Available Online: http://www.ejpau.media.pl/volume19/issue4/art-10.html
EFFECT OF COMPOSTED SEWAGE SLUDGE ON THE RATE OF C, N AND P MINERALIZATION IN SANDY SOIL
Monika Jakubus1, Małgorzata Graczyk2
1 Department of Soil Science and Land Protection, Poznań University of Life Sciences, Poland
2 Department of Mathematical and Statistical Methods, Poznań University of Life Sciences, Poland
Composting sewage sludge is an interesting alternative to recycling waste
as a compost, the more such produced composts are valuable sources of nutrients
and organic matter. Unfortunately, most of nutrients, and especially nitrogen
and phosphorous are present in hardly available forms. As a result the rate of
releasing of available nitrogen and phosphorus forms from compost may be slowly.
The objective of this study was to evaluate changes in carbon, nitrogen and phosphorous
mineralization in sandy soil incubated with two doses of composted sewage sludge
(30 and 120 Mg per hectare) over period of 180 days. Carbon mineralization was
determined by the measurement of soil respiration (CO2 emission). Besides, total
carbon mineralization (TCM) and nitrification index (NI) were calculated. The
data showed that with regard to the unamended soil, both the 30 and 120 Mg per
hectare treatments similarly influenced on analyzed properties but the effect
was more visible in the case of the higher compost dose. The dose of compost
amounting to 120 Mg∙ha-1 caused considerable differences between the analysed
parameters. Additionally it was found, that compost prepared on the basis of
sewage sludge is an valuable fertilizer but at the same time slowly releases
nutrients at available forms. For statistical testing, the analysis of variance
and post-hoc examination were used.
Composting sewage sludge is an interesting alternative to recycling waste as a compost, the more such produced composts are valuable sources of nutrients and organic matter. Unfortunately, most of nutrients, and especially nitrogen and phosphorous are present in hardly available forms. As a result the rate of releasing of available nitrogen and phosphorus forms from compost may be slowly. The objective of this study was to evaluate changes in carbon, nitrogen and phosphorous mineralization in sandy soil incubated with two doses of composted sewage sludge (30 and 120 Mg per hectare) over period of 180 days. Carbon mineralization was determined by the measurement of soil respiration (CO2 emission). Besides, total carbon mineralization (TCM) and nitrification index (NI) were calculated. The data showed that with regard to the unamended soil, both the 30 and 120 Mg per hectare treatments similarly influenced on analyzed properties but the effect was more visible in the case of the higher compost dose. The dose of compost amounting to 120 Mg∙ha-1 caused considerable differences between the analysed parameters. Additionally it was found, that compost prepared on the basis of sewage sludge is an valuable fertilizer but at the same time slowly releases nutrients at available forms. For statistical testing, the analysis of variance and post-hoc examination were used.
Key words: analysis of variance, compost, total carbon mineralization (TCM), nitrification index (NI), available N and P.
The amount of sewage sludge generated from sewage sludge treatment plants in Poland is around 550 000 Mg of dry matter per year . According to the Polish legal regulations , such wastes from 2016 are not deposited at disposal sites. In view of the above it is proposed to manage municipal sewage either by combustion, co-combustion or by composting. Composting of sewage sludge together with other structure-forming waste materials is a common and generally accepted method of disposal for this noxious waste [9, 11]. Thus, produced composts are valuable sources of nutrients and organic matter, which is of significance in agricultural and horticultural production. There are many papers dealing with the benefits of composted sewage sludge on different soil properties: physical, chemical, physico-chemical and biological [2, 5, 22, 27]. The use of composted sewage sludge is a very important strategy to comply with the Landfill Directive  and to the “end-of-waste” policy in Europe . Application of such organic soil amendments also fulfils the postulate of Thematic strategy for soil protection . That document concerns essential problems related to soil degradation. Among other things, the decline of organic matter was stressed as one of many factors causing soil degradation.
