2021 Volume 20 Issue 1 Pages 49-55
In order to clarify the nitrogen absorption characteristics of Japanese yam ‘Inabu-2 gou’, we investigated the dry matter weight and nitrogen absorption of each part at different times when the nitrogen application rate was changed. The total amount of nitrogen uptake in stems and leaves increased significantly from July to August and reached the maximum in August. On the other hand, the dry weight and amount of nitrogen uptake of new rhizosphere increased after August. Total nitrogen absorption peaked in September. Therefore, it was considered that the nitrogen supply until September was significant for the growth of Japanese yam. Especially, the nitrogen supply from July to August when the growth of foliage increased was considered to be important. The weight, Brix value, and viscosity of the new rhizosphere cultivated without nitrogen fertilization were not different from those with nitrogen fertilization (30 g-N・m–2). The estimated value of nitrogen mineralization from the soil of the experimental field was higher than the total value of nitrogen absorption at each time. This suggests that the soil may supply the necessary nitrogen with mineralized nitrogen even under the condition that polyethylene mulch is applied but nitrogen is not.
