Does the type of fertilizer you use change how much nitrate washes into nearby water? Nitrate (a chemical found in fertilizers) can seep out of soil when it rains or when you water plants. Too much nitrate in runoff harms rivers and lakes. You fill four pots with soil and carpet grass. Each pot gets a different fertilizer: cow manure, compost, liquid inorganic, or granule inorganic. You water the pots over three days and collect the runoff in trays underneath. Using a nitrate test kit, you measure the nitrate level in each tray's water. The inorganic fertilizers produce much higher nitrate levels in the runoff than the organic ones.