`AU Buck IV` is a new and distinct Chinese chestnut cultivar that is blight resistant, precocious and an annual bearer. It produces a medium to heavy crop load each year and a large sized nut. Nut drop begins about October 10 and continues for a 5-6 week period. A high percentage of nuts produced drop during the first 4 weeks of the period that nuts drop from this cultivar. `AU Buck IV` is a small tree that is broadly elliptic in shape with high, upright to spreading and diffuse branches that was 8.23 meters tall with a canopy covering an area of 30.19 square meters at 15 years old. `AU Buck IV` is the fourth cultivar to mature and drop nuts in a series of four Chinese chestnut cultivars that will provide for a continuous nut drop of a high energy wildlife food source from late August through mid-to-late November.