search
Contact Us
HOME

  • Crossref logo
  • Crossref Similarity Check logo
Journal Search Engine

to

Search Advanced Search Adode Reader(link)
Download PDF Export Citaion korean bibliography PMC previewer
ISSN : 2287-5824(Print)
ISSN : 2287-5832(Online)
Journal of The Korean Society of Grassland and Forage Science Vol.44 No.4 pp.294-300
DOI : https://doi.org/10.5333/KGFS.2024.44.4.294

Zeolite and Sulfuric Acid Mixture Reduces the Ammonia and Greenhouse Gas During Manure Composting and Utilize as Fertilizer on Maize Cropping

Sang-Hyun Park1, Tae-Hwan Kim1*, Bok-Rye Lee1,2*
1Department of Animal Science, Institute of Agriculture Science and Technology, College of Agriculture & Life Science,
Chonnam National University, Gwangju 61186, Republic of Korea
2Biotechnology Research Institute, Chonnam National University, Gwangju 61186, Republic of Korea
* Corresponding author: Tae-Hwan Kim, Department of Animal Science, Institute of Agriculture Science and Technology, College of Agriculture & Life Science, Chonnam National University, Gwangju 61186, Korea, Tel: +82-62-530-2126, E-mail: grassl@chonnam.ac.kr
* Bok-Rye Lee, Department of Animal Science, Institute of Agriculture Science and Technology, College of Agriculture & Life Science, Chonnam National University, Gwangju 61186, Korea, Tel: +82-62-530-0217, E-mail: turfphy@jnu.ac.kr
December 11, 2024 December 26, 2024 December 26, 2024

Abstract


This study aimed to evaluate the effectiveness of a zeolite and sulfuric acid mixture (ZS) as an air filter to mitigate the emissions of ammonia (NH3), nitrous oxide (N2O), and methane (CH4) during the composting of cattle manure. Compared to the control group (blank), ZS reduced NH3 emissions by 91.4%, N2O emissions by 33.6%, and CH4 emissions by 20.0% over the 100-day composting period. Additionally, sulfuric acid in the ZS reacted with NH3, storing it as ammonium sulfate [(NH4)2SO4], which can serve as a source of nutrients such as nitrogen (N) and sulfur (S). To evaluate the fertilizing efficiency of [(NH4)2SO4] in ZS for maize growth, we applied four treatments: control (non-N fertilizer), collected ZS (cZS), cattle manure (organic fertilizer, OF), and urea (chemical fertilizer, CF). Compared to the control, cZS increased total dry weight (DW) by 48%, total digestible nutrients (TDN) by 7.3%, and crude protein (CP) by 77.8%. No significant differences were found among the applications of cZS, OF, and CF. These results suggest that the zeolite mixed with sulfuric acid effectively reduces hazardous gas emissions such as NH3, CH4, and N2O during cattle manure composting. Furthermore, the collected zeolite can potentially be reused as fertilizer, suggesting a positive opportunity for resource recycling to mitigate environmental pollution.


Ammonia , Cattle manure , Methane , Nitrous oxide , Zeolite

초록

    Ⅰ. INTRODUCTION

    Livestock manure is a significant source of fertilizer, containing essential nutrients such as nitrogen (N), phosphorus (P), potassium (K), and sulfur (S). It benefits the soil by contributing organic matter, which can improve soil structure, aeration, and moisture retention. However, animal manure also contributes to environmental pollution by emitting greenhouse gases like nitrous oxide (N2O) and methane (CH4), as well as causing nitrogen loss through ammonia (NH3) and nitrate (NO3-) leaching. CH4 is produced through the anerobic decomposition of the organic matter remaining in manure. Over the past 200 years, atmospheric CH4 concentrations have risen by 11.5% (Park et al., 2006), and its global warming potential is 27.2 times greater than that of carbon dioxide (CO2) (Hilgert et al., 2022). N2O is generated from the storage and treatment of animal manure through the combined processes of nitrification and denitrification of the N contained in the manure. The N2O is a minor gas that contributes to global warming and depletes ozone (O3) in the stratosphere (Rodhe, 1990) and has a global warming potential 273 times higher than that of CO2 (US EPA, accessed 10/24/2022). NH3 is primarily produced through the decomposition of animal feed and waste, resulting in elevated concentrations within animal housing facilities (Ndegwa et al., 2008). This compound emits strong odors and presents numerous adverse environmental impacts upon atmospheric release. The NH3 reacts with nitrogen oxides and sulfur oxides in the air, forming particulate matter (PM) such as ammonium nitrate and ammonium sulfate, which can contribute to respiratory and cardiovascular diseases (Battye et al., 2003;Lan et al., 2024).

