A good compost heap is a matter of providing the appropriate environmental conditions for microbial life.
Humus depends on the action of living soil organisms, such as bacteria, protozoa, fungi, and certain kind of beetles, meaning that the heap with the most living organisms that are in it the more humus it will produce.
As humus decomposes, plant residues are converted into stable forms that are stored in the soil, and are used by plants as food. This does well to the garden as it helps the plants to grow and to stay alive. The amount of humus that is found in the soil also affects the important physical properties of the soil structure, for example the colour, texture and the moisture holding capacity.
Having different soil samples from 2 different locations could change the amount of humus and minerals that is found in the soil, depending on what waste is on particular location.
Compost heap
Variables
The variables that we used in this experiment are,
- Amount of H2O in the soil (g)
- Temperature of the soil (C*)
- The location of the soil.
- Depth of the soil (cm)
- The percentage of humus in the soil (%)
All our variables will be are, the amount of H2o in the soil, the location, amount of soil, the percent of humus found, depth of the soil, and the temperature of the soil. Our in put variable is the location of the soil.
For fair testing, we would have to keep the following variables the same, amount of soil, temperature, depth of soil, and amount of H2o.
Our output variable is the percentage of the humus.
Prediction
I think that when I change the location of the soil, that the percentage of the humus found will also change.
I predict that the soil that has the most compost on it will have the highest percentage of humus found. I came to this conclusion because the pile with the most rotting material on it will produce the most humus, there for there is a result of a higher percentage.
Trial experiment
First we set up a trail experiment to see exactly hoe it worked, and to see if there were any adjustments to be made.
The equipment used was, evaporating basin, tripod, Bunsen burner, tongs and a weighing scale.
First we took the evaporating basin and we weighed it, we then put our soil sample into the basin and reweighed it, this way we worked out the weight of the soil sample and then we recorded it. We then put the soil in to a cool oven and dried it to its constant weight. Next we reweighed it to see if the weight was the same. Followed by this we heated the soil very strongly over a Bunsen burner, the high temperature oxidise the humus. We allowed the sample to cool and then reweighed it, until the weight was constant. We recorded all theses results in the table below. Subsequently we worked out the weight of the humus in the soil, by subtracting the weight of heated soil pus the basin, from the weight of the dried soil plus the basin. This is how we got our percentage of humus,
% Humus in sample = weight of humus in soil sample
X 100
Original weight of soil sample
(Before drying)
For reliability in this experiment we repeated it 3 times also for terms in accuracy. For safety you we had to wear goggles and pick the evaporating basin up with tongs, because it was very hot.
Diagram
Table of results for our trial experiment.
The changes that we made to improve our experiment were to use less soil. Instead of using 40 grams of soil we will use 20 grams, because the drying of the soil took to long. We thought that we might change the amount of time that the soil is dried for; instead of leaving it dry dor 30 mins we changed it to 20 mins. This will speed up the experiment a bit more.
Final experiment
For our final experiment we kept it that same way in which we done the experiment just made the alterations of the time we left it to dry and the amount of soil that we used.
Table of results
Results of experiment of A and B.
To work out the weight of the humus in the soil sample, I subtracted the weight of the heated soil plus the basin, from the weight of the dried soil plus the basin. To work out the percentage of humus, I used the formal shown in the trial experiment, where you divide the weight of the humus in the soil sample by the original weight of the soil sample before the drying and times that by 100.
Analysis
There is no specific trend or pattern for the individual results of this experiment. Garden B obviously had a higher percentage of humus in the soil then garden A did. Garden A ranged from 2.8% to 3.6% of humus in the soil, Garden B ranged from 11.5% to 11.9%.
The best result I obtained was the last of the three experiments every time. The percentage was always higher third time around. The soil only took 10 minutes each time to dry to its constant weight.
Which may have been caused by the location of the soil. This must mean that there was a lot of decomposition taken place. Where there is decomposition happening that means that humus will be detectable at the end of the process. As sample B had a higher percentage of humus this suggests that the gardener looking after that soil treated his compost with care and provide for the microbes and insects.
My prediction was fairly correct because I said when you change the input variable that was the location of the soil, that the out put variable which was the % of humus would also change and it did. Garden A’s results were totally different from garden B’s results because of the different locations where the soil was situated. As when the location changed there was a dramatic change in humus levels. This could have occurred because the garden with least amount of humus in the soil had poor levels of living soil organisms like bacteria, protozoa, fungi and certain types of beetles as humus is reliable upon these.
Evaluation
In my experiment I could have repeated the experiment a few more times to make it more accurate and the values of my results more sufficient but this would have taken up a lot of time. I think the method that I used was the only one appropriate, as it did help us to obtain quite accurate results, which allowed us to investigate out problem and find out the answers.
There were some inaccurate results in out experiment, which may have been due to not drying out the soil for a long enough period of time, which would mean that water would have still been in the soil, and that would have caused inaccuracy while we were weighing the two soil samples. The person who was in charge of timing the experiment in burning the soil, may have timed it wrong, which may have made a fault in our results from the weight of the soil after it had been burnt. This would have affected all the results of the humus, as you nee the other results to work out the calculations of the percentage of the humus. The weighing scales that we used may not have been accurate enough as there might not have been the right number of decimal places, which would have caused inaccurate results of the soil.
Our results did match up with other peoples experiment so our results must have been quite accurate.
If there was a further investigation to this experiment, I think I would have chosen what waste materials would have been the best to put on to a compost heap. I would use the same locations as I did in this investigation, but I would separate some of the waste materials and put them into, two separate compost heaps, to see which heap would decompose the quickest, I think that this investigation could be help full to any keen gardener, if they wish to make a compost heap.