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Influence of fertilisation with sewage sludge-derived preparation on selected soil properties and prairie cordgrass yield
Environmental Research 156 (2017) 775–780
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Influence of fertilisation with sewage sludge-derived preparation on selected soil properties and prairie cordgrass yield
MARK
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Ewa Ociepa , Maciej Mrowiec, Joanna Lach Institute of Environmental Engineering, Czestochowa University of Technology, Brzeźnicka Street 60a, 42-200 Częstochowa, Poland
A R T I C L E I N F O
A B S T R A C T
Keywords: Preparation fertilizer Sewage sludge Brown coal Brown coal ash soil Spartina pectinata
The aim of the study was to evaluate the effect of using a fertilizer obtained from waste substances on selected physical and chemical properties of soil and biomass yield Spartina pectinate. The fertilizer used for soil (C) fertilisation contained sewage sludge (SS), waste soil fractions of brown coal (BC), brown coal ash (BCA) enriched with mineral potassium (K) fertilizer (C+SS+BC+BCA+K). The composition of the preparation was developed by the authors and adjusted to the quality of the fertilised soil and the individual characteristics of the plant. It was assumed that the preparation should replace expensive conventional fertilisation methods, allow for management of waste substances and improve soil properties, leading to a high yield of Spartina pectinata used as energy crop. The plants were grown on the soil from the Huta Częstochowa steelworks effect zone. The soil was light, with acid reaction (pH KCl =5.5), with small contents of such contaminants as Cd and Zn and elevated Pb content. Based on a three-year pot experiment, the paper presents the results of the examinations concerning the effect of fertilisation on soil pH, hydrolytic acidity, sorptive properties, content of humic acids, organic coal and total nitrogen in soil and crop yielding. The effect of the use of the fertilizer (C+SS+BC+BCA+K) was compared with the use of the sludge (C+SS), sludge with mineral fertilizers (C+SS+NPK), mixture of brown coal and mineral fertilizers (C+BC+NPK) and effect of only mineral fertilizers (C+NPK). Fertilisation with (C+SS+BC+BCA+K) led to the increase in soil pH from 5.5 to 6.0, which is considered sufficient for light soils. The fertilised soil was characterized by sorption capacity of ca. 5.8 cmol(+)/kg, and, after fertilisation with O+W+P, reached the value of ca. 8.0 cmol(+) kg−1. Consequently the soil can be regarded as of good quality in terms of its capability to store nutrients. The C:N ratio was also extended from 11:1 (control soil) to 14:1 (C+SS+BC+BCA+K). The yield of Spartina pectinata in the first year was 1.6 and in the third year 2.7 times higher in the case of fertilisation with the investigated mixture as compared to the control.
1. Introduction
the relatively intensive fertilisation with NPK fertilizers with the yearly amounts of N: 100–170, P: 60–80, K: 100–120 kg/ha, leading to high costs (Kowalczyk-Juśko et al., 2004). Furthermore, production of nitrogen-based and phosphorus-based fertilizers is very energy-consuming, which leads to reduction in energy benefits. Production of mineral fertilizers additionally generates several ecological problems. Therefore, from the economic and ecological standpoint, various types of waste should be used as a source of nutrients for plants used as energy crops. The application of a fertilising mixture (C+SS+BC+BCA+K) consisting of sewage sludge (SS), waste earthy fraction of brown coal (BC), ash produced from brown coal (BCA), and enriched with potassium mineral fertilizer (K) was a recommended solution for soil reclamation. The composition of the mixtures and the recommended
This study presents opportunities for management of light and acid soils with slight content of cadmium and zinc contaminants, with elevated content of lead, which are barren and located in the steelworks effect zone. According to the recommendations of the ecological policy, these soils should be subjected to reclamation and used for non-food crop production. The problem of soil contamination and degradation concerns many regions of the world (Ravisankar et al., 2006; Karczewska and Kabała, 2010; Gomiero, 2016). Many authors have emphasized that one of the effective initiatives is to use these soils to grow energy crops (Ociepa et al., 2008; Aronsson et al., 2014; Serapiglia et al., 2013). Studies have demonstrated that Spartine pectinata can be grown on soils with low fertility, but the plants require
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Corresponding author. E-mail address: [email protected] (E. Ociepa).
http://dx.doi.org/10.1016/j.envres.2017.05.003 Received 29 July 2016; Received in revised form 15 April 2017; Accepted 3 May 2017 0013-9351/ © 2017 Elsevier Inc. All rights reserved.
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(Table 1) were added to the bottomless PVC pots (inserted in the soil) with the diameter of 30 cm and height of 80 cm, containing 40 kg of soil. Six fertilising combinations were used, with each combination repeated in three pots. The soil for the pot experiment was obtained from the area located around 1 km north-east of the Huta Częstochowa steelworks. The depth of soil sampling ranged from 0 to 25 cm. Thirty individual samples were obtained to prepare the averaged sample from one area. The number of individual samples was adjusted to the size of the field (1500 m2). The results presented in the study are the mean value of three measurements of the average sample used in the analysis. The pots were filled with soil in the state of its natural humidity, previously sieved using a sieve with mesh size of 5 mm. The fertilizer doses were determined based on the plant demand for nutrients (with particular focus on nitrogen and phosphorus) and soil nutrient abundance. The principles of good agricultural practices were used in order not to cause excessive fertilisation (damages from the standpoint of environmental protection, plant yielding, high costs of cultivation). Differences in the level of fertilizer doses result from different chemical composition of individual substrates. Similar doses of basic nutrients (nitrogen, phosphorus, potassium) were used to compare the effect of different types of fertilisation on the plants tested. Two seedlings of Spartina pectinata were planted in each pot. In the first year of the pot experiment – before planting the seedlings – single doses of the following substances were applied: sewage sludge, brown coal, brown coal fly ash and mineral fertilizers. During the next two years of the pot experiment, mineral fertilisers (the doses of fertilisers are provided in Table 1) were used each spring before the onset of plant vegetation. The samples of soil and plant biomass were obtained during and after completion of the pot experiment. Clean plant biomass from each pot was divided into above-ground and underground parts, and then dried and ground in a laboratory grinder. Prior to further analysis, the plant biomass samples were stored in airtight containers.
doses were determined and tested by the author of this study. The composition and doses of this fertilising mixture were adjusted to the plant demands (Spartina pectinata), soil quality and current legal regulations. Sewage sludge can be used for fertilisation as it contains nutrients and organic substances which are valuable for plants. The value of sludge fertilizers has been presented in numerous studies (Gasco et al., 2004; Ociepa-Kubicka et al., 2016; Suhadolc et al., 2010; Wolski and Zawieja, 2014). However, its biological use is possible only if stringent regulations are met (The Regulation of the Minister of the Environment on municipal sewage sludge of 6 february 2015), as it may contain high amounts of heavy metals and be an organic and microbiological pollution carrier (Kacprzak and Fijałkowski, 2009; Pachura et al., 2016). A potential solution to the reduction of the threats resulting from the application of the sewage sludge is to mix the sewage sludge with brown coal and brown coal ash. The chemical composition and porous structure of brown coal – which results in high sorption properties – allow for the application of earthy forms of brown coal in soil fertilisation. Another important property of brown coal is its durability and susceptibility to microbiological degradation. Brown coal ash is a valuable and rich source of calcium, magnesium and microelements. Brown coal ash introduced to soils increases the sorption complex capacity, water holding capacity and pH of acidic soils (Kwiatkowska, 2007). The aim of the examinations presented in this paper was to determine the effect of fertilisation with preparation made of sewage sludge, brown coal, brown coal ash enriched with potassium fertilizer on soil properties and Spartine pectinata yielding. The following research theses were presented before the examinations: – agriculturally poor soils, contaminated with heavy metals, acidified and barren, can be reclaimed by addition of waste substrates and used as energy crops. – a mixture of sewage sludge, brown coal and brown coal ashes enhanced with potassium fertilizer has a beneficial effect on soil properties and Spartine pectinata yielding.
2.2. Characteristics of soil and fertilising substrates Analysis of the granulometric soil composition showed that, due to the content of floatable fractions (< 10%) and according to the criteria specified by the Instytut Uprawy, Nawożenia i Gleboznawstwa Puławy, this soil should be categorized as very light. With reference to the structure of soil profile and the analysis of soil maps, the soil used for the experiments showed the characteristics of lassie top gelyic soil and belonged to the granulometric group of slightly loamy sand with acidic reaction. The soil was acid with pH 5.5. Table 2 presents characterization of soil and substrates used in the experiment. Fertilising mixtures were prepared from the sewage sludge collected from a mechanical and biological municipal wastewater treatment plant. Sewage sludge (SS) was stabilized, dewatered, and characterized by slightly acidic reaction, high content of organic matter and relatively low content of heavy metals. Sewage sludge used for the experiment showed good fertilising properties due to the content of nitrogen and phosphorous. Physical, chemical and microbiological properties of sewage sludge allowed for the fertilisation of plants not intended for
The results obtained in the study represent the extension and supplementation of the knowledge concerning: – physical and chemical modifications of soil properties, development and yielding of Spartine pectinata, – opportunities for biomass generation for the purposes of renewable energy using unconventional fertilisation methods, – the use of sewage sludge and waste fraction of brown coal and brown coal ashes for soil fertilisation. 2. Materials and methods 2.1. Description of the pot experiment The examinations were based on the analysis of soil and plant samples obtained from a pot experiment. The fertilising substrates Table 1 The investigated fertilisation combinations in the pot experiment. Fertilisation combinations
Fertilisation type and dose
C C+SS C+SS+BC+BCA+K C+SS+NPK
control – 40 kg of soil 40 kg of soil + 2892 g sewage sludge (36 Mg d.m./ha) 40 kg of soil + 1736 g of sewage sludge + 308 g of brown coal + 80 g of brown coal ash (ok.36 Mg d.m./ha) + 2.0 g of potassium salt (100 kg/ha) 40 kg of soil + 1448 g of sewage sludge (18 Mg d.m./ha) + 3.0 g Polifoska 8 fertilizer + 2.0 g calcium ammonium nitrate + 1.0 g ammonium nitrate(300 kg/ha) 40 kg of soil + 1024 g of brown coal (36 Mg d.m./ha) + 3.0 g Polifoska 8 fertilizer + 2.0 g calcium ammonium nitrate + 1.0 g ammonium nitrate (300 kg/ha) 40 kg of soil + 6.0 g Polifoska 8 fertilizer + 4.0 g of calcium ammonium nitrate + 2.0 g of ammonium nitrate (600 kg/ha)
C+BC+NPK C+NPK
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Table 2 The soil and substrates characteristics used in the experiment. Parameter
Unit
Soil Average value
Sewage sludge
Brown coal
Brown coal ash
Substancja organiczna Corg N P K Ca Mg Pb Cd Zn Cu Ni Cr
% d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m.
