Can too much fertilizer actually slow a plant down? A small dose of nitrate helps mung beans grow. But higher doses tell a different story. You plant mung beans in six pots and water each with a different nitrate concentration. The range goes from plain water up to 0.5% nitrate solution. You measure the average height every two days for ten days. The beans with 0.1% nitrate grow tallest at 184 mm. Plain water comes in second. Above 0.3%, growth drops sharply. The highest concentration barely reaches 12 mm.