The study looked at how different types of plants can help prevent soil erosion and conserve water on highway slopes in hilly areas. They planted different kinds of plants and found that annual herbaceous plants like Vitex negundo and Setaria viridis were the best at conserving soil and water in the first year. Perennial herbs like Coronilla varia and Lolium perenne took longer to show their soil and water conservation benefits, but eventually did so in the second and third years. The more plants grew above ground, the better they were at conserving soil and water in the early stages, while the root biomass became more important in later stages.