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Fertilizers On The Growth Rate Of Plants

Paper Type: Free Essay Subject: Biology
Wordcount: 4533 words Published: 3rd May 2017

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This experiment was designed to compare the effectiveness between eggshell and rice husk ash (RHA) on the growth rate of plants, also to compare effectiveness of these two substances as organic fertilizers with the normal used organic soil mix. The methodology employed was by using same amount of subjects (fertilizers), which was three quarter of the pot is occupied by fertilizers. Each fertilizer was tested by using three plants of the same species at the age of two weeks. The readings of eight plants (included two plants that used as control) were collected for three months by weekly. Taking a general overview, the growth rate of plants that used eggshell as fertilizer was higher than that of RHA’s with the mean of growth rate of 37.3% and 13.8% respectively. Statistical testing was demonstrated on the data collected using Kruskal-Wallis’s test and resulted in rejection of null hypothesis which stated that there would be no significant difference between the rates of growth obtained from the plants of these two fertilizers. The results eventually supported the experimental hypothesis that said there was significant difference between growth rate for the plants with eggshell in its soil and RHA’s as the test statistic for the fertilizers was greater than that of critical value at 2.5% significant level.

Key words- Eggshell, Rice Husk Ash, Fertilizer, Plants, Growth rate

Research and Rationale

This experiment aims to investigate two different substances; eggshell and rice husk ash (RHA) which were believed could act as fertilizer to plants, hence evaluating the effectiveness of both in increasing the growth rate of plants.

Many experts believed that the eggshell is made up of 95% of calcium carbonate, CaCO3 or even greater than that. Since it is made up of calcium, then came the idea that it can provides the plant with calcium nutrient. Calcium as what we knew is an essential nutrient for growth and development of cells in plants. Some of the experts said the eggshell not only can provide the plants with solely calcium nutrient, but within 5% of eggshell, there are other trace nutrients such as magnesium, phosphorus, potassium and zinc. All these nutrients are beneficial to the growth and health of organisms [1,2].

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Figure 1: Chemical structure of CaCO3 in eggshell [3].

The calcium carbonate in egg shells is similar to the common soil additive lime that probably the best natural source of calcium for plant. Eggshell mainly consists of calcium carbonate, which was why this compound does not very soluble in water. Despite of their highly insolubility in water, calcium in eggshell improves the plants growth by balancing the pH level of highly acidic soil. This is due to the carbonate, CO3 group that present in eggshell. Plants vary in their capability to absorb nutrients because they have roots with different structure. Other environmental factors, such as water and temperature can give effect on both root growth and nutrient availability. Unless it was grounded into very fine form such as powdered or liquefied form [4]. Eggshell also being sprinkled around the plants to prevent pests like slugs and cutworms from reaching them but it only works if the eggshell was not in powdered or liquefied form. This is because the sharp sided of roughly crushed eggshells that make pests away and this clearly show eggshell can non-toxic pest control too.

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Next, I decided to use RHA as one of my subjects when conducting the experiment because I have heard a lot that it could act as good fertilizer for plants, especially for vegetable plants (but I have used flower plant for my experiment). My hometown is well-known as “Rice Bowl of Malaysia” for the reason of producing nearly more than half of the country’s home grown rice supply. After the paddy fields being harvested, it will be burned to turn into the rice husk ashes. Some research has been done by experts to show there are still nutrients within the ashes of paddy field. RHA consists of more than 80% of Silica and the rest are other essential nutrients such as Phosphorus, Potassium, Magnesium and Calcium. However, it can’t be denied that there were too little essential nutrients present in RHA but in the large amount of RHA, these nutrients might be a lot too [5].

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The eggshell not only gives advantages to the plants by providing nutrients to them but also gives good effect on human bodies. A study done by Dutch has revealed that the eggshells have a lot of beneficial on human as it would give positive effect when combined with other nutrients. Based on double blind placebo study, when nutrients like magnesium, zinc and vitamin D were combined to eggshell, the bone density had increased after one year. Another research at Japan Women’s University, Yokyo also reported the same result when they had conducted the experiment on animal which has osteoporosis. The well combination of vitamin D3 with the eggshell helps in raising the density of bones without gives any obviously increment in blood calcium levels [6]. Even though this study was on mammals, but it still bringing the scope of growth rate of organism, so I had assumed it was more or less will give the good effect on plants too.

