dehydrogenase activity are presented in Table 1. Table 1 : Effect of integrated nutrient management on soil microbial biomass carbon, nitrogen, dehydrogenase activity after harvest of soybean and grain yield SMBC (µg C g Treatments -1 SMBN (µg N g -1 Dehydrogenase activity Grain yield soil) soil) (µg TPF g -1 soil h -1 ) q ha -1 T 1 Control T 2 75% RDF T 3 100% RDF T 4 Incorporation of sugarcane 4t ha T 5 Incorporation of sugarcane 4t ha % RDF T 6 Incorporation of sugarcane 4t ha % RDF T 7 Incorporation of wheat straw 4t ha T 8 Incorporation of wheat straw 4t ha % RDF T 9 Incorporation of wheat 4t h a % RDF T 10 Seed treatment with bradyrhizobium T 11 Seed treatment with bradyrhizobium + 75 % RDF T 12 Seed treatment with bradyrhizobium + 100% RDF SE (m) CD at 5% Initial HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 19 Asian J. Soil Sci., (June, 2012) 7 (1) :

3 DYNAMICS OF SOIL BIOLOGICAL FERTILITY AS INFLUENCED BY ORGANIC & INORGANIC INPUTS UNDER SOYBEAN IN VERTISOL Soil microbial biomass carbon: SMBC as influenced by integrated nutrient management (INM) treatments ranged from µg C g -1 soil in control to µg C g -1 of soil at harvest stage of soybean crop. Amongst the treatment, seed treatment with Bradyrhizobium + 100% RDF registered maximum SMBC and was significantly superior over all other treatments, being followed by crop residues like sugarcane trash and wheat straw incorporation in soil + 100% RDF ( and µg C g -1 soil, respectively. Fertilizer application alone increased biomass carbon over control. Further increase in biomass C was observed due to organics like sugarcane trash and wheat straw as well as seed treatment with Bradyrhizobium alone or conjunction with fertilizers i.e. 32 to 44 per cent increase over control. Wide C:N ratio and short duration of incorporation of organics seem to be probable factors for above variation. However, in long run these organics may cause build up of SMBC. Microbial biomass, though constitutes small fraction of soil organic matter, is an important fraction and fairly labile (Jenkinson and Ladd, 1981). In the present study the soil and climatic conditions were most favourable for crop growth and biochemical transformations. Puranik (1991) reported maximum SMBC due to application of organics in combination with fertilizers for wheat and soybean crop. Estimates of SMBC after harvest of soybean clearly indicated the dominant role played by organics/ bioinoculants in conjunction with recommended fertilizers. Hence, SMBC serves as a temporary sink for plant nutrients and can be used as an index of soil fertility. Soil microbial biomass nitrogen: Various treatments have improved SMBN at harvest of soybean over its initial status (Table 1) which may be contributed to organics, fertilization, rhizodeposition and addition of substantial amount of leaf litter to the soil. Application of fertilizer as well as crop residues alone led to build up of SMBN at harvest. Availability of such carbonaceous substrates (wide C:N ratio) for heterotrophic organisms certainly enhances the microbial activity and thereby SMBN. However, seed treatment with Bradyrhizobium + 100% RDF significantly raised SMBN (30.15 µg N g -1 soil) and was closely followed by crop residues like sugarcane trash (28.33 µg N g -1 soil) and wheat straw (29.24 µg N g -1 soil). There was about 26 to 33 per cent increase in SMBN due to Table 2: Effect of integrated nutrient management on soil microbial population after harvest of soybean Treatments Fungi (CFU g ) Bacteria (CFU g ) Actinomycetes(CFU g ) T 1 Control T 2 75% RDF T 3 100% RDF T 4 Incorporation of sugarcane 4t ha T 5 Incorporation of sugarcane 4t ha % RDF T 6 Incorporation of sugarcane 4t ha % RDF T 7 Incorporation of wheat 4t ha T 8 Incorporation of wheat 4t ha % RDF T 9 Incorporation of wheat 4t ha % RDF T 10 Seed treatment with Bradyrhizobium T 11 Seed treatment with Bradyrhizobium + 75 % RDF T 12 Seed treatment with Bradyrhizobium + 100% RDF SE (m)± C.D. (P=0.05) Initial Table 3 : Correlation coefficient between biological properties of soil Parameters SMBC SMBN Dehydrogenase activity Fungal population 0.70** 0.77** 0.85** Bacterial population 0.80** 0.78** 0.96** Actinomycetes population 0.43** 0.74** 0.95** Grain yield 0.82** 0.79** 0.55** ** indicate significance of value at P=0.01, respectively HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 20 Asian J. Soil Sci., (June, 2012) 7 (1) :

