The study compared different types of corn to understand why some types are better at using nitrogen efficiently. They looked at the roots of two corn varieties, one with high nitrogen use efficiency (LY13) and one with low efficiency (LD981). They found that LY13 had more roots, especially in deeper soil layers, and absorbed more nitrogen, leading to higher grain yield and better use of nitrogen. This was because LY13 had more total root weight, better root distribution, and longer strong root activity, which helped it absorb more nitrogen and produce more grain.