PROPERTIES OF SOIL AND ELEMENTAL COMPISITION OF HUMIC ACIDS AFTER TREATMENT WITH BROWN COAL AND COW MANURE

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1 P O L I S H J O U R N A L O F S O I L S C I E N C E VOL. XLIV/ PL ISSN Soil Chemistry JOLANTA KWIATKOWSKA-MALINA* PROPERTIES OF SOIL AND ELEMENTAL COMPISITION OF HUMIC ACIDS AFTER TREATMENT WITH BROWN COAL AND COW MANURE Received May 18, 2011 Abstract. Soil organic matter (SOM) is an essential soil constituent, influencing soils physical, chemical and biological properties. Recently, a growing interest in looking for alternative sources of organic matter, such as for example brown coal waste material and compost has been observed. It was found that brown coal waste material or cow manure, 10 years after application in soil resulted in changes in physicochemical properties of the soil and structure of humic acids (HAs) extracted from the soil. HAs extracted from the soil treated with brown coal waste material had higher carbon and lower nitrogen contents compared to the samples to which cow manure was added. HAs of amended soils had higher content of oxygen functional groups compared with non-treated ones. Therefore, brown coal waste material may be an equivalent to natural sources of SOM in terms of agriculture and ecosystems protection. The organic contents of soil and the biological diversity are necessary to sustain numerous soil functions. The concept of soil quality has recognized soil organic matter as an important attribute that has a great deal of control over many of the key soil functions [16]. The content and quality of humic substances (HS) are directly and indirectly determined by physical, chemical and environmental soil properties. However, soil organic matter varies among environments and management systems, generally increasing with higher mean annual precipitation [2], with lower mean annual temperature [10], with higher clay content [14], with an intermediate grazing intensity [20], with higher crop residue inputs and cropping intensity [7], with native vegetation compared with cultivated management [2], and with conservation tillage compared with conventional tillage *Asst. Prof. J. Kwiatkowska-Malina, Dsc.; Warsaw University of Technology, Department of Spatial Planning and Environmental Sciences, Warsaw University of Technology, Pl. Politechniki 1, Warsaw, Poland.

2 44 J. KWIATKOWSKA-MALINA [18]. Diversity of organic matter as well as different environmental conditions create varying structures and compositions, and thus differences in properties of HS [22]. The parameters which are changing in the transformation (humification) process, besides the degree of polydispersity of the molecules of HS is the elemental composition of HAs [4]. It is suggested that there has been a steady decline in levels of Soil Organic Matter (SOM) across much of Poland. Consequently, a significant problem is the maintenance of a constant level of SOM, or even its increase, particularly in sandy soils. The basic sources of SOM are plant residues, organic fertilizers and the substance obtained from different materials of organic origin. A growing interest in the different, alternative sources of organic matter (e.g. brown coal waste material and compost) has been observed in recent years [3, 11, 15]. The content and quality of SOM is crucial for its fertility, which is closely related to the concentration of nutrients [1]. The aim of this study was to compare properties of humic acids (HAs) isolated from different sources of organic matter (brown coal waste material and cow manure) based on elemental composition. MATERIAL AND METHODS The experiments were carried out in Skierniewice located on E N (Poland). Soil samples originated from Haplic Luvisols, WRB formed from loamy sand on light clay in stoneware pots of 40 cm diameter and 120 cm height, sank into the ground. To the soil Tertiary earthy soft brown coal from Konin Basin deposits and cow manure were applied in doses of 140 and 630 g per pot, which is equivalent to 5 tof organic carbon per ha. Non-amended soil was used as a control. Ten years after introducing soft brown coal and cow manure, soils were sampled from the 0-25 cm horizon, air-dried, sieved (1-mm) and analyzed. The following parameters in soil samples