Tomato Fertilizer Experiment Design: Testing N, P, K Individually and Combined

Science project on tomato fertilization? Use sterile peat moss, 5 treatment groups, and measure what matters.

Experimental Setup

1. Medium: Pure peat moss (no nutrients)
2. 5 groups (10+ plants each):
   • Control: No fertilizer
   • N-only: Urea (46-0-0)
   • P-only: Triple superphosphate (0-46-0)
   • K-only: Potassium chloride (0-0-60) or potassium sulfate (0-0-50 + S)
   • Complete: Balanced organic (e.g., 5-5-5) or N+P+K combined
3. Source fertilizers: Home Depot, Lowe's, Craigslist, local gardeners
4. Apply at equivalent N rates (calculate from labels)

Measurements

• Germination rate, days to emergence
• Weekly: height, leaf count, stem diameter
• Flower/fruit set timing and count
• Final: root mass, fruit yield, total biomass
• Visual: color, pests, disease

Why This Works

Peat moss eliminates soil variability. Single-nutrient groups show deficiency symptoms clearly. Complete group shows synergy. Control shows baseline.

N-P-K Law

Every fertilizer label shows %N-%P-%K by law. Find it. Use it. The numbers don't lie—but they don't tell the whole story without biology.

Good luck. Document everything. Science is in the details.