The study looked at how different amounts of nitrogen fertilizer affected the growth and yield of spring maize in Northeast China. They found that using the right amount of nitrogen can increase grain yield, with a ratio of 1:2:2 being the most effective. Applying too much nitrogen early in the season can lead to nitrogen loss, while high nitrogen levels later on can leave excess in the soil after harvest. To get high yields and use nitrogen efficiently, farmers should match fertilizer amounts to the crop's needs at different stages and the soil's nutrient levels.