were determined:ph H2O and ph KCl were determined potentiometrically, hydrolitic acidity (Hh) and total exchange basic (TEB) cations by the Kappen s method, the total organic carbon (TOC) by the Tiurin method, and the total nitrogen (Nt) content-by the Kjeldahl method. Additionally, cations exchange capacity (CEC) and base saturation (BS) were calculated. Humic acids (HAs) were extracted using the IHSS standard method [21]. The following analyses were carried out to characterize extracted HAs. UV-VIS spectra with a Lambda 20 Perkin-Elmer Analyzer. Solutions of 0.02% HAs solutions in 0.1 M NaOH were used. Based on the absorbance values measured at the wavelengths: 280 (A 280 ), 400 (A 400 ), 465 (A 465 ), 665 nm (A 665 ) the following coefficients were calculated: A 2/4 absorbances ratios at

3 PROPERTIES OF SOIL AND ELEMENTAL COMPISITION OF HUMIC ACIDS 45 wavelengths of 280 and 465 nm, A 2/6 - absorbances ratio at wavelengths of 280 and 665 nm, A 4/6 - absorbances ratio at wavelengths of 465 and 665 nm, as well as log K = log A log A 600. The elemental composition - with a CHN 2400 Perkin-Elmer Analyser. The oxygen content was calculated from the difference [100% - (%C+%H+%N)] in relation to the ashless sample weight. The results obtained expressed in atomic percentage were used to calculate the H:C, O:C, N:C, O:H ratios, and internal oxidation degree referring to the formula [25]: = (2O+3N-H):C. The parameters of thermal decomposition using the Differential Scanning Calorimetry (DSC) method with a Perkin Elmer DSC 7, equipped with an automatic thermal analysis program. HAs of 5 mg were placed in an aluminium pan. DSC traces were recorded by heating HAs from 50 to 550 C at a rate of 20 C min -1 under a 20 cm 3 min -1 air flow. RESULTS AND DISCUSSION Basic properties of studied soil samples are given in Table 1. Applying the organic matter as brown coal waste material and cow manure into soil resulted in changes in the physico-chemical properties of the soil. Applying cow manure into soil did not influence significantly soil reaction ph (ph H2 O =5.9; ph KCl =4.8) in comparison to control soil (not amended soil). The highest increase in soil reaction ph (ph H2 O =6.9; ph KCl =6.6) was found in the case of brown coal waste material. This was the effect of the role of organic matter in soil which has the ability to moderate major changes in the soil ph. Organic matter buffers the soil against major swings in ph by either taking up or releasing H + into the soil solution, making the concentration of soil solution H + more constant. The result of applying organic matter from brown coal was a stable ph close to neutral. It is the same in the literature about the effect of organic matter on soil reaction [22]. TABLE 1. BASIC PROPERTIES OF SOIL SAMPLES AMENDED WITH DIFFERENT SOURCES OF ORGANIC MATTER Sample Dose (g per pot) ph TOC Nt H 2 O KCl (g kg -1 ) TOC:Nt Control soil Soil + brown coal Soil + cow manure

4 46 J. KWIATKOWSKA-MALINA The application of brown coal waste material in the soil caused a significant increase of TOC (Table 1). In the A horizon (0-25 cm), the contribution of TOC derived from decomposing brown coal organic matter increases with doses from 7.6 (control soil) to 15.3 g kg -1 of the total carbon. Normally, accumulation of soil organic carbon at the soil surface is a result of surface placement of crop residues and a lack of soil disturbance that kept residues isolated from the rest of the soil profile [6]. A more rapid increase in carbon content has been suggested by Valera et al. [24] for a Spanish mine soil, with a carbon content of 30 g kg -1 after only 5 years of revegetation. In addition [19] showed the same situation of the reclamation sites. In the subject with cow manure, the TOC slightly increased to 8.3 g kg -1 compared to the control soil. This data may indicate that, after ten years, sites ameliorated with brown coal, accumulated carbon in light mineral soil and contain more carbon compared to soil in natural conditions. However, a comparison of absolute amounts of TOC accumulation in soil in warmer and drier climates is smaller than in soil in cooler and moister climates [6]. It is well-known that sandy textured soils do not favour physical protection of easily biodegradable substrates and microorganisms