– 11.3 ± 0.7 1.0 ± 0.1 0.67 ± 0,10 0.74 ± 0.10 0.67 ± 0.11 0.62 ± 0,05 39.0 ± 1.3 1.18 ± 0.07 122.2 ± 6.9 8.3 ± 0.5 7.0 ± 0.3 13.0 ± 1.1
44.3 ± 1.3 – 35.0 ± 0.9 19.0 ± 1.1 6.9 ± 0.6 9.8 ± 1.8 3.6 ± 0.5 41.0 ± 3.0 2.1 ± 0.2 860.0 ± 9.0 121.0 ± 16.0 19.3 ± 5.9 21.8 ± 3.9
– 498 ± 3.8 6.5 ± 0.9 1.1 ± 0.1 0.7 ± 0.1 30.2 ± 2.3 9.0 ± 0.8 3.0 ± 0.5 0.09 ± 0.01 15.3 ± 2.5 10.1 ± 0.9 4.2 ± 1.0 10.0 ± 0.8
– – – 0.9 ± 0.1 0.2 ± 0.0 202.0 ± 12.9 8.0 ± 1.6 60.0 ± 6.0 3.0 ± 0.4 101.0 ± 7.1 26.0 ± 1.0 36.5 ± 1.3 67.3 ± 3.1
– pH in 1 M KCl, using the potentiometric method by means of the CyberScan pH meter 10 according to the PH-ISO-10390:1997 standard, – hydrolytic acidity, by means of the Kappen modified method according to the PN-R-04027. – the total sum of alkaline cations in soil, determined with the Kappen method – the organic carbon content was determined by the modified Tiurin colorimetric method in accordance with PN-ISO 14235:2003. – the overall Kjeldahl nitrogen quantity was determined in accordance with PN-ISO 11261:2002 using a BUCHI 426 mineralizer and a BUCHI 323 distilling apparatus. – humic acids were determined using extraction with the solution containing 0.1 M HCl and 0.1 M Na4P2O7 with 1:1 ratio (Stevenson, 1982). – total heavy metals in the soil were evaluated using the plasma spectrophotometer ICP-AES (Thermo) according to the PN-ISO 11047: 2001 standard following the mineralization of the material in the mixture of concentrated HCl and HNO3 acids and using the 3:1 ratio (aqua regia). – the overall phosphorus (in the phosphate from) was determined by means of the molybdate method in accordance with PN-EN 1189–2000. – the content of Ca and Mg in soil were determined with plasma spectrophotometer ICP-AES (Thermo) according to the PN-ISO 11047:2001 after the mineralization of test material in the concentrated nitric acid in the Uni Clever microwave mineralizer (Plasmotronik). – the potassium was determined by the Egner-Rieham method (PN-R04023:1996) by extracting it with a calcium lactate solution and determining the colour of the phosphomolybdate complex on an HACH spectrophotometer for a wavelength of L =660 nm.
human consumption and production of forage (The Regulation of the Minister of the Environment on municipal sewage sludge of 6 February 2015). Sewage sludge was introduced to the soil once for three years at the amount of 36 Mg d.m./ha at the acceptable dose in compliance with laws and regulations to 45 Mg d.m./ha. The Regulation of the Minister of the Environment on municipal sewage sludge of 6th February 2015 permits to use sewage sludge once a year, or – at adequately higher doses – once every two and three years. The amount of sewage sludge used was adapted to the type and use of the soil, its nutrient content, the quality of municipal sewage sludge and soil, and the plants’ demand for phosphorus and nitrogen. Brown coal (BC), which was the primary substrate for the applied fertilising mixtures, was collected from the Brown Coal Mine in Belchatow, Poland. Brown coal showed the characteristics of soft brown coal, i.e. earthy coal. The particle size of brown coal used for the experiments was less than 3 mm, the water content was 29.8% and the reaction was acidic. Due to physical and chemical properties, brown coal could be applied for plant fertilisation. The content of toxic heavy metals was very low and could not have a significant impact on the total concentration of heavy metals in the investigated soil. Brown coal ash (BCA) was obtained from the third dust collector for exhaust gases generated in the process of brown coal combustion in the power plant in Belchatow. Brown coal ash was added to organic and mineral mixture to increase pH, and, thus, to deacidify the soil. Furthermore, brown coal ash was a significant source of Ca and Mg. Due to physical and chemical properties, it could be applied for plant fertilisation. The following mineral fertilisers were used for the preparation of fertilising mixtures: Polifoska 8 – a commercially available fertiliser (24% of phosphorous P2O5, 24% of potassium K2O, 8% of nitrogen), calcium ammonium nitrate (28% of nitrogen NH4NO3, CaCO3, MgCO3), ammonium nitrate (13% of NH4NO3, Ca) and potassium salt (52% of K2O, 18% of S). Due to its good adaptation to Polish soil-climate conditions, Spartina pectinata was selected for the study. This long-lasting grass comes from North America, where continual work is being done to improve the technology of its cultivation, especially on marginal land. Spartina pectinata is one of the more promising plant species useful for energy. Like other C-4 species, it has high growth rates, and intense and efficient photosynthesis (Boe et al., 2009; Fraser and Kindscher, 2005). Spartina seedlings were obtained from the experimental field of the Warsaw University of Life Sciences in Skierniewice.
Statistical analysis of the results obtained in the study was based on the analysis of variance and one-way regression. Detailed analysis of significance of differences between the results obtained from individual fertilising combinations compared to the control was made using the Student's t-test at the level of significance set at p=0.05 (*). Mathematical analyses were made using the STATISTICA computer software. Microsoft Office Excel 2007 spreadsheet was used to determine standard deviations, with its values denoted with ± symbol.
2.3. Testing methods
3. Results and discussion
All samples of the soil fertilised with the investigated fertilisation combinations (after a 3-week period of reaching the geochemical equilibrium) and plant biomass harvests were tested for:
3.1. Effects of fertilisation on pH The soil used in the experiment showed acidic reaction (pH in 1 M 777
Environmental Research 156 (2017) 775–780
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Table 3 The effects of fertilisation on pH and hydrolytic acidity. Fertilisation combination
pH
H2O
pH
Table 4 The effects of the applied fertilisation on sorption capacity of soil. Fertilisation combination
Soil hydrolytic acidity Hh cmol (+)/kg
KCl
After reaching the geochemical equilibrium (before plants collection) C 5.9 ± 0.1 5.5 ± 0.1 2.80 ± 0.03 C+SS 6.2* ± 0.1 5.8* ± 0.1 2.50* ± 0.05 * * C+SS+BC+BCA +K 6.3 ± 0.1 6.0 ± 0.0 2.38* ± 0.03 5.9* ± 0.1 2.42* ± 0.04 C+SS+NPK 6.3* ± 0.2 C+BC+NPK 5.9ns ± 0.1 5.6 ns ± 0.2 2.78 ns ± 0.13 C+NPK 6.0ns ± 0.1 5.6ns ± 0.2 2.84 ns ± 0.03 After plant collection I C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
5.9 ± 0,1 6.1* ± 0,0 6.3* ± 0,1 6.2* ± 0,1 5.9ns ± 0,0 5.9 ns ± 0,1
5.5 ± 0,1 5.8* ± 0,1 6.0* ± 0,2 5.9* ± 0,1 5.5 ns ± 0,0 5.4 ns ± 0,1
5.7 ± 0,2 6.0 ± 0,1 6.3* ± 0,0 6.1* ± 0,2 5.9ns ± 0,2 5.7 ns ± 0,1
5.4 ± 0,1 5.7* ± 0,1 5.9* ± 0,0 5.8* ± 0,1 5.5* ± 0,1 5.3 ns ± 0,2
2.58* ± 0,03 2.73* ± 0,06 3.11 ns ± 0,01
After plan collection III C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
5.6 ± 0.1 5.9* ± 0.1 6.2* ± 0.0 6.0* ± 0.1 5.9* ± 0.1 5.6 ns ± 0.2
5.2 ± 0.1 5.6* ± 0.1 5.8* ± 0.0 5.7* ± 0.1 5.5* ± 0.1 5.3 ns ± 0.1
3.15 ± 0.06 2.80* ± 0.05 2.55* ± 0.09 2.70* ± 0.23 2.85* ± 0.05 3.13* ± 0.04
Significance at a confidence level: (*) p=0.05;
Tsorption capacity
cmol (+)kg−1 soil
2.78 ± 0,11 2.58 ns ± 0,20 2.40* ± 0,05 2.45* ± 0,09 2.75 ns ± 0,03 3.02* ± 0,03
After plant collection II C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
S- sum of basic exchange cations
Content of Vdegree of humic acids sorption [%] complex saturation with bases %
After equilibration biochemical C 3.00 ± 0.05 C+SS 5.70* ± 0.16 C+SS+BC+BCA+K 6.34* ± 0.07 C+SS+NPK 5.10* ± 0.05 C+BC+NPK 4.60* ± 0.10 C+NPK 3.66* ± 0.07
5.80 8.30 8.72 7.52 7.38 6.50
51.7 69.9 72.7 67.8 62.3 56.3
0.74 ± 0.01 0.90* ± 0.01 1.10* ± 0.06 0.95* ± 0.01 1,00* ± 0.04 0.80 ns ± 0.10
after the end of experiment C C+SS C+SS+BC+BCA+K C+SS+NPK C+BC+NPK C+NPK
5.83 8.25 8.68 7.25 7.26 6.85
46.0 66.1 70.6 62.8 60.7 54.3
0.70 ± 0.03 0.90* ± 0.05 1.20* ± 0.03 1.10* ± 0.05 1.15* ± 0.07 0.80* ± 0.00
2.68 ± 0.03 5.45* ± 0.13 6.13* ± 0.10 4.55* ± 0.14 4.41* ± 0.47 3.72* ± 0.19
Significance at a confidence level: (*) p=0.05;
ns
- non-significant result
introduced to soil with the crops. Plant roots accumulate metal ions from alkaline soils, which leads to reduction in Ca and Mg in the soils. However, insignificant changes in soil pH observed during the 3-year experiment showed a favourable effect of the applied fertilisation on maintaining the stability of soil environment.
