Effect of organic materials on the chemical properties of saline soil in the Yellow River Delta of China

Abstract

A 180-day incubation experiment was conducted to investigate the effect of different organic materials on the chemical properties of coastal soil with high salinity and relatively low pH. Four organic materials (three kinds of plant residues: straw, composted straw, and fresh reed; and one kind of poultry manure: chicken manure) were applied at a ratio of 15 g·kg^‒1 to samples of costal saline soil from the Yellow River Delta of China. The results showed that the soil pH and exchangeable sodium percentage (ESP) decreased, whereas soil cation exchangeable capacity (CEC) and macronutrient concentrations increased, regardless of the type of organic material used. All treatments showed a remarkable increase in soil soluble organic carbon (SOC) during the 180-day incubation. The peak values of SOC in descending order were chicken manure, reed, composted straw, straw, and control soil. At the end of incubation, the highest level of SOC occurred in the straw-amended soil, followed by composted straw, reed, and chicken manure-amended soils. Soil respiration rate and available nitrogen were significantly influenced by the type of material used. Although reed-amended soil had a relatively high SOC and respiration rate, the ESP was reduced the least. Considering the possible risk of heavy metals caused by chicken manure, it is proposed that straw and composted straw are the more efficient materials to use for reclaiming costal saline soil and improving the availability of macronutrients.

Keywords

organic material / soil organic carbon / salt-affected soil / ESP / respiration rate

Introduction

Saline soil is distributed in more than 100 countries with a variety of properties ( Rengasamy, 2006). Excessive amounts of salt have adverse effects on the physical and chemical properties of soil, as well as, on microbiological processes and plant growth. Organic materials such as mulch manures, plant residues, municipal solid wastes, and agricultural manures are currently used to ameliorate saline soil ( Nardi et al., 2004; López-Piñeiro et al., 2007; Zanuzzi et al., 2009; Jones et al., 2012). The application of organic materials to saline soils can improve surface soil fertility, soil structure, and permeability, thus, enhancing salt leaching, reducing surface evaporation, inhibiting salt accumulation in surface soils, and releasing carbon dioxide during respiration and decomposition ( Raychev et al., 2001). Furthermore, the application of organic matter increases the quantity and quality of total organic carbon, nitrogen, phosphorus, and other nutrients. Such fertilization also facilitates microbial biomass and some soil enzymatic activities such as urease, alkaline phosphatase, β-glucosidase, and dehydrogenase ( Tejada and Genzalez, 2006; Zanuzzi et al., 2009).

Plant residues are one of the most widely used organic materials. The chemical composition of a given plant residue plays an important role in the initial stages of residue decomposition, which is a complex process affected by the chemical and physical properties of both residues and soils ( Xu et al., 2006). The chemical composition of plant residues can differ considerably, depending on the plant species, sources of nitrogen, stage of plant growth, and edaphic and climatic conditions ( Yan and Schubert, 2000).

Sodic soils, especially saline sodic soils, distribute widely and occur within at least 75 countries ( Qadir et al., 2007). Saline sodic soils containing CaCO₃ are common in arid and semiarid regions of the world ( Qadir et al., 2005; Mahmoodabadia et al., 2013). In the present study, the organic materials were chosen based on their availability near the experiment site. The objective of this study was to evaluate the efficacy of different types of organic materials. A number of chemical, biological, and physical properties were measured to examine the processes that occurred in salt-affected soils of coastal zones treated with organic materials. It was hypothesized that any improvement in soil nutrient content or secondary reaction resulting from the microbial decomposition of the material were attributed to the chemical composition of the material.

Materials and methods

Study area

The Yellow River Delta wetlands (37°35′N to 38°12′N and 118°33′E to 119°20′E) are located at the mouth of the Yellow River, flowing to the sea on the north border of Shandong Province, China. With the rapid development of modern industries and agricultural processes, the Yellow River Delta wetlands have degraded because of fresh water shortage. In addition, high evaporation and tidal intrusion have resulted in the accumulation of salts (mainly Na⁺ and Cl^‒) in the surface soil layers ( Wang et al., 2011). There are currently 442.9×10³ hectares of land experiencing salinization. This accounts for half of the total area of the Yellow River Delta, in which severely and slightly salt-affected lands compose 28.4% of the area ( Li, 2008). The study area was located in the degraded wetlands with high salinity and low biodiversity of plant communities.