However, composting of sewage sludge has both benefits and drawbacks. Composting is a bio-oxidative process which mineralizes the simplest and humifies the more complex organic matter. Composting quickly reduces environmental risks related to the occurrence of pathogens and phytotoxic substances. On the other hand, this process leads to the loss of valuable agribiological properties, i.e. it may result in detrimental losses of C, N and to the secondary immobilization of available P forms . Finally, as a consequence of composting process obtained, matured compost is characterised by fairly homogenous organic matter with a higher molecular weight and limited amounts of nitrogen and phosphorous transformed into soluble, available forms that may be taken up by plants. In view of these facts, the fertilizing effect of such compost can be controversial, its transformation in soil and environmental fate depends on several factors connected with soil properties, moisture, microbiological activity as well as the C, N and P status in soil.
Therefore, the aims of that study have been to assess the dynamic of organic carbon mineralization and the rate of release of available nitrogen and phosphorus forms in a sandy soil incubated with compost applied at two doses.
MATERIAL AND METHODS
Soil used in this experiment was collected from the top layer (0–25 cm) of arable field. The soil was classified as Lessive soil according to World Reference Base for Soil Resources . Commercially available compost was produced as a mixture of sewage sludge (50%), sawdust (20%), wood cutting (10%) and wheat straw (20%) by the aerated-pile method. The basic properties of soil and compost are presented in Table 1. Sewage sludge compost was added to soil at doses corresponding to 0 (control soil, T0), 30 (TI, 10 g/pot) and 120 Mg (TII, 40 g/pot) of dry matter per hectare. Samples of 1 kg dried soil were weighed in triplicate and were thoroughly mixed with mentioned above amounts of compost. Each mixture was wetted to 60% field capacity and placed in 1L volume plastic boxes with alkali traps containing NaOH to avoid CO2 loss or entry. During the incubation process the boxes were closed. All boxes were opened and aerated for approximately 3 min on each sampling day to maintain aerobic conditions and simultaneously the NaOH in each beaker was replaced. The samples were incubated at 25°C for 180 days. Moisture losses were controlled and corrected during incubation.
Table 1. Characteristic of soil and compost used at the experiment
Carbon mineralization was determined by the measurement of soil CO2 respiration. The evolved CO2 was trapped in 20 ml 0.5 mol L-1 NaOH and assessed with 1 mol L-1 HCl to a phenolphthalein endpoint. The titration measurements were recorded at 12 incubation dates corresponding to the following days from the beginning of the experiment: 1, 3, 7, 10, 14, 21, 35, 56, 84, 120, 150 and 180. After CO2 measurements individual replications of each experimental treatment were eliminated, dried and then subjected to analysis.
The following parameters of chemical soil properties were determined: contents of organic carbon (Corg), total nitrogen (Ntot), amounts of available phosphorous (P2O5) and mineral nitrogen (N-NH4 and N-NO3). The above properties were determined by methods commonly applied in soil science analyses . Thus, organic carbon was measured using wet digestion with sulphuric acid and an aqueous potassium dichromate mixture, with the digests being back-titrated for the residual potassium dichromate with ferrous sulphate. Total nitrogen was analysed by the Kjeldahl distillation method after wet digestion with sulphuric acid and selenium powder. Mineral N was extracted with 1 mol L-1 NaCl at a 1:10 dry soil: solution ratio with 1 h shaking. The extracted solutions were analysed by the distillation method. Available P was extracted with buffered calcium lactate. Phosphorous was analysed colorimetrically as described by Murphy and Riley .
The chemical analyses of compost were conducted on dried samples. Total organic carbon (TOC) and total nitrogen (Ntot) were determined using Vario Max CNS. The mineral nitrogen (N-NH4 and N-NO3) content was determined after extraction in 2 mol dm-3 KCl (2 h, 1:20, w/v). The available P content of compost was determined colorimertically using the molybdate-blue method  after extraction in 0.5 mol dm-3 NaHCO3 at pH 8.5 (1/2 h, 1:40, w/v) as described by Olsen and Dean .
