Dynamics of soil organic matter and humic acid contents as influenced by land use changes

Transcription

1 1334 แก นเกษตร 45 ฉบ บพ เศษ 1 : (2560). KHON แก นเกษตร KAEN AGR. 45 J. ฉบ บพ เศษ 45 SUPPL. 11 : :(2560). (2017). Dynamics of soil organic matter and humic acid contents as influenced by land use changes Benjapon Kunlanit 1* ABSTRACT: The purpose of this study was to investigate distribution of soil organic matter and humic acids as influenced by land use changes. Soil samples were collected from 5 soil depths, i.e. 0-15, 15-30, 30-60, 60-80, and cm under three land uses, including paddy, cassava, and deciduous dipterocarp forest lands located around Donwhan sub-district, Muang district, Maha Sarakham province. The air-dried soil samples were subjected to determine soil organic matter by Walkley and Black wet digestion method and humic acid contents using a procedure following the International Humic Substance Society method. The results showed that whole SOM and humic acid contents were higher under forest land than cultivation land, e.g. paddy and cassava plantations. When considering soil depths in all land uses, the topsoils (0-15 cm) showed higher SOM sequestration than the subsoils ( cm). Humic acid contents were higher under subsoils than topsoils with the exception of those under the paddy land. The results of this study demonstrated that changes of forest land to cultivation land without appropriate management led to low soil fertility. Keywords: soil organic matter, land use change, humic acid, Northeast Thailand Introduction Approximately 0.42 million hectares throughout Northeast Thailand suffer from extensive soil degradation (Bowichean et al., 2013). The low fertility soils in this region have been further degraded by inappropriate agricultural land management, for instance, deforestation for cultivation and intensive agricultural land uses without appropriate management and conservation. These human activities on low fertility sandy soils can lead to continuing soil degradation, low crop productivity and sustainability. The conversion of natural tropical ecosystems to agricultural systems, including paddy field, cassava, sugarcane and rubber tree, may accelerate the degradation of the soil. Agricultural systems without appropriate management lead to low soil fertility. This implies not only a change in soil chemical properties, but also a reduction in biodiversity (Lavelle et al., 1992; Hairiah et al., 2001). Soil organic matter (SOM) or soil organic carbon (SOC) is considered to be an indicator for soil fertility (Vityakon, 2011). Vityakon (1991 as cited by Vityakon, 2007) reported that SOC content in a sandy loam soil cultivated with cassava and paddy rice for over 10 years were reduced to 6.1 and 5.5 g C kg -1, respectively, accounting for about 40% loss as compared to soil under forest ecosystems (10.2 g C kg -1 ). In addition, SOC content under rice cultivation for years was decreased by approximately 70% compared to forest soil (Naklang et al., 1999). This indicates that land use strongly influences SOC accumulation in the long term. Unfortunately, dynamics of chemical composition 1 Department of Agricultural Technology, Faculty of Technology, Mahasarakham University, Maha Sarakham 44150, Thailand * Corresponding author: benjapon.k@msu.ac.th