Soils

Soil samples were taken from the top and subsoil layers (0–20 cm) of the reference sites, and were air-dried, crushed, sieved through a 2 mm sieve, and then mixed thoroughly prior to analysis and fertilization experiments. The soil contained 66.31% clay, 8.45% silt, and 25.24% sand. The pH was 7.82; electrical conductivity (EC), 6.95 mS·cm^‒1; total nitrogen content, 0.68€g·kg^‒1; total carbon 5.27€g·kg^‒1; exchangeable sodium content, 18.94 cmol·kg^‒1, and calcium and sodium contents 6.93 and 17.95 g·kg^‒1, respectively. The cation exchangeable capacity (CEC) was 52.35 cmol·kg^‒1; and the exchangeable sodium percentage (ESP) was 36.17%.

Organic materials

The organic materials used in the experiment included three types of plant materials: reeds, straw, and composted straw (Table 1). They were chosen to represent a wide range of organic materials that were available either as by-products from nearby industries or as crop materials that grow in situ as a green manure. In this study, chicken manure was included for comparison because it was commonly used to fertilize salt-affected soil. All materials were ground and passed through a 0.5 mm sieve before application.

Incubation study design

Each type of material was added to air-dried soil at a ratio of 15 g·kg^‒1 soil and then mixed thoroughly before incubation. Each treatment was repeated 3 times. Oven-dried amended soil (150 g) was added to 150 mL glass vials, and mixed with 50 g of deionized water to achieve a gravimetric water content of 25% (70% field capacity). The samples were then incubated at 25°C in covered plastic containers with approximately 10 mm of water in the base to minimize water loss from the soil surface. Each vial was weighed weekly, and water was added to maintain 30% gravimetric water content. The soil was sampled on day 0, 1, 3, 7, 14, 28, 42, 56, 70, 90, 120, and 180 of the incubation for chemical analysis. The cation exchangeable capacity (CEC) and exchangeable cations were only tested on day 14. Three replicates of each treatment were sampled. The soils were transferred into a plastic bag and mixed by gently shaking before sub-sampling for chemical analyses.

Chemical and physical analyses

Electrical conductivity and pH were measured in a 1/5 (w/v soil/solution ratio) aqueous solution with a conductivity meter (DDS-11A) and pH meter (FE20K) after shaking for 1 h in an end-over-end shaker. Texture analysis was performed by sieve-pipette method (Lu, 2000). Soluble cations and soluble organic carbon (SOC) were extracted in deionized water at a soil and water ratio of 1:10 respectively, by shaking for 2 hrs, centrifuging, and filtering. The extracts were frozen until ready for analysis. Soil organic carbon was determined by oxidizing organic matter in soil samples with K₂Cr₂O₇ in concentrated sulphuric acid for 30 min followed by titration of the excess K₂Cr₂O₇ with ferrous ammonium sulphate ( Lu, 2000). Exchangeable cations were extracted with 1 mol·L^‒1 CH₃COONH₄ according to Zhou ( Zhou et al., 2007). Inductively coupled plasma-optical emission spectroscopy was used to measure the K, Na, Ca, and Mg concentrations (iCAP 6300, Thermo Fisher Scientific, USA). In order to determine the available nitrogen content, soil was extracted with 1 mol·L^-1 KCl (1:10 w/v soil:solution ratio) by shaking for 1 h in an end-over-end shaker. The suspensions were centrifuged for 15 min at 3500 r·min^-1, and the supernatant was recovered and frozen until analysis. Soil respiration was determined by the titration method of HCl absorption by NaOH ( Lu, 2000). The CEC values were determined by the ammonium acetate buffer exchange method according toLu ( Lu, 2000). The ESP was also calculated by the following formula:

\mathrm{ESP}={\displaystyle \frac{N{a}_x}{CEC}},

in which Na_x was exchangeable sodium.