ns
- non-significant result
KCl – 5.5). Although the effect of fertilisation on changes in the soil pH was insignificant, it has to be emphasized that, after reaching the geochemical equilibrium, the soil fertilised with C+SS+BC+BCA +K, C+ SS and C+SS+NPK reached pH close to 6.0, which is sufficient for light soils (Table 3). After completion of the pot experiment, a slight decrease in the soil pH was observed for all the applied fertilisation combinations as compared to the initial pH before the experiment. The decrease in the soil pH after a 36-month period ranged from 0.1 to 0.3, depending on the fertilisation combination. At the same time, soil hydrolytic acidity Hh (Table 3) was found to be increased and a slight decrease in the sum of basic exchange cations (S) was observed (Table 4). Less significant changes in pH were observed for the soils fertilised with brown coal (max. 0.1) in comparison to the soils fertilised with other combinations. This is likely to have been caused by a slower rate of brown coal organic matter decomposition. It has to be pointed out that the rate of organic matter decomposition for brown coal is relatively slow compared to other organic fertilisers: green fertilisers > crop straw > manure > peat > brown coal (Kwiatkowska, 2007). Decomposition of the soil organic matter results in the formation of carbonic acid. Furthermore, mineralization of soil organic matter results in non-metal oxides, such as SO42- or NO3-, that can form acids with water. As observed during the experiment, these processes can cause the pH decrease and hydrolytic acidity increase (see Table 3). The decrease in pH after some time from the use of the sewage sludge was also observed by Vasseur et al. (2000), and Forsberg and Ledin (2006). In the first year after application of the sewage sludge, these researchers observed an increase in soil pH, followed by its decrease. Furthermore, these authors emphasized that this phenomenon was primarily due to the acidifying character of the carbon dioxide formed during the decomposition of the organic matter. Under specific conditions, acid rains can also have a significant effect on soil acidification. The decrease in soil pH during the experiment might result from many other processes. Some amount of calcium was
3.2. Effects of fertilisation on sorption properties of soil and the content of humic acids The buffer capacity depends on sorption complex properties; therefore, a substantial part of the study was devoted to the analysis of changes in soil sorption properties with respect to the fertilisation used. It must be emphasized that sorption properties characterized by such parameters as content of exchangeable base cations, sorption capacity and degree of the sorption complex by saturation with alkali are numbered among the most important soil features which have an indirect effect on soil fertility. It is good that soil has sorption capacity with can regulate reaction, accumulate nutrients and neutralise harmful substances (Balintova et al., 2012; Scanferla et al., 2012). The soil used in the experiment showed sorption capacity of 5.8 cmol(+)/kg, which is means moderate sorption conditions. The data available in the literature show that the average sorption capacity of sandy soil ranges from 3.0 to 8.0 cmol(+)/kg (Bednarek et al., 2004; Mercik, 2004). Many researchers have demonstrated that sorption capacity greater than 6.5 cmol (+)/kg reflects good properties of the soil with respect to its capacity to store nutritional compounds. The fertilisation used in the study improved sorption properties of the soils studied. This was demonstrated by an increase in the sum of the exchange cations and a significant increase in sorption capacity of the soil and the degree of sorption complex saturation with base. The soil fertilised with SS+BC+BCA showed the sorption capacity higher than 8.0 cmol(+) kg−1, which suggests good sorption conditions (Table 4). Many studies have found that sewage sludge, due to its high content of organic matter, improves the structure and the sorption complex of light soils (Wang et al., 2008; Blake and Goulding, 2002; Hao and Chang, 2002; Stańczyk-Mazanek and Stepniak, 2013). Fertilising properties of brown coal result from the permanent enrichment of soil with organic substance. Fertilisation with the mixture of sewage sludge, brown coal and brown coal ash resulted in a significant increase in the degree of sorption complex saturation with 778
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sludge used for fertilisation led to the excessive mineralization of the organic nitrogen compounds in soils. Therefore, mixing sewage sludge with brown coal (with higher C:N ratio) should be recommended as the C:N ratio in the final mixture is the sum of the C:N ratio of all substrates used for preparation of the mixture. Increasing the C:N ratio in the mixture results in the reduced mineralization of organic nitrogen compounds in favor of biological sorption. This represents a very advantageous fertilising effect.
bases. It amounted to ca. 20% for all the experiments. After the completion of the experiments, the fertilised soil continued to show higher values of sorption capacity and the degree of sorption complex saturation with bases in comparison to the soil with no fertilisation. The results indicated a direct relationship between the reaction of soil and its sorption properties. With the increase in soil pH, the decrease in the hydrolytic acidity and the increase in the sum of bases (especially sorption complex saturation with bases) were observed. Humic acid content was evaluated for each fertilising combination before the plants collection and after each harvest. In the control soil, before the collection of plants, the humic acid content was low (0.74%). Fertilisation led to the increase in the humic acids content from 0.06% to 0.36%, depending on the type of fertilisation. This effect was noticed to the greatest extent after the introduction of the mixture of carbon coal sewage sludge and carbon coal ashes to the soil, as well as carbon coal enriched in mineral fertilisers (Table 4). The effects of soil enrichment in the humic acids were observed over the entire duration of the experiment. The long-term increase in humic acid contents in the sewage sludge fertilised soils was documented by Jouraiphy et al. (2005). The increase in humic acids content shows the significance of soil enrichment in humic substances. Studies have shown that brown coal humic acids in the form of mono- and divalent cations of salts have a beneficial effect in the case of difficult agricultural conditions by stimulation of specific biological processes (Kwiatkowska, 2007).
3.4. Effect of fertilisation on plant yield The study examined growth and development of plants. A 3-year period of the experiment showed that the yield of Spartina pectinata depended statistically significantly on a fertilisation combination. The results of the whole experiment showed the slowest plant growth for the control, whereas the highest plant yields were obtained from the soil fertilised with the mixture of sewage sludge, brown coal, brown coal ash and potassium salt (C+SS+BC+BCA+K) and sewage sludge enriched with mineral fertilizers (C+SS+NPK). The average aggregate yield from the period of 3 years for these fertilisation combinations was ca. 460 g per pot and was 2.3 times higher than the control. High plant yields from the soil fertilised with sewage sludge accounted for the high content of nutritional compounds and a beneficial effect of sewage sludge on physical, chemical and biological properties of the soil. Many researchers have characterized sewage sludge as a fertiliser with properties of gradual and slow release of N and P due to the mineralization of organic matter (Gasco et al., 2004; Ociepa-Kubicka et al., 2016; Suhadolc et al., 2010). A significantly slower rate of plant growth was observed for fertilisation with brown coal and mineral fertilisers (C+BC+NPK). However, the yields were significantly higher for this fertilisation combination compared to the control (Table 5). The results obtained by Ociepa (2011) showed lower yields of maize and Virginia fanpetals cultivated on the soil fertilised only with brown coal in comparison to the soil fertilised with sewage sludge and the mixture of sewage sludge and brown coal but still 20% higher than the yield from the soil with no fertilisation. The effects of fertilisation combinations on the plant yield were observed in the first year of the experiments. However, the yields were low in comparison to the yields from the second and third year of vegetation. With reference to the dynamics of plant yields, the plants in the third year entered into the stage of full productivity (Fig. 1). This finding is consistent with the results of the study of energy crops (Ociepa, 2011; Pulford and Watson, 2003).
