After the water content experiment has been done I will then move on to humus content, I can only do the humus experiment after the moisture experiment otherwise I would evaporate water as well as burn off humus so I would not get an accurate result. To find the humus content I heat the remaining dry soil on a high flame for half an hour, all the humus (dead animal and plant matter) is burned off and the remaining soil in measured to see how much weight has been lost. The result of how much is lost is the amount of humus that was in the soil.
The soil pH is very simple, first I will add 3 grams of the soil from each area to 20mls of water, mix them well and add 5 drops of universal indicator. When I add the universal indicator it will turn an orange to red for acidic soil or green to purple for alkaline soil.
To do a soil profile I must have a gas jar, 50grams of soil and 200mls of water for each area of the experiment. First I will add the soil from each area into a separate gas jar, then I will add the water to the soil, after all the water is added it is mixed well so that all the soil will be lose and freely moving in the jar. The soil in the jar will be left for three days for the soil particles to separate and settle into different layers so I can see what the soil is made up of.
APPARATUS
- Quadrate (1/2 meter square)
- Light Meter
- Glass Jam Jar
- Trowel
- Bunsen Burner
- Crucible
- Oven
- Clay Triangle
- Tripod
- Thin Wire Mesh
- Funnel
- Beaker
- Gas Jars
- Preserving Fluid
- Plastic Bag
- Universal Indicator
- Dropper
- Perspex
METHOD
I started by taking 20 quadrates from each area, by randomly placing the square down on the grass in different areas, in this way we get a bigger spread of results so we get an overview of a lager area rather than a small area or a transect line. After completing the two lots of 20 quadrates I continued with soil samples from the two areas and by setting up pit fall traps. First I took a bag of soil from the areas DH and SH in the holes I had made I placed jam jars with perspex balanced on three stones over the top, to avoid water collecting in the jar. The aim of a pit-fall trap is to capture bugs, so we can see what kind of insect life lives in that area, so I can compare it with the other area. Then I took the soil samples up to the lab so that I could run the following series of tests. I started with pH test, as it is the simplest of them. First I added 3 grams of soil to 20ml of water and then added 5 drops of universal indicator to find the pH, I did this for both areas and found that in each case the sample turned a murky green, indicating a pH of 10. I continued with moisture content, by putting 10 grams of each soil into separate evaporating dishes, I placed these in the oven for 4 days, this evaporated all the moisture from the soil, leaving just pure soil and humus.
After completing the moisture content I did the humus content, this measures the amount of dead animal and plant material in soil. I did this by putting the remaining soil from the moisture experiment into a crucible. It was heated for half an hour on a strong flame and all the humus burned off leaving just pure soil.
RESULTS
pH
In the test to find the pH of the soil, the indicator turned the water a murky green in both cases, indicating an alkaline solution and when I checked it on the pH scale it was a pH10.
Water Content
After the samples came out of the oven all the water had evaporated leaving dry soil, after weighing these were the results: -
If the soil weighs 8.0g after heating, then I take away 8.0 from 10.0 to give 2.0g, this is the amount of water lost from SH. I did the same with DH and these were the results I got: -
I can see from these figures that the percentages of water lost were: -
Humus
After being heated for half an hour over a strong flame, I weighed the remaining soil and I came out with the following set of results:
If we take this away from the remainder of the moisture content experiment then we will get the amount of grams of humus burned off: -
To find the percentage of humus in the soil I must first put this into a fraction: -
For School House 2.4 = 3 = 30%
8 10
For the Dining Hall 1.4 = 7 = 15.55%
9 45
Light Intensity Readings
Unfortunately when I came to do the light readings for the two areas, the light intensity meter was broken. I was unable to get a copy of them for my results section.
Pit-Fall Traps
I was unable to get any results from the traps as they were sabotaged by other pupils.
Soil Profile and Quadrates
The results for the soil profile and quadrates are on the following pages.
OBSERVATIONS
Quadrates
I have noticed that in the area SH there is a wide abundance of Moss and Grass and there is a very small amount of anything else. This will be because the grass and moss are better at coping with small amounts of light rather than a direct, stronger beam of light. But in the area DH there is a lager range of the plants including small buck-weed, but there is a lot less moss in this area. This will be because the buck-weed, daisies, dandelions plantains and grass will be better at processing direct sunlight and they will be better at fighting for space than moss.
Water content
I have noticed that there was a lager amount of water in the soil in the area of SH, this will be because there is less evaporation going on due to the leaves and trees above stopping the sunlight and warmth reaching the soil, where as in the area DH there is plenty of sunlight reaching the soil so there is a moderate amount of evaporation.
Humus Content
I noticed that the level of humus content was higher in SH than DH this would be because all the leaves on the trees above the area fall off, land and de-compose here so this will add greatly to the amount of dead plant life in this area, where as in the area DH there is only one tree in the whole area and it will only produce a small amount of leaf litter compared to the twenty odd trees in SH.
Soil Profile
I noticed that there was a lager amount of humus, roots and leaves in the SH gas jar. Once again this will be linked to the large amount of humus in the SH area’s soil. I also noticed a small layer of silt, this would be there because this is the lightest and the finest of the humus/ soil particles, and the rest of this layer is suspended in the water. I have also noticed some roots floating around in the area DH, this will be because when I was digging up the sample I dug up some grass roots too.
CONCLUSION
There are many ways I could improve the investigation to make the whole thing more accurate. Firstly, using the light meter would have made it a lot more accurate as the light is one of the key factors to this investigation. Secondly I could have done more quadrates, and then taken averages to create a more rounded and accurate set of results. Thirdly I could have set a large amount of pitfall traps, to see the variety of different organisms, and then I could identify the creatures that live in that area. Fourthly I could measure how much rain falls in each of the areas using a rain gauge and calculate the difference of rainfall in each area.
To extend this experiment I could investigate the rainfall and seasonal changes to see if the weather and climatic changes have anything to do with the growth of plant life in the different areas. I could also see if the water content of the earth has an effect on the plant life. To check the effect of water content on the plant life I could section off five areas covering them so that only water I have measured can come into contact with the ground. One area would be given the average amount of water that could be expected as rainfall for the time of the year, the second area would be given 25% more, the third 75% more than the average. The fourth and fifth areas would be given 25% and 75% less water than the average rainfall expected for the time of year. This experiment would take place over a period of weeks so that the plant life would have time to adjust to the amounts of water being given.
EVALUATION
My investigation on the whole went according to plan, I was unable to get two sets of results due to failure of equipment and had a anomalous result. The first failure was the light intensity meter broke, so I could not get a result for this. The second failure was due to our pit-fall traps being sabotaged by other pupils, we didn’t get a results for that either. My only anomalous result was on quadrate 11 of the School House area, where I got a total of 170% ground coverage, when the others areas averaged around 100%, this was probably due to a bad estimate on my part. My prediction of higher amounts of moss (57%) in the shaded area was correct, but I didn’t expect to find such a high percentage of grass (33%). The plantain count at the School House site (2%) was lower than I had predicted.
My prediction for the Dining Hall area was correct in that there was a high percentage of grass (40%), but less daisies (9%) than expected. During the experiment I discovered large amounts of buck-weed (33%) among the grass, this plant has a small leaf surface area, therefore could be expected to thrive in this sunny place.
The results show that the narrower leafed plants i.e. plants with a small surface area, thrive in the sunshine but tend to do less well in shaded areas. Whereas moss and plants with a large surface area can thrive in reduced light conditions.
By
Robert Clark 11TL
Windsor School