Total C mineralization (TCM) and nitrification index (NI) were calculated using the following equations proposed by Hernandez-Apaolaza et al. :
An assessment of the data normality is necessary for many statistical tests, as the normal data is an underlying assumption in a parametric testing. We used two methods of assessing the normality. One of them relies on the statistical test and the second one on the visual inspection. We were working on the Shapiro-Wilk test and using a Q-Q (quantile-quantile) plots to determine whether the data sets for studied properties are normally distributed.
The design of the experiment was establish as factorial experiment containing two factors: the composition of the composts (with three levels) and terms (with twelve levels). In accordance to the nature of the experiment, we study each property separately. In order to provide a statistical test whether or not the contents of the appropriate nutrients in soil, treated with the compost at two doses, are equal, the analysis of variance (Anova) is proposed [19, 21]. In the case when analysis of variance indicates the significant differences between considered groups there the question appears, which of the compared groups are responsible for the rejection of null hypothesis. Several methods to assess which group influences on the rejections of null hypothesis in analysis of variance have been proposed in the literature [19, 21]. To pursue this goal, the post-hoc examination and the Tukey procedure are used. This strategy is concerned with determining pair-wise comparisons between groups, i.e. between composts as well as between the terms. Additionally, in order to set out the trends in changes, the correlation matrix for appropriate pairs of the analysed parameters was determined. The statistical calculations were performed with STATISTICA 12 software. In our research, we take the recommended significant level 0.05. Furthermore, the bag plots for visualising data of studied properties, which are complement to the calculations, are presented. The bag plot allows to visualise the location, spread, trends in changes of the data set. The graph displays the location of median and the inner part (called the bag) and contains at most 50% of the data points. The outside loop involves almost all the observations, except observation flagged as the outliers.
RESULTS AND DISCUSSION
The test of normality
In order to check whether the observations are normally distributed, we utilized the Shapiro-Wilk test. For each studied property, the p-value was greater than the chosen alpha level 0.05 and the null hypothesis that the data came from a normally distributed population cannot be rejected. The p-values are equal to 0.15807, 0.15859, 0.87510, 0.0847, 0.05432, 0.35768, 0.14532, for , Corg, TCM, Ntot, Nmin, NI and , respectively. Moreover, for an additional verification to the Shapiro-Wilk test, we performed Q-Q plots, which validated the hypothesis that all properties came from normally distributed population cannot be rejected.
The effect of compost on C mineralization
Modern farming practices, such as intensive cropping, tillage and removal of crop residues, as well as decreasing manure and slurry application resulting from decreasing populations of farm animals, all contribute to the depletion of soil organic matter reserves and low nutrient availability in arable land [14, 16]. To enhance productivity and restore degraded soils, fertilizers application is often necessary. Thus, the use of composted sewage sludge has become particularly important in the restoration of organic matter with significant amounts of C, N and P [17, 25]. Our results showed that incubation of sandy soil with two doses of compost increased the contents of organic carbon, total and mineral nitrogen and plant available phosphorous. The increase of nutrient contents was especially visible and statistically significant in the case of the soil fertilized with compost at the dose of 120 Mg∙ha-1 compared to control soil (Fig. 1, Tab. 2). The application of compost to the sandy soil at two doses also resulted in the increase of CO2 emission in comparison to unamended soil. Both 30 and 120 Mg∙ha-1 treatments presented similar mineralization pattern. The data presented in Figure 1 indicated that from the 21st day of incubation the rate of compost mineralization in the sandy soil increased, which was reflected in higher CO2 levels. Maximum rates of soil respiration were observed at the end of experiment, because the amounts of CO2 were 12 (TI) and 13 (TII) times higher in relation to the values obtained at the beginning of the experiment. Soil respiration measurements over 21 days show that amendments with stabilised organic matter, such as compost, resulted in an increase in CO2 emission of about 1.6 (TI) and 2.4 (TII) times in comparison to the control soil (Fig. 1). Besides, the statistical significant differences are recorded for soil fertilized with the highest dose as compared to the control soil (Tab. 2, 4). The values of CO2 evolved during the incubation process of control soil (T0) and soil from TI were comparable, which may be attributed to the influence of native organic matter. It may be partly explained by the negative correlation coefficient between evolved CO2 and organic C obtained for the control soil (Tab. 5).