3.3. Effect of fertilisation on the content of organic carbon and total nitrogen in soil Organic carbon content in the soil without fertilisation was 11.30 mg g−1. Fertilisation with C+BC+NPK resulted in the highest increase in the organic carbon content (ca. 8.0 mg g−1). A lower increase in the organic carbon content was obtained with the mixture of C+SS+BC+BCA+K (ca. 7.0 mg g−1), whereas fertilisation with C+NPK resulted in the lowest increase in the organic carbon content (ca. 3.0 mg g−1). A loss of organic carbon was observed over the experiment. Organic carbon losses are the result of ongoing soil processes, primarily mineralization, carbon dioxide (CO2) and methane (CH4) emissions into the atmosphere and soluble organic carbon leaching to groundwater (DOC) (Lal, 2000). In the case of organic fertilisers, the same effect has been observed by other researchers (Kitczak et al., 2010; Suhadolc et al., 2010). The loss of Corg in the case of fertilisation with brown coal was lower, which was reflected by a slower rate of mineralization of brown coal organic matter compared to sewage sludge. Total nitrogen in the control before planting the seedlings was 1.00 mg g−1. Addition of fertilising substrates significantly increased the nitrogen content in the soils. The increase in nitrogen content in the soils fertilised with sewage sludge is consistent with the findings of other researchers (Mihalache et al., 2014; Lima et al., 2009). After completion of the experiment, nitrogen content was higher in all fertilisation combinations compared to the control. Plants can collect only mineral nitrogen from soil, accounting for merely several per cent of total nitrogen. Therefore, an insignificant decrease in total nitrogen was observed during the experiment. This resulted from collecting nitrogen from the soil by plants and microorganisms. Fertilisation with brown coal led to an increase in the C:N ratio in the soils from the pot experiment. An increase in the C:N ratio from 11:1 (the control) to 14:1 was observed for the fertilisation with the mixture of brown coal enriched with NPK. Furthermore, this effect was also observed in the case of fertilisation with the mixture of sewage sludge, brown coal, brown coal ash and potassium salt (C+SS+BC+BCA+K). The increased C:N ratio in the soils after the use of these fertilisation combinations was maintained after the last harvesting of the plants. This shows the effectiveness of using mixtures of sewage sludge and brown coal for soil fertilisation. The low C:N ratio of 10:1 in sewage
4. Conclusions The increase in agricultural fertility of weak soils should be aimed in particular at their enrichment in organic matter and regulation of their reaction. Determining the economical and ecological benefits and finding adequate plant species adjusted to particular soil and climate conditions seems to be critical. Table 5 The average yield of Spartina pectinata in the pot experiment [g d.m. per pot]. Fertilisation combinations
C C+SS C+SS+BC+BCA+K C+SS+NPK C+BC+NPK C+NPK
Spartina pectinata 1st harvesting
2nd harvesting
3rd harvesting
38.0 ± 1.8 60.1* ± 3.9 62.0* ± 4.6 64.3* ± 3.8 50.0* ± 2.9 63.0* ± 4.1
66.1 ± 4.1 160.2* ± 8.7 155.3* ± 7.8 170.1* ± 7.3 87.8* ± 5.0 158.0* ± 8.6
92.0 ± 4.3 210.6* ± 8.7 245.0* ± 11.1 225.4* ± 14.2 148.2* ± 7.4 176.0* ± 7.0
Significance at a confidence level: (*) p=0.05;
779
ns
- non-significant result
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metals in oxidising sulphide mine tailings. Sci. Total Environ. 358, 21–35. Fraser, A., Kindscher, K., 2005. Spatial distribution of Spartina pectinata transplants to restore wet prairie. Restor. Ecol. 13 (1), 144–151. Gasco, G., Martinez-Inigo, M., Lobo, M., 2004. Soil organic matter transformation after a sewage sludge application. EJEAF Che 3, 716–723. Gomiero, T., 2016. Soil degradation, land scarcity and food security: reviewing a complex challenge. Sustainability 8 (281), 1–41. Hao, X., Chang, C., 2002. Effect of 25 annual cattle manure applications on soluble and exchangeable cations in soil. Soil Sci. 2 (2), 126–134. Jouraiphy, A., Amir, S., Gharoos, M., 2005. Chemical and spectroscopic analysis of organic matter transformation during composting of sewage sludge and green plant waste. Int. Biodeter. Biodegrad. 56, 101–108. Kacprzak, M., Fijałkowski, K., 2009. Mycorrhiza and sewage sludge effect on biomass of sunflower and willow during phytoremediation of degraded terrains with in zinc foundry zone. Environ. Prot. Eng. 35 (2), 181–187. Karczewska, A., Kabała, C., 2010. The soils polluted with heavy metals and arsenic in Lower Silesia – the need and methods of reclamation. Sci. J. Wroc. Univ. Environ. Life Sci. Ser. Agron. 576, 59–80. Kitczak, T., Czyż, H., Kiepas-Kot, A., 2010. Influence of the way and term of sewage sludge on the chemical composition of soil and lawn. Annu. Set. Environ. Prot. 12, 207–218. Kowalczyk-Juśko, A., Kościk, B., Kościk, K., 2004. Prairie cordgrass (in Polish). Agroenergetyka 3 (9), 14–15 (in Polish). Kwiatkowska, J., 2007. Evaluation of brown coal as an effective source of organic matter in anthropologically transformed soils. Eng. Prot. Environ. 10 (1), 75–85 (in Polish). Lal, R., 2000. Soil carbon and greenhouse effect. Polish agriculture and water quality protection. Educ. Pap. 6, 22–36 (in Polish). Lima, D., Santos, S., Scherer, W.H., Duarte, C.A., Santos, E., Esteves, I.V., 2009. Effects of organic and inorganic amendments on soil organic matter properties. Geoderma 150, 38–45. Mercik, S. (Ed.), 2004. Agricultural Chemistry. Warsaw University of Life Sciences SGGW Publishing House, Warsaw (in Polish). Mihalache, M., Ilie, L., Madjar, R., 2014. Translocation of heavy metals from sewage sluge amended soil to plant. Rev. Roum. Chim. 59 (2), 81–89. Ociepa, E., 2011. The effect of fertilization on yielding and heavy metals uptake by maize and virgina fanpetals (Sida Hermaphrodita). Arch. Environ. Prot. 37 (2), 123–129. Ociepa, A., Lach, J., Gałczyński, Ł., 2008. Benefits and limitations arising from the development of soils polluted by heavy metals under the crops of industrial-energetic plants. Proc. ECOpole 2 (1), 231–235 (in Polish). Ociepa-Kubicka, A., Pachura, P., Kacprzak, M., 2016. Effect of unconventional fertilization on heavy metal content in biomass of giant miscanthus. Desalin. Water Treat. 57 (3), 1230–1236. http://dx.doi.org/10.1080/19443994.2015.1033132. Pachura, P., Ociepa-Kubicka, A., Skowron-Grabowska, B., 2016. Assessment of the availability of heavy metals to plants based on the translocation index and the bioaccumulation factor. Desalin. Water Treat. 57 (3), 1469–1477. http://dx.doi.org/ 10.1080/19443994.2015.1017330. Pulford, I.D., Watson, C., 2003. Phytoremediation of heavy metal-contaminated land by trees a review. Environ. Int. 29, 529–540. Ravisankar, R., Rajalakshmi, A., Manikandan, E., 2006. Mineral characterization of soil samples in and around salt field area, Kelambakkam, Tamilnadu, India. Acta Cienc. Indica Phys. 32 (3), 341–346. Scanferla, P., Marcomini, A., Pellay, R., Girotto, P., Zavan, D., Fabris, M., Collina, A., 2012. Remediation of a heavy metals contaminated site with a botanical garden: monitoring results of the application of an advanced s/s technique. Chem. Eng. Trans. 28, 235–240. http://dx.doi.org/10.3303/CET1228040. Serapiglia, M.J., Cameron, K.D., Stipanovic, A.J., Abrahamson, L.P., Volk, T.A., Smart, L.B., 2013. Yield and woody biomass traits of novel shrub willow hybrids at two contrasting sites. Bioenergy Res 6, 533–546. Stańczyk-Mazanek, E., Stepniak, L., 2013. Properties of sorption complex and humic acids in sandy soils fertilized with sewage sludge. Chem. Eng. Trans. 32, 499–504. http:// dx.doi.org/10.3303/CET1332084. Stevenson, F., 1982. Humus Chemistry. Genesis, Composition, Reactions. John Wiley and Sons, New York. Suhadolc, M., Schroll, R., Hagn, A., Dórfler, U., Schloter, M., Lobnik, F., 2010. Single application of sewage sludge – Impact on the quality of analluvial agricultural soil. Chemosphere 81, 1536–1543. Vasseur, L., Cloudier, C., Ansseau, C., 2000. Effects of repeated sewage sludge application on plant community diversity and structure under agricultural field conditions on Podolic soils in ekstern. Que. Agric. Ecosyst. Environ. 81, 209–216. Wang, X., Chen, T., Ge, Y., Jia, Y., 2008. Studies on land application of sewage sludge and its limiting factors. J. Hazard. Mater. 160, 554–558. Wolski, P., Zawieja, I., 2014. Hybrid conditioning before anaerobic digestion for the improvement of sewage sludge dewatering. Desalin. Water Treat. 52 (19–21), 3725–3731.
Fig. 1. Dynamics of plant yields in the subsequent years of cultivation (the total yield =100%) Fertilisation combinations: 1 – C, 2 – C+SS, 3 –C+SS+BC+BCA+K, 4 – C+SS +NPK, 5 – C+BC+NPK, 6 – C+NPK.
