1. From the point of planting soil, the soil where Dioscorea opposita grows is hard, sticky and hard, which is not easy to grow; Sandy soil iron stick yam grows in sandy soil with high sediment concentration and high water content, so the soil is loose. Henan specialty dried yam # Tiegun yam # Students of Jienong University

Secondly, from the appearance, loam iron stick yam is relatively short, about 30-50 cm, and very few are more than 60 cm. Uneven thickness, irregular shape, crooked, not too straight, not as good as sand yam. The sand iron stick yam is quasi-cylindrical, about 2 cm in diameter and usually 40 cm to 80 cm in length. There are also a few more than 100cm, which are relatively straight. The epidermis is grayish brown, densely covered with fine hairs, and has dark spots of purple.

Third, from the taste point of view, glutinous iron stick yam has less water and is more sticky. Boiled in water for a long time, it is more solid and soft. The water content of iron stick yam is slightly higher in sandy soil, and its taste is not as good as that of iron stick yam in loam.