Fig. 1. Bag plots for analysed parameters
Table 2. Analysis of variance
Table 3. p-values for Tukey test of multiple comparisons: terms
Table 4. p-values for Tukey test of multiple comparisons: compost
Table 5. Correlation matrices for soils with composts
During composting, organic matter is stabilized by aerobic decomposition based on the microbiological activity and the main products of their transformation are fully mineralized compounds such as CO2, NH4, H2O and stabilised organic matter, resulting in a depletion of the more labile organic pools. However, Bustamante et al.  reported that stable compost may nonetheless contain a significant portion of readily available organic carbon. Therefore, we should expect an increasing trend of C mineralization in incubated soil. The obtained data presented such a change of C content in soil immediately after amendments (after 14–21 days). A possible explanation could be that the increase in soil respiration after compost amendment is due to a preferential degradation of the more labile fraction of the dissolved organic fraction. The almost unchanged contents of organic carbon in soils within this experiment confirm that statement (Fig. 1, Tab. 2). During 180 days of incubation Corg did not change significantly and its level in the beginning and at the end was comparable for soil from each experimental treatment. Statistical values given in Table 3 show that organic matter introduced in the form of compost first of all was very stable and hardly subjected to mineralization process. The differences between the amounts of evolved CO2 for particular experiment treatments in all terms beginning the 56th day of the experiment were not statistically significant (Tab. 3). The data presented in Tables 2 and 4 indicated that the duration of the experiment had no effect on Corg contents in each experimental treatments, however, its level was different for soils of particular treatments and the highest amounts were recorded for soil fertilized with compost at a dose of 120 Mg∙ha-1.
Organic matter transformation can be shown by some index values such as the total C mineralization coefficient (TCM) . Figure 1 shows that TCM gradually, day by day during the incubation process increased markedly in soil amended with compost. In relation to values obtained at the beginning of experiment, the final results over 180 days were 12-fold higher for soils from TI and TII, and 9.0 times for the control soil. However, as is shown at Table 2 and 4, the observed differences were only statistically significant for soil fertilized with compost at dose equivalent to 120 Mg∙ha-1 in comparison with the control soil. Irrespective of that, it should be stressed that final TCM values were lower for soils TI and TII in comparison with data obtained from the control soil (Fig. 1). The incubation process continued over day 84 (date 9) in a statistical significant manner did not affect the TCM values found for soil treatments (Tab. 3). The results illustrate and testify that the labile pool of the organic C fraction was small in composted sewage sludge and the composting process reduced the proportion of labile C by stabilizing organic compounds. The study of Sevilla-Perea et al.  also reported such a possibility. Values of TCM were positively correlated with the amounts of evolved CO2 in each soil from the experimental treatments (Tab. 5). This may be attributed to the above-mentioned possibility of mineralization of native soil organic matter.
Nitrogen and phosphorous changes
Nitrogen and phosphorous are biogenic compounds and their cycles in the environment are strongly dependent on organic matter transformations. Mineralization of organic matter provides large amounts of the nutrients transformed into plant available forms, but simultaneously they may also become immobilized . Unfortunately, effective sewage sludge treatment by composting processes produces a biosolids which is a strongly stabilized source of low to very low N contents and availability . Moreover, the degree of compost stability also plays an important role in the balance of N mineralization-immobilization processes in amended soil. These transformations of nitrogen were observed in our experiment and were strongly manifested in the case of mineral nitrogen (Fig. 1). Overall, total N concentration significantly increased from day 1 to 180 in all treatments with the greatest increase in the control soil by 54%. Total N concentration in the control soil and amended with a compost dose of 30 Mg∙ha-1 at the end of the experiment (date 12) was higher by 50% in relation to amounts assessed at the beginning of incubation (Fig. 1). A similar pattern of changes was observed in the case of mineral N (Fig. 1). Application of compost at two doses as well as a lack of such treatment over 180 days of soil incubation caused an increase of mineral N contents by 75% (T0), 80% (TI) and 70% (TII), with the differences being statistically significant (Tab. 4). The soil incubated with a compost dose of 120 Mg∙ ha-1 showed the maximum content of mineral N at day 7 (date 3) and then it dropped sharply until day 84 (date 9). From the 84th day mineral N concentration slowly increased, reaching at the end 41.45 mg∙kg-1 (Fig. 1). The level of mineral N in soil TI was higher about 28% in comparison to values obtained for the control soil, but these differences were not confirmed statistically (Tab. 4). Regardless of the above, Figure 1 illustrates a similar trend for changes in mineral N levels in soils of both treatments. After an initial increase of Nmin amounts in soil (until day 10) it subsequent declined with time (until day 84). Following by the increase in nutrient levels was noticed (Fig. 1). It is proved on the basis of statistical values presented in Table 3.
