Increasing crop yields while reducing environmental impacts are a great challenge to ensuring food security and environmental quality for the world agriculture. Increasing planting density appropriately is one of the most effective strategies for increasing maize (Zea mays L.) yield. In China, overuse of nitrogen (N) fertilization on maize has resulted in excessive N surplus in the soil and environmental impacts. To address this challenge we conducted 212 site-year field experiments at two planting densities of 60000 and 75000 plants per ha with the same inputs of N. Results showed that maize yield could be increased 5.59% across China and 10.5%, 2.7%, 5.2% and 10.3% respectively in Southwest (SW), Huanghuaihai (HM), North (NM) and Northwest (NW) maize regions without extra inputs of N. The Life-cycle assessment showed that reactive N loss intensity and GHG intensity decreased by 2.2% to 10.2% across different regions of China, indicating that yield increase could be achieved without extra N inputs and further negative environmental impacts if planting density was increased by 15000 plants per ha under the current condition of excessive N surplus in China. If farmers in China increase maize planting density by 15000 per ha across the whole country the total maize production from the same planting area of 2017 would be 290 Mt which will be close to the expected demand of 315 Mt by 2030 while reducing the environmental impacts of intensive agriculture.
