Science Fair Project: Testing Nitrogen Effects on Bean Growth

Designing a controlled experiment on nitrogen's effect on bean plant height? Here's a precise, reproducible method using individual fertilizer components to isolate nitrogen as the variable.

Materials

• Urea (46-0-0) — nitrogen source
• Triple super phosphate (0-46-0) — phosphorus source
• Muriate of potash (0-0-60) — potassium source
• Bean seeds (bush beans work well for 2-week trials)
• Containers, potting mix, measuring tools

Stock Solution Preparation

1. P/K Solution: Mix 2 tbsp (0-46-0) + 1.5 tbsp (0-0-60) in 1 gallon water ≈ 2000 ppm P & K.
2. N Solution: Mix 2 tbsp urea (46-0-0) in 1 gallon water ≈ 2000 ppm N.

Creating Treatment Levels

Dilute stock solutions to ~100 ppm for plant use (1 part stock : 20 parts water). Vary only the nitrogen solution volume per treatment while keeping P/K constant:

• Control: 0 ml N solution + full P/K
• Low N: 25 ml N solution + full P/K
• Medium N: 50 ml N solution + full P/K
• High N: 100 ml N solution + full P/K

Top off each to same total volume with water. Apply same volume to each plant.

Experimental Tips

• Use 10+ plants per treatment for statistical validity.
• Control light, temperature, water, and container size.
• Measure stem height daily at same time.
• Record leaf count, color, and any abnormalities.
• Bush beans are ideal—fast germination, compact, measurable in 2 weeks.