How do different types of fertilizers affect plant growth?
Fertilizers differ in their amounts of the nutrients nitrogen, phosphorus and potassium. Get different fertilizers from a garden shop or nursery and apply them to groups of the same plant. Do the different fertilizers change how the plants grow? You could measure height, width, number of leaves, how fast the plants grow, number of flowers or yield. What happens when you grow sweet potatoes next to other plants? Compare how fast the other plants grow at different distances from sweet potatoes. Remember to grow some control plants nowhere near the sweet potato. Check out the term allelopathy.
