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JOURNAL OF RESEARCH IN NATIONAL DEVELOPMENT VOLUME 8 NO 2, DECEMBER, 2010


 

EFFECT OF LOW DENSITY POLYETHYLENE (LDP) WASTE ON PHYSICAL CHARACTERISTICS OF AGRICULTURAL LAND

 

A.I.Ayinla and P. Eleke

Department of Agricultural Engineering, Kaduna Polytechnic, Kaduna, and

                                                                   S.G.Sara

National Institute of Water Resources, Kaduna

E-mail: aibrahimayinla@gmail.com

 Abstract

 The aim of this paper is to examine the extent of Low Density Polyethylene (LDP) impact on the physical characteristics of agricultural soil. The parameters that were studied for are temperature effects, bulk density and total porosity.   A rectangular portion of an agricultural land of homogenous area of 10m by 5m was selected and subdivided into two equal plots. While a plot was treated with LDP trashes, the other was left bare.   The temperatures of the two plots were recorded in situ; the bulk density was determined using core method and total porosity was evaluated using empirical formula.   The results show that temperature of treated portion with LDP increased faster. At 9am, it was 23.80C, after 2 hours, a 100C different was recorded and at subsequent 2 hours interval, 110C, and 140C differences were recorded respectively, the last 2hours (17pm) the temperature became constant. The soil classification was loamy, the bulk density was found to be 1.21g/cm3 with total porosity of 54% before treatment. The bulk density of Plot A was 1.51g/cm3 with total porosity of 43%, while Plot B has bulk density of 1.91g/cm3 and total porosity of 55%. It was concluded that soil in plot A gained solar energy due to the heat gained by the LDP plus the original heat of the soil, hence, raising the soil temperature. The study recommends sorting of LDP from point of generation.  

 

Keywords:Polyethylene, waste, soil, temperature, land   

 


Introduction:

Polyethylene is a low density product of polymer which implies the name as Low Density Polyethylene (LDP). LDP represents the majority of thermoplastics (Tajeddin, Abdulrahman, Abdulah, Ibrahim and Yusuf, 2009) currently used as food packaging materials and other household materials. The production and consumption of these polymers increasingly popular has it been widely used in Agricultural land as mulching (El-Nemr, 2006; Yaqub and Shahzad, 2009; Girma and Abdulrahman, 2005), as weed control (Shahzad and Ghaffar, 1984; Horowitz, Rege and Herzlinger, 1983), as pathogenicity control ( Yaqub and Shahzab , 2009; Shahzab and Ghaffar, 1984; Sanerborn and Saxena, 1987) and enhancing high yield in some crop production. Example is the use of LDP as a mulching material for tomato, increased the yield from ratio 650:854, 232:447 and 441:660 (Girefe et al, 2005). But despite the functional use, it has caused disturbing feeling to the environment as well as agricultural land itself.

 

At a sufficiently low temperature, all polymers are hard, rigid solids, but as temperature rises, each polymer eventually obtains an adequate thermal energy to enable its chains to move freely and behave like a viscous liquid (Cowie, 2008). With application of heat, thermoplastic resins can be shaped, formed, moulded or extruded (Gabriel, 1995). Thermoplastics composed of chemically cross-linked molecular chains, which set at the time the plastic is first formed, these resins will not melt, but rather disintegrate at a temperature lower than its melting point when sufficient heat is added (Mahmood and Hagheeghatpadjooh, 2004). They further stressed that polyethylene especially LDP are resistant against degradation and micro-organism attacks. So as this is generated, stored, collected, transported and finally disposed (waste-stream) to an unpopular site which later finds its way into the agricultural field either through dumping or erosion when rain falls.

 

Soil of agricultural field is a fundamental resource for food production, as such; it is the most important possession and input of farmers. Proper soil management is one key factor threatening sustainability of the agricultural soil (Smith et al; 1995). Intensive and sustainable crop production in tropical soils requires soil management practices in order to prevent yield failures. But today, the situation is now being threatened by improper disposal of LDP aided by wind, animals or water.

 

The littering of agricultural field with these LDP has called for the concern as part of the measures to maintain proper land management and sustenance of agricultural soil. It is therefore the aim of this paper to examine the extent of degradation on physical characteristics of agricultural field for the sustenance of soil and food production.