2 2 was decreased by appproximately 70% 7 compareed to forest sooil (Naklang et e al., 1999). TThis indicates that land use KAEN stronngly es SOC accum mulation in thee long term. Unfortunately, U, dynamics off chemical composition KHON AGR.influence J. 45 SUPPL. 1 : (2017) of SOM, i.e. humic aciid within soil profile p under different d land uses in the trropical sandy soils are pooorly known 2001).acid Therefore, is study designedsarakham to investigate d was shown distribution of SOMinand huumic acid of(hairiah SOM, eti.e.al.humic withinthsoil profilewasunder province Figure 1. There withinuses soil pro under laand use chan contents land different inofiles the tropical sandy soilsges. are were three land uses employed in this study, poorly known (Hairiah et al. 2001). Therefore, this including deciduous dipterocarp forest Mateerials metthods N; E), cassava changed study was designed to investigate distribution of and ( Studyand sitte humic and soilacid SOM contents within soil profiles from forest for 5 years( N; A study site for sand paddy lands M changed Muang districct infrom Maha Sarakham S for >10 under land use changes. soil sammpling aroundd Donwhan E), sub-district, forest province was shown in Figure 1. There were three t landyears( uses employed in thisn;study y, including deciduous de). Nine dipterocaarp forest(16 N; ' changedpoints from 1 E cassava E), m were forest collected for 5 years(16 0 N; Materials ' and methods from ' each land ' E), and paddy lands changed froom forest use for >10 years( ' E). Each Nine during the dry seasonn; in ' March g points were e collected froom each landd use during the drypoint seasson in March Each (i.e. Study site and soil included 5 soil depths 0-15, study 30-60,cmm) , and cm). pointa inc luded 5site soil for d soil(i.e. depths 0-15, 15-30,around , 60-80,15-30, annd Donwhan sub-district, Muang district in Maha Figure 1 A map showing location of soil sites around Maha Sarakham in Northeast Thailand. Figure 1 A map showiing location of soil sites aroundd Maha Saraakham in Northeasst Thailand. Soil analysis subsequent determination of the unreduced Soil samples were subjected to determine dichromate by oxidation-reduction titration with Soil analysis soil particle sizes using pipette method (modified ferrous sulfate (FeSO4) (Rayment and Higginson, Soil samples were subjeccted to determ mine soil parrticle sizes ussing pipette m method (modified from from Dewis and Freitas, 1970; Sangmanee, 2008). 1992). For humic acid contents, air-dried soils after screeening througgh a 2 mm Dewis annd Freitas, 19770; Sangmanee, 2008). Foor SOM analyssis, air-dried soils For SOM analysis, air-dried soils after screening after screeningsthrough a 2 mm mesh sieve were through a 2 mm mesh sieve, were determined by determined using a procedure following the potassium dichromate (K 2Cr 2O 7) oxidation International Humic Substance Society method (Walkley and Black wet digestion) and (modified from Swift et al., 1996; Tan, 2003).

3 1336 แก นเกษตร 45 ฉบ บพ เศษ 1 : (2560). Climate and temperature during the experiment periods The average precipitation and temperature covering soil periods (July 2015-June 2016) from the Northeastern Metecorological Center in Maha Sarakham province was revealed in Figure 2. from the Northeastern Metecorological Center in Maha Sarakham province was revealed in Figure 2 Climate condition and average temperature ( ๐ C) during July 2015-June Figure 2 Climate condition and average temperature ( ๐ C) during July 2015-June Statistical analysis Analysis of variance pertaining to a randomized complete block design (RCBD) and related statistical analysis were performed employing Statistics 8.0 (Analytical Software, 2003).Mean comparison of different treatments was done by least significant difference (LSD) and standard error of the means (SEM). Results and Discussion cm were sand and sandy loam, respectively. Soil texture under forest land at 0-60 cm is loamy sand, but at and cm were sandy loam and sandy clay loam, respectively. That is, the textures were finer with depth increasing exception of the texture at cm depth under paddy land (Table 1). Soil texture is finer with increasing depth because this subsoil ( cm) is B horizon where higher clay has accumulated (Riise et al., 2002). Soil texture within soil profile under different land uses Soil texture under paddy and cassava land uses at 0-80 cm were loamy sand, while at

4 KHON KAEN AGR. J. 45 SUPPL. 1 : (2017) Table 1 Soil texture characteristics under different land uses. Land use types Soil depths Particles (%) Soil textures (cm) Sand Silt Clay Paddy field Loamy sand Loamy sand Loamy sand Loamy sand Sand Cassava field Loamy sand Loamy sand Loamy sand Loamy sand Sandy loam Forest land Loamy sand Loamy sand Loamy sand Sandy loam Sandy clay loam Dynamics of soil organic matter under different land uses Whole contents of SOM throughout the profile cm showed a trend to be higher under the forest than paddy and cassava land uses (P>0.05) (Figure 2). Contents of SOM under three land uses were highest at 0-15 cm followed by 15-30, 30-60, and cm, respectively (P<0.01). At 0-15 cm, the contents showed a trend to be higher in forest than paddy and cassava lands. At and cm, SOM contents showed a trend to be higher in paddy than forest and cassava lands (P>0.05). However at and cm, the contents were higher in forest than cassava and paddy lands (P>0.05) (Table 2). The whole SOM contents decreased as much as 28.6 and 11.3%from changes of forest to cassava and paddy lands, respectively (Figure 2). Likewise in Northeast Thailand, Thantrakanpong (2002) reported that SOC contents under changes from forest to cassava and paddy lands decreased up to 78.2 and 23.6%, respectively. In Ethiopia, Emiru and Gebrekidan (2013) revealed that SOM under alteration of forest to cultivation lands decreased by as much as 31.8%. In the current study, higher SOM accumulation that was found in topsoils compared with subsoils in all land uses may result from decomposing dead organisms and fallen litter as well as root exudates. Moreover, minimum precipitation during the dry season in March (Figure 1) may lead to less SOM movement to subsoils. Similarly, Riise et al. (2002) reported that dissolved organic carbon accumulation was higher in topsoil than in subsoils.