Recent studies from University of Calcutta again revealed eggshell do lots more than just offering the calcium whether to plants or human. They have demonstrated that the eggshell could help in prevent further climate change by its capability to absorb greenhouse gas Carbon Dioxide nearly seven times its own weight. They also suggested that a weak acid could make the shell acts as the Carbon Dioxide adsorbant which is by separating the membrane from its shell [7]. This study has clearly showed that organic fertilizers like egg shells are eco-friendly.

On the other side, The National Agricultural Research Center and Takata Engineering Corp. of Japan have successfully developed the quality fertilizer from RHA. They created the fertilizer which has highly soluble of Silicic Acid on October 2004 which was purely from RHA. This was done by using specific technology developed by their company and they believed that by applying this fertilizer back to the paddy fields, a rich harvest of rice could be yielded [8]. While there is one studies approved that RHA contains source of potassium which could help in growth of plants. This indirectly can constraint some chemical fertilizers [9].

Hence this investigation is such an attempt to explore personally how effective are both substances to act as fertilizers. There are many benefits will be contributed to the environment by using both eggshell and RHA as fertilizer domestically. Not only organisms could taste the benefits but the environment would also be free from other current problems.

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Experimental Hypothesis

The soil mixtures of eggshells and rice husk ashes will not lead to the same rates of growth on plants because they having different compositions of nutrients within the mixture (fertilizers) itself.

Null Hypothesis

There is no significant difference between the rates of growth obtained from the plants which were planted using the eggshells and the rice husk ashes in the soils.


Manipulated variable : Type of fertilizers (Crushed Eggshells, Rice Husk Ashes (RHA))

Responding variable : Growth rate of plants (based on number of leaves calculated)

Fixed variable : Type of plants (Murraya paniculata, commonly called orange

jasmine), amount of water and light provided, age of the plants

(two weeks old)


10 inch flower pots, cultivator, plastic storage bag, rolling pin, gloves and airtight container.


Orange jasmine plants (two weeks of age, organic soil mix, chicken eggshells, rice husk ashes and piped water.

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A trial experiment has been conducted for exactly three weeks just to determine which fertilizers could lead to the most noticeable result in its growth rate.

Number of plants used = 4 (2 were using eggshells and 2 were using rice husk ashes)

Crushed eggshells (in powdered form) was mixed with the readily mixed organic soil and put into the flower pot right after the plants were in. The amount of powdered eggshells put into the pot was half of the pot itself. While for another two plants, the organic soil was mixed with the rice husk ashes. The plants were watering 2 times per day regularly and were put under the shady place.

Trial Result

Observation was carried out for three weeks.

The trial results showed that the mixture of eggshell and the soil gave just a little more production of leaves (thus its growth rate increasing) compared to the RHA’s. Based on this trial results I decided to continue the real experiment by using both the eggshells and the RHA as the fertilizers because both of the subjects (fertilizers) shown the increment in plant’s growth rate. Moreover, there were only slightly differences between both of their growth rate.

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Real Experimental Procedures

I have used powdered eggshell which I assumed that it would give faster and noticeable results. While for RHA, it was readily in fine structure after being burned.

First for eggshells fertilizer, the eggshells were rinsed under cold water and dried completely. They were stored in an airtight container before being used.

The eggshells were placed in the plastic storage bag and rolling pin was used to crush them as fine as possible before being grinded into powdered form.

Then, the fine powdered eggshell was mixed with the soil (organic soil mix) thoroughly by using cultivator with three quarter of the mixture was the eggshell itself.

Before the soil mixture was put into the pot, holes under the pot were closed with small rocks so that the holes’ sizes were not too big.

The mixture was put onto the pot right after the plant was in. Lastly, to moisten the soil, plant was watered. Step 3 till 5 was repeated for the next two plants.

While for the other three plants, the same organic soil mix was mixed with the rice husk ashes (RHA) which was three quarter of the mixture must be from RHA only. The holes under the pots were closed with small rocks too. This step was repeated for another two plants.

