Microbial biomass and activity under different ages of rubber tree plantations in northeast Thailand.

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1 KHON แก นเกษตร KAEN 43 AGR. ฉบ บพ เศษ J. 43 SUPPL. 1 : (2558). 1 : (2015). 963 KHON KAEN AGR. J. 43 SUPPL. 1 : (2015). Microbial biomass and activity under different ages of rubber tree plantations in northeast Thailand. Porntip Puttaso 1, Pimupsorn Panomkhum 1, Rattiyapon Rungthong 1, Arunee Promkhumbut 2, Naruemol Kaewjampa 1 and Phrueksa Lawongsa 1,3* ABSTRACT: Microbial biomass and activity are the main biological indicators of soil quality and assessing changes in soil ecosystems. This study aims to investigate microbial biomass and respiration as an indicator of microbial activity in soil which turnover and accumulate nutrient from rubber tree plantations. Four treatments were conducted, including 1) 3 years rubber tree plantation, 2) 11 years rubber tree plantation, 3) 17 years rubber tree plantation and 4) 27 years rubber tree plantation. Physical and chemical properties of soil were also examined. The highest carbon dioxide emission was examined in 27 years for mgco 2 kg -1 day -1 and the highest microbial biomass-c and microbial biomass-n were found in 11Y for and 5.12 mg/kg, respectively. The greatest amount of C and N stocks in soil were also observed in 27 years. Interestingly, the most efficiency of the microbial community, metabolic quotient-c (qco 2 ), was in 11 years. These findings suggested that microbiological activity were responsive to age of rubber tree plantations. Keywords: Hevea brasiliensis, soil respiration, microbial biomass, soil nutrient, tree age. Introduction The rubber tree (Hevea brasiliensis) is an important economic crop in Thailand. The total area of rubber tree plantation was approximately 3.4 M ha -1 (Rubber Research Institute of Thailand, 2014). In Thailand, rubber tree can be grown in many areas which are unsuitable for other commonly cultivated cash crops. Nowadays, Rubber tree plantations are extended to northeast Thailand with included different climate and also environment compare to southern Thailand which is the traditional area. The growth and production of rubber tree may be varied by the influence of many environmental factors such as the amount of rainfall, soil moisture, soil characteristics and biological properties. Previous studies showed that different age group of rubber trees affected available soil nutrient and soil carbon stock (Promruksa and Smakgahn, 2014; Saengruksawong et al., 2012). One of the major roles which involves in decomposition and transformation of organic materials and nutrient sink, which are mostly derived from above and below ground plant residues, is soil microorganisms. Soil microbial biomass, the living part of soil organic matter, functions as a transient nutrient sink and is responsible for releasing nutrient from organic matter which is used by plants (Smith and Paul, 1990). Microbial activity included microbial res- 1 Department of Plant Science and Agricultural Resources, Land Resources and Environment Section, Faculty of Agriculture, Khon Kaen University. 2 Department of Plant Science and Agricultural Resources, Program in System Approaches in Agriculture, Faculty of Agriculture, Khon Kaen University. 3 Agricultural Biotechnology Research Center for Sustainable Economy: (ABRCSE), Faculty of Agriculture, Khon Kaen University. * Corresponding author: phrula@kku.ac.th

2 964 แก นเกษตร 43 ฉบ บพ เศษ 1 : (2558). piration also acts as the main biological indicators of soil quality and respond to changes resulting from agronomic practices (Araújo et al., 2008). This study aims to investigate the impact of different ages of rubber tree plantation on microbial biomass and activity related to main soil functions such as nutrient turnover, mineralization and immobilization. The data of microbial properties will be guideline to recognize the nutrient turnover in rubber tree plantation systems. Materials and methods Study sites The study sited was located in Tha Phra subdistrict, Khon Kaen province. Four treatments used in this research, including 1) 3 years rubber tree plantation (3Y) (16 29 N; E), 2) 11 years rubber tree plantation (11Y) (16 46 N; E), 3) 17 years rubber tree plantation (17Y) (9 22 N; E) and 4) 27 years rubber tree plantation (27Y) (16 29 N; E). Tapping for rubber begins when the trees are 7 years old. The soil is characterized as a Ban Phai soil series. Soil studies were conducted by digging for five soil samples at depth 0-25 cm. Soil analysis Soil studies were conducted by digging for five soil samples in rubber tree plantation cultivar RRIM600 age 3, 11, 17 and 27 years old. Soil sampling was carried out in May Soil characteristic analyses were done by studying the physical and chemical properties of the soil (Table 1). Physical properties studied include soil moisture, bulk density of the soil through the core method and particle-size distribution and soil texture by hydrometer method. Chemical properties studied include soil reaction by ph meter method in ratio of 1:2.5 with water, total nitrogen (Total N) by micro Kjedahl method (Bremner, 1960), available phosphorus concentration by Bray II and colorimetric method (Bray and Kurtz, 1945), exchangeable potassium level by extracting with ammonium acetate 1N, ph 7.0 and measured by flame photometer, organic carbon in soil by wet oxidation method (Walkley and Black, 1934). Calculations of carbon and nitrogen stock were also evaluated Pan et al (2013). Soil microbial biomass-c and microbial biomass- N Microbial biomass-c and microbial biomass- N were measured in fresh soil immediately after sampling by the chloroform fumigation extraction technique (Amato and Ladd, 1988). For microbial biomass-c, 10 g of soil was extracted with 50 ml of 0.5 M K 2 SO 4. Microbial biomass-c in the extracts was determined after oxidation with K 2 Cr 2 O 7. Microbial biomass-n was determined by the ninhydrin-reactive N method (Amato and Ladd, 1988). Briefly, after 36 h fumigation, 10 g of soil was extracted with 50 ml of 1 M KCl. Microbial biomass-c and microbial biomass-n were calculated as the difference between fumigated and unfumigated values and employing K EC factor of 0.33 (Sparling and West, 1988) and K EN factor of 3.1 (Amato and Ladd, 1988) in the calculation. Soil respiration Alkaline trap method was used to measure field CO 2 -emission, a small glass jar containing 20 ml of 1 M NaOH was placed in a closed metal chamber (16 cm diameter and 29 cm height) and

