The amount of nitrogen used on rice plants affects how much rice is produced. When less nitrogen is used, the rice grains are smaller because the plants put more energy into their leaves. But when more nitrogen is used, the grains are also smaller because the plants grow too quickly. To get the best rice, the number of spikelets per rice plant should be around 194. This study looked at different types of rice plants in China and found that using 150 kg of nitrogen per hectare is best for growing good quality rice.