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Find out the percentage of humus in the soil.

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Two pupils live next door to each other. The father of one pupil is a keen gardener and he recycles all the biodegradable household and garden waste in his compost heap, which he then spreads over his garden. The pupil after a biology lesson on microbes claimed that the soil from his garden would contain a higher percentage of humus than his neighbours. Investigate his claim.

For our experiment we have to find out the percentage of humus in the soil.


Waste from the kitchen and garden don’t have to be thrown away. It can be condensed and reuse as a fertilizer through the process that is called composting.

A compost heap can be built by layering different kinds of waste in a bin, leaving a small space between the layers so that the air in side can circulate. Air us demanded for the aerobic microbes in the heap so that they can function and work properly, with out the air the anaerobic microbes, which don’t need air, will take over the compost heap and the process will go slow.

Bacteria play an important role as recyclers in the compost. Just like fungi it feeds on dead and dying organisms, breaking down their tissue and cells into nutrient rich molecules some of which remain in the soil and water, which is known as decomposition.

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                                                (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.


Table of results for our trial experiment.

Weight of Evaporating Basin (g)

Weight of Evaporating Basin & soil (g)

Weight of Evaporating Basin & soil after 24 hrs (g)

Weight of Evaporating Basin  & soil after 25 hrs (g)

Weight of dry soil (g)

Weight of Evaporating Basin & soil after 10 mins burning (g)

Weight of Evaporating Basin & soil after 30 mins burning (g)

Weight of humus in soil. (g)









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.

Weight of Evaporating Basin (g)

...read more.


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.

...read more.

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