    Numerous strategies have been explored to mitigate emissions of NH3 and greenhouse gas. One effective technique involves the use inhibiting urease or nitrification. Applying urease inhibitors such as hydroquinone (HQ) N-(n-butyl) thiophosphoric triamide (NBPT), and phenyl phosphorodiamidate (PPDA) can slow the hydrolysis of urea in the soil (Wang et al., 1991). In addition, directly injecting manure or incorporating it into the soil can decrease NH3 and N2O emissions. Park et al. (2018a) reported that using the injection technique for pig slurry application resulted in a reduction of NH3 and N2O emissions by 40% and 33%, respectively, when compared to the broadcasting method. Zeolite features porous structure that can accommodate various cations and demonstrates a significant cation exchange capacity. During the composting process, the addition of zeolite has been shown to lower NH3 emissions. Kithome et al. (1999) found that zeolite, which has a high affinity for NH4+ ions, reduces NH3 emission by lowering the concentration of free NH4+ ions. Additionally, CH4 emissions can be physically adsorbed by the molecular sieve structure of zeolite (Lee et al., 2000).

    Sulfuric acid is a highly corrosive mineral acid used in agriculture to acidify pig slurry, thereby mitigating NH3 emissions (Kai et al., 2008;Park et al., 2015). Additionally, the chemical reaction between 1 mol of sulfuric acid and 2 mol of NH3 produces ammonium sulfate [(NH4)2SO4], which can be utilized as fertilizer. This compound serves as an important source of both nitrogen and sulfur nutrients for plants, promoting healthy growth and improving soil fertility. Nitrogen is essential for plant protein synthesis and overall growth, while sulfur plays a crucial role in the formation of amino acids and enzymes, contributing to various metabolic processes in plants (Ekbic et al., 2024;Sharma et al., 2024). In this study, we evaluated the adsorptive potential of zeolite and sulfuric acid mixture in reducing hazardous gases such as NH3, CH4, and N2O emitted during cattle manure composting. Additionally, we assessed the fertilizer efficacy of the collected zeolite-sulfuric acid mixture (in the form of ammonium sulfate) as a nitrogen and sulfur source for maize growth.

    Ⅱ. MATERIAL and METHODS

    1. Experiment design

    The experiment was conducted at a local livestock farm in Damyang-gun, Chonnam. The raw cattle manure was composted with rice hulls at a ratio of 1:5 (w/w) in the container (0.6 m diameter and 1.2 m height). Natural zeolite and sulfuric acid were mixed at a ratio of 5:1 (w/v) and filled into a column connected to the manure composting container. This experiment was organized into two steps. The first experiment involved two treatments: 1) control (C) and 2) zeolite mixed with sulfuric acid (ZS). The chemical composition of the natural zeolite is shown in Table 1. The emissions of NH3, CH4, and N2O gases generated during the composting process of cattle manure over 100 days were analyzed. After the first experiment, the zeolite mixed with sulfuric acid was collected from the column to assess its fertilizing efficiency. The second field experiment included four treatments: 1) control (non-N fertilizer, only water), 2) collected zeolite and sulfuric acid mixture (cZS), 3) compost (organic fertilizer, OF), and 4) urea (chemical fertilizer, CF).

    2. Plant growth and harvest

    Forage corn (Zea mays, c.v. Pioneer-35P95) was sown on May 5th using a randomized complete block design comprising three replications in distinct plots. Each treatment block measured 2 m × 3 m. The maize was planted in rows, maintaining a seed spacing of 20 cm between plants and a row spacing of 65 cm. The soil chemical properties of the field experiment site are presented in Table 2. The plot of treatments (cZS, OF, and CF) was uniformly applied at a rate of 200 kg N ha-1 (340 L) before 2 weeks of seedling. Each plot received a specified quantity of chemical fertilizer to maintain the application ratio of P2O5:K2O to 150:150 ha-1. Maize was harvested 122 days after seeding, on September 2nd.