 

Materials and methods

Description of experiment

A rectangular portion of an agricultural land of a homogenous area of 10m by 5m was selected. The length was then divided into two equal parts. The trashes of LDP which was about 15 years in existence was sought for, carefully selected and collected at a well known dump site at Km 30 along Abuja road. The two plots were labeled as A and B. Plot A was tilled to about 20cm depth and treated with trashes of polyethylene to a certain extent and Plot B was also tilled and left bare (LDP) to serve as controls. Both plots were allowed to expose to solar energy.

 

Experimental Analysis

Particle size distribution was determined on the two plots using hydrometer method as described by Gee and Bander, (1986). For the temperature, the experiment was carried out in-situ, a total of four (4) plastic pipes of 12mm diameter and about 1m in height were selected and inserted into the soil at a depth of 5cm, then the thermometer were placed in them at 10cm depth . This process was performed for both plots; and soil temperature was recorded from 9am to 5pm at 2 hours interval. The experiment was carried out around March / April 2008.

 

Bulk density

Before tilling and application of treatment into the plots, bulk density was determined, and when tilling and application of treatment was completed, bulk density was also carried-out. The core samples were used to determine the dry bulk density using the core method as outlined by Blake and Hartge, (1986). The total porosity from Bulk density data using the formular below was evaluated.

              TP = (1 - ) x 100

where, TP = Total Porosity; BD = Bulk Density;  PD = Particle Density (assumed to be 2.65g/cm3).


 

Results and discussions

Result:

Table 1: Soil particle size distribution of plot before altering

Particle size distribution

Volume (%)

Sand

35

Silt

40

Clay

25

Classification

Loamy

Bulk density

1.21g/cm3

Total porosity

54

 

 

 

 

 

 

 

 

 

Table 2: Reading of Temperature (oC) on the plot A and Temperature (OC) on plot B

Period

Temp (OC) on plot A

Mean Temp(OC)

Plot B

Mean Temp(OC)

 

1

2

3

4

 

1

2

3

4

 

9am

22

25

24

23

23.8

14

13

14.6

14

13.9

11am

33

34

34

34

33.8

20

19.7

21

19

19.9

13pm

44

45

45

46

45

25

32

30

32

29.8

15pm

17pm

59

59

59

59

58

59

59

59

59.3

59

34

35

36

36

36

36

36

36

35.5

36

 

 

        Table 3: Bulk density and Total porosity of Plot A and B

Treatment

BD (g/cm3)

TP (g/cm3)

Plot A

1.51

43

Plot B

1.19

55.1

 

Table 4: Soil temperature-Crop condition of some crops

Crops

Favourable temperature limits

Germination

Growth

Corn

7-10O C

27-30OC

Potato

5-8 OC

16-21O C

Oats

8 OC

21O C

Citrus

 

25 OC

            Source: Brady, (1991).


 

 

 

 

Discussion

The particle size distribution of original plot before tilling and application of treatment, indicated 35% sand, 40% silt, and 25% clay, given the textural classification of loamy soil (Table 1). The class has moderately coarse, medium, and fine texture with a bulk density of 1.21g/cm3.

 

Table 2 shows and presented temperature records at four (4) designated points on both plots. Plot A shows the highest solar heat trapped into the soil, probably due to the presence of  LDP trashes as presented, while plot B shows lower temperature increment. Soil temperature was significantly raised in comparison, from 13.9OC to 23.8OC at 9am. Two hours later the mean temperature on plot A was raised to 33.8OC and plot B was 19.9OC. Within six hours, the mean temperature at plot A w as raised to 59.3OC whereas plot B maintained a reasonable soil temperature of 35.5OC. The most favourable limits of temperature are from 27OC- 32OC (Brady, 1991). Comparing the two plots, their efficiency to transfer solar heat to the soil was more in Plot A than in Plot B. LDP modifies the caloric balance, hence, allows an additional take up of solar energy by up to 4% increasing of energy absorption, probably due to its own solar accepted (Maged, 2006). So does, Table 4 indicated some crops and their temperature that favour them at germination and growing stages.

 

The original bulk density of the soil before tampered with it was 1.21g/cm3 with total porosity of 54%. After tilling without any treatment added to the soil, the bulk density was almost equal to the original soil condition, 1.19g/cm3. The treated Plot A has 1.51g/cm3 with total porosity of 43% as presented in Table 3.

