Factors Causing Submergence Damage on Soybean Seedling Emergence under No-Till Culture Conditions

Abstract

Soybean yield in Aichi prefecture, Japan, has been low and unstable due to excess soil moisture during seeding time. We have been developing the production technology including no-till culture to reduce such problems. This study aimed to identify the causes for the submergence damage in no-till culture. In the field experiment, the rainfall on the following day of seeding substantially damaged the seedling emergence, and the damage was more severe in hollowed and portions more distant from the drainage in the field. In the pot experiments under no-till conditions, seedling emergence was damaged by 24-h flooding treatment on the seeding day and 4 days after seeding, while under tilling conditions, the treatment on 3 and 5 days after seeding also damaged the emergence. Experiments on water absorption of the germinating seeds suggested that the damage by the flooding on the seeding day in the pot experiment was caused by the destruction of seed structure due to rapid water absorption. On the other hand, the damage by the flooding 3 to 5 days after seeding may be caused by oxygen deficiency because the seedling emergence force derived from elongating hypocotyl peaked at 5 days after seeding when the seedling may require oxygen most. It is concluded that the reduction or avoidance of the submergence damage during the first 5 days is the key to stable no-till seeding during rainy season in the region.