1. Introduction

1.1 Background Research

Before we started our experiment, we had to do some research on the subject. We managed to find a few articles, journals and books related to the subject and managed to gather enough information to get started with planning our set-up. An example of some information we discovered is that pondweed are susceptible to the effects of NPK,
meaning pondweed will be affected by NPK, whether if we add in a little or a lot.

1.2 Research Questions 

The following are our research questions:
  1. If we expose samples of pondweed to different amounts of NPK, how will it affect them? We chose this question as we wanted to find out how we could make us of the positive and negative effects of pondweed in different situations. Hence, if we were able to find out how pondweed is affected by NPK, we could use pondweed to it’s benefits such as influencing the amount of oxygen in a pond or a reducing the risk of soil erosion.
  2. Will they be affected negatively or positively and to what extent. We chose this question as we wanted to know if NPK would affect how pondweed would grow, and that if the positive/negative effects of pondweed would be affected by NPK if it were to be used together with pondweed,

     1.3 Hypothesis
Our hypothesis is that when the amount of NPK in the water rises, the concentration of pondweed in the water would increase. We also predict that if too much NPK were to be mixed in the water, the pondweed in the water will become yellowish and die eventually. Hence, when there is more NPK (nitrogen, phosphorus and potassium) in in the water, the concentration of pondweed in the water would increase until a certain point, where the concentration of pondweed would not increase any further due to the high concentrated amounts of NPK.

The independent variable is:
- The amount of NPK mixed with the water or the amount of NPK to water ratio. Refer to figure 4.1 for the values. The amount of NPK is not affected by any other variable in the experiment.

The dependent variable are:
- The value of Formazin Turbidity Unit (FTU) of the set-up.
- The amount of NPK mixed with the water or the amount of NPK to water ratio changes, as the value of Formazin Turbidity Unit would be affected by the growth of the pondweed.

The controlled variables are as follows:


  1. The type of pondweed that we will be using, which would be taken from the same source. 
  2. Where the pondweed are going to grow in, namely the conditions of growth which would be the lab, such as the air quality and the amount of light (natural and artificial). 
  3. The volume of water in the set-ups, this is directly related to the independent variable but is not part of the independent variable as it will not change no matter the increment or decrement of the values of the independent variable. 
  4. The number of stirs and speed of the stirring, as the fertiliser which is diluted in the water would be affected, hence, we would ensure that this variable is controlled by making sure that it is the same person stirring all the set-ups. 
  5. The stirrer being used should also remain the same while ensuring that all the fertiliser has dissolved properly. 
  6. The quality of water in the set-ups also have to be the same, which would be ensured by using the same source of water.

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