5 1338 แก นเกษตร 45 ฉบ บพ เศษ 1 : (2560). Figure 2 Whole soil organic matter contents (Mg/ha) throughout the profile cm depth under different land uses. Horizontal bars represent SEM. Table 2 Dynamics of soil organic matter contents (%) within the soil profile under land use changes. Soil depths (cm) Land use types Paddy field Cassava Forest F-test CV (%) a 0.43 a 0.72 a ns b 0.28 b 0.31 b ns bc 0.15 c 0.16 c ns c 0.09 c 0.11 c ns c 0.07 c 0.09 c ns F-test ** ** ** CV (%) Means in a same column followed by the different lowercase letters are significantly different by LSD (P<0.01, **). ns, not significantly different (P>0.05). Dynamics of humic acid as influenced by land use changes Whole contents of humic acid were highest under forest throughout the profile (0-100 cm) compared with cassava and paddy lands, respectively (P<0.01) (Figure 3). Disturbed soil by plowing for >10 years may lead to less humic acids formation as seen by lowest humic acid contents in paddy soil. When considering each depth under different land uses, soil humic acid contents were higher under forest than cassava and paddy land uses (P<0.01), while under each land uses with different depths, humic acid content were higher at the subsoils ( cm) than topsoils (0-60 cm) under forest and cassava lands (Table 3). Humic acid contents under altering forest to cassava and paddy lands decreased as much as 40.1 and 78.4%, respectively (Figure 3). Similar to a study in Nigeria, Jamala and Oke (2013) found that natural forest (6.8 g kg -1 ) had higher contents of humic acids than cultivation land (3.4 g kg -1 ). In addition, Thantrakanpong (2002) reported that humic acid contents were higher under forest land than cultivation land, i.e. rice, cassava and

6 KHON KAEN AGR. J. 45 SUPPL. 1 : (2017). sugarcane plantations. That is, fewer disturbances by agricultural activities may lead to humic substances formation as seen by higher contents of humic acids throughout the soil profiles under forest and cassava, than that which was seen in paddy soil. Moreover, humic acids might be moved from topsoils with lower clay contents and accumulated at subsoils with higher clay contents as evident by high humic acid contents in subsoils under forest and cassava lands. It is speculated that humic acids are vital cementing agents to form aggregates, especially microaggregates (Bronick 1339 and Lal, 2005), leading to soil C sequestration. This study pointed out that forest soil had high humic acid contents leading to enhanced SOM accumulation. On the other hand, C under paddy soil may be labile C constituents and easily lost to deeper soil (>100 cm depth) in the initial stage of the decomposition processes. As indicated by Kunlanit et al. (2014), rice straw containing high cellulose contents was easily decomposed during the first 2 weeks after incorporation, which led to low accumulation of aromatic C constituents (such as humic acids) in soil. Figure 3 Humic acid contents (Mg/ha) throughout the profile (0-100) cm under different land uses. Lowercase letters represent significant differences (P<0.05) along with SEM. Table 3 Changes of humic acid contents (%) in soil profile (0-100 cm) under different land uses. Soil depths (cm) Land use types Paddy field Cassava Forest F-test CV (%) C B eb ca ca ca ** ** C db ca ** C bb ba ** C ab aa ** F-test ns ** ** CV (%) Means in a same column followed by the different lowercase andsame row followed by different uppercase letters are significantly different by LSD (P<0.01 (**). ns; not significantly different (P>0.05).

