New maize hybrids had larger and deeper post-silking root than old ones

• We examined whether stay-green maize had larger and deeper roots than early-senescing maize at silking and maturity.
• Dry weight, total length and vertical distribution of roots were compared in six maize varieties in two years.
• Stay-green maize had larger root but the same root length and vertical distribution compared with early-senescing maize at silking.
• Total root length of stay-green maize exceeded that of early-senescing maize at maturity, with more deep roots.

Since new maize (Zea mays L.) varieties have higher grain yield, a larger root system with longer total root length and more deep roots is expected for more water and nutrient uptake and shoot biomass accumulation. To compare the differences in root dry weight (DW), total root length, vertical root distribution and post-silking root mortality in the 0–60 cm soil profile between old and new maize varieties with different leaf longevity, a two-year field experiment with six maize varieties with early-senescing (old varieties) and stay-green leaves (new varieties) was conducted. Although the new varieties had larger root DW at silking, which corresponded to their larger shoot biomass, the total root length and vertical root distribution of all six varieties were the same in the 0–60 cm soil profile at the same stage. At maturity, the difference in root DW between the old and the new varieties enlarged, and the total root length of the new varieties exceeded that of the old varieties, with more deep roots. Longer post-silking root length and more roots in deeper soil layers of the new varieties is beneficial for water acquisition in the deep soil layer and nutrient interception such as nitrate in leachate.