The C loss in the first several days (day 7 (chicken manure), 14 (composted straw and reed), and 42 (straw)) were estimated using the following equation ( Clark et al., 2007):

\mathrm{\%}\mathrm{F}\mathrm{e}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{C}\mathrm{l}\mathrm{o}\mathrm{s}\mathrm{s}={\displaystyle \frac{\mathrm{Re}\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{d}\mathrm{C}-\mathrm{Re}\mathrm{s}\mathrm{p}\mathrm{i}\mathrm{r}\mathrm{e}\mathrm{d}\mathrm{C}\mathrm{o}\mathrm{f}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{t}\mathrm{r}\mathrm{o}\mathrm{l}\mathrm{C}}{\mathrm{A}\mathrm{d}\mathrm{d}\mathrm{e}\mathrm{d}\mathrm{C}}}\times \mathrm{100},

and then using measurements of soil total C:

\mathrm{\%}\mathrm{F}\mathrm{e}\mathrm{r}\mathrm{t}\mathrm{i}\mathrm{l}\mathrm{i}\mathrm{z}\mathrm{e}\mathrm{r}\mathrm{C}\mathrm{l}\mathrm{o}\mathrm{s}\mathrm{s}={\displaystyle \frac{\mathrm{L}\mathrm{o}\mathrm{s}\mathrm{s}\mathrm{of}\mathrm{a}\mathrm{m}\mathrm{e}\mathrm{n}\mathrm{d}\mathrm{e}\mathrm{d}\mathrm{s}\mathrm{o}\mathrm{i}\mathrm{l}\mathrm{C}-\mathrm{L}\mathrm{o}\mathrm{s}\mathrm{s}\mathrm{o}\mathrm{f}\mathrm{c}\mathrm{o}\mathrm{n}\mathrm{t}\mathrm{r}\mathrm{o}\mathrm{l}\mathrm{s}\mathrm{o}\mathrm{i}\mathrm{l}}{\mathrm{A}\mathrm{d}\mathrm{d}\mathrm{e}\mathrm{d}\mathrm{C}}}\times \mathrm{100.}

.

Statistics

The statistical data was presented in the form of mean±standard deviation and analyzed statistically by the least significant difference (LSD) test calculated at p<0.05. Correlations of organic materials with soil chemical properties were determined on the basis of the Pearson product-moment correlation coefficient with the help of Microsoft Excel.

Results

pH

The pH of the treated soils increased in the beginning of the incubation study (from day 1 to day 4), and then decreased after day 4 except for the reed treated soil (Fig. 1(a)). The addition of fresh reed residue rapidly decreased the soil pH to 7.3 on day 14, whereas the corresponding pH of the control soil was 7.8. The soil pH increased gradually after day 14 and maintained around 7.5. However, for the chicken manure amended soil, the soil pH increased to 8.1 on day 3 and remained at 7.78. The pH of the straw and composted straw-modified soils was similar to that of the control soil until day 56, after which it decreased.

Electronic conductivity

The chicken manure, reed, and composted straw soils showed a smaller increase in EC, as compared to the control soil (Fig.1(b)). All of the treated soils showed a slow increase in EC with incubation time. The EC of the treated soils decreased in the order of chicken manure (highest reduction), composted straw, reed, straw, and control soil (least reduction) on day 56.

Exchangeable cations on day 14

The effect of material on the concentration of exchangeable cations was notable from day 0. There was little change in exchangeable cations and the CEC (Table 2) during incubation. Therefore, the result determined on day 14 can represent substantially the situations of the whole incubation course. The CEC increased slightly in all of the treated soils due to increases in the Ca²⁺, Mg²⁺, and K⁺ concentrations. This, along with decreased exchangeable Na in the treated soils, resulted in significantly reduced ESP compared to the control soil. The Chicken manure amended soil showed the greatest reduction of ESP, due to a high content of Ca²⁺, whereas reed amended soil showed a slightest reduction of ESP, due to the low content of Ca²⁺.The ESP values of the straw and the composted straw-amended soils were significantly lower than those of the reed-amended soil. The sequence of reduction of ESP from the highest to the lowest was chicken manure, composted straw, straw, and reed, respectively.