leading to further losses of soil organic matter [9, 23]. In general, soil organic matter turnover rates are determined by the proportion of old (stable) and younger (less resistant) organic matter. Soils with a low organic matter content contain relatively high proportions of young soil organic matter, resulting in rapid initial organic matter decomposition. The Nt content ranged from 0.4 to 0.9 g kg -1 (Table 1). The application of brown coal waste material in soil caused an increase of Nt of almost 50%, compared to control soil. Consequently, a significant increase of the TOC : Nt ratio was observed in this object. The highest value of TOC to Nt ratio of 17 obtained for a soil sample with brown coal waste material was due to the highest carbon content in this object. In other experiments with the brown coal derived preparation amendments similar results were obtained [13]. The organic matter from different sources applied in soil demonstrates longterm positive effects on the basic properties and physico-chemical parameters of the sandy soil. Selected physico-chemical properties of soil after the application of brown coal waste material and cow manure are presented in Table 2. A decrease of hydrolytic acidity (Hh) was observed in the case of both organic matter applied, from 4.1 cmol (+) kg -1 (control soil) to value of 0.8 cmol (+) kg -1 with brown coal waste material and 3.4 cmol (+) kg -1 in the case of cow manure. This phenomenon was observed ten years after the application of organic matter (brown coal waste material). The brown coal waste material and cow manure improved sorption properties of sandy soil (Table 2). The high sorption capacity of the brown coal waste material significantly influenced the total exchange basic (TEB), cations exchange capacity (CEC) and base saturation (BS) of amended soil. A significant increase in soil

5 PROPERTIES OF SOIL AND ELEMENTAL COMPISITION OF HUMIC ACIDS 47 TABLE 2. EFFECT OF ORGANIC MATTER FROM DIFFERENT SOURCES ON SELECTED PHYSICO-CHEMICAL PROPERTIES OF SOIL SAMPLES AMENDED WITH DIFFERENT SOURCES OF ORGANIC MATTER Sample Dose (g per pot) Hh TEB CEC BS (cmol(+) kg -1 ) (%) Control soil Soil + brown coal Soil + cow manure Hh hydrolitic acidity, TEB total exchange basic, CEC base saturation. sorption capacity as well as the degree of the saturation of sorption complex with alkali of the soil under study was found. The TEB of soil with organic matter application ranged between 3.0 cmol(+) kg -1 (cow manure) and cmol(+) kg -1 (brown coal waste material). Sorption capacity of soil amended with brown coal waste material increased two-fold (from 6.7 to 14.4 cmol(+) kg -1 ), while the degree of saturation with alkali was near 93%. Typical values for the CEC of soils dominated by kaolinite and amorphous oxides range from 2 to 6 cmol(+) kg -1 [5, 8]. In addition the TOC content of soil did not explain an additional significant part of CEC. This proved the assumption that differences in CEC in this soil were due to differences in soil organic matter content. Thanks to its sorption abilities, organic matter contained in the brown coal waste material also increased the buffering properties of soil. It is very significant that the improvement of soil sorption properties was at that level ten years after the application of brown coal waste material. A relatively constant concentration of organic carbon after about ten years of the experiment suggested that the mineralization process of organic matter introduced with brown coal was rather slow. It is of great importance in the case of sandy and degraded soils, in which organic matter content is usually low. As results from the present study, brown coal waste material used just once significantly improved soil properties. The activity of it was both direct and indirect. The first resulted from its chemical composition, i.e. the content of macroand micro-elements, while the second was caused by its structure, especially by the well developed porous system [11]. Therefore, it can be indicated that organic matter introduced with brown coal waste material is relatively stable and resistant to quick mineralization. As a result, after one-step introduction, in an agro melioration dose, it can be a resource of humus-creating substances for a long time.

