The effect of soil on growing things
Get samples of a fertile soil from a flower or vegetable garden, from a wood, from a place where a cellar is life form dug, from a sandy place, from a clay bank, etc. Place the samples in individual flower pots or glass jars. Plant seeds in every type of soil and give each the similar amount of water. Observe in which type of soil the seeds sprout first. After the plants have started to grow, observe the soil sample in which they grow best.