1 Introduction

The soil environment has the capacity to retain, modify, and improve contaminants through a combination of physical, chemical, and biological activities [1]. It also aids and safeguards populations of microbes and other biota that participate in the cycling of macro-elements and nutrients [2]. The soil environment promotes the digestion and storage of organic carbon. The benefits of the soil environment are gradually affected by some anthropogenic activities including crude oil exploration [3], improper pesticide usage, unrestrained hydrocarbon product burning, a rise in population, and advancements in technology [4]. Other factors may be deliberate or unintentional natural occurrences, such as production procedures [5], mineral extraction, inadequate environmental management and waste disposal practices [6], illegal waste dumping, underground storage tank leaks, abandoned mines, and other industrial activities [7]. All these activities have contributed to the entry of both organic and inorganic chemicals into the soil thereby changing their natural composition [8], oil spills are the most frequently polluting substances [9]. Their reaction with the soil leads to buildup of persistent poisonous substances, chemicals or disease-causing agents and causes unfavorable impact on plant development, animal health, and human health [10]. The physiochemical characteristics of soils are impacted by oil pollution from spills [11] and sometimes contaminate ground water.

When the soil is polluted, the farmland, rivers, ground water, and woods suffer the effects which affect the economic resources of the communities [12]. The pollution could be acute or chronic in agricultural soil and plant growth [13]. According to reports, soil conditions caused by oil pollution can prevent plants from accessing some important mineral elements and cause some non-essential minerals to accumulate in dangerous amounts [14].

The current concentration, environmental behavior, exposure routes, or potential toxicity of a chemical to human health or ecosystem must be characterized in order to identify soil as contaminated [15]. Several strategies have been used to successfully limit the mobility and toxicity of petroleum hydrocarbon-contaminated soils by employing microorganisms to biodegrade dangerous organic chemicals into innocuous by-products like CO2 and water [8], the bioremediation process can minimize exposure and amount of pollution while also immobilizing or eliminating the pollutant [16]. Increasing the soil organic matter (SOM) in contaminated soil which causes the encapsulation of organic contaminants, can also help with cleanup [17]. Fertilizers are one of the earlier identified bioremediation methods, it add nutrients to the soil thereby fostering the growth of plants and also give energy to hydrocarbon degrading microorganisms [18].

Fertilizers are chemical that are added to soil to improve crop productivity, it also serve as food for micro-ogarnisms, examples are manure, animal dung, poultry dropping, inorganic fertililizer and biochar etc. [19]. Inorganic released its nutrients at faster rate in soil than the organic ones, thus easily get to crops and micro-organisms [20], it easily contaminate ground water due to poor water holding capacity. Physical and chemical properties of manure encourage beneficial mico-organiams to grow and increase soil nutrients and pH. In other hand, biochar is also fertilizer that is produced when biomass is carbonized at temperature above 300 \(^\circ{\rm C}\) in limited supply or absence of oxygen [21]. The advantage of biochar to soil include enhancement of soil fertility, water holding capacity, increase in soil pH. Biochar also increase cation exchange capacity, pore in biochar also encourage micro-ogansm to grow [22]. Biochar also released its nutrients slowly, it also stimulate degrading micro-organisms. It adsorb organic and inorganic contaminants in soil. This decrease the liability and concentration of hydrocarbon poison thereby reducing crop and water toxicity [23]. Capacity of biochar for organic molecule degradation due to the stimulating the activities of indigeneous micro-oganisms is well reported [24]. Interaction of fertilizers on petroleum hydrocarbon polluted soil has been reported in several studies to stimulate petroleum hydrocarbon degrading microbes and also improve physico-chemical properties of soil of polluted soil [25].

In the study of Wu et al., [26], the total petroleum hydrocarbon concentrations of soil near oil wells was found to have higher concentration petroleum hydrocarbon than in the adjacent soil (control soil). Their study also revealed declined in the available phosphorus concentration, the study also revealed that petroleum hydrocarbon pollution could affect soil fertility and physical properties of soil.