6 48 J. KWIATKOWSKA-MALINA The absorbance values for the amended soil samples were higher compared to the control, which may indicate higher carbon contents in these HAs (Table 3). However, it is not clearly evident with respect to the elemental composition of HAs (Table 4). The values of A 2/4, A 4/6 and A 2/6 absorbance ratios of HAs extracts from soil with brown coal waste material were higher, while for the object with cow manure they were lower than in the control soil. The HAs extracted from the amended (with cow manure or brown coal waste material) soil samples contained more carbon and less nitrogen than the HAs extracted from the control (Table 3) and were characterised by higher values of the H:C ratio, whereas the N:C ratio was lower. Moreover, a considerably higher value of the parameter was observed for an object with brown coal waste material compared to the control soil. TABLE 3. SPECTRAL PROPERTIES OF SOIL SAMPLES AMENDED WITH DIFFERENT SOURCES OF ORGANIC MATTER ALKALINE EXTRACTS Sample A 280 A 465 A 600 A 665 A 2/4 A 2/6 A 4/6 logk Control soil Soil + brown coal Soil + cow manure TABLE 4. ELEMENTAL COMPOSITION (IN ATOMIC PERCENTAGE), ATOMIC RATIOS AND A DEGREE OF INTERNAL OXIDATION ( OF HUMIC ACIDS (HA S ) EXTRACTED FROM SOIL SAMPLES AMENDED WITH DIFFERENT SOURCES OF ORGANIC MATTER Object C H N O H:C O:C O:H N:C Control soil Soil + brown coal Soil + cow manure internal oxidation degree. The DSC curves of HAs extracted from the amended soil showed a strong endo-thermal characteristic in the low-temperature region (~140 C), and an exo-thermal characteristic in the high-temperature region (~500 C) (Fig. 1). These thermal effects were probably assigned to dehydration, loss of peripheral polysaccharide chains and/or oxidation and polycondensation of aromatic nuclei of the molecule. The relative intensity of the exotherm curves seem to be related to the humification degree [12, 17].

7 PROPERTIES OF SOIL AND ELEMENTAL COMPISITION OF HUMIC ACIDS 49 Heat flux Temperature ( C) Fig. 1. DSC curves of humic acids (HAs) extracted from soil samples amended with different sources of organic matter. CONCLUSIONS 1. It was found that soil amendment with both sources of organic matter resulted in an increase in the: soil ph, content of organic carbon, and total nitrogen. The resulting higher values of C:N ratio were characteristic for typical Polish arable soils. 2. HAs extracted from the soil treated with brown coal waste material had higher carbon and lower nitrogen contents compared to the samples to which cow manure was added. Simultaneously, the addition of brown coal caused an increase in carbon content in HAs particles and, consequently increased values of the H:C ratio. 3. HAs extracted from amended soils showed higher absorbance values in the UV-VIS region, higher contents of oxygen functional groups, and were more resistant to thermal decomposition compared with the control. HAs molecules from soil with brown coal were also richer in aromatic structures and more resistant to decomposition. 4. Organic matter from the brown coal relatively slowly undergoes transformation and, thus, is expected to cause permanent soil enrichment with HS. Organic matter from brown coal is more resistant to fast decomposition (mineralization) as compared to cow manure and shows higher long-term sorption capacity. Therefore, brown coal waste material may be an equivalent to natural sources of SOM in terms of agriculture and ecosystems protection. REFERENCES [1] B a r a n c i k o v a G., S e n e s i N., B r u n e t t i G.: Geoderma, 78, 251, [2] B u r k e I. C., Y o n k e r C. M., P a r t o n W. J., C o l e C. V., F l a c h K., S c h i m e l D. S.: Soil Sci. Soc. Am. J., 53, 800, [3] D ê b s k a B., M a c i e j e w s k a A., K w i a t k o w s k a J.: Rostlinna Vyroba, 48(1), 33, 2002.