    3. Gas emission sampling

    The modified acid trap system was used to measure NH3 emissions, as described by Ndegwa et al. (2009) was utilized. Each compost container was linked to NH3 trapping tubes that contained 150 mL of 0.2 mM sulfuric acid. A vacuum system generated airflow through the chambers at a consistent rate of 1.5 L per minute, allowing for the expulsion of NH3-scrubbed air. NH3 emissions were measured daily for the initial 55 days and subsequently at 5-day intervals. N2O and CH4 were collected from sealed containers using syringes and preserved in 10 mL vacutainer tubes prior to analysis. The sampling of N2O and CH4 was performed in the morning at 09:00 to reduce diurnal fluctuations in flux patterns. N2O emissions were assessed daily for the first 10 days and then at 10-day intervals thereafter. The collection of CH4 emissions followed the same procedure as that for N2O, with CH4 being sampled daily for the first 35 days and then at 10-day intervals afterward.

    4. Measurements and chemical analysis

    Total nitrogen content in zeolite was assessed using the Kjeldahl digestion method. The concentration of NH3 was measured colorimetrically using Nessler’s ammonium color reagent following microdiffusion in a Conway dish (Kim and Kim, 1996). N2O and CH4 concentrations were measured with a gas chromatograph (7890A, Agilent Technologies, USA) equipped with a thermal conductivity detector (TCD). N2O fluxes were calculated according to the method described by Guo et al. (2012). The fluxes for N2O and CH4 were determined using the following equation.

    F = ρ × ( P / 760 ) × ( V / A ) × Δ C / Δ t ) × [ 273 / ( 273 + T ) ] ,
    (1)

    where F represents the N2O flux or the CH4 flux, ρ denotes the density of N2O or CH4 at 0°C and 760 mm Hg (kg m-3), V is the volume of the chamber, A indicates the area from which N2O or CH4 was released into the chambe, and △C/△t refers to the rate of N2O or CH4 accumulation within the chamber. T represents the air temperature inside the chamber in Celsius, while P is the air pressure at the experimental site. Given that the experimental site is situated very close to sea level, P/760 is approximately equal to 1. Cumulative emissions of NH3, N2O, and CH4 throughout the total period of experiment were calculated by integrating all daily measurements and estimating periods.

    The nutritional value of the maize harvested at cutting time was evaluated using subsamples collected for dry matter (DM) yield. The maize samples underwent analysis for crude protein (CP) in accordance with the methods outlined by the AOAC (1990). Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were quantified using the technique described by Van Soest et al. (1991) with a Dosi-Fiber extractor (Dosi-fiber, Barcelona). Total digestible nutrients (TDN) were calculated using the ADF-based equation: TDN = 88.9 – (0.779 × % ADF).

    5. Statistical analysis

    Duncan’s multiple range tests were employed to compare the means across three replications for different treatments. Unless specified otherwise, conclusions are drawn from the differences between the means, with significance set at p<0.05, utilizing SAS 9.1.3 software.

    Ⅲ. RESULTS AND DISCUSSION

    In this study, we evaluated the effectiveness of a zeolitesulfuric acid mixture (ZS) in reducing the emissions of ammonia (NH3), nitrous oxide (N2O), and methane (CH4) during the composting process of cattle manure conducted in containers. The gases emitted during this process were passed through a column filled with the ZS. During the composting process, NH3 was consistently generated, especially in the first 55 days when a significant amount was produced (Fig. 1A). The NH3 concentration measured during the composting process sharply increased in the midterm phase and then gradually decreased thereafter (Kim et al., 2006). The NH3 emission significantly reduced while passing through the ZS column compared to the control. Notably, the total NH3 emission decreased by 91.4% as a result of the ZS during the composting period of 100 days (Fig. 1B). This result indicates that zeolite possesses significant potential for NH3 mitigation. Zeolite, with its porous structure, effectively adsorbs cations such as NH3, leading to a notable decrease in concentration (Park et al., 2014;Kim, 2016;Cataldo et al., 2021). NH3 reacts chemically with sulfuric acid to form (NH4)2SO4, which leads to a more significant reduction in NH3 (Park et al., 2018b).