Next, two plants were planted using the soil organic mix only, no other substances.

The plants were watered with piped water to moisten the soil mixture twice a day.

The observation was carried for three months (12 weeks) and numbers of leaves were calculated by each week and the growth rate was determined.

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Risk Assessment

The rinsed out eggshells could be added up with the compost but the eggshell was made sure to be rinsed out first so that it was not rotten in the compost which would attract other insects and flies to reach the plants.

Cultivator was used carefully during mixing up the eggshell and RHA with the organic soil and when the cultivator was used to mix the soil evenly one more time inside the pot, cultivator was handled more carefully as to avoid touching the young roots.

Gloves were worn while crushing the eggshells to avoid any injuries. The leaves were left not too wet and not too dry. This is because excess moisture may promote the growth of bacteria thus lead to less oxygen availability as to compete with the growing bacteria, infection and diseases will also develop. The soils contents should be kept constantly moist but not wet. When the contents were too dry, the process of eggshell degrading and other nutrient delivering process will take too long to respond.

The holes under the flower pots were closed using small sizes of rocks for both fertilizers used (not for control). The open holes allowed the powdered eggshell and RHA to be carried along with water, this eventually will reduce the reliability of my experiment, so the holes were closed using the small rocks.

Any grasses that growing inside the pots were pulled out as to avoid interspecific competition with the plants.

Data collection in the real experiment

Number of plants used = 8 (three was using eggshell, three was using rice husk ashes and another two acted as the control)

Observation on their number of leaves and flowers were carried out for about three months.

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Mean of number of leaves calculated

Growth rate, % =

Differences between mean numbers of leaves of each week with the mean at its initial X 100

Mean of number of leaves at its initial


Growth Rate (%)

Plants with eggshell (with 577 leaves at initial)

Plants with eggshell (with 577 leaves at initial)

Plants with eggshell (with 577 leaves at initial)

Statistical Analysis

As there were three samples, I have chosen Kruskal- Wallis procedure to perform this test (by using Chi-square distribution) because I want to show that from these three samples of soil mixtures, all of them are not contributing in the same growth rate of the plants.

α = 0.025

df = k – 1 = 3 – 1 = 2 ; k= number of samples used

Thus, the critical value at the significance level of 2.5% is () = 7.38C:UsersuserDocuments6UNchisquare.jpg

Table 4: The values which a random variable with the distribution on v degrees [10]

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Figure 4: Graph of distribution with experimental critical value

(Kruskal-Wallis Test is always right-tailed)


An analysis using Kruskal-Wallis Test pointed out that calculated test statistic, H was greater than the critical value at 2.5% significant level. There was significant difference between the number of leaves for the plants (growth rate) with eggshell in its soil and plant with RHA in soil. Hence, null hypothesis is rejected and the experimental hypothesis is accepted.

Data Analysis

In my experiment, eggshell and RHA were used as both showed increasing reading of their growth rate after conducting the trial experiment. This indicated that both has their own potential in bringing plants the essential additional nutrients so that growth rate increasing. For the real experiment I had used only two plants were using organic soil mix as their only fertilizer in order to maintain the control state. The plants under the control condition increased steadily throughout the weeks but still cannot outweigh the other plants which were using eggshell and RHA. This approved that the experimental hypothesis was true.

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In table 2, it shown that all readings for mean of numbers of leaves were increasing except for week 12 of the eggshell. From 924 mean number of leaves in week 11, it reduced by nine leaves in the next week. This could be the lack of other nutrients besides of plenty calcium present in it. Lack of uptake of other nutrients will lead to more deficiency in plant. For instance, lack in iron could be the reason of reducing of numbers of leaves as it (iron) involved in reaction of cell growth.

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After bar chart of figure 2 was plotted, I had assumed that my earlier thought of using eggshell as fertilizer was far more effective compared to others was definitely correct. This is because the plotted graph was obviously showing that plants with eggshell in soil increasing in significantly huge amount in the growth rate (%). Plant with the eggshell in its soil has greater number of leaves thus shown that its growth rate was significantly higher compared with the plants with RHA. However, plants that using RHA also showing the increments but just in small percentage throughout the weeks. This might be the lack of essential nutrients in RHA compared to in eggshell. As being stated earlier, RHA mainly made up of Silica which as far as I know don’t involve in plant growth at all. I considered this experiment successful because of both eggshells’ and RHA’s showed their effectiveness by increasing the growth rate of plants while compared to the plants that only used normal organic soil mix.