8 50 J. KWIATKOWSKA-MALINA [4] D ê b s k a B., S z o m b a t o v a N., B a n a c h - S z o t t M.: Polish J. Soil Sci., 42(2), 131, [5] D u x b u r y J. M., S m i t h M. S., D o r a n J. W., J o r d a n C., S z o t t L., V a n c e E.: In: Dynamics of Soil Organic Matter in Tropical Ecosystems (Eds Coleman, D.C., Oades, J.M., Uehara, G.). University of Hawaii Press, Honolulu, HI, 33, [6] F r a n z l u e b b e r s A. J.: Soil Till. Res., 66, 95, [7] F r a n z l u e b b e r s A. J., H o n s F. M., Zuberer, D.A.: Soil Till. Res., 47, 303, [8] G a l l e z A., J u o A. S. R., H e r b i l l o n A.J.: Soil Sci. Soc. Am. J., 40, 601, [9] H a s s i n k J.: Soil Biol. Biochem., 26, 1221, [10] J e n n y H.: The Soil Resource. Ecological Studies, Springer, New York, 37, [11] K w i a t k o w s k a J., D ê b s k a B., M a c i e j e w s k a A., G o n e t S.: Roczn. Glebozn., 54, (3-4), 31, [12] K w i a t k o w s k a J., P r o v e n z a n o M. R., S e n e s i N.: Geoderma, 148, 200, [13] M a c i e j e w s k a A., K w i a t k o w s k a J.: Humic Substances in Ecosystems, 5, 57, [14] N i c h o l s J. D.: Soil Sci. Soc. Am. J., 48, 1382, [15] P a r r J., H o r n i k S. B.: Soil Microb. Ecology, New York, 545, [16] P o w l s o n D. S., S m i t h P., C o l e m a n K., S m i t h J. U., G l e n d i n i n g M. J., K o r s c h e n s M., F r a n k o U.: Soil Till. Res., 47, 263, [17] P r o v e n z a n o M. R., O u a t m a n e A., H a f i d i M., S e n s e i N. B.: J. Thermal Analysis and Calorimetry, 61, 607, [18] R a s m u s s e n P.E., C o l l i n s H. P.: Adv. Agron., 45, 93, [19] R u m p e l C., K o g e l - K n a b n e r I., H u t t l R. F.: Plant and Soil, 213, 161, [20] Schnabel R.R., Franzluebbers A.J., Stout W.L., Sanderson M.A.,Stuedeman n J. A.: The Potential of US Grazing Lands to Sequester Carbon and Mitigate the Greenhouse Effect. Lewis Publishers, Boca Raton, FL, 291, [21] S c h n i t z e r M.: In: Page B.L., Miller R.H., Keeney D.R., (Eds.), Methods of Soil Analysis, Part 2, 581, [22] S c h n i t z e r M., M c A r t h u r D. F. E., S c h u l t e n H. -R., K o z a k L. M., H u a n g P. M.: Geoderma, 130, 141, [23] S o l l i n s P., H o m a n n P., C a l d w e l l B. A.: Geoderma, 74, 65, [24] Valera C., Vazquez C., Gonzylez- Sangregorio M. V., Leiros M. C., Gil- Sot r e s F.: Soil Sci., 156, 193, [25] Z d a n o v J. A.: Biochimija, 30, 6, 1257, W AŒCIWOŒCI GLEBY I SK AD PIERWIASTKOWY KWASÓW HUMINOWYCH PO WPROWADZENIU WÊGLA BRUNATNEGO I OBORNIKA Po dziesiêciu latach od wprowadzenia wêgla brunatnego lub obornika do gleby stwierdzono poprawê w³aœciwoœci fizyko-chemicznych gleby oraz zmiany w strukturze wyekstrahowanych z gleby kwasów huminowych (KH), na co wskazuje wzrost zawartoœci wêgla w sk³adzie pierwiastkowym oraz wartoœci stosunku H:C. Zaobserwowano wy sze wartoœci absorbancji w zakresie UV-VIS, wy sze zawartoœci tlenowych grup funkcyjnych i wiêkszy udzia³ struktur aromatycznych a tak e wiêksz¹ odpornoœæ na rozk³ad termiczny. Substancja organiczna wprowadzona z wêglem brunatnym do gleby ulega powolnej mineralizacji, co powoduje d³ugotrwa³e wzbogacenie gleby w substancje humusowe w tym w KH.