Other researchers [9, 22, 24] also found high mineralization rates, expressed by realising N mineral, in the early weeks of incubation, which later decreased with time. This phenomenon is related to nitrogen immobilization, often associated with inputs of organic matter with high C:N ratios. Once again the importance of the composting process in stabilizing organic compounds and reducing the proportion of soluble C, N and P forms should be stressed. The importance of susceptibility of organic matter to mineralization was confirmed by correlation coefficients (Tab. 5). Significant positive correlations between total nitrogen and values of TCM or evolved CO2 were found for the control soil (T0) and soil amended with compost at 120 Mg ha-1 (TII). A lack of such a relationship for mineral N may indicate both very low concentrations of labile N and a slow rate of compost decomposition, which was confirmed by correlation matrices given in Table 5. In addition, the nitrification process should also be taken under consideration. Nitrification is a critical process of the nitrogen cycle and it contributes to the availability of soil N to plants and soil microorganisms . Among other things, soil nitrification is regulated by CO2, organic C availability and soil texture. In our experiment the nitrification index was assessed for experimental treatments (Fig. 1). Unfortunately, the values of NI did not significantly correlate with other analysed parameters (Tab. 5). Moreover, throughout the 180-day incubation period NI showed low sensitivity to experimental factors, because the values were comparable for each treatment from day 1 to 120 and ranged from 35.8 to 59.1% (T0), from 42.6 to 64.2% (TI) and from 42.9 to 97.1% (TII). Over 120 days of the incubation experiment NI values decreased and were comparable for these soils. These values ranged from 35.6 to 39.5% and significantly differed from the data calculated for soils examined at the beginning of the experiment (Fig. 1). Nevertheless, N nitrification was considerably enhanced by higher dose of compost (Tab. 4). Incorporation of higher dose of compost into the soil caused statistically significant differences between values of NI (Tab. 4). In turn, the duration of the experiment had no marked effect on that parameter. A similar effect in soil incubated with composted sewage sludge is reported by Hernandez-Apaolaza et al. .
Both sewage sludge and compost prepared on the basis of this waste are well-known sources of P. However, compost contains lower levels of the available P fraction as a consequence of the composting process and thus it releases lesser amounts of this nutrient. A considerable body of literature [7, 8, 13] presents that organic matter as compost or biowastes is a very important and valuable source of P. Application of such organic substances may increase P solubility and decrease its precipitation in soil. Duong et al.  stated that P availability strongly depends on the chemical composition of composts and their texture, with fine-textured composts being preferred due to their greater effect on available P. Besides Jakubus  proved that the release rate of P from composts strongly depends on the share of sewage sludge in composting mixture. Higher bioavailable amounts of phosphorus were observed particularly in composts with small shares of sewage sludge, characterized by rapid organic matter decomposition. Some of the obtained results indicated such a possibility. An applied compost was fine-textured, contained 50% of sewage sludge with high amounts of available P (Tab. 1), thus when supplied to the soil at higher dose, it caused a considerable increase in the amounts of available P (Fig. 1, Tab. 2).
