Abstract

People are often torn over whether or not to use fertilizers on their plants and crops. With the recent price spikes in nitrogen fertilizers and studies concluding that nitrogen might be leaking into drinking water, people are thinking twice about using them. The object of this experiment to test nitrogen based fertilizers to see if they have an effect on plants. For this particular experiment, Saintpaulia Ionantha (African Violets) will be used along with Miracle Grow for house plants. I hypothesize that the fertilizer will have an effect on the plants, causing the ones fertilized to grow larger and faster than the plants not given fertilizer. Variables observed in the experiment included height, number of leaves, and number of flowers for each plant. After all the data had been collected and analyzed, the experiment showed that the plants given nitrogen based fertilizer grew larger than the plants not given fertilizer, therefore the hypothesis was accepted.

Introduction

As we all know, the world population grows everyday, and everyday more and more emphasis is being placed money and damage to the environment. Fertilizers of any sort can become very expensive, especially nitrogen based ones. That is one of the reasons people today ask if fertilizer really works or not. To the average person who just fertilizes their flower garden, cost usually is not a major concern. These people only want their flowers to grow large and beautiful. On the other hand, to people who own farms or nurseries and depend on the plants for a living, cost is a major concern. 

There have also been a few studies recently concerning the safety of using nitrogen based fertilizers. Many times when the nitrogen is in the nitrate form, the crop is unable utilize the entire amount of fertilizer it is given. This leaves the remaining nitrogen to run with water from the soil into groundwater systems or drainage systems (Jiusheng et al, 2005).

One problem with fertilizer though is that it only stays in the soil for a few days, then has to be reapplied. Urea’s half life, for example, is only about 6 days immediately following transplanting and then falls to only 3 days (Sheehy et al 2005). This fact once again raises the question, are fertilizers worth the extra money and possible harm to the environment?

Objective/Hypothesis

The objective of the experiment is to show effects of nitrogen based fertilizers in hopes of answering the question do fertilizers really work. If the null hypothesis is correct, plants given the fertilizer mixture will not grow larger than plants given no fertilizer. If the hypothesis is correct, plants given fertilizer will grow larger than the plants not given fertilizer and it could be said that yes, fertilizers do work and are worth purchasing.

Methods and Materials

Materials for this experiment are all easily acquired. The materials include 6 plants, 6 pots, potting soil, nitrogen fertilizer (Miracle grow for house plants was used in this experiment), water and a plastic container for the fertilizer mixture. This experiment can be found at http://www.sciencebuddies.org/mentoring/project_ideas/PlantBio_ p012.shml. The original experiment called for eight plants, but due to time and budget issues, only six were used for this experiment.

To begin this experiment, one must first acquire all materials needed. Then, measure equal amounts of potting soil into each of the six pots. Moisten the soil with equal amounts of water, and label 3 pots with “fertilizer” (the treatment group) and three pots with “no fertilizer” (the control group). Now, plant one plant in each of the pots and place near a sunny window. Mix a container of fertilizer according to instructions on the package. Water each plant once a day, and give the fertilizer group the fertilizer mixture once a week. Record the observations in a notebook once a week. Observations should include stem height, number of leaves and number of flowers.

The experiment is being conducted in my apartment, where the plants have access to sunlight and I have easy access to the plants for observations and watering. At the end of the experiment, the values recorded were used to compare the sets of plants and determine which set grew the most. Graphs and tables were then constructed using Microsoft Excel of the comparison.

Results

At the conclusion of the experiment, one can see that the group watered with nitrogen fertilizer once a week grew larger than the group given only water.

Figure 1 shows the height in centimeters each plant grew during the eight week period. Plants 1 through 3 were the treatment given fertilizer and plants 4 through 6 were the control group only given water. The treatment group grew an average of 4.0 cm while the control group only grew an average of 2.6 cm.

Figure 1: Height grown in centimeters of each plant over an 8 week period.

Figure 2 shows the number of new leaves each plant grew during the same eight week period. It is also evident in figure 2 that the treatment group given fertilizer made more progress than the control group without fertilizer. The treatment group grew an average of 11.3 leaves while the control group grew an average of 3.7 leaves.

Figure 2: News leaves grown by each plant over an 8 week period.

Figure 3 shows the number of new flowers each pant produced during the experiment. The treatment group grew and average of 8.3 new flowers while the control group grew and average of 4.7 leaves. After looking at the numbers produced by the experiment, one can see that the treatment group given the fertilizer grew larger than the control group, accepting the hypothesis.

Figure 3: Number of new flowers grown by each plant over and 8 week period.

Conclusions

·          For maximum growth most soils need to be fertilized

·          Nitrogen based fertilizer makes plants grow larger

·          Too much or too little fertilizer has no effect

Acknowledgements

The author would like to thank Elizabeth Yokley for her assistance in gathering the data used for this experiment.