2016 Volume 84 Issue 1 Pages I_39-I_46
This study aimed to clarify the relationship between the occurrence of rhizophore lesion and soil water transport properties using a numerical analysis in Chinese-yam upland fields in the Kamikita region of Aomori Prefecture in 2014. We investigated the impact of planting trenches formed using either chain-type or wheel-type trenchers on soil physical and chemical properties and moisture transport characteristics. The soil of a wheel-type trencher test plot at a depth of z > 70 cm was found to have low permeability; thus, the difference in the method of formation of the planting trench was revealed to have a significant effect on the water transport properties of soil at a depth of z > 70 cm. In response to the above, in the wheel-type trencher test plot during the heavy rain period in August 2014, the soil in the vicinity of tuber of the Chinese-yam was saturated. In addition, the results of numerical analyses revealed that, if the saturated condition persists for a long period, it poses a high risk of moisture damage to the Chinese-yam in the test plot for the wheel-type trencher. Thus, these results indicate a high probability that microbism and malformation around the tubers of Chinese-yams occur during this period.