As a consequence, only in soils TI and TII the positive correlation coefficients between P content and evolved CO2 or P content and values of TCM were recorded (Tab. 5). This may be interpreted as a potentially considerable pool of labile P in compost, which directly affects available P during incubation of soil fertilized with compost. In comparison to the contents recorded in soil at day 1, soil samples from TII representing the last day of the experiment contained 2.2-fold higher amounts of P (Fig. 1). Soil incubated with the lower dose of compost (TI) and the control soil (T0) also showed increased nutrient contents, which in soil samples on the last day of the experiment the amount of available P increased approximately 80 and 50%, respectively.
The common characteristic of organic matter transformation in soil was connected with a similar trend of quantitative changes in P levels, which proceed in the same manner independently of the experimental treatment. As shows by data presented in Figure 1, from day 84 a considerable increase in available P levels was observed in soil representing all the treatments, but it was particularly significant in the case of TII. The importance of higher dose of compost in a remarkable increase of the P pool in the soil was shown by statistical results presented in Table 4. The observed increase in available P contents in soil treatments was found for day 84 of incubation, while comparable and stabile amounts of nutrients found after day 84 should be attributed both to the essential role of native organic matter and a very big input of applied organic substances introduced to soil in the form of compost. A possible explanation of the observed phenomenon is related to the contents of P assessed for particular soil treatments at the last day of incubation (date 12) differed significantly in comparison to the amounts determined for soils collected before the 84th day of the incubation experiment (Tab. 3).
The compost prepared on the basis of sewage sludge, applied into the sandy soil at two doses should be evaluated as a valuable source of carbon, nitrogen and phosphorous. Particularly, the compost applied at higher dose of 120 Mg∙ha-1, needs to be considered as an interesting source of mineral nitrogen and available phosphorous as an alternative to mineral fertilization. Nevertheless, the study confirms that compost may act as a slow release fertilizer and a native soil organic matter plays an important function in transformations of nutrients. From the point of view of cultivation technology, we need to consider the fact that mineralization of C, N and P in soil amended with compost prepared with sewage sludge proceeds with low rate and release rate of mineral forms of N and P will be also slow. The proposed and utilized statistical method Anova is a proper instrument to indicate if there are the differences in the dynamic of organic carbon mineralization and the rate of release of available nitrogen and phosphorus forms. Moreover, a presented post hock analysis is a sufficient tool to indicate of which of the considered differences we should focus on.
- Bai J., Gao H., Deng W., Yang Z., Ciu B., Xiao R., 2010. Nitrification potential of marsh soils from two natural saline-alkaline wetlands. Biol. Fertil. Soils, 46, 525–529.
- Bustamante M.A., Said-Pullicino D., Paredes C., Cecilia J.A., Moral R., 2010. Influences of winery-distillery waste compost stability and soil type on soil carbon dynamic in amended soils. Waste Manage, 30, 1966–1975.
- Central Statistical Office 2015. Warszawa.
- Council Directive 1999/31/EC of 26 April 1999 on the landfill waste disposal. OJ L, 182, 16.7. p. 1.
- Duong T.T.T., Penfold C., Marschner P., 2012. Amending soils of different texture with six compost types: impact on soil nutrient availability, plant growth and nutrient uptake. Plant Soil, 354, 197–209.
- Duong T.T.T., Verma S.L., Penfold C., Marschner P., 2013. Nutrient release from compost into surrounding soil. Geoderma, 42–47, 195–196.
- Galvez-Sola L., Morales J., Mayoral A.M., Marhuenda-Egea F.C., Martinez-Sabater E., Perez-Murcia M.D., Bustamante M.A., Paredes C., Moral R., 2010. Estimation of phosphorus content and dynamics during composting: Use of near infrared spectroscopy. Chemosphere, 78, 13–21.
- Garcia-Albacete M., Martin A., Cartagena M.C., 2012. Fractionation of phosphorus biowastes: Characterisation and environmental risk. Waste Manage, 32, 1061–1068.
- Giannakis G.V., Kourgialas N.N., Paranychianakis N.V., Nikolaidis N.P., Kalogerakis N., 2014. Effects of municipal solid waste compost on soil properties and vegetables growth. Compost Scie. Util., 22, 116–131.