Based on figure 3, it shown that mean of growth rate by using eggshell as fertilizer has great difference to both RHA’s and the control’s. The mean of growth rate (%) due to eggshell as the fertilizer is 23.5% higher than RHA’s. So, the percentage difference between both is 63% which is more than half. By comparing between the eggshell’s and the control’s, the difference is 27.7% and it is significantly huge compared to the difference of growth rates’ mean between RHA’s and the control’s which is only 4.2%. Thus, the act of eggshells as fertilizer proved to be more effective than the RHA’s.

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Error bars are displayed on each fertilizer used to represent the overall distribution of the data. Upper error for RHA was not overlapping with the range of value within the error bar of eggshell. So again, these two mean of growth rate percentages differ significantly. This supported the idea that by using the eggshells as fertilizer, the plant’s growth rate would be higher compared the RHA as fertilizer.

Plotted graph in figure 2 shown the trend that sort of normal distribution but as the sample used was small; I can’t predict well whether the data obtained was normal or not, so the test of Kruskal-Wallis was used. This test demonstrated that there was sufficient evidence that there has been a change/difference (not identical) in growth rate between the most major nutrient present in soil and the most minor nutrient present in soil. Growth rate here was referring to the number of leaves calculated [11, 12, 13]. Eggshell was made up of more than 95% calcium carbonate while the rest 5% can be calcium phosphate, magnesium carbonate, soluble and insoluble proteins [1].

This indirectly would provide plants the calcium they need. Constant availability of calcium would help in encouraging the cell division of plant continuously. Plus, with the presence of calcium, the aeration and drainage of soil will improve. Good soil aeration would help the process of delivering essential nutrients to the roots run smoothly [14]. For RHA, most of it consists of Silica and just a little of other nutrient that needed by plants available such as potassium [9]. This will be discussed in evaluation part.

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In order to minimize the degree of errors and increase the reliability in taking the readings and calculating, large samples were used for each fertilizer. Just for the trial part, I used two plants for both eggshell’s fertilizer and RHA’s fertilizer. While for the real experiment I have used three plants for both fertilizers and also two plants were used to act as the control for the experiment. As being stated earlier, for control I only used organic soil mix for its soil, no additional substances added. Moreover, this experiment has been conducted for nearly three months to observe the continuity of the results. All plants were planted first for a month using the explants. The eggshell was crushed into powdered form in order to help it degraded faster. Numbers of leaves was chose to be the measure of growth rate because it was the most noticeable outcome for younger plants and the easiest way readings to be taken.

Throughout the experiment, no anomalous readings were obtained. However, there was reduction in number of leaves produced for eggshell’s fertilizer. Besides that, the leaves turned yellowish, some of them had yellow spots on the surface while the premature leaves started to fall-off. This happened during last week of observation (week 12). Having lack of uptake of other nutrients might be the reason why. I assumed that eggshells on week 12 have fully decomposed into calcium; this eventually would make the calcium to accumulate in root part. This accumulation might cause less or avoid the uptake of other nutrients that needed for plant growth such as Nitrogen, Phosphorus, Magnesium, Potassium and Zinc. Excessive Calcium caused Iron deficiency, because besides acts as an Oxygen carrier, Iron involved in reaction of cell division and growth. However, it can’t be denied there was high probability that the multiple deficiencies occurred at the same time, so leads to the symptoms on plants. The same concept applied when there is other nutrient present excessively; as one nutrient present excessively this will lead to other nutrients less uptake [15, 16].

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Nevertheless, the growth of plant relies on both internal and external conditions since its seed germination. Vital external factors like water, sunlight, temperature and oxygen could give huge effect on the plant itself not solely depend on the nutrients uptake from the root [17]. Then, to make the outcomes reliable and no anomalous cases happen, I have placed the subjects (plants) all in the same location, which could be considered as shady and not being hitting by sunlight directly; as to minimise the rate of transpiration within the plants.

