4. Discussion

4.1 Key findings & Analysis of results

From the results, we can see that the pondweed is growing larger and larger due to the decreased visibility and the increase in turbidity of the water. We can see that the samples with 5 and 7.5 grams of fertilizer grew the most due to the percentage of turbidity increased. Although, the samples with 10 to 15 grams of fertilizer barely grew in the 5 days with only an average of 42 percent increase in mass.

4.2 Explanation of key findings

The pondweed clearly grew a lot when exposed to 5 to 7.5 grams of NPK as that is the optimal amount that benefits the pondweed due to the size the pondweed has grown when in the samples. But looking at the table, when exposed to too much NPK like in the 10 to 15 grams of NPK samples, the pondweed is unable to grow as much or at all due to the overwhelming amounts of NPK.

Our key findings was also backed up by an article by Yard, C. & Care, G. (2016), which states, “ Nitrogen is part of the chlorophyll molecule, which gives plants their green color and is involved in creating food for the plant through photosynthesis. Lack of nitrogen shows up as general yellowing (chlorosis) of the plant. Because nitrogen can move around in the plant, older growth often yellows more than the new growth.
Phosphorus is involved in the metabolic processes responsible for transferring energy from one point to another in the plant. It's also critical in root development and flowering. Because phosphorus moves slowly through the soil, it's important to work it into the soil, where it's needed by the roots.
Potassium helps regulate plant metabolism and affects water pressure regulation inside and outside of plant cells. It is important for good root development. For these reasons, potassium is critical to plant stress tolerance.” Hence, this shows the effects of NPK on plant growth.
However, our findings on how adding too much NPK would affect plant growth negatively is also backed up by an website post by Aggie Horticulture (2016), which states, that plants can wilt when given a heavy dose of fertilizer salts and how plant growth slows down due to salt built-up by excess fertilisation. This shows that it is indeed true that adding too much NPK could cause negative effects on plant growth.

4.3 Evaluation of Hypothesis

The final conclusion matches our hypothesis. Judging from our data, we can conclude that adding 2.5 grams of NPK makes little difference to the mass of pondweed but 5 to 7.5 grams of NPK is the optimal amount of NPK for the best growth of pondweed. When the amount of NPK reaches 10 to 15 grams, the pondweed will be negatively affected by reducing the rate of growth and possibly killing the plant.

Other than the fact that adding too much NPK could negatively affect the plant growth of pondweed, we also concluded that the positive/negative effects of pondweed would not be vastly affected if NPK were to be mixed in the water containing pondweed.

4.4 Limitations and Areas for improvement

Despite our project being a success, we could spend more time on researching data, and planning our timeline better. As we were running out of time, some parts of the project was rushed and sloppy.

During the experiment, we also met with countless difficulties, such as when we were handling with the cling wrap.This is not only due to the fact that we were not proficient in using this item but also the fact that the cups were almost fully filled, hence, we had to be extra careful, making sure that there would not be any spills. We also had to think of different solutions to solve our issues, as during the experiment, we had to change our set-ups due to the items which we purchased failing.

One more area of improvement for our experiment is the location of the experiment. For this experiment, all the set-ups were kept in the engineering lab. Since the lab is used and lights are switched off and on, the temperature ranges from time to time with different conditions of the surroundings, there were a lot of variables we did not take in account and into consideration. The amount of sunlight also varied for each cups, as there was a slight distance between each cup, and the angle of which the light is shining also affected the results of the experiment. Hence, we feel that we should have done the experiment in a controlled environment where there will be less outside factors affecting the growth of the pondweed. This ensures the results of the experiment to be more reliable and more accurate than right now. Such an environment can be stimulated by placing the set-ups in a box with heaters, where it is closed off from everything else. Therefore, no or fewer natural elements will affect the results of our experiment, delivering a more accurate result. The results would also be more accurate as there will be little to no changes in the surroundings.

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