- Hernandez-Apaolaza L., Gasc J.M., Guerrero F., 2000. Initial organic matter transformation of soil amended with composted sewage sludge. Biol. Fertil. Soils., 32, 421–426.
- Jakubus M., 2013a. Evaluation of maturity and stability parameters of composts prepared with sewage sludge. Fresen. Environ. Bull., 22, 11a, 3398–3414.
- Jakubus M., 2013b. Wybrane zagadnienia z gleboznawstwa i chemii rolnej. Wydanie II rozszerzone i uaktualnione, Poznań. Uniwersytet Przyrodniczy w Poznaniu [In Polish].
- Jakubus M., 2016. Estimation of phosphorus bioavailability from composted organic wastes. Chem. Spec. Bioavailab. 28, 1–4, 189–198. DOI: 10.1080/09542299.2016.1227687
- Jaskulski D., Kotwica K., Jaskulska I., Piekarczyk M., Osiński G., Pochylski B., 2012. Elementy współczesnych systemów uprawy roli i roślin-skutki produkcyjne oraz środowiskowe. Fragm. Agron., 29 (3), 61–70.
- Journal of Law. Ordinance of the Economy Minister. Warszawa. 8 January 2013.
- Kopiński J., Kuś J., 2011. Wpływ zmian organizacyjnych w rolnictwie na gospodarkę glebową materią organiczną, Probl. Inż. Roln., 2, 47–53.
- Mugnai S., Masi E., Azzarello E., Mancuso S., 2012. Influence of long-term application of green waste compost on soil characteristics growth, yield and quality of grape (Vitis vinifera L.). Compost Sci. Util., 20, 1, 29–33.
- Murphy J. Riley J.P., 1962. A modified single solution method for determination of phosphate in natural water. Anal. Chim. Acta, 27, 31.
- Oktaba W., 1967. Metody statystyki matematycznej w doświadczalnictwie. PWN, Warszawa.
- Olsen S.R., Dean L.A., 1965. Methods of soil analysis. Part 2. Black C.A. (Ed.) in Chief. Madison, Wisconsin USA, 1035–1049.
- Platt Cz., 1978. Problemy rachunku prawdopodobieństwa i statystyki matematycznej. PWN, Warszawa.
- Rigby H., Clarke B.O., Pritchard D.L., Meehan B., Beshah F., Smith S.R., Porter N.A., 2016. A critical review of nitrogen mineralization in biosolid-amended soil, the associated fertilizer value for crop production and potential for emissions to the environment. Sci. Total Environ., 541, 1310–1338.
- Saveyn H., Eder P., 2014. End-of-waste criteria for biodegradable waste subjected to biological treatment (compost and digestate): Technical proposal. JRC. Report EUR 26425 EN.
- Sevilla-Perea A., Almendos G., Mingorance M.D., 2014. Quadratic response models for N and P mineralization in domestic sewage sludge for mining dump reclamation. Appl. Soil Ecol., 75, 106–115.
- Sciubba L., Cavani L. Negroni A., Zanaroli G., Fava F., Ciavatta C., Marzadori C., 2014. Changes in the functional properties of a sandy loam soil amended with biosolids at different application rates. Geoderma, 221–222, 40–49.
- Thematic strategy for soil protection. Commission staff working document. Communication from the commission to the council, the European parliament, the European economic and social committee and the committee of the regions. COM(2006) 231.
- Weber J., Kocowicz A., Bekier J., Jamroz E., Tyszka R., Debicka M., Parylak D., Kordas L., 2014. The effect of a sandy soil amendment with municipal solid waste (MSW0 compost on nitro gen uptake efficiency by plants. European J. Agronomy, 54, 54–60.
- WRB. World Reference Base for Soil Resources. 2003. Polish Soil Science Society. Toruń, 106.
Accepted for print: 22.12.2016
Department of Soil Science and Land Protection, Poznań University of Life Sciences, Poland
Department of Mathematical and Statistical Methods, Poznań University of Life Sciences, Poland
Wojska Polskiego 28
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