GROWTH PERFORMANCE OF CUCUMBER (CUCUMIS SATIVUS L.) IN SPENT ENGINE OIL CONTAMINATED SOIL AMENDED WITH COMPOST OF URENA LOBATA L

Studies to investigate the growth performance of Cucumis sativus L. (variety Nandini 731 F1) in spent engine oil contaminated soil amended with compost of Urena lobata was investigated at the University of Port Harcourt Ecological Centre. The soil samples were polluted at four different concentrations, namely, 2%, 3%, 4% and5% with spent engine oil and amended with decomposed Urena lobata at the rate of 0.25kg per 3kg of soil alongside a control (0%). The growth parameters examined were: plant height, number of leaves, leaf area, stem girth and sprouting percentage. The study showed that the control treated with compost gave the highest values for plant height 23.73cm, number of leaves 16.33, leaf area 84.73cm and stem girth 2,2cm while the 5% contamination recorded the lowest values for plant height 1.83cm, number of leaves 1.33, leaf area 2.19cm and stem girth 0.1cm. The number of leaves significantly (P<0.05) decreased with increase in the concentrations of spent engine oil from 2% to 5%. The 0% + compost treatment recorded the highest number of leaves while the number of leaves for 0% alone was comparable to 2%, 3% treatments but higher than 5% treatments. The growth parameters decreased with increase in the levels of contamination, however the application of Urena lobata significantly increased the plant height, number of leaves, leaf area and stem girth at P< 0.05. This study suggests that compost of Urena lobata is an effective organic supplement for remediation of spent engine oil contaminated soil where Cucumis sativus is cultivated.


INTRODUCTION
Spent engine oil which is also known as used motor oil is produced when new engine oil (or motor oil) is subjected to high temperature and high mechanical strain. It is a brown-to-brown liquid mixture of heavy metal contaminants such as zinc, lead, and chromium that come from engine parts as they wear down, including low to high molecular weight(C 15 to C 18 ) aliphatic and aromatic hydrocarbons, polychlorinated biphenyls, chlorodibenzofurans, lubricating additives and decomposition products (Wang et al., 2000).There are improper disposals of spent engine oil during manual oil changing operation which is not recycled but spilled and dumped by automobile and generator mechanics into runoff, gutters and open vacant plots, thereby polluting both soil and water (Anoliefo et al., 2000). In addition, the oil is also released into the environment from exhaust system during engine use and due to engine leaks (Osubor et al., 2003). In Nigeria and some other developing countries about 20 million gallons of spent engine oil are generated annually from mechanic workshops and discharged carelessly in the environment (Faboya, 1997). It is a common and toxic environmental contaminant not naturally found in the environment (Dominguez-Rosado and Pitchel, 2004).
Soil is a key component of natural ecosystems because environment sustainability depends largely on a sustainable soil ecosystem (Adriano et al.,1998).When soil is polluted, the ecosystem is altered, and agricultural activities are affected. Contamination of soil by used lubricating oil is rapidly increasing due to global increase in the usage of petroleum products (Mandri and Lin 2007).
Environmental pollution with petroleum and petrochemical products has attracted much attention in recent decades. The presence of different types of automobiles and machinery has resulted in increase in the use of lubricating oil. Spillage of used motor oils such as diesel or jet fuel contaminates our natural environment with hydrocarbon (Hussain et. al., 2008).
Contamination of the soil by spent engine oil creates an unsatisfactory condition for life in the soil, which is due to the poor aeration it causes in the soil, immobilization of soil nutrients, loss of water-holding capacity, lowering of soil pH, and reduction in soil catalase enzyme activity (Sathiya-Moorth et al., 2008) According to Udo and Fayemi (1975) growth of plants in oil polluted soil was generally retarded and chlorosis of leaves results, coupled with dehydration of the plants indicating water deficiency. High oil concentrations in soil not only reduce the amount of water and oxygen available for plant growth (McGill,1980) but also can interfere with soil-plant-water relations through direct physical contact, (coating of root tissues) thereby adversely affecting plant growth (Baker,1971).
Urena lobata is an annual in sub tropic and perennial in the tropics. It is a dicotyledonous weed which belongs to the family Malvaceae. Cucumber (Cucumis sativus L.) belongs to the Cucurbitaceae family. It is a creeping vine that roots in the ground. The plant has large leaves that form a canopy over the fruit. The fruit of the cucumber is roughly cylindrical, elongated with tapered ends, and may be as large as 60 centimeters (24in) long and 10 centimeter (3.9in) in diameter. Cucumbers are commonly harvested while still green. They can be eaten raw or cooked, or pickled. The seeds are edible and the thin skin does not require peeling (Herbst 2001).
This study was conducted to evaluate the growth performance of Cucumis sativus in spent engine oil contaminated soil amended with compost of Urena lobata.

Source of Materials:
The experiment was carried out at the University of Port Harcourt Ecological Centre. Soil samples sourced from a site at the University of Port Harcourt were used for the study. The seeds of Cucumber (Cucumis sativus Nandini 731 F1 variety) were obtained from Songhai Rivers Development Initiative (SRDI) Bunu/Tai Local Government Area in Rivers State. Perforated nursery bags were bought from Choba, while the spent engine oil was sourced from a mechanic workshop in Rukpokwu Town, Obio/Akpor Local Government Area of Rivers State.

