my first draft...
INTRODUCTION
An increasing interest has emerged with respect to the importance of microbial diversity in soil habitats. The extent of the diversity of microorganisms in soil is seen to be critical to the maintenance of soil health and quality, as a wide range of microorganisms is involved in important soil functions (P. Garbeva et al., 2004).
Life is vital to soil and soil is vital to life. A thin layer of soil covers most of the earth’s land surface. This layer, varying from a few cm to 2-3 m in thickness, might appear insignificant relative to bulk of the earth. Yet it is in thin layer of soil that the plant and animal kingdoms meet the mineral world and establish a dynamic relationship (Thompson & Troeh, 1996). Soils vary widely from place to place (King, 2008), and were considered as geological residues and as reservoirs of nutrients for plant growth (Brandy, 1998). Beneath the soil, a mass of loose mineral matter lacking the influence of living things is frequently encountered (Thompson & Troeh, 1996), and specific flora and fauna were inhabiting it (Brandy, 1998). Soil science plays a key role in agriculture, helping farmers to select and support the crops on their land and to maintain fertile, healthy ground for planting (King, 2008.)
Over the 10,000 years since agriculture began to be developed, peoples everywhere have discovered the food value of wild plants and animals, and domesticated and bred them (Microsoft® Encarta® 2009). Agriculture was the key development that led to the rise of civilization, with the husbandry of domesticated animals and plants (i.e. crops) creating food surpluses that enabled the development of more densely populated and stratified societies. In 2007, about one third of the world's workers were employed in agriculture. However, the relative significance of farming has dropped steadily since the beginning of industrialization, and in 2003 – for the first time in history – the services sector overtook agriculture as the economic sector employing the most people worldwide (http://en.wikipedia.org/wiki/Agriculture/08102009).
The fertility of soil depends not only on its chemical composition, but also on the quantitative nature of microorganisms inhabiting it (Rao, 1999). Microorganisms are very diverse and live in all parts of the biosphere where there is liquid water, including soil, hot springs, on the ocean floor, high in the atmosphere and deep inside rocks within the Earth's crust. Microorganisms are critical to nutrient recycling in ecosystems as they act as decomposers. As some microorganisms can fix nitrogen, they are a vital part of the nitrogen cycle, and recent studies indicate that airborne microbes may play a role in precipitation and weather (http://en.wikipedia.org/wiki/Microorganism/08102009). Soil is a living organism and it needs to be appreciated as such, as a dynamic system that works in concert with plants. Microorganisms decompose and ferment organic matter into humus, containing nutrients and hormones, nutrients and minerals in a useable form to the plants via the root ecology. Microorganisms cohere soil particles and soil structure containing nitrogen and other fertilizing compounds (Cicerone and Oremland, 1998).
STATEMENT OF THE PROBLEM
According to Rondon et al. (1999), the study of microbial diversity represents a major opportunity for advances in biology and biotechnology.
Microorganisms decomposed organic matters and are the originators of the soil. They flourish and manufacture vital sustenance for growing plants. Microorganisms are important in growing crops and they also take part of the soils entire mass. On the other hand, deforestation, overgrazing by livestock, and agricultural practices that fail to conserve soil are three main causes of accelerated soil loss. Other acts of human carelessness also damage soil. These include pollution from agricultural pesticides, chemical spills, liquid and solid wastes, and acidification from the fall of acid rain.
This study will be conducted to answer the following questions:
- What are the physical and chemical properties of the soil in the selected mango plantations?
- What is the degree of abundance of soil microorganisms in selected mango plantations?
- Which of soil microorganisms, the Gram-positive bacteria, the Gram-negative bacteria or fungi will have the greater abundance in mango plantations?
- Which mango plantation has the highest abundance of soil microorganisms?
- What is the relationship between soil microbial abundance with the soil’s physico-chemical properties?
- What will be the trend in the soil’s microbial abundance and physico-chemical properties?
OBJECTIVES OF THE STUDY
This study aims to:
1. To determine the physical and chemical properties of the soil in the selected mango plantations,
2. To determine microbial abundance of the selected mango plantations,
3. To determine which mango plantation has the highest microbial abundance,
4. To determine which of the microorganism has the greatest abundance in mango plantations,
5. The relationship between soil microbial abundance with the soil’s physico-chemical properties, and
6. The trend in the soil’s microbial abundance and physico-chemical properties.
SIGNIFICANCE OF THE STUDY
Mango plantation is one means of profit in Zamboanga del Sur together with other agricultural crops such as corn, rice, banana and coconut. Through this study, this might help out the locality in understanding the value of microorganisms present in the soil and its importance in crop production. This study would also provide certain knowledge of the apparent outcome brought by agricultural activities and practices such as excessive use of fertilizers.
SCOPE AND LIMITATION
This research will be conducted at mango plantations in selected municipalities in Zamboanga del Sur. The study is limited only to the soil’s physical and chemical properties such as pH, moisture content, water holding capacity and texture. Practices and methods used by the property-owner to improve crop production and natural catastrophes will also be investigated for background study. Only the abundance of microorganisms will be examined and identification and classification of microorganisms will be excluded.
METHODOLOGY
Site and duration of study
The study will be conducted at Dinas, Guipos, Pitogo and San Miguel which are all located within Zamboanga del sur. Mango cultivated areas are present in this locale and is one means of income in the locality. The study will be conducted this October 2009 which will include gathering of samples as well as analyses of the said samples.
