The researchers evaluated different types of maize to see which ones are best at using nitrogen efficiently. They tested 30 genotypes at a research station in Zambia, using different levels of nitrogen fertilizer. They found that some genotypes were better at producing grain with less nitrogen compared to others. Six lines stood out for producing more grain per unit of nitrogen applied. Some genotypes were also better at moving nitrogen from the plant to the grain. This study shows that certain maize varieties can be more efficient in using nitrogen, which could help farmers save money on fertilizers and increase maize production.