3 KHON KAEN AGR. J. 43 SUPPL. 1 : (2015). left for 24 h. The CO 2 -emission trapped was subsequently determined by back titration with 0.5 M HCl after precipitating the carbonate with excess 0.5 M BaCl 2. Soil respiration, i.e., CO 2 -emission was computed according to the equation described by Anderson (1982). Statistical analysis This experiment has been designed as the completely randomized design (CRD). F-test along with method of Duncan s multiple range test (DMRT) was used to analyze the differences of the average on each experiment. Results and discussion The data of physical and chemical properties of soil are shown in Table 1. The results showed 965 that soil samples of all treatment were sandy soil. The highest bulk density as 0.38 g/cm 3 was found in rubber tree before tapping (3Y). The highest soil moisture was observed in 17Y. The ph of soil in rubber tree plantations aged 3, 11, 17 and 27 years old were in the range between 4.48 and 5.1 that showed moderate acid soil indicated as Ban Phai soil series. Total N and exchangeable K were increased related to increasing age of rubber tree. However, no significantly difference between age group was observed in available P. The results indicate that higher C and N stocks in soil were found in 27Y which related to higher plantation age (Table 1) suggesting a accumulation of litter fall over a long period which was consistent with data reported by Promraksa and Smakgahn (2014). Table 1 Physical and chemical properties of soil. Soil properties Rubber tree (ages) F-test CV (%) Soil texture sand sand sand sand - - Bulk density (g/cm 3 ) 0.38 a 0.34 c 0.35 bc 0.37 ab * 4.28 Soil moisture (%) 4.00 c 5.79 b 7.72 a 6.24 b * 8.44 Soil ph 4.86 ab 4.48 b 4.76 ab 5.10 a * 6.32 Total N (%) b b a a * Available P (mg/kg) ns Exchangeable K (mg/kg) c b a a * Carbon stock in soil (t C/ha) c bc ab a * In each row, means followed by the same letter do not differ statistically from each other at P<0.05 according to DMRT test, ns; non-significance. When comparing rubber tree plantations of different ages, the rates of CO 2 -emission (soil respiration) were affected by age of rubber tree plantation. The highest CO 2 -emission was found in 27 years for mgco 2 kg -1 day -1 followed by 11 years, 17 years and 3 years, respectively