The results of this study lead to the following conclusions: 1. The overall analysis of the effect of the substrates used in the study showed that fertilisation with the mixture of sewage sludge, brown coal, brown coal ash and potassium fertiliser (C+SS+BC+BCA +K) had the most advantageous effect on physical and chemical properties of soils. 1. The use of the mixture of sewage sludge, brown coal, brown coal ash and potassium fertiliser (C+SS+BC+BCA +K) resulted in the following effects: the increase in pH by ca. 0.5, the increase in sorption capacity by ca. 3.0 cmol(+) kg−1, the increase of humic acid content in soil by ca. 0.5% and increase of C:N ratio from 11:1 to 14:1. 2. The yield of Spartina pectinata biomass depended on a fertilisation combination and harvesting year. The highest yields were obtained for fertilisation with C+SS+BC+BCA+K, C+SS+NPK and C+NPK. The aggregate yield of Spartina pectinata for these fertilisation combinations was 2.2−2.3 times higher than the yield obtained in the case of the soil with no fertilisation. 3. Spartina pectinata can be cultivated on light soils that are slightly contaminated with zinc and cadmium using unconventional fertilisation with the mixtures of sewage sludge, brown coal and brown coal ash. This study was supported by BS_PB- 401-306-11. References Aronsson, P., Rosenqvist, H., Dimitriou, I., 2014. Impact of nitrogen fertilization to shortrotation willow coppice plantations grown in Sweden on yield and economy. Bioenergy Res. 7 (3), 993–1001. http://dx.doi.org/10.1007/s12155-014-9435-7. Balintova, M., Holub, M., Singovszka, E., 2012. Study of iron, copper and zinc removal from acidic solutions by sorption. Chem. Eng. Trans. 28, 175–180. http://dx.doi.org/ 10.3303/CET1228030. Bednarek, R., Dziadowiec, H., Pokojska, U., Prusinkiewicz, Z., 2004. Environmental and Soil Research. Polish Scientific Publishers PWN, Warsaw (in Polish). Blake, L., Goulding, K.W.T., 2002. Effects of atmospheric deposition, soil pH and acidification on heavy metal contents in soils and vegetation of semi-natural ecosystem sat Rothamsted Experimental Station, UK. Plant Soil 240, 235–251. Boe, A., Owens, V., Gonzales-Hernandez, J., Stein, J., Lee, D.K., Koo, C., 2009. Morphology and biomass production of prairie cordgrass on marginal lands. Glob. Change Biol. Bioenergy 1 (3), 240–250. Forsberg, L.S., Ledin, S., 2006. Effects of sewage sludge on pH and plant availability of
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Influence of fertilisation with sewage sludge-derived preparation on selected soil properties and prairie cordgrass yield
MARK
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Ewa Ociepa , Maciej Mrowiec, Joanna Lach Institute of Environmental Engineering, Czestochowa University of Technology, Brzeźnicka Street 60a, 42-200 Częstochowa, Poland
A R T I C L E I N F O
A B S T R A C T
Keywords: Preparation fertilizer Sewage sludge Brown coal Brown coal ash soil Spartina pectinata
The aim of the study was to evaluate the effect of using a fertilizer obtained from waste substances on selected physical and chemical properties of soil and biomass yield Spartina pectinate. The fertilizer used for soil (C) fertilisation contained sewage sludge (SS), waste soil fractions of brown coal (BC), brown coal ash (BCA) enriched with mineral potassium (K) fertilizer (C+SS+BC+BCA+K). The composition of the preparation was developed by the authors and adjusted to the quality of the fertilised soil and the individual characteristics of the plant. It was assumed that the preparation should replace expensive conventional fertilisation methods, allow for management of waste substances and improve soil properties, leading to a high yield of Spartina pectinata used as energy crop. The plants were grown on the soil from the Huta Częstochowa steelworks effect zone. The soil was light, with acid reaction (pH KCl =5.5), with small contents of such contaminants as Cd and Zn and elevated Pb content. Based on a three-year pot experiment, the paper presents the results of the examinations concerning the effect of fertilisation on soil pH, hydrolytic acidity, sorptive properties, content of humic acids, organic coal and total nitrogen in soil and crop yielding. The effect of the use of the fertilizer (C+SS+BC+BCA+K) was compared with the use of the sludge (C+SS), sludge with mineral fertilizers (C+SS+NPK), mixture of brown coal and mineral fertilizers (C+BC+NPK) and effect of only mineral fertilizers (C+NPK). Fertilisation with (C+SS+BC+BCA+K) led to the increase in soil pH from 5.5 to 6.0, which is considered sufficient for light soils. The fertilised soil was characterized by sorption capacity of ca. 5.8 cmol(+)/kg, and, after fertilisation with O+W+P, reached the value of ca. 8.0 cmol(+) kg−1. Consequently the soil can be regarded as of good quality in terms of its capability to store nutrients. The C:N ratio was also extended from 11:1 (control soil) to 14:1 (C+SS+BC+BCA+K). The yield of Spartina pectinata in the first year was 1.6 and in the third year 2.7 times higher in the case of fertilisation with the investigated mixture as compared to the control.
1. Introduction
the relatively intensive fertilisation with NPK fertilizers with the yearly amounts of N: 100–170, P: 60–80, K: 100–120 kg/ha, leading to high costs (Kowalczyk-Juśko et al., 2004). Furthermore, production of nitrogen-based and phosphorus-based fertilizers is very energy-consuming, which leads to reduction in energy benefits. Production of mineral fertilizers additionally generates several ecological problems. Therefore, from the economic and ecological standpoint, various types of waste should be used as a source of nutrients for plants used as energy crops. The application of a fertilising mixture (C+SS+BC+BCA+K) consisting of sewage sludge (SS), waste earthy fraction of brown coal (BC), ash produced from brown coal (BCA), and enriched with potassium mineral fertilizer (K) was a recommended solution for soil reclamation. The composition of the mixtures and the recommended
This study presents opportunities for management of light and acid soils with slight content of cadmium and zinc contaminants, with elevated content of lead, which are barren and located in the steelworks effect zone. According to the recommendations of the ecological policy, these soils should be subjected to reclamation and used for non-food crop production. The problem of soil contamination and degradation concerns many regions of the world (Ravisankar et al., 2006; Karczewska and Kabała, 2010; Gomiero, 2016). Many authors have emphasized that one of the effective initiatives is to use these soils to grow energy crops (Ociepa et al., 2008; Aronsson et al., 2014; Serapiglia et al., 2013). Studies have demonstrated that Spartine pectinata can be grown on soils with low fertility, but the plants require
⁎
Corresponding author. E-mail address: [email protected] (E. Ociepa).
http://dx.doi.org/10.1016/j.envres.2017.05.003 Received 29 July 2016; Received in revised form 15 April 2017; Accepted 3 May 2017 0013-9351/ © 2017 Elsevier Inc. All rights reserved.
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(Table 1) were added to the bottomless PVC pots (inserted in the soil) with the diameter of 30 cm and height of 80 cm, containing 40 kg of soil. Six fertilising combinations were used, with each combination repeated in three pots. The soil for the pot experiment was obtained from the area located around 1 km north-east of the Huta Częstochowa steelworks. The depth of soil sampling ranged from 0 to 25 cm. Thirty individual samples were obtained to prepare the averaged sample from one area. The number of individual samples was adjusted to the size of the field (1500 m2). The results presented in the study are the mean value of three measurements of the average sample used in the analysis. The pots were filled with soil in the state of its natural humidity, previously sieved using a sieve with mesh size of 5 mm. The fertilizer doses were determined based on the plant demand for nutrients (with particular focus on nitrogen and phosphorus) and soil nutrient abundance. The principles of good agricultural practices were used in order not to cause excessive fertilisation (damages from the standpoint of environmental protection, plant yielding, high costs of cultivation). Differences in the level of fertilizer doses result from different chemical composition of individual substrates. Similar doses of basic nutrients (nitrogen, phosphorus, potassium) were used to compare the effect of different types of fertilisation on the plants tested. Two seedlings of Spartina pectinata were planted in each pot. In the first year of the pot experiment – before planting the seedlings – single doses of the following substances were applied: sewage sludge, brown coal, brown coal fly ash and mineral fertilizers. During the next two years of the pot experiment, mineral fertilisers (the doses of fertilisers are provided in Table 1) were used each spring before the onset of plant vegetation. The samples of soil and plant biomass were obtained during and after completion of the pot experiment. Clean plant biomass from each pot was divided into above-ground and underground parts, and then dried and ground in a laboratory grinder. Prior to further analysis, the plant biomass samples were stored in airtight containers.
doses were determined and tested by the author of this study. The composition and doses of this fertilising mixture were adjusted to the plant demands (Spartina pectinata), soil quality and current legal regulations. Sewage sludge can be used for fertilisation as it contains nutrients and organic substances which are valuable for plants. The value of sludge fertilizers has been presented in numerous studies (Gasco et al., 2004; Ociepa-Kubicka et al., 2016; Suhadolc et al., 2010; Wolski and Zawieja, 2014). However, its biological use is possible only if stringent regulations are met (The Regulation of the Minister of the Environment on municipal sewage sludge of 6 february 2015), as it may contain high amounts of heavy metals and be an organic and microbiological pollution carrier (Kacprzak and Fijałkowski, 2009; Pachura et al., 2016). A potential solution to the reduction of the threats resulting from the application of the sewage sludge is to mix the sewage sludge with brown coal and brown coal ash. The chemical composition and porous structure of brown coal – which results in high sorption properties – allow for the application of earthy forms of brown coal in soil fertilisation. Another important property of brown coal is its durability and susceptibility to microbiological degradation. Brown coal ash is a valuable and rich source of calcium, magnesium and microelements. Brown coal ash introduced to soils increases the sorption complex capacity, water holding capacity and pH of acidic soils (Kwiatkowska, 2007). The aim of the examinations presented in this paper was to determine the effect of fertilisation with preparation made of sewage sludge, brown coal, brown coal ash enriched with potassium fertilizer on soil properties and Spartine pectinata yielding. The following research theses were presented before the examinations: – agriculturally poor soils, contaminated with heavy metals, acidified and barren, can be reclaimed by addition of waste substrates and used as energy crops. – a mixture of sewage sludge, brown coal and brown coal ashes enhanced with potassium fertilizer has a beneficial effect on soil properties and Spartine pectinata yielding.