Soluble organic carbon

All of the treatments showed a remarkable increase initially and then decrease in the content of SOC during incubation, but remained higher than the control (Fig. 2(a)). The chicken manure amended soil showed the highest SOC concentration among all of the treatments, with a peak value of 673.9 mg C·kg^‒1 soil on day 7. The reed and composted straw samples had the second and third highest concentrations of soil SOC on day 14, respectively. The straw sample showed minimal rises in SOC concentration on day 28. The descending order of SOC concentration on day 180 was straw, composted straw, reed, chicken manure, and control soil, respectively.

The chicken manure showed the fastest decomposition rate for the initial 7 days (almost 40%), followed by the reed sample (19%; Fig. 2(b)). On day 180, the loss of C in the samples was 77%, 63%, 62%, and 41%, respectively.

Respiration rate

All treated soils showed a rapid increase in respiration rate and then decreased slowly. The peak values were significantly influenced by the type of material applied (Fig. 2(c)). Chicken manure-amended soil had the greatest value, with peak respiration rate on day 7. The reed, composted straw, and straw-treated soils showed similar soil respiration rates with maximum rates occurring on day 14, 14, and 28, respectively. Cumulative respiration was found to be the highest in the chicken manure soil (Fig. 2(d)). The reed, composted straw, and straw-amended soils had similar cumulative respiration, although the straw soil had the lowest increase in cumulative respiration initially.

Available nitrogen and available phosphorus

All treated soils showed a brief increase in available nitrogen first followed by a decline and then a slow increase again. The extent of change and duration of soil available nitrogen were markedly influenced by the type of material used (Fig. 3(a)), and all of the treated soils had content of nitrogen higher than control at the end of incubation.

All of the organic materials inputs showed an increase in available phosphorus concentration up to day 14, followed by a slow decrease compared with the control. Chicken manure-treated soil had high available phosphorus concentration compared with the other organic materials and the control (Fig. 3(b)). After day 42, the available phosphorus concentration in the chicken manure sample decreased to 550 mg·kg^‒1, while available phosphorus concentrations of the other treatments and the control were similar.

Correlations

The correlations between organic material properties and soil chemical properties were calculated (Table 3). The soil pH correlated significantly with the SOC/TN ratio of organic materials added. The exchangeable Ca²⁺ was highly correlated with the Ca²⁺ content of the materials. The soil SOC was affected by the SOC and total nitrogen (TN) of the materials. The soil CEC correlated with Ca²⁺ content. In addition, the ESP highly correlated with the Na⁺ content and negatively correlated with the Ca²⁺ content of the materials. The pH value and Ca²⁺ content of the materials significantly influenced the soil pH. The soil available nitrogen was the most influenced by pH, SOC, and total phosphorus (TP).

Discussion

Changes in soil pH and EC

This study showed that soil pH correlated most significantly with the SOC/TN ratio of plant residues added (Table 3). Straw samples had a high SOC/TN ratio (5.03) that caused a slight increase of pH at the beginning of the incubation and a decrease thereafter. The increase in pH resulted from the release of an alkaline component that is derived from organic N ammonification, while nitrification of mineralized residue causes the decrease in soil pH. The composted straw and reed had relatively lower SOC/TN ratios resulting from moderately soluble carbon and relatively high total nitrogen that contributed to nitrification.

Despite having the lowest SOC/TN ratio, chicken manure resulted in a marked increase in soil pH on the first day of the incubation. This was attributed to both the release of alkali matter resulting from organic N ammonification of the chicken manure and its direct effects on soil. In previous studies, the application of chicken manure reduced pH values of alkaline soil ( Pathak and Rao, 1998; Yao et al., 2007) and increased pH values of acid soil ( Khalil et al., 2005). However, the chicken manure used in this study had a higher pH value, and thus the pH increase may result from the direct contribution of organic compounds in the chicken manure to the soil pH, which is supported by the significant correlation between the pH of the soil and the pH of the materials (Table 3).