4 966 แก นเกษตร 43 ฉบ บพ เศษ 1 : (2558). (Table 2). Which in 27 years of rubber tree made as the highest amount of biomass fallen above ground (not shown data) and has cumulative of litters and has moisture, temperature suitable for the activity microbe and can turnover to be the energy source for microbes to produce high CO2- emission but in 3 years of rubber tree have less amount fallen above ground than 27 years therefore made less CO 2 emission. An enhancement of the CO 2 -emission by longer time age of rubber tree can be considered as the highest amount of biomass fallen above ground which can turnover to be the energy source for microbes to produce high CO 2 -emission. CO 2 -emission can also be varied by the effect of soil temperature, moisture, nutrients and plant age (Promraksa and Smakgahn, 2014). The increase of SOC with time was observed. The accumulation of SOC was highest in 27 years. Reduction in latex yield at later age (27yerars) might have resulted in the increase of below-ground organic carbon input (Zhang, 2007) Soil microbial biomass was also influenced by age of rubber tree. The greater MBC was examined in 11 years. The most efficiency of the microbial community, metabolic quotient-c (qco 2 ), was also found in 11Y indicated that more efficiency of heterotrophic microorganisms to convert organic carbon into microbial biomass (Anderson and Domsch, 1990). Lower qco 2, suggesting that microbial communities in 11 years was more efficient in carbon use than the communities in the other treatment. Interestingly, qco 2 were higher in treatments under 17 years and 27 years showing a small microbial biomass with high respiration (Table 2). Table 2 Soil organic carbon (SOC), Microbial biomass Carbon (MBC), CO 2 -emission rates, Metabolic quotient (qco 2 ), Microbial quotient-c (q mic ), Total N, Microbial biomass Nitrogen (MBN) and Microbial quotient-n (q min ) in soils under rubber tree plantations. Soil Properties Treatment 3Y 11Y 17Y 27Y F-test CV(%) SOC (mg/kg) 1,505 c 2,110 bc 4,327 ab 4,696 a * MBC (mg/kg) a a b b * CO 2 -emission (mgco 2 kg -1 day -1 ) c b b a * Metabolic quotient(qco 2 ) (mgco 2 / mg Microbial biomass-c/day) c b a * Microbial quotient-c (q mic ) (Microbial biomass-c/soc) a a b b * Total N (mg/kg) b b a a * MBN (mg/kg) 1.46 c 5.12 a 2.09 c 3.44 b * Microbial quotient-n (q min )( Microbial biomass-n/total N) b a c c * In each row, means followed by the same letter do not differ statistically from each other at p<0.05 according to DMRT test.

5 KHON KAEN AGR. J. 43 SUPPL. 1 : (2015). Conclusion The higher age of rubber plantation shows more carbon and nitrogen accumulation in soil. Greater microbial biomass-c and microbial biomass-n emphasize the importance of nutrient immobilization in rubber tree plantation suggesting an improvement in soil microbial biomass efficiency. Acknowledgements This work was supported by a grant from Jeunes Equipes Associées à l IRD program (JEAI) and Agricultural Biotechnology Research Center for Sustainable Economy, Khon Kaen University. References Amato, M., and J. N. Ladd Assay for microbial biomass based on ninhydrin reactive nitrogen in extracts of fumigated soil. Soil Biol Bio. 20: Anderson, J. M., and K. H. Domsch Application of ecophysiological quotients (qco 2 and qd) on microbial biomass from soils of different cropping histories. Soil Biol Bio. 22: Anderson, J. P. E Soil respiration. In: Page AL, Miller RH, Keeney DR (eds) Agronomy monograph number 9, part II. Chemical and biological properties, 2nd edn. American Society of Agronomy and Soil Science Society of America, Madison, : Araújo, A. S. F., V. B. Santos, and R. T. R. Monteiro Responses of soil microbial biomass and activity for practices of organic and conventional farming systems in Piauí state, Brazil. Eur J Soil Biol. 44: Bray, R. H., and L. T. Kurtz Determination of total, organic, and available forms of phosphorus in soils. Soil sci. 59: Bremner, J. M Determination of nitrogen in soil by the Kjeldahl method. J.Agr. Sci. 55: Pan, G., L. Li, L. Wu., and X. Zhang Storage and sequestration potential of topsoil organic carbon in China s paddy soils. Global Change Biol. 10: Promruksa, W. and K. Smakgahn Carbon stock in soil rubber plantation. J. Appl. Phytotechnol. Environ. Sanit. 3: Rubber Research Institute of Thailand Statistic. Available Source stat_index.htm., 3 December (In Thai) Saengruksawon, C., S. Khamyong, N. Anongrak, and J. Pinthong Growths and carbon stocks of para rubber plantations on phonpisai soil series in northeastern Thailand. Rubb. Thai J. 1: Smith, L., and E. A. Paul The significance of soil microbial biomass estimations. In: Soil biochemistry (Bollag J.M., Stotzky G., eds). Dekker, NY. Pp : Sparling, G. P Soil microbial biomass, activity and nutrient cycling as indicators of soil health. In: Biological indicators of soil health (Pankhurst C., Doube B.M., Gupta V.V.S.R., eds). CAB Int, Cambridge. Pp : Sparling, G. P, and A. W. West A direct extraction method to estimate soil microbial C: calibration in situ using microbial respiration and 14 C labeled cells. Soil Biol Biochem. 20: Walkley, A., and I. A. Black An examination of the Degtjareff method for determining soil organic matter, and a proposed modification of the chromic acid titration method. Soil sci. 37: Zhang, M., X. Fu, W. Feng, and X. Zou Soil organic carbon in pure rubber and tea-rubber plantations in South-western China. Tropical Ecol. 48: