Wednesday, June 18, 2008

Fertilizer Experiment

Problem: Which chemical makeup of fertilizer: 10-10-10, 30-20-10, or 10-20-30 grows the tallest soybeans?

Hypothesis: I believe that the combination 10-20-30 fertilizer will grow the tallest soybeans. I believe this because soybeans do not need a lot of nitrogen, since they can get nitrogen from the atmosphere, they do not need a lot of phosphorus, since an increase in the amount of phosphorous does not increase the yield of the seed, and they need high amount of potassium, since soybeans use a lot of potassium.

3 Soybeans
3 Pots
Fertilizer 10-10-10
Fertilizer 30-20-10
Fertilizer 10-20-30

1. Line up and label the three pots 1, 2, 3 respectively.
2. Fill each pot with 3 cups of soil.
3. In pot one add 1 tbsp of fertilizer 10-10-10.
4. In pot two add 1 tbsp of fertilizer 30-20-10.
5. In pot three add 1 tbsp of fertilizer 10-20-30
6. Water each pot until the soil is slightly moist – make sure that each pot gets the same amount of water.
7. Each day measure the height of the soybean and record the measurement in a chart.
8. Add water to each pot as needed – make sure that they each get the same amount
9. Repeat steps 7 and 8 for two weeks.

Conclusion: After completing the experiment, I discovered that my hypothesis was incorrect. Although the heights of all of the soybeans were similar after 2 weeks of incubation, the fertilizer with the chemical content of 10-10-10 was 1mm taller. Thus the best fertilizer for a soybean is fertilizer 10-10-10. I believe this is because the plants were in a controlled environment and the potting size was too small for the high amount of potassium concentration in the soil.

Fertilizer and Soybeans

Where do plants get their nutrients?

Just like humans, plant growth and development is affected by the amount of nutrients the plant has in its environment. Many soils are rich in nutrients; however, other soils are completely nutrient diminished. For plants that are growing in nutrient diminished soil, some humans add chemicals to make up for these deficits, and increase crop yields. We commonly refer to these chemicals as fertilizers (Kidder).

There are many different kinds of fertilizers, with many different chemical make ups. The easiest way to find out what components are in the fertilizer bag is by reading the numbers on the bag. Every bag of fertilizer has three numbers that look very similar to this; 10-10-10. Although these numbers are not always the same, they do always represent the same chemicals, and they are always in the same order. This order is Nitrogen-Phosphorous –Potassium. The nitrogen helps with stem and leaf growth, the phosphorous helps with seed germination and root growth, while potassium promotes flower and fruit formation (How Stuff Works, 2008).

How do plants get their nutrients?

Although plants may live in very nutrient rich environment, they may not get the nutrients that they need if there is no water for these nutrients to be absorbed into. Plants absorb the nutrients from the environment through very tiny root hairs. This mechanism of absorption is referred to as diffusion. Once the nutrients enter the root hairs, they are taken to different parts of the plant where they are used to build organic compounds such as vitamins, proteins, and lipids.
Soybeans are very similar to any other type of plant; they need nutrients to live. Many states in the US, such as Kansas and Mississippi, grow soybeans as a main crop. This is important to their agriculture, and can proven through the multiple research projects they have conducted to determine the effects of fertilizers on the soybean (Mississippi, 2008).

Soybeans can convert nitrogen from the atmosphere into a useable nutrient. If the soybean has not been planted in an environment for a significant period of time, there is enough nitrogen in the soil for them to survive. However, if soybeans have inhabited an environment for a longer period of time, they have likely depleted the nitrogen and nitrogen fertilizers are very much needed (Kansas, 2007). As for phosphorous, as long as soybeans have 12mg of phosphorus they will grow. Adding more phosphorous does not cause the amount, or size of the crop to increase. For potassium, soybeans tend to use relatively large amounts while they grow. Many locations that grow soybeans tend to have high levels of potassium in the local environment, so they do not need to add a fertilizer high in potassium.

When I look at the above information I can tell that depending on where the soybean grows, a different fertilizer is needed to grow a health plant. A soybean growing in a farmer’s field for the first time will likely need a fertilizer with relatively low amounts of nitrogen and potassium, and a medium amount of phosphorous, while a soybean growing in a pot will likely need a fertilizer high in potassium, and has medium levels of nitrogen and phosphorous.

Ferguson, Richard B. (Aug, 2003). Fertilizer Recommendations for Soybeans. Neb Guide, Retrieved June 18, 2008, from
How Stuff Works, Inc., (2008). What is Fertilizer and What Does it Do?. Retrieved June 18, 2008, from How Stuff Works Web site:
Kansas State University, (2007). Soybean Scene. Retrieved June 16, 2008, from K-State Research and Extention Web site:
Kidder, Gerald Plant Nutrients and Fertilizers for the Non-Farmer. Retrieved June 18, 2008, from University of Florda Web site:
Mississippi State University Extention Service, (2008,April 3). Crops: Soybean. Retrieved June 16, 2008, from MSU Cares Web site: