How does the amount of fertilizer affect the

height of a soybean plant?

By I.M. Scientist

Purpose QuestionWhat is the effect of amount of fertilizer on

the height of a soybean plant measured in centimeters?

Background Research1. What is fertilizer?Fertilizer is a supplement that contains 3

macronutrients that plants need: nitrogen, phosphorus, and potassium. The numbers on a bag of fertilizer tell the percent of each of these macronutrients. The rest of the stuff just provides a vehicle to deliver the macronutrients.

Background Research2. What do soybeans need to grow?Soybeans grow best in full sun and in warm

weather. They prefer a rich soil, high in nitrogen, with a pH between 5.5 and 7. Soil should be kept moist and well-drained for optimum growth.

Background Research3. What different types of fertilizer are

there?Fertilizer can be quick release vs. slow

release, liquid (which is more quick release) vs. solid, organic (which tends to focus on only one nutrient so has to be mixed). Fertilizer also differs in the percent of macronutrients.

Materials Soybean seeds Soil Tap water 12 ounce plastic cups Permanent marker Miracle Gro brand fertilizer Measuring cup Ruler Cell phone camera Paper Pencil

Procedures Gather materials Label cups A, B, C, D, E, and F using a permanent marker Fill each cup with 4 ounces of soil, measured using a measuring cup Place 2 soybean seeds on top of soil in the center of the cup Cover seeds with 4 more ounces of soil Pack down soil lightly Add 1 ounce of tap water to each cup using the measuring cup Add 1 ounce of fertilizer to cups A and B using the measuring cup Add 2 ounces of fertilizer to cups C and D using the measuring cup Set cups on window sill in the sun, 3 inches away from the window For 10 days, measure height of plant using a ruler at 5:00 pm. Record

values in table. Take pictures of plants every other day for 10 days using cell phone

camera. Water each cup with 1 ounce of tap water every other day. After 10 days, plant soybeans in the ground or bring to school. Project is

complete.

HypothesisThe cup containing the most fertilizer will

cause the soybean plant to grow the tallest because fertilizer provides plants with extra nutrients to grow.

Cup & Condition

Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day 10

1 oz.fertilizer

0 0 0 0 0.5 0.6 0.8 0.8 0.9 1.1

1 oz.fertilizer

0 0 0 0.4 0.4 0.5 0.7 0.8 0.8 0.9

2 oz.fertilizer

0 0 0 0.5 0.7 0.7 0.9 1.0 1.1 1.3

1 tsp fertilizer

0 0 0 0.6 0.6 0.8 0.9 1.1 1.2 1.3

No fertilizer

0 0 0 0 0 0 0.3 0.4 0.4 0.5

No fertilizer

0 0 0 0 0 0 0 0 0 0

Data -- The effect of amount of fertilizer

on height of soybean plants

Height of soybeans in cm over 10 days

0 1 oz. 2 oz.0

0.2

0.4

0.6

0.8

1

1.2

1.4

Effect of amount of fertilizer on average growth of soybean plant over 10 days

Amount of fertilizer added

Heig

ht

in c

mData

Data AnalysisAverage growth of beans

With no fertilizer: 0.5 + 0 = 0.25 cm 2

With 1 oz. fertilizer: 1.1 + 0.9 = 1.0 cm 2

With 2 oz. fertilizer: 1.3 + 1.3 = 1.3 cm 2

Data AnalysisThe expected results of this experiment were that the soybeans

grown with 2 oz. of fertilizer would grow the most and the soybeans grown without fertilizer would grow the least. The actual results matched the expected results. The average growth in the two trials using 2 oz. was 1.3 cm, the average growth in the two trials using 1 oz. was 1.0 cm, and the average growth in the two trials without fertilizer was 0.25 cm. Even if the soybean that did not grow is not counted, the growth was still only 0.5 cm.

One source of error is that the growing beans were transferred from one location to another (school to home) after three days so that their growth could be measured every single day. To correct for this, the beans should be planted in a location that is accessible at all times.

ConclusionThe purpose of this experiment was to determine the effect of

amount of fertilizer on the height of soybean plants. The hypothesis being tested was that adding more fertilizer would cause plants to grow taller. To test this hypothesis, soybeans were grown from seed for 10 days using no fertilizer, 1 oz. of fertilizer, and two oz. of fertilizer. They were given the same amount of water and exposed to the same amount of sunlight and measured at the same time every day. The results of this experiment support the hypothesis. At the end of 10 days, the plants with 2 oz. of fertilizer had grown an average of 1.3 cm, the plants with 1 oz. of fertilizer had grown an average of 1.0 cm, and the plants with no fertilizer had grown an average of 0.25 cm.

CitationsMackey, Betty. "Preparing Garden Soil." TLC Home gardening tips. n.

page. Web. 12 May. 2012. <http://tlc.howstuffworks.com/home/preparing-garden-soil6.htm>.

none, none. "How to Grow Soybeans." Gardener's Network. n. page. Web. 12 May. 2012. <http://www.gardenersnet.com/vegetable/soybean.htm>.

none, none. "Understanding Different Types of Fertilizer." Life123. n. page. Web. 12 May. 2012. <http://www.life123.com/home-garden/gardening-tips/soil-fertilizers/understanding-different-types-of-fertilizers.shtml>.