Effects on Anions and Cations Dynamics of the Cropped Soil by Excess Irrigation Treatment during the Growing Period of Chinese Yam in the Byobusan Sand Dune in Aomori Prefecture

Abstract

The ultimate goal of the present study was to identify the factors determining the occurrence of tuber damages in Chinese yam in the large-scale agricultural land in the Byobusan-area, Aomori Prefecture developed by the agricultural land development and reclamation project by the government enterprise. To identify effect on anions and cations distribution in soil under excess irrigation, control and test plots were settled. The latter was subjected to excessive irrigation in a Chinese-yam-planting field of the Shariki construction field, where a deep underdrainage system has been installed. Moreover, the tubes with porous cup to collect the soil pore water were installed at depths of 10, 30, 50, 70, 100, and 150 cm in the plots. To understand the anions and cations dynamics of the cropped soil, the concentration of water-soluble ions (e.g., NO₃^-, SO₄^2-, Ca²⁺), pH, and electrical conductivity (EC) of the soil pore water at each depth during the growing period of Chinese yam was measured. Consequently, the NO₃^- content exceeded 100 mg/L at the depth of 10-30 cm in the control plot in mid-August, owing to leaching and accumulation of solutes depending on rainfall and irrigation patterns. However, in the treatment plot subjected to excessive irrigation, the NO₃^- content exceeded 100 mg/L at a depth of approximately 50 cm from late August to early September. The spatiotemporal dynamics of soil water quality corresponding to precipitation and irrigation patterns during the growth period of the Chinese yam became clear.