Plant Growth in Different Soils

We planted radish seeds (because they sprout quickly) in gravel, topsoil, sand, and clay and then we observed them every day for five days. Gravel, sand, and topsoil all sprouted, while clay had no growth at all. We noticed the topsoil sprouted faster than gravel and sand. We also observed the topsoil had the healthier-looking sprouts. Gravel's sprouts were a bit brown in color, and sand's sprouts were more withered. The kids were surprised the seeds grew in gravel and sand! We discussed that gravel and sand were not providing as much nutrients as the topsoil, hence the pitiful sprouts. Also, clay didn't produce plant growth because it is too packed together to allow roots to grow. We concluded topsoil was the best soil with regards to plant growth.