In the same vein, the study undertaken by Mekonnen et al. [27], in similar location of the study area soil, the petroleum hydrocarbon PHC) concentration of 1, 242–5200 mg/kg was found in petroleum hydrocarbon contaminated soils. Kim et al. [28] reported a concentration of 3, 307 mg/kg in soil. Bahar et al. [29] reported PHC concentration of 559.87–107, and 189.63 mg/kg from hydrocarbon contaminated soils. In a recent research undertaken by Chaithanya et al. [30] in soil sample obtained from shore line, total petroleum hydrocarbon of 4928.80 mg/Kg was discovered. The researchers also discovered low nutrients concentration when compared with control soil samples, sodium (0.57–0.73 cmol/Kg), potassium (1.10–164 cmol/Kg), magnesium (2.13–2.70 cmol/Kg), and calcium 5.98–2160 cmol/Kg). Therefore, it becomes necessary clean soil that is polluted with petroleum hydrocarbon. Numerous researchers have adopted the use organic matter/ fertilizers such as inorganic fertilizer, organic fertilizer to stimulate micro-organisms degrading microbes [31]. Inorganic fertilizer is not cost effective and could cause soil leaching while nutrients level in some organic fertilizer is usually low [32]. Many Fertilizer admixtures also has limitation such as prolong remediation and lack of nutrients in soil at the end of remediation period [33], due to shortage or lack of nutrients in soil at the end of remediation period, farmers spent a lot money in revitalization of soil.

Sayed et al. [34] investigated the efficacy of biological–chemical-biological total petroleum hydrocarbon removal, they reported 68.3% removal of petroleum hydrocarbon pollutant removal, they also asserted that the performance of this strategy is 1.7 times effective than bioremediation alone, the strategy also reported 2.1 times effectiveness than using chemical oxidation alone. Investigation of six months remediation of polluted soil undertaken by Adedeji et al. [35], it was discovered that LOFBA fertilizer formulated from chicken droppings, cow dung, and periwinkle shell recorded a of 80.04% than NPK fertilizer (57.38%), the author stated that LOFBA enhanced reduction of total petroleum hydrocarbon than NPK. Despite this performance, there is need to search for fertilizers that can give higher reduction of PHC pollutant at a shorter period and this time retained more nutrients at end remediation period. Our research is aimed to fill this gap in identifying fertilizer combinations that will be more effective in the reduction of PHC soil and also retained more nutrients at the end of remediation. Poultry manure, PM is a mixture of poultry dropping and wood shaving litter, PM has been reported in several studies as a fertilizer with remarkable macro- nutrients content [36]. Poultry manure biochar, PMB is a biochar produced from PM, it is produced by carbonization of PM at a temperature above 300 \(^\circ{\rm C}\) in limited supply of air [37]. Biochar supply nutrients, raise pH soil, modify the physical, chemical and biological property of soil, encourage the growth of microorganisms, increases soil water holding capacity, stimulate the release of nutrients already present in soil [38]. In addition, biochar adsorbs petroleum hydrocarbon pollutant and limit the movement of pollutants through the soil. Biochar is not easily broken down like manure by microbial action, this quality sustain hydrocarbon biodegrading microorganism throughout remediating period [39]. To the best of our knowledge, the use of fertilizers admixtures like PM + PMB has not been discussed, also no research has focused on fertilizers mixture that will retained more nutrients at the end of remediation period. Therefore, the results of this study will provide necessary information on the fertilizers combination that will be more effective in the reduction of petroleum hydrocarbon pollutant in soil and at the same time retained more nutrients in soil after remediation.

2 Materials and methods

2.1 Study area, soil and fertilizers samples collection, biochar Production,soil pollution treatment, soil amendment and design

The experiment was conducted at Mosogar Delta State, South-South Nigeria, Mosogar lies in latitude 50 53! 5’’ N and longitude 50 44! 1’’ E. Delta state have two climate condition, the wet and the dry season. The wet season is between April and October and the dry season lied between November to March and the mean rainfall is about 1500mm to about 2900 mm [40]. The annual mean temperature of Delta state is about 25.70C, relative humility is moderately high, remarkably during March to Novermber; the occupation of inhabitant is farming and hurting.

A composite soil sample from the study area comprises five random sample were collected at a depth of 0–30 cm. The soil was air dried, debris such as leaves, roots and stone were removed. Thereafter, it was crushed in a porcelain mortar and passed through 2 mm sieve. Samples were kept in polythene bags that have been previously treated with chromic acid and properly labeled prior physico-chemical analysis of soil.

