The researchers studied how applying nitrogen fertilizer directly to the root zone of maize plants can improve crop yield and reduce environmental impact. They tested different nitrogen application rates and methods over two years in China. They found that using the root zone fertilization method increased maize yield by 4% compared to the traditional surface broadcasting method. The optimal nitrogen rate for summer maize was found to be between 180-225 kg per hectare when using the root zone fertilization method, reducing the need for nitrogen fertilizer by 14%. This method also improved nitrogen use efficiency and overall productivity of the crop.