Soil EC was significantly influenced by the type of material used. The addition of organic materials increased soil EC (Fig.1(b)), which is supported by the results of Clark et al. ( 2007) and Lee ( 2010). Such changes in EC may be explained by the mineralization of the organic materials.

Changes in soil ESP

The ability of organic materials to make a favorable impact on soil ESP depended on the content of exchangeable cation, especially Ca²⁺ in the organic materials ( Walker and Bernal, 2008).

Composting treatments of straw favored the release of cations. The amount of exchangeable Ca²⁺, Mg²⁺, and K⁺ in the composted straw samples was slightly higher than those in the straw soil samples, and as a result, the ESP in the composted straw sample decreased more. It is well known that fresh residues have more available cations and nutrients. A previous incubation study showed that adding green residues might reduce the ESP of alkaline subsoil ( Harris and Rengasamy, 2004).

This study showed that ESP significantly correlated with the number of favorable cations contained in organic materials (Table 3), rather than with the pH of the organic materials, which is in accordance with the conclusion of Abd Elrahman (2012). Abd Elrahman et al. found that the effect was better using gypsum than using 50% gypsum and 50% citric acid on salt-affected soil with a pH of 7.2. For calcareous sodic soils, sulfuric acid, as an effective amendment, has been used in amelioration. Some studies were performed to investigate the efficiency of sulfuric acid in soil crusting prevention ( Amezketa et al., 2005) and its application in saline-sodic soil reclamation ( Sadiq et al., 2003). Additionally, Yazdanpanah et al. ( 2013) reported that the relative efficiency of organic amendments in depleting sodium from soil column depends on the application of sulfuric acid associated with irrigation water in calcareous saline-sodic soils.

Changes in soil carbon

The maximum SOC in treated soils correlated with that of the materials (Table 3). Compost or fresh materials largely consisted of highly bio-available low molecular weight compounds that strongly influence the initial stages of material decomposition. Therefore, soils amended with chicken manure, reed, and composted straw showed higher SOC. Organic materials increased microbial activity, resulting in consumption of soluble matter and in turn reduced the SOC. This study showed that the incorporation of organic materials in costal saline soil resulted in a loss of C ranging from 41% to 68% (Fig. 2(b)). Other incubation studies also showed a wide range of mineralization rates varying from 6% to 64% measured over periods of 25–174 days. The organic materials differ in C/N ratios, and soil texture ranges from sands to clays. Soil types include non-saline, alkali soil, saline soil, acid soils, calcareous sodic soils, and soils with pH values varying from 4.2 to 10.0 ( Khalil et al., 2005; Bertrand et al., 2006; Xu et al., 2006; Clark et al., 2007).

The decomposition rate of plant residues is influenced by their source and chemical properties. Composted plant residue has a rapid decomposition rate and high soluble carbon content in the initial stages of incubation. No obvious differences were found in the amounts of soluble carbon between compost and straw samples. On the other hand, previous studies showed that green residues also had growth materials, which could be decomposed and utilized ( Woods and Raison, 1983; Clark et al., 2007). In this study, the plant residues from mature crops such as straw and composted straw had lower concentrations of readily degradable organic material and a slow C loss rate. This was evidenced by the lower initial rates of soil respiration and the higher remaining C content when they were incorporated into this clay soil (Fig. 2(b)). Chicken manures showed a higher mineralization rate than plant residues. A similar result was also observed by Khalil et al. ( 2005). On the other hand, some studies showed plant residues decomposed faster than farmyard manures derived from different sources and disposal methods ( Zhou et al., 2008).

Chicken manure is traditionally regarded as an excellent organic material for soils. In spite of this, chicken manure has its disadvantages. Omeira et al. ( 2006) compared pH and EC from different chicken types and production systems, and the results suggested possible salinization caused by the application of litter with high EC values. Yao et al. ( 2007) further suggested that even in a region with abundant rainfall like Guangzhou (China), there is still potential risk for secondary soil salinization when high rates of chicken manure are applied. Additionally, although chicken manure undergoes a rapid decomposition of C, it is regarded as a major source of heavy metals in the human food chain mainly through plant uptake and animal transfer ( Rogival et al. 2007; Zhuang et al. 2009 ). Therefore, some caution does need to be taken when chicken manure was used because of the possible risk of heavy metal and possible secondary soil salinization. While straw and composted straw decomposed slowly during the 180-day incubation, they demonstrated long-term effectiveness and improved the degraded soil.

