How does the amount of fertilizer affect the height

of a soybean plant?

By I.M. Scientist

Purpose Question

What is the effect of amount of fertilizer on the height of a soybean plant measured in centimeters?

Introduction

Fertilizer is a supplement that contains 3 macronutrients that plants need: nitrogen, phosphorus, and potassium (Evans, 2000). The numbers on a bag of fertilizer tell the percent of each of these macronutrients (Evans, 2000). The rest of the stuff just provides a vehicle to deliver the macronutrients (Evans, 2000). 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) (Kopec, 1994; Evans, 2000). Fertilizer also differs in the percent of macronutrients (Evans, 2000).

Previous studies show soybeans grow best in full sun and in warm weather (National Soybean Research Laboratory). They prefer a rich soil, high in nitrogen, with a pH between 5.5 and 7 (National Soybean Research Laboratory). Soil should be kept moist and well-drained for optimum growth (National Soybean Research Laboratory).

Hypothesis

The cup containing the most fertilizer will cause the soybean plant to grow the tallest because fertilizer provides plants with extra nutrients to grow.

Materials

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

Procedures1. Gather materials2. Label cups A, B, C, D, E, and F using a permanent marker3. Fill each cup with 4 ounces of soil, measured using a measuring cup4. Place 2 soybean seeds on top of soil in the center of the cup5. Cover seeds with 4 more ounces of soil6. Pack down soil lightly7. Add 1 ounce of tap water to each cup using the measuring cup8. Add 1 ounce of fertilizer to cups A and B using the measuring cup9. Add 2 ounces of fertilizer to cups C and D using the measuring cup10. Set cups on window sill in the sun, 3 inches away from the window11. For 10 days, measure height of plant using a ruler at 5:00 pm. Record

height in cm.12. Take pictures of plants every other day for 10 days using cell phone

camera.13. Water each cup with 1 ounce of tap water every other day.14. After 10 days, plant soybeans in the ground or bring to school. Project is

complete.

Data

Height of Soybean for Over 10 Days (Cm) Cup and Condition Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7 Day 8 Day 9 Day 10 A: 1 oz fertilizer 0 0 0 0 0.5 0.6 0.8 0.8 0.9 1.1 B: 1 oz fertilizer 0 0 0 0.4 0.4 0.5 0.7 0.8 0.8 0.9 C: 2 oz fertilizer 0 0 0 0.5 0.7 0.7 0.9 1.0 1.1 1.3 D: 2 oz fertilizer 0 0 0 0.6 0.6 0.8 0.9 1.1 1.2 1.3 E: No fertilizer 0 0 0 0 0 0 0.3 0.4 0.4 0.5 F: No fertilizer 0 0 0 0 0 0 0 0 0 0

The effect of different amounts of fertilizer on height of soybean

Sample Calculations

Average growth of beans (Day 10)

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 Analysis

The 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.

A future experiment could examine if this hypothesis held true for higher amounts of fertilizer. Additionally, a future experiment could investigate the effects of different types of fertilizer on soybean height.

ReferencesEvans, E. (2000). A gardener’s guide to fertilizing trees and shrubs.

Retrieved from: http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/text/fertilizing.html#types

Kopec, D.M. (1994). Easing the roller coaster ride with slow release fertilizer. Retrieved from: http://turf.arizona.edu/tips1094.html

National Soybean Research Laboratory. Soybean production basics. Retrieved from: http://www.nsrl.illinois.edu/general/soyprod.html