4 RITU THAKARE AND SANJAY BHOYAR various treatments over control. P fertilization exerts beneficial effect on root proliferation, nodulation and biochemical transformations in soil. The results corroborate the findings of Ghoshal and Singh (1995) and Patil and Puranik (2001) who reported increase in SMBN in fertilizer and wheat straw treated plots, respectively under dryland condition. Release of nutrients much depends on the turnover rate of SMBC and N. The present study clearly indicate the beneficial effect of integrated nutrient management practices in achieving sustainability in crop production and soil health. Soil biological quality indices (BSQI) assume great significance in soil health management. Soil dehydrogenase activity : Soil enzymes play a major role in chemical and biochemical transformations, also affects the rate at which nutrients become available to plants. Enzyme dehydrogenase responds much more rapidly to crop residues and biofertilizer. Its activity varied from 4.16 to µg TPF g -1 soil h -1 (Table 1). Amongst the treatments, seed treatment with Bradyrhizobium + 100% RDF recorded the highest dehydrogenase activity followed by incorporation of wheat 4 t ha % RDF (21.16 µg TPF g -1 soil h -1 ). Thus, results clearly point out the enhancement of dehydrogenase activity due to integrated nutrient management in soybean. Application of carbonaceous substrate to soil resulted in increased microbial growth as well as enzyme activities (Manna et al., 1996; Parham et al., 2002). Enzyme activity is considered as an index of microbial activity and soil fertility (Burns, 1982). Seed treatment with biofertilizer had substantially raised dehydrogenase activity as compared with control and fertilizer alone treatments at the harvest of soybean. Thus, organics plays significant role in enzyme activity of soil. Microbial population : Role of organics in altering the dynamics of soil biota is quite evident from the results (Table 2). Their population was significantly influenced by different treatments involving fertilizer and organics after harvest of soybean. Fungal population was highest where wheat 4 t ha % RDF was applied followed by sugarcane 4 t ha % RDF. The increase in fungal population as a result of incorporation of crop residues in conjunction with inorganic fertilizers was reported earlier (Thakare and Gupta, 2003). Bioinoculants alone slightly increased fungal population. However, bacterial population was maximum i.e CFU g -1 x 10 7 in seed treatment with Bradyrhizobium + 100% RDF and closely followed by seed treatment + 75% RDF, wheat straw + 100% RDF and sugarcane trash + 100% RDF. Crop residues coupled with fertilizer exerted a stimulating influence on the preponderance of bacteria in soil and signifies the importance of carbonaceous organic residues in proliferation of their population (Mukherjee et al., 1990). Actinomycetes population exhibits similar trend, being maximum in seed treatment + 100% RDF (25.0 CFU g -1 x 10 6 ). Fertilizer alone did not show notable impact on soil biota. Judicious use of fertilizers with crop residues resulted in triggering soil microbial population. Activities of soil organisms play a major role in nutrient cycling, organic matter decomposition and turnover. A large diverse and active population of organisms should be the most important indicator of a healthy soil. Soil microbial population showed significantly positive correlation with SMBC, SMBN and dehydrogenase activity (Table 3). Grain yield : Grain yield of soybean (Table 1) was significantly increased due to the application of integrated treatments. Seed treatment with Bradyrhizobium along with 100% RDF recorded maximum grain yield (24.59 q ha -1 ) and was found at par with treatment involving wheat 4 t ha % RDF (22.60 q ha -1 ). Similar findings were reported by Dikshit and Khatik (2003). Thus, while attempting high crop production, recent agro techniques in farming need to be adopted which help in enhancing soil biological activities as well as soil fertility. Thus, maintenance of soil health is of paramount significance for achieving sustainable crop yields. Grain yield of soybean was positively significantly correlated with SMBC, SMBN and dehydrogenase activity (Table 3). Conclusion: Conjunctive use of wheat straw and sugarcane trash with inorganic fertilizers substantially improved soil microbial biomass carbon, soil microbial biomass nitrogen, dehydrogenase activity and microbial population. These treatments are most effective and ideal for improving soil health and soybean yield in semiarid region. The results pertaining to SMBC and SMBN are useful in predicting the pool of nutrient availability in soil and will help to unravel the complexities of the processes associated with biocycling of organic resources like crop residues for maintaining soil health and achieving sustainable crop yields. Literature Cited Burns, R.C. (1982). Enzyme activity in soil: Location and possible role in microbial ecology. Soil Biol. Biochem., 14: Dhingra, O.D. and Sinclair, J.B. (1993). Basic plant pathology methods, CBS Publisher, New Delhi, pp Dikshit, P.R. and Khatik, S.K. (2002). Influence of organic manure in combination with chemical fertilizer on production, quality and economic feasibility of soybean in Typic Haplustert of Jabalpur. Legume Res., 25(1): Dkhar, V.S. and Mishra, R.R.(1983). Dehydrogenase and urease activity of maize (Zea mays L.) field soils. Plant & Soil., 70: HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 21 Asian J. Soil Sci., (June, 2012) 7 (1) :

5 DYNAMICS OF SOIL BIOLOGICAL FERTILITY AS INFLUENCED BY ORGANIC & INORGANIC INPUTS UNDER SOYBEAN IN VERTISOL Ghoshal, N. and Singh, K.P. (1995). Effects of farm yard manure and inorganic fertilizer on the dynamics of soil microbial biomass in a tropical dryland agroecosystem. Biol. & Fertility Soils., 19: Howard, P.J.A. (1972). Problems in the estimation of biological activity in soil. Oikos., 23(2): Jenkinson, D.S. and Ladd, J.N. (1981). Soil biochemistry. Marcel Dekker, New York, 415pp. Jenkinson, D.S. and Powlson, D.S. (1976). The effect of biocidal treatments on metabolism in soil I. Fumigation with chloroform. Soil Biol. Biochem., 8: Klein, D.A., Loh, T.C. and Goulding, R.L. (1971). A rapid procedure to evaluate dehydrogenase activity of soils low in organic matter. Soil Biol. Biochem., 3: Manna, M.C., Kundu, S., Singh, M. and Takkar, P.N. (1996). Influence of FYM on dynamics of microbial biomass and its turnover and activity of enzymes under a soybean- wheat system on a Typic Haplustert. J. Indian Soc. Soil Sci.,44(3): Mukherjee, D., Ghosh S.K. and Das A.C. (1990). A study on the chemical and microbiological changes during decomposition of straw in soil. Indian Agric., 34:1-10. Parham, J., Deng S., Raun, W. and Johnson, G. (2002). Long term cattle manure application in soil. I. Effect of soil phosphorus levels, microbial biomass C and dehydrogenase and phosphatase activity. Biol.& Fertility Soils, 35(5): Patil, Rita B. and Puranik, R.B. (2001). Microbial biomass C and N as influenced by cropping systems and nutrient management. PKV Res. J., 25(2): Puranik, R.B. (1991). Soil Biomass. Report of FAO/UNDP training at Colorado state university USA ; submitted to Dr. Panjabrao Deshmukh Vidyapeeth, AKOLA, M.S.(India). Thakare, Ritu and Gupta, V.R. (2003). Effect of cropping systems and nutrient management on microbial population in vertisol. PKV Res. J., 27(2): ******** ****** **** HIND AGRICULTURAL RESEARCH AND TRAINING INSTITUTE 22 Asian J. Soil Sci., (June, 2012) 7 (1) :