Even though RHA consists just a little essential nutrients required by plant (80.26% Silica) [5], it does provided the root system a good drainage and aeration like the eggshell’s fertilizer did but even better. This is because RHA is highly porous, lightweight and has fine structure compared to eggshell. So, high probability all nutrients within the RHA could be delivered to the root effectively despite of small percentage of required nutrients present.

The results were considered to be valid and reliable since the experiment was carried out for such a long period of time and being controlled with low degree of errors and large sample size.

Limitations and Modifications

While conducting this experiment, some limitations appeared. In the case of crushing the eggshell, the result could be better if the food processor was used despite of using the normal grinder. The external factors such as temperature, humidity and light were barely to be controlled throughout this experiment. The mixture of each fertilizer with the organic soil also could be biased; this is regarding the difference in size of particles of the eggshell and the RHA. RHA is finer in its structure and partially soluble when diluted with water.

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Contradict; the eggshell was not so fine even in the powdered form or even insoluble in water. So this gave rises in different dilution of fertilizers in the pot. The eggshell might be more concentrated in its mixture compared with RHA. Some of RHA could be flow out along with water left the root with lesser nutrient availability. Size of pot used (10 inches) should be different to each fertilizer used. This is because both fertilizers do not has same solubility level corresponding of the same weight used. For RHA, the flower pot used should be bigger than the eggshell’s.

Lastly, I assumed that even though my results obtained via this experiment could be different to other’s experiment out there, I believe the reason of different species of plant used would be matter. Different species would act differently, as there are uncontrollable genes flows within the species itself.

This investigation could have been improved by using other method. The eggshell may be degraded further if the inner lining is removed and continue with using the acid solution to it after the heating process is carried out. But the acid must be choosing correctly so that the soil would not be too acidic thus affect the growth later on. It is the best to use Sulphuric Acid as it can reduce the pH better than other acids would. Different chemicals and testing methods will extract different quantities of nutrient from soil. Therefore, different testing methods could be used for different soil properties.


The eggshell as fertilizer is more effective compared to RHA and normal used organic soil mix. The mean of numbers of leaves of eggshell’s always outweighed the mean numbers of leaves of RHA’s. The different growth rates resulted in both fertilizers used because both of eggshell and RHA having different compositions of nutrients within (fertilizers) itself. Plant with the eggshell in its soil has greater number of leaves thus shown that its growth rate was significantly higher compared with the plants with RHA. The Chi-square distribution gave critical value, 7.38 which was smaller than test statistic worked out by Kruskal-Wallis’s test, test statistic, H = 15.03. Since H (15.03 > 7.38), so it falls in the rejection region of null hypothesis, H0. Hence, null hypothesis is rejected and the experimental hypothesis is accepted.

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Evaluation of sources

A range of sources have been selected to use in my study. For source 1, it is a website that owned and managed by a professor from department of chemistry in Frostburg State University, Frederick A. Senese which I considered as convincing explanations has been voiced out.

Next, sources 2, 5 and 9 are scientific journals that specifically designed for the subjects I have used in my experiment; 2- eggshell, 5 and 9- rice husk ash. These pieces should have a high level of scientific credibility as they were written by experts at their cutting edge of their respective field, for instance the author for source 2 was the past president of world’s poultry sciences association, Hunton P. Plus, I assumed those have undergone intensive reviews before being published so all of these journals are trustable.

Sources 3, 4, 6, 10- 13 and 15-16 are free-content web-based information which I believed is continually improved and updated, that leading to upward trend of quality, thus the information could be assumed as reliable. Source 7, is a well-known free online news source that giving out the latest research news on variety of topics hence the information presented on the website should be correct. Same goes to source 8, it is also provided the most recent information but more specific on environmental topics from Japan. It presents information from most reputable sources including government, educational and industrial so no biased viewpoints will appear. Sources 14 and 17 are published books hence the explanations it contains must be factual and reliable, unless the information given turn out to be out of date.

All in all, I do not hesitate to say that the sources I have referred to are reliable and trustable.

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