Introduction
	An abundance of bacteria are able to thrive in everyday soil. A teaspoon of soil alone generally contains anywhere between 100 million and 1 billion bacteria. Many of these bacteria enrich the soil by performing activities such as fixing atmospheric nitrogen and carbon, producing organic matter essential for plant growth, and by decomposing recalcitrant compounds. In order to stimulate plant growth, many farmers utilize fertilizers. One popular fertilizer is cow manure, due to its relative abundance (one cow can produce 750 kg of manure each month) and its beneficial effect on the soil. Concentrations of nitrogen, phosphorus, and bacteria in the soil are augmented by the addition of cow manure. 

Problem
What is the effect of cow manure on bacterial growth in soil?
	If the soil sample has been saturated with cow manure over a period of at least several months, then it will have greater bacterial variety and more bacterial colonies because cow manure greatly increases the concentrations of nitrogen, phosphorus, and thus bacteria, in the soil.

Variables
Independent:  presence of cow manure
Dependent:  bacterial growth (variety and number)
Control:  soil not exposed to cow manure
Constants:  location from which soil was obtained, soil concentration in solution

Materials
5 Ziploc bags, gloves, garden spade, microscope, 5 plates treated with agar, graph paper transparency, soil samples from Bergey’s Dairy, soil samples from a non-exposed area, sterile pipettes, sterile transfer loops, beakers, graduated cylinder, water, wax or tape
(to seal plates), bleach solution (to destroy bacteria upon completion of experiment), balance 

Procedure
1. Prepare five plates with agar.
2. Obtain soil samples from a non-exposed (control) area and an area exposed to cow manure.  Use gloves and a garden spade to place the soil in the Ziploc bags.
3. Make the soil mixture by combining 9 mL of water and 1 g of the control soil in a beaker. 
4. Streak the plate by dropping one to two drops of the soil mixture in the center of the plate with a pipette.  Gently smear the drops both horizontally and vertically using a transfer loop. 
5. Seal with paraffin wax.
6. Repeat steps 3-5 for another control and three trial plates.  Be sure to use a new pipette and transfer loop for each plate.
7. Observe the plates under the microscope after 24 hours. Take note of colony number (use the graph paper) and type (by shape).
8. Observe once a day for four days and record observations.
9. Use bleach to destroy the bacteria when observations are complete.

Observations

Observations of the Controls

Control 1:
Bacteria:  irregular shape, smooth edges, and smooth surface- 2 round shape, smooth edges, smooth surface- 3

Number of colonies: 1,152

*This plate had a thick gel layer, it appears that mold has grown over parts of the colony
Bacterial Sizes:  Most are around 1-2 mm but are very hard to observe due to         colonies having overgrown the plate and grown close together.  There are several dozen colonies per 1cm square.

Control 2:
Bacteria:  smooth surface, lobate edges, irregular shape- 1 irregular shape, smooth edges, smooth surfaces- 2 round shape, smooth edges, smooth surface- 3

Number of colonies: 864

*This plate had a much thinner layer of gel on the bottom and less mold than control 1

Bacterial Sizes:  On plate control 2 there were one 1mm, two 3mm, three 5mm,
and three .1, .2, and .5mm sized colonies.  There were also about a dozen
colonies per five-centimeter square, but plate two also had some mold
growth.

Observations in Trial 1
Number of Bacteria: 1,621
Bacteria observed
Punctiform bacteria:  22
Round bacteria:  63
--2  W/S
--58  W/Wr
--3  S/S
Irregular Bacteria:  41
--4  W/Wr
--1  S/Wr
--19  L/S
--2  L/Cd
--13  L/Wr
--2 C/S

Key:
	Column 1		Column 2
	W=wavy		S=smooth
	S=smooth		Wr=wrinkled
	L=lobate		Cd=contoured
	C=curled

Observations in Trial 2

Number of Bacteria:  1,081

Bacteria observed
Punctiform bacteria:  23
Round bacteria:  57
--35  S/S
--1  W/S
--7  W/Wr
--7  C/S
--5  C/Wr
--1  L/S
Irregular bacteria:  81
--4  W/Wr
--2  W/S
--22  C/Wr
--16  C/S
--35  L/Wr

Key:
	Column 1		Column 2
	W=wavy		Wr=wrinkled
	S=smooth		S=smooth
	C=curled
	L=lobate

Sources of Error  
Bacteria were not observed on the appropriate days, the control soil sample was obtained on school grounds, research did not reveal what types of colonies are commonly seen in soil