2.2. Characteristics of soil and fertilising substrates Analysis of the granulometric soil composition showed that, due to the content of floatable fractions (< 10%) and according to the criteria specified by the Instytut Uprawy, Nawożenia i Gleboznawstwa Puławy, this soil should be categorized as very light. With reference to the structure of soil profile and the analysis of soil maps, the soil used for the experiments showed the characteristics of lassie top gelyic soil and belonged to the granulometric group of slightly loamy sand with acidic reaction. The soil was acid with pH 5.5. Table 2 presents characterization of soil and substrates used in the experiment. Fertilising mixtures were prepared from the sewage sludge collected from a mechanical and biological municipal wastewater treatment plant. Sewage sludge (SS) was stabilized, dewatered, and characterized by slightly acidic reaction, high content of organic matter and relatively low content of heavy metals. Sewage sludge used for the experiment showed good fertilising properties due to the content of nitrogen and phosphorous. Physical, chemical and microbiological properties of sewage sludge allowed for the fertilisation of plants not intended for
The results obtained in the study represent the extension and supplementation of the knowledge concerning: – physical and chemical modifications of soil properties, development and yielding of Spartine pectinata, – opportunities for biomass generation for the purposes of renewable energy using unconventional fertilisation methods, – the use of sewage sludge and waste fraction of brown coal and brown coal ashes for soil fertilisation. 2. Materials and methods 2.1. Description of the pot experiment The examinations were based on the analysis of soil and plant samples obtained from a pot experiment. The fertilising substrates Table 1 The investigated fertilisation combinations in the pot experiment. Fertilisation combinations
Fertilisation type and dose
C C+SS C+SS+BC+BCA+K C+SS+NPK
control – 40 kg of soil 40 kg of soil + 2892 g sewage sludge (36 Mg d.m./ha) 40 kg of soil + 1736 g of sewage sludge + 308 g of brown coal + 80 g of brown coal ash (ok.36 Mg d.m./ha) + 2.0 g of potassium salt (100 kg/ha) 40 kg of soil + 1448 g of sewage sludge (18 Mg d.m./ha) + 3.0 g Polifoska 8 fertilizer + 2.0 g calcium ammonium nitrate + 1.0 g ammonium nitrate(300 kg/ha) 40 kg of soil + 1024 g of brown coal (36 Mg d.m./ha) + 3.0 g Polifoska 8 fertilizer + 2.0 g calcium ammonium nitrate + 1.0 g ammonium nitrate (300 kg/ha) 40 kg of soil + 6.0 g Polifoska 8 fertilizer + 4.0 g of calcium ammonium nitrate + 2.0 g of ammonium nitrate (600 kg/ha)
C+BC+NPK C+NPK
776
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Table 2 The soil and substrates characteristics used in the experiment. Parameter
Unit
Soil Average value
Sewage sludge
Brown coal
Brown coal ash
Substancja organiczna Corg N P K Ca Mg Pb Cd Zn Cu Ni Cr
% d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg g−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m. mg kg−1 d.m.
– 11.3 ± 0.7 1.0 ± 0.1 0.67 ± 0,10 0.74 ± 0.10 0.67 ± 0.11 0.62 ± 0,05 39.0 ± 1.3 1.18 ± 0.07 122.2 ± 6.9 8.3 ± 0.5 7.0 ± 0.3 13.0 ± 1.1
44.3 ± 1.3 – 35.0 ± 0.9 19.0 ± 1.1 6.9 ± 0.6 9.8 ± 1.8 3.6 ± 0.5 41.0 ± 3.0 2.1 ± 0.2 860.0 ± 9.0 121.0 ± 16.0 19.3 ± 5.9 21.8 ± 3.9
– 498 ± 3.8 6.5 ± 0.9 1.1 ± 0.1 0.7 ± 0.1 30.2 ± 2.3 9.0 ± 0.8 3.0 ± 0.5 0.09 ± 0.01 15.3 ± 2.5 10.1 ± 0.9 4.2 ± 1.0 10.0 ± 0.8
– – – 0.9 ± 0.1 0.2 ± 0.0 202.0 ± 12.9 8.0 ± 1.6 60.0 ± 6.0 3.0 ± 0.4 101.0 ± 7.1 26.0 ± 1.0 36.5 ± 1.3 67.3 ± 3.1
– pH in 1 M KCl, using the potentiometric method by means of the CyberScan pH meter 10 according to the PH-ISO-10390:1997 standard, – hydrolytic acidity, by means of the Kappen modified method according to the PN-R-04027. – the total sum of alkaline cations in soil, determined with the Kappen method – the organic carbon content was determined by the modified Tiurin colorimetric method in accordance with PN-ISO 14235:2003. – the overall Kjeldahl nitrogen quantity was determined in accordance with PN-ISO 11261:2002 using a BUCHI 426 mineralizer and a BUCHI 323 distilling apparatus. – humic acids were determined using extraction with the solution containing 0.1 M HCl and 0.1 M Na4P2O7 with 1:1 ratio (Stevenson, 1982). – total heavy metals in the soil were evaluated using the plasma spectrophotometer ICP-AES (Thermo) according to the PN-ISO 11047: 2001 standard following the mineralization of the material in the mixture of concentrated HCl and HNO3 acids and using the 3:1 ratio (aqua regia). – the overall phosphorus (in the phosphate from) was determined by means of the molybdate method in accordance with PN-EN 1189–2000. – the content of Ca and Mg in soil were determined with plasma spectrophotometer ICP-AES (Thermo) according to the PN-ISO 11047:2001 after the mineralization of test material in the concentrated nitric acid in the Uni Clever microwave mineralizer (Plasmotronik). – the potassium was determined by the Egner-Rieham method (PN-R04023:1996) by extracting it with a calcium lactate solution and determining the colour of the phosphomolybdate complex on an HACH spectrophotometer for a wavelength of L =660 nm.
human consumption and production of forage (The Regulation of the Minister of the Environment on municipal sewage sludge of 6 February 2015). Sewage sludge was introduced to the soil once for three years at the amount of 36 Mg d.m./ha at the acceptable dose in compliance with laws and regulations to 45 Mg d.m./ha. The Regulation of the Minister of the Environment on municipal sewage sludge of 6th February 2015 permits to use sewage sludge once a year, or – at adequately higher doses – once every two and three years. The amount of sewage sludge used was adapted to the type and use of the soil, its nutrient content, the quality of municipal sewage sludge and soil, and the plants’ demand for phosphorus and nitrogen. Brown coal (BC), which was the primary substrate for the applied fertilising mixtures, was collected from the Brown Coal Mine in Belchatow, Poland. Brown coal showed the characteristics of soft brown coal, i.e. earthy coal. The particle size of brown coal used for the experiments was less than 3 mm, the water content was 29.8% and the reaction was acidic. Due to physical and chemical properties, brown coal could be applied for plant fertilisation. The content of toxic heavy metals was very low and could not have a significant impact on the total concentration of heavy metals in the investigated soil. Brown coal ash (BCA) was obtained from the third dust collector for exhaust gases generated in the process of brown coal combustion in the power plant in Belchatow. Brown coal ash was added to organic and mineral mixture to increase pH, and, thus, to deacidify the soil. Furthermore, brown coal ash was a significant source of Ca and Mg. Due to physical and chemical properties, it could be applied for plant fertilisation. The following mineral fertilisers were used for the preparation of fertilising mixtures: Polifoska 8 – a commercially available fertiliser (24% of phosphorous P2O5, 24% of potassium K2O, 8% of nitrogen), calcium ammonium nitrate (28% of nitrogen NH4NO3, CaCO3, MgCO3), ammonium nitrate (13% of NH4NO3, Ca) and potassium salt (52% of K2O, 18% of S). Due to its good adaptation to Polish soil-climate conditions, Spartina pectinata was selected for the study. This long-lasting grass comes from North America, where continual work is being done to improve the technology of its cultivation, especially on marginal land. Spartina pectinata is one of the more promising plant species useful for energy. Like other C-4 species, it has high growth rates, and intense and efficient photosynthesis (Boe et al., 2009; Fraser and Kindscher, 2005). Spartina seedlings were obtained from the experimental field of the Warsaw University of Life Sciences in Skierniewice.
Statistical analysis of the results obtained in the study was based on the analysis of variance and one-way regression. Detailed analysis of significance of differences between the results obtained from individual fertilising combinations compared to the control was made using the Student's t-test at the level of significance set at p=0.05 (*). Mathematical analyses were made using the STATISTICA computer software. Microsoft Office Excel 2007 spreadsheet was used to determine standard deviations, with its values denoted with ± symbol.