Sample gathering
Soil samples will be collected randomly and will be taken from the top layer to a depth of 5 cm. To each municipality, five 5m x 5m plots will be established serving as replicates. Five soil cores will be collected from each plot. Samples will then be homogenized, making one replicate. Then the soil samples will be removed through hands. Samples will then be stored at 4ºc until use.
Physical properties of soil
The moisture content will be measured by oven drying the samples at 45ºC for 48 hours. Then it will be computed through this formula:
(beaker + fresh soil sample) – (beaker + oven dried)
MC = ______________________________________________ X 100 %
(beaker + oven dried soil) – (beaker)
The colour of the soil will be determined through ocular inspection. Soil samples will be first air-dries and the standard soil colour chart will be use to determine the colour of soil from each site (Oyama & Takehara, 1997; Munsell Book of Color, 1976).
The water-holding capacity will be measured using the aspirator method. A weighed cup will be filled with soil oven-dried at 45ºC for 48 hours. The cup with soil as weighed cup will be pound with water and vacuumed. After it will be drained completely, it will be weighed again. The amount of retained per weight of dry soil will be calculated using this formula:
(glass filter + fresh soil sample) – (glass filter + oven dried)
MC = _____________________________________________________ X 100 %
(glass filter + oven dried soil) – (glass filter)
The soil texture will be determined using the modified ‘jam jar’ experiment (Anonymous 2000; Gardeners supply company,2002). In this experiment, soil samples will be sieved using a mesh size of 2 mm to remove large soil separates like rocks and cobbles. Then 500 g will be measured out and will be placed in a 600mL graduated cylinder. 400mL of water will be added to it. The lid will be screwed on and it will be shaken vigorously for 5 minutes, tipping it upside-down. The graduated cylinder will be then left until the soil was settled down and the water become clear. Layers will be formed where the sand (heaviest) layer is at the bottom, silt formed the next layer, and clay (lightest) is at the top. The total height of the settled soil will be measured using a transparent ruler on a millimeter scale followed by the measurement of each of the three formed layers. The percentages of sand, silt and clay will be determined using this formula:
Height of Formed
___________________________ X 100
Total Height of Settled Soil
Chemical Properties of the Soil
The pH of the soil at each site will be determined using an electrode pH meter where a 1:2.5 slurry of soil and distilled water will be used. The soil samples will be sieved to homogenize and remove the big soil separates, litter and soil macrofauna. 5 grams of each fresh soil will be measured and suspended in 12.5 mL distilled water (Tateishi et al. 1989; Mabuhay et al., 2004).
Microbial Abundnce
Dilution Plate Count Technique
This procedure will be conducted as described by (Tateishi et al., 1989). This technique is based on the principle that a complete detachment and dispersion of cells from the soil will give rise to discrete colonies when incubated on a petri plate containing nutrient media. Each group of microorganisms will be enumerated using different specific microbial medium.
For the bacteria, an albumin medium was used. This mediumwas prepared using 0.25 g egg albumin, 1 gram glucose, 0.5 g K2HPO4, 0.2 g Mg SO4, 7H2O, trace Fe2(SO4)3, and 15 grams agar dissolved in 1000ml distilled water (pH=7) (Tateishi et al., 1989b). Fungi will be enumerated using Rose Bengal medium which contained 10 g glucose, 5 g peptone, 0.5 g MgSO4, 7H2O, 0.03 g Rose Bengal and 20 agar dissolved in 1000ml water, then by ocular inspection it will be classified to yeast and molds. Actinomycetes will be enumerated using dextrose-nitrate medium containing 1 g dextrose, 0.5 g KNO3, 1 g K2HPO4, 0.1 MgSo4, 7H2O, 0.1 g KCl and 15 g agar for 1000 ml distilled water (Acea and Carballas, 1996).
Twenty grams of homogenized soil samples will be dispensed in 180 ml sterile water in a 250-ml Erlenmeyer flask (Tateshei et al., 1989; Mabuhay et al., 2004). The flask will be covered with a rubber stopper and shaken vigorously for 10 minutes. This established a 10-1 dilution. Ten ml from this soil suspension will be then transferred to a 200ml flask with 90 ml sterile water, and will be shaken to make a 10-2 dilution. These serial dilutions will be continued until the desired dilution 10-2 is reached.
Fifteen ml of the specific prepared media will be placed individually into test tubes. There will be three subsamples made from each replicate. Sterilization will be done to prevent contamination. In each of the test tubes with melted agar at around 45°C, 1ml of the soil suspension (10-5 dilution) will be inoculated using sterile syringe. It will be rotated gently between the hands to ensure uniform distribution and will be then poured aseptically into its respective pre-labeled Petri plates. The Petri plates will be incubated, at 37°C for 48 hours for bacteria, and at 25°C for 7 days for fungi.
After the required incubation period, the number of colonies will be counted. The mean of the three sub-samples and three replicates will be obtained. The colony forming units (CFU) of bacteria and fungi present per gram of soil will be calculated using this formula:
average no. of colonies X dilution factor
CFU/g = _____________________________________________________
Volume plated in ml
Where: CFU = colony forming units
Dilution factor = reciprocal of the final dilution
Data Analysis
Data for moisture content, water-holding capacity, and microbial abundance will be subjected to Analysis of Variance (ANOVA) to the significant differences between the study sites. Duncan’s Multiple Range Test will also be used to compare means.
(I forgot the Review of Related Literature... ooopppssss)
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