 

The results show that, the presence of LDP reduces the total porosity by 11% when compared to the original bulk density of the soil. Some certain pore spaces might have been blocked by the LDP presence. The holding of water by the soil in such situations will be ephemerons, because the expected water in the root zone has been blocked and finally available for easy evaporation as heating increases. The effect of this is that the complete circulation of air into the soil will be impeded, hence suffocating the microbial inhabitants. Also, all the physical, biological and chemical processes will be affected as reduction of microbial activities in soil will be slow down as reported by Brady, (1991).

 

Conclusion / Recommendation.

It has been proved that LDP is a polymer that cannot be degradable for a long year, and most effects of these has been very visible in our environment. Any agricultural land holding waste LDP is in a very bad situation, because the study shows that the total porosity of the study land decreased by 11% which is very significant to the management and sustainability of the agricultural soil. Also, the temperature was rapidly increased, hence endangering the crop roots as well as impeding the soil’s biological, physical and chemical processes. It can be therefore suggest that:

 

Sorting is a part of environmental solid waste management right from our homes, sorting of LDP waste should be done before disposing. Individuals and industries should be orientate and educate on proper disposal of any of the substances. The process of waste recycling should be of concern to government, agencies and environmentalists.

 

 References

 Blake, G.R.  and  Hartge, K.H, (1986): Bulk density. In Klute A. Methods of analysis (15) pp 365-375.

 

Cowie, J.M.G., (2008): Polymers: Chemistry and Physics of modern materials,   Third ed. Boca Raton.

 

Fouzia, Y., Saleem, S. and Pak. J. B.(2009): Effect of solar heating by Poly-mulching on Sclerotial viability and pathogenicity of sclerotium Rolfsil on Muncbean and Sunflower, 41(6): 3199-3205.

 

 Gabriel, L.H., Yoo and Yukong(1995); History and physical chemistry of high density polyethylene (HDPE). Uc patent 5,461,093; Brodeg. Poly composition chemically bonded with starch and a process for preparing thereof.

 

Gee, G.W. and Bander, J.W (1986): Particle size analysis. In Klute A.(ed). Methods of analysis Part 1, 2nd ed. Agronomy monographer no ASA and SSSA. Madison,WL.

 

Giraffe, S., Girma, A. and Abdul-Rahman (2005); Effect of soil solarization on Orobanche soil seed bank and tomato yield in central Rift valley of Ethiopia.

 

Horowitz, M.Y. Rege and Herzhinger, G. (1983); Soil Solarization for Weed Control, Weed Sc. Israel, 31: 170-179.

 

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Maged, A. E, (2006);  Effect of mulch types on soil Environmental Condition and their Effect on the Growth and yield of cucumber plants, J. Applied Sc. Res. 2(2); 67-73. 

Mahmood and Hagheeghatpadjooh (2004); Preparation of Brodeg. Low density poly by starch-urea composition for agricultural application, Iran J.Chem. & Chem. Eng. Vol. 23 No 1.

 

Ndubisi M.C. (2009): Physical properties of an Ultisol under plastic film and No-Mulch and their effect on the yield of Maize. 5(5): 25-30. J of American science

 

Samerborn J. and M.C Saxena (1987). Effect of soil solarization or orobanche spp. Infestation and other in Faba- bean and lentils. Umeratu of Hohenheim, Institute of plant production in tropics & sub trop.

 

Shahzad, S. and Ghaffar, A. (1984). Effect of plastic mulching on the population of R. Solani and its infection on Mingbean. 25th Annual Nat. Sc. Conf. (16-18 Feb, 1991, Karanchi, pg 23).

 

Singh, R.K, R.P Shukla and R.S Dwiredi (1990). Effect of solar treatment on germination of selerotia sclerotium rolfsii Sacl.. and on other soil Mycoflora. Bio. & Fertility of Soil 10: 152-154.

 

Smith, J., G. Weber, M.V. Manyong, and M.A.A, Fakorede,. (1995): System dynamics and heterogeneity: The key to unlocking W.A.s potentials. The case of maize in Nigeria, Paper presented at the maize W/shop July 9,12,1995. Kellogg Centre, Michigan State University, East Landsing, MI USA.

 

Tajeddin, B., Abdulrahman, R., Abdullah, L. L., Ibrahim, N. A., and Yusuf, Y. A., (2009):  Thermal properties of LDP-filled Kenaf cellulose composites. World Journal of Agric. Sciences. 1 (2): 143-147. (DOSI Publications).