Changes in soil nitrogen and phosphorus

The chicken manure-added soil had more available nitrogen than the control due to its higher TN and lower C/N ratio. The available nitrogen in the plant residue-treated soil decreased at the beginning and then rose slowly resulting from its high C/N ratio in the residues. A similar result was found by Khair et al. ( 2014). In general, soil nitrogen immobilization or mineralization depends on the organic nitrogen content, C/N ratio, and availability of C in the materials. Nitrogen immobilization was expected in the soil as the C/N ratio exceeds 25 (some studies propose 30), which is the threshold for mineralization of organic nitrogen ( Powlson et al., 2001; Khan et al., 2008; Lakhdar et al., 2009). Organic materials offer abundant decomposable energy sources (mainly carbon) and nitrogen source to microbes. As consumption of organic matter proceeded, the amount of organic matter decreased, and microbial activities slowed down. This resulted in net nitrogen mineralization, and thus, increased the available nitrogen. It is concluded that the plant residues decomposed in soils and caused nitrification or immobilization as a function of their C/N ratio and time when the material was added.

The optimum pH range of ammonification is 6.5–7.5. Nitrogen mineralization was more sensitive to salinity and pH than C mineralization ( Pathak and Rao, 1998; Khalil et al., 2005). In this study, the result showed that the pH of the organic materials did not have a disadvantageous influence on nitrogen mineralization. Furthermore, nitrogen mineralization significantly correlated with the composition of the organic materials (C/N). However, Walpola and Arunakumara (2011) reported, on the contrary, that nitrogen mineralization was restrained by the high pH of calcareous saline soil, and had nothing to do with the composition of organic materials.

The application of organic materials could promote transformation between different forms of phosphorus. This could improve phosphorus availability in soils ( Zhao et al., 2006). The present study suggests that the available phosphorus in soil was related to the C/P ratio of the organic materials added. Low C/P ratios presented dominant mineralization over immobilization as reported by Zhao et al. ( 2006). Chicken manure with a low C/P ratio could remarkably increase available phosphorus in soil. Plant residues with a high C/P ratio present dominant immobilization over mineralization. These results are consistent with the findings of other studies using various types of materials. For example, Madejón et al. ( 2003) reported that phosphorus added to the soil through organic materials could be immobilized by the humic fraction and absorbed by the soil, thus reducing phosphorus availability.

Conclusions

The application of chicken manure and plant residues at a ratio of 1.5% under incubation could reduce the pH and ESP, and improve the SOC, available nitrogen, available phosphorus, and the respiration rate of treated soils. These organic materials have different time course effects on soil properties. The chicken manure-amended soil had high SOC content, available nitrogen content, available phosphorus content, respiration rate, and low ESP due to the high soluble organic matter content, high Ca²⁺ content, and lower C/N ratio in the chicken manure. The fresh matter reed had available nutrients that increased the soil respiration rate and organic carbon, but only slightly reduced the ESP due to low Ca²⁺ content. The composted straw and straw had a relatively moderate effect on the physical, chemical, and biological properties of soil samples. Composted straw had high available nutrients, while straw had a slow release of nutrients, which favored the sustained effect of its organic matter. Consequently, the addition of these organic materials may be a good strategy for the amelioration of coastal salt-affected soil.

References

[1] Abd Elrahman S H, Mostafa M A M, Taha T A, Elsharawy M A O, Eid M A (2012). Effect of different amendments on soil chemical characteristics, grain yield and elemental content of wheat plants grown on salt-affected soil irrigated with low quality water. Annals of Agricultural Science, 57(2): 175–182

[2] Amezketa E, Aragüés R, Gazol R (2005). Efficiency of sulfuric acid, mined gypsum, and two gypsum by-products in soil crusting prevention and sodic soil reclamation. Agronomy Journal, 97(3): 983–989

[3] Bertrand I, Chabbert B, Kurek B, Recous S (2006). Can the biochemical features and histology of wheat residues explain their decomposition in soil? Plant and Soil, 281(1–2): 291–307

[4] Clark G J, Dodgshun N, Sale P W G, Tang C (2007). Changes in chemical and biological properties of sodic clay subsoil with addition of organic amendments. Soil Biology and Biochemistry, 39(11): 2806–2817

[5] Harris M A, Rengasamy P (2004). Sodium affected subsoils, gypsum, and green -manure: interactions and implications for amelioration of toxic red mud wastes. Environmental Geology, 45(8): 1118–1130

[6] Jones B E H, Haynes R J, Phillips I R (2012). Addition of an organic amendment and/or residue mud to bauxite residue sand in order to improve its properties as a growth medium. Journal of Environmental Management, 95(1): 29–38

[7] Khair T S Al-Busaidi, Buerkert A, Joergensen R G (2014). Carbon and nitrogen mineralization at different salinity levels in Omani low organic matter soils. Journal of Arid Environments, 100–101: 106–110

[8] Khan K S, Gattinger A, Buegger F, Schloter M, Joergensen R G (2008). Microbial use of organic amendments in saline soils monitored by changes in the ¹³C/¹²C ratio. Soil Biology and Biochemistry, 40(5): 1217–1224

[9] Khalil M I, Hossain M B, Schmidhalter U (2005). Carbon and nitrogen mineralization in different upland soils of the subtropics treated with organic materials. Soil Biology and Biochemistry, 37(8): 1507– 1518

[10] Lakhdar A, Rabhi M, Ghnaya T, Montemurro, Jedidi N, Abdelly C (2009). Effectiveness of compost use in salt-affected soil. Journal of Hazardous Materials, 171(1–3): 29–37

[11] Lee J (2010). Effect of application methods of organic fertilizer on growth, soil chemical properties and microbial densities in organic bulb onion production. Scientia Horticulture (Amsterdam), 24(3): 299–305

[12] Li J L (2008). Research on the effect of saline wetland from pulp wastewater irrigation in Yellow River Dleta. Dissertation for Ph.D Degree. Qingdao: Ocean Univiersity of China, 15–16(in Chinese)

[13] López-Piñeiro A, Murillo S, Barreto C, Muñoz A, Rato J M, Albarrán A, García A (2007). Changes in organic matter and residual effect of amendment with two-phase olive-mill waste on degraded agricultural soils. Science of the Total Environment, 378(1–2): 84–89

[14] Lu R K (2000). Methods for chemical analysis of soil agriculture. Beijing: China Agricultural Science and Technology Press, 108–110; 238–240 (in Chinese)

[15] Madejón E, Burgos P, López R, Cabrera F (2003). Agricultural use of three organic residues:effect on orange production and on properties of a soil of the ‘Comarca Costade Huelva’ (SWSpain). Nutrient Cycling in Agroecosystems, 65(3): 281–288

[16] Mahmoodabadia M, Yazdanpanah N, Sinobas L R, Pazira E, Neshat A (2013). Reclamation of calcareous saline sodic soil with different amendments (I): Redistribution of soluble cations within the soil profile. Agricultural Water Management, 120: 30–38

[17] Nardi S, Morari F, Berti A, Tosoni M, Giardini L (2004). Soil organic matter properties after 40 years of different use of organic and mineral fertilizers. European Journal of Agronomy, 21(3): 357–367

[18] Omeira N, Barbour E K, Nehme P A, Hamadeh S K, Zurayk R, Bashour I (2006). Microbiological and chemical properties of litter from different chicken types and production systems. Science of the Total Environment, 367(1): 156–162

[19] Pathak H, Rao D L N (1998). Carbon and nitrogen mineralization from added organic matter in saline and alkali soils. Soil Biology and Biochemistry, 30(6): 695–702

[20] Powlson D S, Hirsch P R, Brookes P C (2001). The role of soil microorganisms in soil organic matter conservation in the tropics. Nutrient Cycling in Agroecosystems, 61(1/2): 41–51