Contamination of Soil:
A 3x5 factorial arrangement fitted into completely randomized design were used, each treatment were replicated three times. Top loamy soil weighing 3kg for each bag was used. The soil was mixed thoroughly with different levels of spent engine oil namely, 0%, 2.0%, 3.0%, 4.0% and 5.0% v/w and placed in perforated nursery bags labelled based on each treatment. The bags were perforated at the bases and sides to allow for aeration and drainage. The bags were kept for one week for the oil to acclimatize to the soil before the commencement of the remediation study.

Treatment with amendment:
The compost of Urena lobata was used to ameliorate the spent engine oil contaminated soil. The remediation treatment was carried out by adding 0.5kg of each ameliorating materials to different levels of pollution (2%, 3%, 4%, and 5%) in 3kg of soil and were thoroughly mixed before being transferred into the nursery bags.

Germination Procedures:
After the decomposition of Urena lobata compost, 4 seeds of Cucumis sativus were sown. 2-3 days after planting the seeds sprouted and at one week after planting, the seedlings of Cucumis sativus were thinned down to two seedlings and the percentage sprouting for each remediation treatment was calculated as: Percentage germination = No. of germinated seeds x 100 No. of seeds sown

Growth and biochemical parameters:
The following growth and biochemical parameters were analyzed: plant height (cm), leaf number, stem girth, leaf area, pH and heavy metals.
The plant height was measured with a metre tape in centimetres from the soil surface to the plant apex. The leaves of the plant of the various treatments were counted visually. The number obtained was then recorded appropriately against each sample. The stem girth was determined using thread to encircle the circumference of the stem at 2cm above soil level. The thread was then measured on 10cm ruler and length covered recorded as stem girth.
Leaf area was determined by measuring the length and breadth of the leaf and correction factor of 0.75 was used to multiply the length and breadth measurement following the procedure of Agbogidi and Eshegbeyi (2006). The leaves of the test crop were rinsed with distilled water and dried. The dried plant materials of each sample were macerated into powdered form using pestle and mortar. The powder form was sieved through a 0.2mm wire mesh to obtain fine powdered form. Each sample of the powdered materials was kept in small bottles for analysis.

Statistical Data Evaluation:
Data collected for each parameter were subjected to analysis of variance (ANOVA) using Microsoft Excel 2010 version. Means were compared using the least significant Difference (LSD) (Steel and Torrie,1960).

RESULTS
The pH of the spent engine oil and elemental components are presented in Table  1. The plant height of Cucumis sativus significantly (P<0.05) decreased with increase in contamination levels of spent engine oil. The soil amended with Urena lobata without contamination recorded the highest value (Fig.1).
The number of leaves significantly (P<0.05) decreased with increase in the concentrations of spent engine oil from 2% to 5%. The 0% + compost treatment recorded the highest number of leaves while the number of leaves for 0% alone was comparable to 2%, 3% treatments but higher than 5% treatments. (Fig.1).
The highest value of stem girth was recorded in 2% and 3% spent engine oil amended soils. The stem girth decreased with increase in spent engine oil contamination levels (Fig.1). The control amended with Urena lobata recorded the highest value than the control without amendment.
The leaf area significantly (P<0.05) decreased with increase in the contamination levels of spent engine oil. The soil amended with Urena lobata without contamination recorded the highest value (Fig.1).  0% + compost 2% 3% 4% 5%

Levels of contamination
Leaf area (cm2)

DISCUSSION
The incorporation of Urena lobata to spent engine oil contaminated soil at lower concentration significantly improved the growth of Cucumis sativus. This study shows that Urena lobata is helpful in improving soil fertility and reducing the toxicity of the spent engine oil on plants. The potentials of similar vegetative components of plant have previously been reported by (Chen andLee,1997, Akonye andOnwudiwe, 2004). As a means of remediating soils polluted with petroleum derivatives or crude oil, soil amendments such as sawdust, peat, waste cotton and organic manures are added to soil (Tanee and Akonye, 2009). A soil amendment increases the ability of the soil matrix to supply biologically available water and nutrients to microorganisms that are capable of degrading the target compounds (Davis and Wilson, 2005). The reduced plant height of Cucumis sativus in spent engine oil contaminations may be attributed to the stress imposed by artificially created drought conditions as well as the spent engine oil exposition suffered by plant roots due to the root inability to get sufficient water and nutrient from the soil (Unegbu et al. 2012). Post oil spill rehabilitation measures are designed to enhance soil recovery and crop improvement. The use of remediation practices that will stimulate and enhance the proliferation of microbial population for enhanced degradation of spent engine oil pollutants is desirable (Lei et al. 2005). Therefore the use of Urena lobata as indicated in this study was a contributing factor in the growth of Cucumis sativus in amended soils.

CONCLUSION
This study showed that the compost Urena lobata remediated the soil contaminated with spent engine oil by improving the growth performance of the crop and reducing the toxicity of the metals. Therefore the use of compost will enhance and improve spent engine oil contaminated soil especially where Cucumis sativus is cultivated.