    The N2O emissions primarily occur through aerobic nitrification and anaerobic microbial denitrification. In aerobic nitrification, NH4+ is oxidized to NO2 - and then further oxidized to NO3-. In contrast, during anaerobic microbial denitrification, NO3- is decreased to gaseous nitrogen compounds (Gilsanz et al., 2016). Thus, the key factors determining N2O emissions are the availability of NH4+ for nitrification into NO3--N and the availability of soluble organic carbon for denitrification. Compared to NH3 emission, N2O emission increased by 60 days after composting. However, this rise in N2O emissions declined within one month (Fig. 2A). The later peak of N2O emission, which occurs after the NH3 pattern, clearly indicates the nitrification process from NH4+ to NO3-. This process is the initial substrate required for denitrification to produce N2O (Subbarao et al., 2006;Gilsanz et al., 2016). The same phenomenon of N2O emission occurred during material preparation, thermophilic and maturation stages reported by Szanto et al. (2007) and Zheng et al. (2020). The total N2O emission throughout the composting period of measurement was 0.86 mg N kg⁻¹ in the control and 0.57 mg N kg⁻¹ in the ZS treatment, indicating a decrease of 33.6% in the ZS treatment (Fig. 2B).

    During the composting process, carbon components are converted into carbon dioxide (CO2) or transformed into humic material through a process known as humification. In contrast, these components can be emitted as CH4 under anaerobic conditions. According to Peigné and Girardin (2004), key factors influencing CH4 production and emission during composting include the characteristics of the raw materials, the height and shape of the compost pile, control of moisture content, and the frequency of turning the compost. Methane was continuously produced during the composting process, and a significant reduction pattern was observed due to the ZS treatment (Fig. 3A). Cumulative CH4 emission decreased by 20% in the ZS treatment during composting (Fig. 3B). Zeolite possesses a high cation exchange capacity, allowing it to effectively adsorb NH₄⁺ from the soil, which consequently lowers NH3 and CH4 emissions. Ali et al. (2022) reported that the single use of zeolite has resulted in a notable reduction in CH4 emission by an average of 12%.

    During cattle manure composting, NH3 was captured through a chemical reaction with H2SO4 in the ZS column and stored as (NH4)2SO4. This substance is potentially used as a source of N and S nutrition. These nutritions play a role in synthesizing organic compounds, including amino acids and proteins, in higher plants. (Hesse et al., 2004). After composting, the ZS was collected and analyzed for the total N to assess its potential as a fertilizer. Before the composting experiment, the nitrogen content of the ZS was 0.03%. However, after the completion of the composting experiment, the nitrogen content of the ZS was analyzed to be 0.22% (data not shown). To evaluate the effect of collected ZS (cZS), organic fertilizer (OF), and chemical fertilizer (CF) were applied to the maize field based on the same nitrogen application rate. Forage yield and nutrient composition as affected by zeolite, organic, and chemical fertilizers are summarized in Table 3. The DM yield of maize was significantly higher in plots applied with cZS, OF, and CF, with an increase of 48%, 45%, and 51%, respectively, compared to control, only water. However, there were no significant differences in DM between three different types of fertilizer (cZS, OF, and CF). Similar tendencies of nutrient value were observed. ADF and NDF decreased by 10.7% and 20.3% (on average 3 fertilizer treatments), respectively, compared to the control, while CP and TDN increased by 7.3% and 77.8% (on average 3 fertilizer treatments) compared to the control.

    Taken together, the hazardous gases emitted from cattle manure composting are passed through the column containing zeolite and sulfuric acid mixture, significantly reducing the emission of NH3, N2O, and CH4. Furthermore, the collected zeolite mixed with sulfuric acid after the composting process, which stores (NH4)2SO4, would be a fertilizer source of nitrogen and sulfur nutrients.

    Ⅳ. ACKNOWLEDGEMENTS

    This study was financially supported by the National Research Foundation of South Korea (NRF-2022R1C1C2011575).

    Figure

    KGFS-44-4-294_F1.gif

    Daily (A) and cumulative (B) emission of ammonia (NH3) after passing through the control (C, blank) and zeolite mixed with sulfuric acid (ZS, black) during 100 days of composting. Values are presented as means ± standard deviation (n = 3). Different letters represent significant difference at p<0.05 between treatments.