2.3. Testing methods
3. Results and discussion
All samples of the soil fertilised with the investigated fertilisation combinations (after a 3-week period of reaching the geochemical equilibrium) and plant biomass harvests were tested for:
3.1. Effects of fertilisation on pH The soil used in the experiment showed acidic reaction (pH in 1 M 777
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Table 3 The effects of fertilisation on pH and hydrolytic acidity. Fertilisation combination
pH
H2O
pH
Table 4 The effects of the applied fertilisation on sorption capacity of soil. Fertilisation combination
Soil hydrolytic acidity Hh cmol (+)/kg
KCl
After reaching the geochemical equilibrium (before plants collection) C 5.9 ± 0.1 5.5 ± 0.1 2.80 ± 0.03 C+SS 6.2* ± 0.1 5.8* ± 0.1 2.50* ± 0.05 * * C+SS+BC+BCA +K 6.3 ± 0.1 6.0 ± 0.0 2.38* ± 0.03 5.9* ± 0.1 2.42* ± 0.04 C+SS+NPK 6.3* ± 0.2 C+BC+NPK 5.9ns ± 0.1 5.6 ns ± 0.2 2.78 ns ± 0.13 C+NPK 6.0ns ± 0.1 5.6ns ± 0.2 2.84 ns ± 0.03 After plant collection I C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
5.9 ± 0,1 6.1* ± 0,0 6.3* ± 0,1 6.2* ± 0,1 5.9ns ± 0,0 5.9 ns ± 0,1
5.5 ± 0,1 5.8* ± 0,1 6.0* ± 0,2 5.9* ± 0,1 5.5 ns ± 0,0 5.4 ns ± 0,1
5.7 ± 0,2 6.0 ± 0,1 6.3* ± 0,0 6.1* ± 0,2 5.9ns ± 0,2 5.7 ns ± 0,1
5.4 ± 0,1 5.7* ± 0,1 5.9* ± 0,0 5.8* ± 0,1 5.5* ± 0,1 5.3 ns ± 0,2
2.58* ± 0,03 2.73* ± 0,06 3.11 ns ± 0,01
After plan collection III C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
5.6 ± 0.1 5.9* ± 0.1 6.2* ± 0.0 6.0* ± 0.1 5.9* ± 0.1 5.6 ns ± 0.2
5.2 ± 0.1 5.6* ± 0.1 5.8* ± 0.0 5.7* ± 0.1 5.5* ± 0.1 5.3 ns ± 0.1
3.15 ± 0.06 2.80* ± 0.05 2.55* ± 0.09 2.70* ± 0.23 2.85* ± 0.05 3.13* ± 0.04
Significance at a confidence level: (*) p=0.05;
Tsorption capacity
cmol (+)kg−1 soil
2.78 ± 0,11 2.58 ns ± 0,20 2.40* ± 0,05 2.45* ± 0,09 2.75 ns ± 0,03 3.02* ± 0,03
After plant collection II C C+SS C+SS+BC+BCA +K C+SS+NPK C+BC+NPK C+NPK
S- sum of basic exchange cations
Content of Vdegree of humic acids sorption [%] complex saturation with bases %
After equilibration biochemical C 3.00 ± 0.05 C+SS 5.70* ± 0.16 C+SS+BC+BCA+K 6.34* ± 0.07 C+SS+NPK 5.10* ± 0.05 C+BC+NPK 4.60* ± 0.10 C+NPK 3.66* ± 0.07
5.80 8.30 8.72 7.52 7.38 6.50
51.7 69.9 72.7 67.8 62.3 56.3
0.74 ± 0.01 0.90* ± 0.01 1.10* ± 0.06 0.95* ± 0.01 1,00* ± 0.04 0.80 ns ± 0.10
after the end of experiment C C+SS C+SS+BC+BCA+K C+SS+NPK C+BC+NPK C+NPK
5.83 8.25 8.68 7.25 7.26 6.85
46.0 66.1 70.6 62.8 60.7 54.3
0.70 ± 0.03 0.90* ± 0.05 1.20* ± 0.03 1.10* ± 0.05 1.15* ± 0.07 0.80* ± 0.00
2.68 ± 0.03 5.45* ± 0.13 6.13* ± 0.10 4.55* ± 0.14 4.41* ± 0.47 3.72* ± 0.19
Significance at a confidence level: (*) p=0.05;
ns
- non-significant result
introduced to soil with the crops. Plant roots accumulate metal ions from alkaline soils, which leads to reduction in Ca and Mg in the soils. However, insignificant changes in soil pH observed during the 3-year experiment showed a favourable effect of the applied fertilisation on maintaining the stability of soil environment.
ns
- non-significant result
KCl – 5.5). Although the effect of fertilisation on changes in the soil pH was insignificant, it has to be emphasized that, after reaching the geochemical equilibrium, the soil fertilised with C+SS+BC+BCA +K, C+ SS and C+SS+NPK reached pH close to 6.0, which is sufficient for light soils (Table 3). After completion of the pot experiment, a slight decrease in the soil pH was observed for all the applied fertilisation combinations as compared to the initial pH before the experiment. The decrease in the soil pH after a 36-month period ranged from 0.1 to 0.3, depending on the fertilisation combination. At the same time, soil hydrolytic acidity Hh (Table 3) was found to be increased and a slight decrease in the sum of basic exchange cations (S) was observed (Table 4). Less significant changes in pH were observed for the soils fertilised with brown coal (max. 0.1) in comparison to the soils fertilised with other combinations. This is likely to have been caused by a slower rate of brown coal organic matter decomposition. It has to be pointed out that the rate of organic matter decomposition for brown coal is relatively slow compared to other organic fertilisers: green fertilisers > crop straw > manure > peat > brown coal (Kwiatkowska, 2007). Decomposition of the soil organic matter results in the formation of carbonic acid. Furthermore, mineralization of soil organic matter results in non-metal oxides, such as SO42- or NO3-, that can form acids with water. As observed during the experiment, these processes can cause the pH decrease and hydrolytic acidity increase (see Table 3). The decrease in pH after some time from the use of the sewage sludge was also observed by Vasseur et al. (2000), and Forsberg and Ledin (2006). In the first year after application of the sewage sludge, these researchers observed an increase in soil pH, followed by its decrease. Furthermore, these authors emphasized that this phenomenon was primarily due to the acidifying character of the carbon dioxide formed during the decomposition of the organic matter. Under specific conditions, acid rains can also have a significant effect on soil acidification. The decrease in soil pH during the experiment might result from many other processes. Some amount of calcium was
3.2. Effects of fertilisation on sorption properties of soil and the content of humic acids The buffer capacity depends on sorption complex properties; therefore, a substantial part of the study was devoted to the analysis of changes in soil sorption properties with respect to the fertilisation used. It must be emphasized that sorption properties characterized by such parameters as content of exchangeable base cations, sorption capacity and degree of the sorption complex by saturation with alkali are numbered among the most important soil features which have an indirect effect on soil fertility. It is good that soil has sorption capacity with can regulate reaction, accumulate nutrients and neutralise harmful substances (Balintova et al., 2012; Scanferla et al., 2012). The soil used in the experiment showed sorption capacity of 5.8 cmol(+)/kg, which is means moderate sorption conditions. The data available in the literature show that the average sorption capacity of sandy soil ranges from 3.0 to 8.0 cmol(+)/kg (Bednarek et al., 2004; Mercik, 2004). Many researchers have demonstrated that sorption capacity greater than 6.5 cmol (+)/kg reflects good properties of the soil with respect to its capacity to store nutritional compounds. The fertilisation used in the study improved sorption properties of the soils studied. This was demonstrated by an increase in the sum of the exchange cations and a significant increase in sorption capacity of the soil and the degree of sorption complex saturation with base. The soil fertilised with SS+BC+BCA showed the sorption capacity higher than 8.0 cmol(+) kg−1, which suggests good sorption conditions (Table 4). Many studies have found that sewage sludge, due to its high content of organic matter, improves the structure and the sorption complex of light soils (Wang et al., 2008; Blake and Goulding, 2002; Hao and Chang, 2002; Stańczyk-Mazanek and Stepniak, 2013). Fertilising properties of brown coal result from the permanent enrichment of soil with organic substance. Fertilisation with the mixture of sewage sludge, brown coal and brown coal ash resulted in a significant increase in the degree of sorption complex saturation with 778
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sludge used for fertilisation led to the excessive mineralization of the organic nitrogen compounds in soils. Therefore, mixing sewage sludge with brown coal (with higher C:N ratio) should be recommended as the C:N ratio in the final mixture is the sum of the C:N ratio of all substrates used for preparation of the mixture. Increasing the C:N ratio in the mixture results in the reduced mineralization of organic nitrogen compounds in favor of biological sorption. This represents a very advantageous fertilising effect.
bases. It amounted to ca. 20% for all the experiments. After the completion of the experiments, the fertilised soil continued to show higher values of sorption capacity and the degree of sorption complex saturation with bases in comparison to the soil with no fertilisation. The results indicated a direct relationship between the reaction of soil and its sorption properties. With the increase in soil pH, the decrease in the hydrolytic acidity and the increase in the sum of bases (especially sorption complex saturation with bases) were observed. Humic acid content was evaluated for each fertilising combination before the plants collection and after each harvest. In the control soil, before the collection of plants, the humic acid content was low (0.74%). Fertilisation led to the increase in the humic acids content from 0.06% to 0.36%, depending on the type of fertilisation. This effect was noticed to the greatest extent after the introduction of the mixture of carbon coal sewage sludge and carbon coal ashes to the soil, as well as carbon coal enriched in mineral fertilisers (Table 4). The effects of soil enrichment in the humic acids were observed over the entire duration of the experiment. The long-term increase in humic acid contents in the sewage sludge fertilised soils was documented by Jouraiphy et al. (2005). The increase in humic acids content shows the significance of soil enrichment in humic substances. Studies have shown that brown coal humic acids in the form of mono- and divalent cations of salts have a beneficial effect in the case of difficult agricultural conditions by stimulation of specific biological processes (Kwiatkowska, 2007).