7 1340 แก นเกษตร 45 ฉบ บพ เศษ 1 : (2560). Conclusions Whole SOM and humic acid contents were higher under forest land than cultivation land, e.g. paddy and cassava plantations. When consideringsoil depths in all land uses, the topsoils (0-15 cm) showed higher SOM sequestration than the subsoils ( cm). Humic acid contents were higher under subsoils than topsoils with the exception of the paddy land. Future in-depth studies were recommended on the mechanisms of aggregate formation as influenced by land use changes to elucidate how C in aggregate contributes to C sequestration. Acknowledgement This research was financially supported by Mahasarakham University 2016 and the Soil Organic Matter Management Research Group, Khon Kaen University. Special thanks to P.T. Higgins for his assistance in editing the paper. References Bowichean, R., S. Thanachit, S. Anusontpornperm, and I. Kheoruenromne Green manuring effect on yield of cassava-sweet corn sequential cropping on degraded sandy soil, Northeast Thailand. Kasetsart Journal. 47: Bronick, C.J. and R. Lal Soil structure and management: a review. Geoderma. 124:3-22. Dewis, J., and F.Freitas Physical and chemical methods of soil and water analysis. Soils bulletin No. 10 Food and Agriculture Organization of the United Nations, Rome. Emiru, N. and H. Gebrekidan Effect of land use changes and soil depth on soil organic matter, total nitrogen and available phosphorus contents of soils in Senbat watershed, Western Ethiopia. ARPN Journal of Agricultural and Biological Science. 8: Hairiah, K., S. E. Williams, D. Bignell, M. Swift, and M. Van Noordwijk Effects of land use change on belowground biodiversity. ASB Lecture Note 6A.International Centre for Research in Agroforestry, Bogor, Indonesia. Jamala, G.Y. and D.O. Oke Humic substances and Mineral-Associated soil organic carbon as influenced by land use in Southeastern Adamawa State, Nigeria. IOSR Journal of Environmental Science. 5: Kunlanit, B., P. Vityakon, A. Puttaso, G. Cadisch, and F. Rasche Mechanisms controlling soil organic carbon composition pertaining to microbial decomposition of biochemically contrasting organic residues: Evidence from middrifts peak area analysis. Soil Biology & Biochemistry. 76: Lavelle, P., A.V. Spain, and S. Martin Impact of soil fauna on the properties of soil in the humid tropics. In: Lal, R., A. Sanchez (Eds.), Myths and Science of Soils in the Tropics. Proceedings of an International Symposium Sponsored by Division A-6 of the American Society of Agronomy, The World Association of Soil and Water Conservation, and the Soil and Water Conservation Society, in Las Vegas, Nevada, 17 October 1989, pp Naklang, K., A. Whitbread, R. Lefroy, G. Blair, S. Wonprasaid, Y. Konboon, and D. Suriyaarunroj The management of rice straw, fertilisers and leaf litters in rice cropping systems in Northeast Thailand. I. Soil Carbon Dynamics. Plant & Soil. 209: Rayment, G. E. and F. R. Higginson Australian Soil and Land Survey Handbook, Australian Laboratory Handbook of Soil and Water Chemical Methods. Australia: Inkata Press, pp Riise, G., P. V. Hees, U. Lundstrom, and L. T. Strand Mobility of different size fractions of organic carbon, Al, Fe, Mn and Si in podzols. Geoderma. 94: Sangmanee, P Effect of organic material quality, soil texture and moisture on soil organic matter and nitrogen transformation.master of Science Thesis in Soil Science, Graduate School, KhonKaen University. 225 p. (in Thai with English abstract). Swift, R.S Organic matter characterization, pp In D.L. Sparks et al. (eds.), Methods of soil analysis, Part 3. Chemical methods. Soil Sci. Soc. Am. Book Series: 5. Soil Science Society of America, Inc., Madison, WI.

8 KHON KAEN AGR. J. 45 SUPPL. 1 : (2017). Tan, K. H Humic matter in soil and the environment, principles and controversies. USA: Marcel Dekker, pp Thantrakanpong, S Changes of different pools of soil organic matter under different land use systems in undulating terrain of Northeast Thailand. Master of Science Thesis in Soil Science, Graduate School, Khon Kaen University.171 p. (in Thai with English abstract). Vityakon, P Relationships between soil organic matter with some chemical properties of soils under different land uses in Northeast Thailand. Thai Journal of Soils and Fertilizers. 13: (in Thai with English abstract) Vityakon, P Degradation and restoration of sandy soils under different agricultural land uses in Northeast Thailand: a review. Land Degradation & Development. 18: Vityakon, P Soil organic matter and soil quality in Northeast Thailand. Department of Plant Science and Agricultural Resources Faculty of Agriculture, Khon Kaen University, Khon Kaen, Thailand.142 p.