    KGFS-44-4-294_F2.gif

    Daily (A) and cumulative (B) emission of nitrous oxide (N2O) after passing through the control (C, blank) and zeolite mixed with sulfuric acid (ZS, black) during 100 days of composting. Values are presented as means ± standard deviation (n = 3). Different letters represent significant difference at p<0.05 between treatments.

    KGFS-44-4-294_F3.gif

    Daily (A) and cumulative (B) emission of methane (CH4) after passing through the control (C, blank) and zeolite mixed with sulfuric acid (ZS, black) during 100 days of composting. Values are presented as means ± standard deviation (n = 3). Different letters represent significant difference at p<0.05 between treatments.

    Table

    Chemical analysis of the natural zeolite

    Soil chemical properties of experimental site

    The content of herbage dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), total digestible nutrients (TDN), and, crude protein (CP) applied control, collected zeolite (cZS), compost (organic fertilizer, OF), and urea (chemical fertilizer, CF)

    Different letters in vertical column represent significant difference at p<0.05.

    Reference

    1. Ali, A., Ali, M.F., Javed, T., Abidi, S.H., Syed, Q., Zulfiqar, U., Alotaibi, S.S., Siuta, D., Adamski, R., and Wolny, P. 2022. Mitigating ammonia and greenhouse gaseous emission from arable land by co-application of zeolite and biochar. Frontiers in Plant Science. 13:950944.
    2. AOAC. 1990. Official methods of analysis (15th ed.). Association of Official Analytical Chemists. Washington D.C.
    3. Battye, W., Aneja, V.P. and Roelle, P.A. 2003. Evaluation and improvement of ammonia emissions inventories. Atmospheric Environment. 37:3873-3883.
    4. Cataldo, E., Salvi, L., Paoli, F., Fucile, M., Masciandaro, G., Manzi, D., Masini, C.M. and Mattii, G.B. 2021. Application of zeolites in agriculture and other potential uses: A review. Agronomy. 11:1547.
    5. Ekbic, E., and Kose, G. 2024. Influence of nitrogen treatments on some nutrient concentration and bioactive compounds of broccoli. BMC Plant Biology. 24:1096.
    6. Gilsanz, C., Báez, D., Misselbrook, T.H., Dhanoa, M.S. and Cárdenas, L.M. 2016. Development of emission factors and efficiency of two nitrification inhibitors, DCD and DMPP. Agriculture, Ecosystems and Environment. 216:1-8.
    7. Guo, Y., Li, B., Di, H., Zhang, L. and Gao, Z. 2012. Effects of dicyandiamide (DCD) on nitrate leaching, gaseous emissions of ammonia and nitrous oxide in a greenhouse vegetable production system in northern China. Soil Science and Plant Nutrition. 58:647-658.
    8. Hesse, R., Nikiforova, V., Gakière, B. and Hoefgen, R. 2004. Molecular analysis and control of cysteine biosynthesis: integration of nitrogen and sulphur metabolism. Journal of Experimental Botany. 55:1283-1292.
    9. Hilgert, J.E., Amon, B., Amon, T., Belik, V., Dragoni, F., Ammon, C., Cárdenas, A., Petersen, S.O. and Herrmann, C. 2022. Methane emissions from livestock slurry: Effects of storage temperature and changes in chemical compostion. Sustainability. 14:9934.
    10. Kai, P., Pedersen, P., Jensen, J.E., Hansen, M.N. and Sommer, S.G. 2008. A whole-farm assessment of the efficacy of slurry acidification in reducing ammonia emission. European Journal of Agronomy. 28:148-154.
    11. Kim, C.G. 2016. Removal of ammonium and nitrate nitrogens from wastewater using zeolite. Journal of the Korea Organic Resource Recycling Association. 24:59-63.
    12. Kim, K.Y., Choi, H.L., Ko, H.J. and Kim, C.N. 2006. Estimation of ammonia emission during composting livestock manure based on the degree of compost maturity. Journal of Animal Science and Technology. 48(1):123-130.
    13. Kim, T.H. and Kim, B.H. 1996. Ammonia microdiffusion and colorimetric method for determining nitrogen in plant tissues. Journal of the Korean Society of Grassland Science. 16:253-259.