3.4. Effect of fertilisation on plant yield The study examined growth and development of plants. A 3-year period of the experiment showed that the yield of Spartina pectinata depended statistically significantly on a fertilisation combination. The results of the whole experiment showed the slowest plant growth for the control, whereas the highest plant yields were obtained from the soil fertilised with the mixture of sewage sludge, brown coal, brown coal ash and potassium salt (C+SS+BC+BCA+K) and sewage sludge enriched with mineral fertilizers (C+SS+NPK). The average aggregate yield from the period of 3 years for these fertilisation combinations was ca. 460 g per pot and was 2.3 times higher than the control. High plant yields from the soil fertilised with sewage sludge accounted for the high content of nutritional compounds and a beneficial effect of sewage sludge on physical, chemical and biological properties of the soil. Many researchers have characterized sewage sludge as a fertiliser with properties of gradual and slow release of N and P due to the mineralization of organic matter (Gasco et al., 2004; Ociepa-Kubicka et al., 2016; Suhadolc et al., 2010). A significantly slower rate of plant growth was observed for fertilisation with brown coal and mineral fertilisers (C+BC+NPK). However, the yields were significantly higher for this fertilisation combination compared to the control (Table 5). The results obtained by Ociepa (2011) showed lower yields of maize and Virginia fanpetals cultivated on the soil fertilised only with brown coal in comparison to the soil fertilised with sewage sludge and the mixture of sewage sludge and brown coal but still 20% higher than the yield from the soil with no fertilisation. The effects of fertilisation combinations on the plant yield were observed in the first year of the experiments. However, the yields were low in comparison to the yields from the second and third year of vegetation. With reference to the dynamics of plant yields, the plants in the third year entered into the stage of full productivity (Fig. 1). This finding is consistent with the results of the study of energy crops (Ociepa, 2011; Pulford and Watson, 2003).
3.3. Effect of fertilisation on the content of organic carbon and total nitrogen in soil Organic carbon content in the soil without fertilisation was 11.30 mg g−1. Fertilisation with C+BC+NPK resulted in the highest increase in the organic carbon content (ca. 8.0 mg g−1). A lower increase in the organic carbon content was obtained with the mixture of C+SS+BC+BCA+K (ca. 7.0 mg g−1), whereas fertilisation with C+NPK resulted in the lowest increase in the organic carbon content (ca. 3.0 mg g−1). A loss of organic carbon was observed over the experiment. Organic carbon losses are the result of ongoing soil processes, primarily mineralization, carbon dioxide (CO2) and methane (CH4) emissions into the atmosphere and soluble organic carbon leaching to groundwater (DOC) (Lal, 2000). In the case of organic fertilisers, the same effect has been observed by other researchers (Kitczak et al., 2010; Suhadolc et al., 2010). The loss of Corg in the case of fertilisation with brown coal was lower, which was reflected by a slower rate of mineralization of brown coal organic matter compared to sewage sludge. Total nitrogen in the control before planting the seedlings was 1.00 mg g−1. Addition of fertilising substrates significantly increased the nitrogen content in the soils. The increase in nitrogen content in the soils fertilised with sewage sludge is consistent with the findings of other researchers (Mihalache et al., 2014; Lima et al., 2009). After completion of the experiment, nitrogen content was higher in all fertilisation combinations compared to the control. Plants can collect only mineral nitrogen from soil, accounting for merely several per cent of total nitrogen. Therefore, an insignificant decrease in total nitrogen was observed during the experiment. This resulted from collecting nitrogen from the soil by plants and microorganisms. Fertilisation with brown coal led to an increase in the C:N ratio in the soils from the pot experiment. An increase in the C:N ratio from 11:1 (the control) to 14:1 was observed for the fertilisation with the mixture of brown coal enriched with NPK. Furthermore, this effect was also observed in the case of fertilisation with the mixture of sewage sludge, brown coal, brown coal ash and potassium salt (C+SS+BC+BCA+K). The increased C:N ratio in the soils after the use of these fertilisation combinations was maintained after the last harvesting of the plants. This shows the effectiveness of using mixtures of sewage sludge and brown coal for soil fertilisation. The low C:N ratio of 10:1 in sewage
4. Conclusions The increase in agricultural fertility of weak soils should be aimed in particular at their enrichment in organic matter and regulation of their reaction. Determining the economical and ecological benefits and finding adequate plant species adjusted to particular soil and climate conditions seems to be critical. Table 5 The average yield of Spartina pectinata in the pot experiment [g d.m. per pot]. Fertilisation combinations
C C+SS C+SS+BC+BCA+K C+SS+NPK C+BC+NPK C+NPK
Spartina pectinata 1st harvesting
2nd harvesting
3rd harvesting
38.0 ± 1.8 60.1* ± 3.9 62.0* ± 4.6 64.3* ± 3.8 50.0* ± 2.9 63.0* ± 4.1
66.1 ± 4.1 160.2* ± 8.7 155.3* ± 7.8 170.1* ± 7.3 87.8* ± 5.0 158.0* ± 8.6
92.0 ± 4.3 210.6* ± 8.7 245.0* ± 11.1 225.4* ± 14.2 148.2* ± 7.4 176.0* ± 7.0
Significance at a confidence level: (*) p=0.05;
779
ns
- non-significant result
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Mycorrhiza and sewage sludge effect on biomass of sunflower and willow during phytoremediation of degraded terrains with in zinc foundry zone. Environ. Prot. Eng. 35 (2), 181–187. Karczewska, A., Kabała, C., 2010. The soils polluted with heavy metals and arsenic in Lower Silesia – the need and methods of reclamation. Sci. J. Wroc. Univ. Environ. Life Sci. Ser. Agron. 576, 59–80. Kitczak, T., Czyż, H., Kiepas-Kot, A., 2010. Influence of the way and term of sewage sludge on the chemical composition of soil and lawn. Annu. Set. Environ. Prot. 12, 207–218. Kowalczyk-Juśko, A., Kościk, B., Kościk, K., 2004. Prairie cordgrass (in Polish). Agroenergetyka 3 (9), 14–15 (in Polish). Kwiatkowska, J., 2007. Evaluation of brown coal as an effective source of organic matter in anthropologically transformed soils. Eng. Prot. Environ. 10 (1), 75–85 (in Polish). Lal, R., 2000. Soil carbon and greenhouse effect. Polish agriculture and water quality protection. Educ. Pap. 6, 22–36 (in Polish). 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Fig. 1. Dynamics of plant yields in the subsequent years of cultivation (the total yield =100%) Fertilisation combinations: 1 – C, 2 – C+SS, 3 –C+SS+BC+BCA+K, 4 – C+SS +NPK, 5 – C+BC+NPK, 6 – C+NPK.
The results of this study lead to the following conclusions: 1. The overall analysis of the effect of the substrates used in the study showed that fertilisation with the mixture of sewage sludge, brown coal, brown coal ash and potassium fertiliser (C+SS+BC+BCA +K) had the most advantageous effect on physical and chemical properties of soils. 1. The use of the mixture of sewage sludge, brown coal, brown coal ash and potassium fertiliser (C+SS+BC+BCA +K) resulted in the following effects: the increase in pH by ca. 0.5, the increase in sorption capacity by ca. 3.0 cmol(+) kg−1, the increase of humic acid content in soil by ca. 0.5% and increase of C:N ratio from 11:1 to 14:1. 2. The yield of Spartina pectinata biomass depended on a fertilisation combination and harvesting year. The highest yields were obtained for fertilisation with C+SS+BC+BCA+K, C+SS+NPK and C+NPK. The aggregate yield of Spartina pectinata for these fertilisation combinations was 2.2−2.3 times higher than the yield obtained in the case of the soil with no fertilisation. 3. Spartina pectinata can be cultivated on light soils that are slightly contaminated with zinc and cadmium using unconventional fertilisation with the mixtures of sewage sludge, brown coal and brown coal ash. This study was supported by BS_PB- 401-306-11. References Aronsson, P., Rosenqvist, H., Dimitriou, I., 2014. Impact of nitrogen fertilization to shortrotation willow coppice plantations grown in Sweden on yield and economy. Bioenergy Res. 7 (3), 993–1001. http://dx.doi.org/10.1007/s12155-014-9435-7. Balintova, M., Holub, M., Singovszka, E., 2012. Study of iron, copper and zinc removal from acidic solutions by sorption. Chem. Eng. Trans. 28, 175–180. http://dx.doi.org/ 10.3303/CET1228030. Bednarek, R., Dziadowiec, H., Pokojska, U., Prusinkiewicz, Z., 2004. Environmental and Soil Research. Polish Scientific Publishers PWN, Warsaw (in Polish). Blake, L., Goulding, K.W.T., 2002. Effects of atmospheric deposition, soil pH and acidification on heavy metal contents in soils and vegetation of semi-natural ecosystem sat Rothamsted Experimental Station, UK. Plant Soil 240, 235–251. Boe, A., Owens, V., Gonzales-Hernandez, J., Stein, J., Lee, D.K., Koo, C., 2009. Morphology and biomass production of prairie cordgrass on marginal lands. Glob. Change Biol. Bioenergy 1 (3), 240–250. Forsberg, L.S., Ledin, S., 2006. Effects of sewage sludge on pH and plant availability of
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