Inorganic fertilizer (NPK NOD 15-15-15- Nodral) and poultry manure (PM) were obtained from Ministry of Agriculture Sapele and Songhaia Integrated Farm, Amukpe- Sapele respectively. The fertilizer and the poultry manure were crushed in porcelain mortar and passed through 2 mm sieve. Samples were stored in polythene and labelled before analysis.

The PM were left to dry, and pyrolyzed in an oven operated at 350 °C according to the method described by Otieno et al. [41]. The resulting biochar were allowed to cool to room temperature overnight, ground to small granules and passed through 2 mm sieve and properly stored [42].

Poultry manure (PM) and Inorganic fertilizer (IF) were collected from and Songhaia Intergrated farm, Amukpe- Sapele and Ministry of Agriculture, Zonal Headquarter, Sapele respectively. The poultry manure and the fertilizer were crushed in porcelain mortar and passed through a 2 mm sieve. Samples were preserved in polythene bags and labelled prior analysis of PM, and IF.

The PM were dry, and carbonized an oven operated at 350 °C.The carbonized biochar was allowed to cool at room temperature overnight [43]. The biochar were crushed to small granules and pass through 2 mm sieve and properly preserved.

Crude oil was obtained from Seplat Development Oil Company drilling sites in Sapele. Crude oil was weathered for 14 days [44].

Crude oil was collected from Seplat Development Oil Company drilling sites, Sapele and weathered for two weeks [45], A 3 kg of unpolluted soil (US), sandy loam soil were measured into 24 different pots, the pots were separated into 3 sets, a set having 8 pots each. The first set of pots containing 3 kg each of US were sparked with 2% (60 g) crude oil and comprehensively homogenized (Fig. 1). The polluted soil samples were allowed on an attenuation of 3 weeks for stabilization period [16]. After the stabilization period, the first pot, second pot, third pot, fourth pot, fifth pot, sixth pot and seventh pot, 18 g PM (poultry manure), 18 g PMB (poultry manure biochar), 18 g IF (inorganic fertilizer), 9 g PM + 9 g PMB, 9 g PM + 9 g IF, 9 g PMB + 9 g IF, 6 g PM + 6 g PMB + 6 g IF were added respectively while eighth pot serve as control (no fertilizer addition) (Table 1). The amended soil was mixed thoroughly, watered with deionized water and maintained at 50% water holding capacity with thorough mixing and incubated for 84 days for proper aeration. Periodic sampling of soil from each container was done 3 weeks interval respectively.

Fig. 1
figure 1

Contaminated Petroleum Hydrocarbon Soil

Full size image
Table 1 Soil pollution and amendment
Full size table

This experiment were also performed for soil that was sparked with 4% (120 g) and 6% (120 g) crude oil, the same weight fertilizers were also used under the same condition (Table 1).

2.2 Determination of physico-chemical properties and total petroleum hydrocarbon (TPH) of the amended Soil

2.2.1 pH

A 20 g of aggregate soil sample was measured into a 50 mL beaker and 20 mL of distilled water was introduced. The soil/water admixture (ratio 1:1) was pause to stand for 0.5 h and agitated occasionally with a glass rod.

The electrodes were cleansed and driven into the soil/water admixture and the pH was read as pH (H2O) [46].

2.2.2 Phosphorus

A 5 g of the soil was measured into a polypropylene bottle and 40 ml of the extracting solution and corked. The mixture was agitated manually for 1 min and filtered with filter paper. The clear supernatant was kept for P assessment [47].

The value of P in the extract was assessed by colometric procedure. 5 mL of the filtrate were pipetted into a 50 mL conical flask and the pH was change to 5 by introducing 3 drops of C6H5NO3 l and some drops of 2 M NH4OH until a yellow colour appeared, 30 mL of water were then introduced followed by 10 mL of C6H8O6 reagent. The solution was then increased to 100 mL mark with distilled water and the absorbance was read in a spectrophotometer at 660 nm.

2.2.3 Nitrogen

A 0.2 g of aggregate soil was measured into a 100 ml Kjedahl digestion flask. One tablet of Se catalyst and 4 ml of concentrated H2SO4 were introduced to the flask and heated on the digester until the solution became clear. The mixture was chilled until just warm to touch and 10 ml distilled water was introduced and the mixture filtered through a filter paper into a 100 ml volumetric flask. The flask was further cleansed with distilled water and the filtrate was increased to 100 ml.

The value of nitrate in the filtrate was examined by colorimetric procedure, 5 mL of the filtrate were pipetted into a 25 ml volumetric flask. 2.5 ml of alkaline phenol, 1 mL of KNaC4H4O6.4H2O and 2.5 ml of NaClO3 were introduced and carefully agitated and increased to the mark with distilled water, thereafter it was determined using colorimeter.

Nitrate standard (1000 ppm) was produced by dissolving 4.7 g of (NH4)2SO4 in 100 ml volumetric flask with distilled water. From the 1000 ppm nitrate standard solution, a 100 ppm nitrate was produced, which was used in preparing 5, 10, 15, 20 and 25 ppm N standards. In each of the standards, 4 mL of H2SO4 and 0.95 g of anhydrous Na2SO4 were introduced and standard were given same treatment as sample above, before making up to the mark. A blank solution was produced without nitrogen but with the same quantity of acid and anhydrous Na2SO4 [48].

2.2.4 Organic carbon

A 5 mL of K2Cr2O7 solution was added to 1 g soil sample in a 250 ml Erlenmeyer flask and agitated sofly to damp the sample thoroughly, 20 ml of concentrated H2SO4 was then added and the mixture was allowed to chill.

100 mL of distilled water was added followed by few drops of Ferroin indicator and the mixture was titrated against 0.5 M FeSO4 solution to a green endpoint. A blank determination was also determined. The blank include 20 mL concentrated H2SO4, 50 mL of the K2Cr2O7 solution, 100 mL distilled water and 5 drops of Ferroin indicator [49].

2.2.5 Potasium, sodium, magnesium and calcium

A 5 g of soil sample was measured into a 250 ml polypropylene bottle and 100 ml of 1 M NH4OAc solution was added. The mixture was agitated for 0.5 h in a mechanical shaker (Heldoph) at 200 rpm for 0.5 h. The supernatant was filtered using filter paper.

The concentration of K+ and Na+ in the extract were assessed by Flame photometer while Absorption Spectrophotometer (Buck Scientific VGP 210 model) were used to determined Mg2+ and Ca2+ [50].

2.2.6 Determination of total petroleum hydrocarbon (TPH) of soil

A 50 ml of solvent (50: 50 admixture of (CH3)2CO and CH2Cl2) was added to 10 g of soil. The admixture was spiked with 1 ml of the surrogate. The admixture were positioned in sonicator and sonicated for 16 min at 70 0C. 10 g anhydrous Na2SO4 was added to the sample until a clear extract appeared. The extract was poured into a round bottom flask. These were replicated once more with addition of 50 ml of solvent mix. The admixture was agitated and drained into round bottom flask. The solvent was later concentrated to 3 ml. The extract was seperated into aliphatic and aromatic fractions using silica gel cartridges eluting with n-hexane and dichloromethane respectively. The two separate fractions extract obtained ware reconcentrated to a final volume of 1 ml (aliphatic and aromatic extract). The concentrated extracts were then fraction and analysed by Gas Chromatography with flame ionization detector [51].

2.3 Results and discussion

Particle size distribution of unpolluted soil (US) analysis revealed that sand had the highest percentage composition (74.46 ± 0.22%), followed by clay (2.19. ± 0.13) and silt (22.35 ± 0.34%), this value suggest that the US is sandy loam s. The pH of US was slightly low (Table 2) this could be attributed to the low level of potassium and magnesium (free bases ion) present in the US. The water holding capacity (WHC) of the US is also slightly low. These suggest poor organic matter content in the US. Soil with low WHC has been reported to be conducive to inorganic fertilizer (IF) leaching [52].

Table 2 Physiochemical properties of the parent soil (PS), poultry manure (PM) and poultry manure biochar (PMB)
Full size table

Results of pH, WHC, and macro-nutrients of fertilizers (N, P, Ca, Mg, K, Na, C) PM and PMB (Table 2) indicate that the application of fertilizers on petroleum hydrocarbon (PHC) soil could be better option for PHC polluted soil remediation.

2.4 Effect of fertilizers interaction on the physiochemical properties of petroleum hydrocarbon polluted soil

The results of fertilizers interaction on the physiochemical properties of soil polluted with three levels of Petroleum Hydrocarbon (PHC) pollution is given in Figs. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22 and Table 2. Soil pH of PM, PMB, IF, PM + PMB, PM + IF, PMB + IF, PM + PMB + IF treated soil decreased from as the rate of PHC increased. This could be due to the presence of methynoic acid [53] and free cation in PHC. Increment in the value of PHC increased the content of organic carbon, many researchers asserted that PHC increment in soil could provide excess carbon that might be unavailable for microbial use [54]. Many studies have proved that PHC hinder air and water penetration in soil, slows down microbiological activity and disrupts soil chemical reactions necessary to make soil nutrients available for plant uptake [55].

Fig. 2
figure 2

Comparison of pH content of soil contaminated with 2% PHC and amended with different fertilizers ratios after the remediation periods

Full size image
Fig. 3
figure 3

comparison of pH content of soil contaminated with 2% PHC and amended with different fertilizers ratios after the remediation periods

Full size image
Fig. 4
figure 4

comparison of pH content of soil contaminated with 6% PHC and amended with different fertilizers ratios after the remediation periods

Full size image
Fig. 5
figure 5

comparison of TOC content of soil contaminated with 2%, PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 6
figure 6

comparison of TOC content of soil contaminated with 4% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 7
figure 7

comparison of TOC content of soil contaminated 6% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 8
figure 8

comparison of available P content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 9
figure 9

comparison of available P content of soil polluted with 4% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 10
figure 10

comparison of available P content of soil polluted with 6% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 11
figure 11

comparison of Na content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 12
figure 12

comparison of Na content of soil polluted with 4% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 13
figure 13

comparison of Na content of soil polluted with 6% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 14
figure 14

comparison of K content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 15
figure 15

comparison of K content of soil polluted with 4% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 16
figure 16

comparison of K content of soil polluted with 6% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 17
figure 17

comparison of Mg content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 18
figure 18

comparison of Mg content of soil polluted with 4% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 19
figure 19

comparison of Mg content of soil polluted with 6% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 20
figure 20

comparison of Ca content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 21
figure 21

comparison of Ca content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image
Fig. 22
figure 22

comparison of Ca content of soil polluted with 2% PHC and amended with different fertilizers ratios after the remediation Periods

Full size image

There was also reduction in the concentration of N, Na, K, Ca, Mg as the PHC concentration increased (Figs. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22), This is because most of the macro-nutrients form a complex with transition metals of PHC at lower pH making them unavailable for plant utilization. This result is in agreement with earlier reports of Zhu et al., [56]. A likely mechanism through which PHC does this is as a result of the presence of transition elements constituents. The PHC is rich in transition elements [57] and characterized by the possession of partially filled d or f orbital‘s in any common oxidation state (metals).Though these free orbitals form coordinate complex with ligands at lower pH (such as NH3 and NO2, H2Oe.t.c) or other elements such as K, Ca, Mg, e.t.c also form complex [58]. When such complexes are formed, the bonded ions lose their ionic properties. The physiochemical properties of PHC amended soil for the remediation periods (Figs. 2, 3, 4, 5, 6, 7, 8) indicate that PM, PMB, IF singly or in combination also changes the physiochemical properties of polluted soil. PMB treated soil gave the highest value of pH followed by PM + PMB treated soil. The soil treated with IF has the lowest value of pH. The highest pH was observed in 2% PHC contaminated soil, while the lowest levels were found in the 6% PHC contaminated soil. The increase in pH observed after fertilizers treatment may be attributed to rapid release of free bases such as K+, Ca2+ and Mg2+ into the soil by the fertilizers thereby significantly increasing the pH and nutrients of the soil and readily providing nutrients for PHC degrading bacteria. However, there is a drop in pH drop as the period of incubation increased (2 l < 42 < 63 < 84 days). The pH depletion may be due to degradation product of petroleum hydrocarbon (organic acid.) Though the observed pH decrease agrees with acceptable standards of Bel et al. [59] after the 84 days remediation period. pH of the study is also within the range reported by Yelampalli et al. [60] for agricultural soil. There was also reduction in the level of N, Na, K. Ca, Mg as the PHC level increases (Figs. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22). The result agrees with earlier reports and the presence of transition elements constituents drives the reaction mechanism with the bonded ions losing their ionic properties [61].

The level of nutrients also boosted upon the application of fertilizers when compared to the control sample. This is attributed to the release of Na, Mg, Ca, K, P to the soil by the fertilizers. However, as the remediating period increased, there was a significant reduction in the level of the nutrients with nitrogen mostly affected. This observation suggests that biodegrading bacteria utilizes the nutrients as energy (food) for the decontamination of PHC polluted soil. The sharp reduction of nitrogen particularly after 84 days remediating period shows that it is the most nutrient needed by bacteria for biodegradation of PHC, total organic carbon also decreased at end of the remediation period. In addition, it was observed in 62 and 84 days remediation period macro-nutrient value retained in soil by PM + PMB fertilizer ranges from 118.73 ± 0.4–121.78 ± 0.5 mg/kg, 24.11 ± 0.2–24.73 ± 0.2 mg/kg, 4.34 ± 0.02–4.87 ± 0.02 mg/kg, 3.79 ± 0.02–4.05 ± 0.02 mg/kg for Na, K, Mg and P respectively, the nutrient value retained in PM + PMB fertilizer at 63 and 84 days remediation period is within nutrient level of agricultural soil [62].

2.5 Effect of fertilizer interaction on petroleum hydrocarbon polluted soil

The effect of fertilizer interaction on PHC polluted at various period of is shown in Figs. 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22. The percentage reduction of control soil sample is lower than the fertilizers treated soil, this could be due low microbial activity in the control soil. However, there was is a significant difference (P < 0.05) in fertilizers admixture and singly fertilizer in the reduction of PHC polluted soil, at end of 84 days remediation period.

The PHC removal by PM + PMB fertilizer is 1.4-fold higher than the result earlier reported by Lai et al. [63], the researchers use poultry manure and cow dung combination in their study. The reduction (over 93%) of PHC pollutant by PM + PMB fertilizer (Figs. 23, 24, 25) observed in the study is also above the earlier study of Ugoma et al. [64], the researcher observe 80.4% reduction of PHC when soil was treated with LOBFA (fertilizer formulated from chicken dropping, cow dung and periwinkles shell). In the same vein, Zou et al. [65] reported 68.3% reduction of PHC when they study the interaction biochemical-chemical-biological fertilizer of PHC polluted soil. The efficiency of PM + PMB fertilizer in the study could be due to adsorptive capacity of biochar and the simultaneous stabilizing effect of PM + PMB in the soil. According to Hoang et al. [66], the mixing of organic manure in addition to inorganic fertilizer will be the better solution to enhance remediation of petroleum hydrocarbon polluted soil.

Fig. 23
figure 23

Percentage reduction of TPH(mg/kg) content of soil contaminated with 2% PHC and amended with fertilizers ratios after 21 days, 42 days, 63 days and 84 days remediation period

Full size image
Fig. 24
figure 24

Percentage reduction of TPH(mg/kg) content of soil contaminated with 4% PHC and amended with fertilizers ratios after 21 days, 42 days, 63 days and 84 days remediation period

Full size image
Fig. 25
figure 25

Percentage reduction of TPH(mg/kg) content of soil contaminated with 6% PHC and amended with fertilizers ratios after 21 days, 42 days, 63 days and 84 days remediation pe

Full size image

2.6 Conclusion

In this study, sandy loam soil was sparked with weathered crude and treated with fertilizers, the results revealed that PM fertilizer and the PMB fertilizer contained remarkable nutrients value. In addition, the pH, water holding capacity, and nutrients of unpolluted soil fertilizers were determined. The pH, nutrient concentration and petroleum hydrocarbon polluted soil was examined in the study. In addition, PM + PMB fertilizer has the highest value of nutrients after the 84 days remediation period. Similarly, PM + PMB fertilizer were more effective in reduction of petroleum hydrocarbon pollutant. Therefore, it is recommended that PM + PMB fertilizer should be used to decontaminate soil that is polluted with petroleum hydrocarbon.