    14. Kithome, M., Paul, J.W. and Bomke, A.A. 1999. Reducing nitrogen losses during simulated composting of poultry manure using adsorbents or chemical amendments. Journal of Environmental Quality. 28:194-201.
    15. Lan, Z., Lin, W. and Zhao, G., 2024. Sources, Variations, and effects on air quality of atmospheric ammonia. Current Pollution Reports. 10:40-53.
    16. Lee, Y., Kim, S.J. and Parise, J.B. 2000. Synthesis and crystal structures of gallium- and germanium-variants of the fibrous zeolites with the NAT, EDI and THO structure types. Microporous and Mesoporous Materials. 34:255271.
    17. Ndegwa, P.M., Hristov, A.N., Arogo, J., Sheffield, R.E., 2008. A review of ammonia emission mitigation techniques for concentrated animal feeding operations. Biosystems Engineering. 100:453-469.
    18. Ndegwa, P.M., Vaddella, V.K., Hristov, A.N. and Joo, H.S. 2009. Measuring concentration of ammonia in ambient air or exhaust air steam using acid traps. Journal of Environmental Quality. 38:647-653.
    19. Park, J.H., Park, S.J., Seo, Y.J., Kwon, O.H., Choi, S.Y., Park, S.D. and Kim, J.E. 2014. Effect of mixed treatment of urea fertilizer and zeolite on nitrous oxide and ammonia emission in upland soil. Korean Journal of Soil Science and Fertilizer. 47:368-373.
    20. Park, K.H., Andrew, G.T., Michele, M., Karen, C. and Claudia, W. 2006. Greenhouse gas emissions from stored liquid swine manure in a cold climate. Atmospheric Environment. 40:618-627.
    21. Park, S.H., Lee, B.R. and Kim, T.H. 2015. Effects of cattle manure and swine slurry acidification on ammonia emission as estimated by an acid trap system. Journal of the Korean Society of Grassland and Forage Science. 35:212-216.
    22. Park, S.H., Lee, B.R., Jeong, K.H. and Kim, T.H. 2018a. Effect of injection application of pig slurry on ammonia and nitrous oxide emission from timothy (Phleum pretense L.) sward. Journal of the Korean Society of Grassland and Forage Science. 38:145-149.
    23. Park, S.H., Lee, B.R., Jung, K.H. and Kim, T.H. 2018b. Acidification of pig slurry effects on ammonia and nitrous oxide emissions, nitrate leaching, and perennial ryegrass regrowth as estimated by 15N-ureaflux. Asian-Australasian Journal of Animal Science. 3:457-466.
    24. Peigné, J. and Girardin, P. 2004. Environmental impacts of farm-scale composting practices. Water, Air, and Soil Pollution. 153:45-68.
    25. Rodhe, H. 1990. A comparison of the contribution of various gases to the greenhouse effect. Science. 248:1217-1219.
    26. Sharma, R.K., Cox, M.S., Oglesby, C. and Dhillon, J.S. 2024. Revisiting the role of sulfur in crop production: A narrative review. Journal of Agriculture and Food Research. 15:101013.
    27. Subbarao, G.V., Ito, O., Sahrawat, K.L., Berry, W.L., Nakahara, K., Ishikawa, T., Watanabe, T., Suenaga, K., Rondon, M. and Rao, I.M. 2006. Scope and strategies for regulation of nitrification in agricultural systems-challenges and opportunities. Critical Reviews in Plant Sciences. 25:303-335.
    28. Szanto, G.L., Hamelers, H.V.M., Rulkens, W.H. and Veeken, A.H.M., 2007. NH3, N2O and CH4 emissions during passively aerated composting of straw-rich pig manure. Bioresource Technology. 98:2659-2670.
    29. Van Soest, P.J., Robertson, J.B. and Lewis, B.A. 1991. Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science. 74:3583-3597.
    30. Wang, Z.P., Van Cleemput, O., Demeyer, P. and Baert, L. 1991. Effect of urease inhibitors on urea hydrolysis and ammonia volatilization. Biology and Fertility of Soils. 11:43-47.
    31. Zheng, J., Liu, J., Han, S., Wang, Y. and Wei, Y. 2020. N2O emission factors of full-scale animal manure windrow composting in cold and warm seasons. Bioresource Technology. 316:123905.
    Copyright © The Korean Society of Grassland and Forage Science. All rights reserved.