A fair experiment
We will have to keep some things the same to make the experiment fair. Here are the things we will keep the same:
- The place where the plants are kept
- They will be measured every week
- They will be watered with the same amount and strength of fertiliser each week
- There will be the same amount of seeds in each pot
- The types of pot will be the same, each with the same amount of holes in the bottom.
- The temperature will be consistent.
The one factor we will change will, obviously, be the strength of fertiliser.
We will measure with a ruler; we will measure the height of the plant in centimetres. We will use a 100cm³ measuring tube to water the plants with.
PREDICTION:
I wondered upon what the general effect of the fertilisers would be on the plant growth and came upon the decision that it would improve the plant growth because from watching the advertisements and realising that a lot of people do use fertilisers that they must be effective.
If the wheat growing with water, as it would if left to grow naturally, were said to be 100% growth, then using the recommended dose of fertiliser (full strength) would, ideally, make the wheat grow 100% more. So the Full strength fertiliser would make the seeds grow 200% altogether. Presuming that the above predictions are correct it would be correct to say that ¼ strength fertiliser made the wheat seeds grow by 125% altogether and ½ strength fertiliser would allow the seeds to grow by 150% altogether. But what about double strength (twice the recommended dose advised by the bottle)? If the normal strength causes the seeds to grow by an extra 100% then it would be logical to conclude that the double strength caused the seeds to grow by 200%. Which would be 300% growth altogether, but I think that this growth would be too great and cause the plant to die and although 200% seems too much I believe that the plant would still grow because of the advertising about fertiliser and the reputation that fertiliser, generally, has of being effective. So I am going to say that my prediction for double strength fertiliser is between 200%-250% because there is a possibility that it may not affect the plants more than the full strength fertiliser.
We used these apparatus:
- Wheat seeds
- Different strengths of fertiliser
- Water
- Disposable plastic cups
- Ruler
- Compost
Safety is vital so it was important that after handling the fertiliser and compost we washed our hands and extremely important that the fertiliser did not come into contact with the eyes or mouth.
Gathering Information
The results were taken weekly so that we would have good results. The seedlings measured were the tallest ten in each pot. The following results are averages.
My predictions seem to be extremely incorrect. The plants that were sustained on water alone grew to an average of 16.8cm. The full strength fertiliser grew to an average of 23.5cm that is only 29% more than 16.8cm; altogether the seeds grew 129%.
The double strength, one that I was most interested in, grew to an average of 22.1, less than the full strength, and 24% more than with water.
Quarter and Half strength were also over-estimated. The quarter strength fertiliser increased the growth by only 6% and the half strength increased the growth by 18%.
CONCLUSION
When looking at the graph it can be seen that the fertiliser seemed to work best in the second week where the plants grew more rapidly than any other time, the steepness of the line shows this. Before that point it was the plants that were watered with water that were growing the best so this backs up the idea that the fertiliser did not have much effect before week 2. After week 2 they grow slower and eventually they would stop growing. If we look at the plant that lived off of water alone we can see that it’s line is beginning to have less of a gradient than the others and this indicates that it had started to stop growing.
Looking at the individual graphs for fertiliser strengths you can see that they take the same patterns as the combined graph of fertilisers. After the first week they start growing extremely fast, this continues for one week and then the pace slows down, we can see this by the gradient.
From this investigation we have found that fertiliser does work but not as well as we are led to believe. The fact that the fertiliser only causes a 30% (rounded to the nearest whole number) is a disappointment because the manufacturers lead you to believe that it will work much better than it actually does.
EVALUATION
Accuracy:
The measuring of the plants was as accurate as possible, as was the watering.
We did not measure they compost to make sure that each pot contained the same amount something we over looked and it would perhaps; have given us more accurate results.
Also some of the seeds grew, but not all. In an ideal situation all the seeds planted would have grown but unfortunately not all of them did.
The results are reliable, in my opinion, there were ways we could have made them more so, but there wasn’t enough time to conduct a very specific experiment. It would have been more accurate to take measurements more than once a week and more accurate if we had perhaps watered them twice a week instead of just one.
Other ways we could have improved this experiment:
- To conduct this experiment during the summer would create better results because of sunlight and warmth.
- To measure, check and feed the plants more than once a week.
- Testing different fertiliser may not have improved the accuracy of the results but it would have increased the range and have being easier to find out which created the greatest increase in growth.
- If the experiment had been done in a natural environment for the seeds. It would have created better results to look at and have produced what would probably happen in a real life situation
- If we had used more seeds we would have had larger results to compare.
I find that the method we used was suitable. We could have watered them more often but that was not possible.