[21] Qadir M, Noble A D, Oster J D, Schubert S, Ghafoor A (2005). Driving forces for sodium removal during phytoremediation of calcareous sodic and saline-sodic soils: a review. Soil Use Manage, 21(2): 173–180

[22] Qadir M, Oster J D, Schubert S, Noble A D, Sahrawat K L (2007). Phytoremediation of sodic and saline-sodic soils. Advances in Agronomy, 96: 197–202

[23] Raychev T, Popandova S, Józefaciuk G, Hajnos M, Sokolowska Z (2001). Physicochemical reclamation of saline soils using coal powder. International Agrophysics, 15: 51–54

[24] Rengasamy P (2006). World salinization with emphasis on Australia. Journal of Experimental Botany, 57(5):1017–1023

[25] Rogival D, Scheirs J, Blust R(2007). Transfer and accumulation of metals in a soil diet-wood mouse food chain along a metal pollution gradient, Environmental Pollution, 145: 516–528

[26] Sadiq M, Hassan G, Chaudhry G A, Hussain N, Mehdi S M, Jamil M (2003). Appropriate land preparation methods and sulphuric acid use for amelioration of salt affected soils. Journal of Agronomy, 2(3): 138–145

[27] Tejada M, Genzalez J L (2006). Crushed cotton gin compost on soil biological properties and rice yield. European Journal of Agronomy, 25(1): 22–29

[28] Walker D J, Bernal M P (2008). The effects of olive mill waste compost and poultry manure on the availability and plant uptake of nutrients in a highly saline soil. Bioresource Technology, 99(2): 396–403

[29] Walpola B C, Arunakumara K K I U (2011). Carbon and nitrogen mineralization of a plant residue amended soil: The effect of salinity stress. Bangladesh Journal of Scientific and Industrial Research, 46(4): 565–572

[30] Wang H, Wang R Q, Yu Y, Myron J M, Zhang L J (2011). Soil organic carbon of degraded wetlands treated with freshwater in the Yellow River Delta, China. Journal of Environmental Management, 92(10): 2628–2633

[31] Woods P V, Raison R J (1983). Decomposition of litter in sub-alpine forests of Eucalyptus delegatensis, E. pauciflora and E. dives. Australian Journal of Ecology, 8(3): 287–299

[32] Xu J M, Tang C, Chen Z L (2006). The role of plant residues in pH change of acid soils differing in initial pH. Soil Biology and Biochemistry, 38(4): 709–719

[33] Yan F, Schubert S (2000). Soil pH changes after application of plant shoot materials of faba bean and wheat. Plant and Soil, 220(1/2): 279–287

[34] Yao L X, Li G L, Tu S H, Gavin S, He Z H (2007). Salinity of animal manure ad potential risk of secondary soil salinization through successive manure application. Science of Total Environment, 383(1–3): 106–114

[35] Yazdanpanah N, Mahmoodabadi M (2013). Reclamation of calcareous salinesodic soil using different amendments: Time changes of soluble cations in leachate. Arab Journal of Geoscience, 6(7): 2519–2528

[36] Zanuzzi A, Arocena J M, van Mourik J M, Faz Cano A (2009). Amendments with organic and industrial wastes stimulate soil formation in mine tailings as revealed by micromorphology. Geoderma, 154(1–2): 69–75

[37] Zhao J J, Guo Y, Chen X, Shi Y, Han X R (2006). Influences of organic material on organic phosphorus fractions and mineralization processes in soils. Soils, 38(6): 740–744(in Chinese)

[38] Zhou H, Liu M, Yu W T (2008). Properties of decomposition and residue of organic materials and its mixture in aquic brown earth. Chinese Journal of Soil Science, 39(6): 1311–1315(in Chinese)

[39] Zhou J Y, Tu M Q, Xiong Y X, Ding F Z (2007). The simultaneous measurement on commutative Ca, Mg, K and Na in the soil by ICP-AES. Resources Environment and Engineering, 21(4): 486–488(in Chinese)

[40] Zhuang P, McBride M B, Xia H P, Li N Y, Li Z A (2009). Health risk from heavy metals via consumption of food crops in the vicinity of Dabaoshan mine, South China. Science of the Total Environment, 407(5): 1551–1561

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg