Influence of Water and Salt Stress on Stem Flow Rate of Soybean Plant (Glycine max Merrill)

Abstract

The objective of this research is to examine the influence of water and salt stress on the stem flow rate of soybean planted in sandy clay loam, loamy sand, and rock wool. The experiments of water stress in sandy clay loam and loamy sand showed that the daily stem flow rate was influenced by soil moisture potential than difference of soil texture when the soil water content changed in the range of available soil moisture. The experiment of salt stress in rock wool showed that if the electrical conductivity of water in rock wool was the same, the daily stem flow rates became different due to the history of liquid fertilizer addition. Furthermore, the daily stem flow was constant under less than 2kPa of osmotic potential, but decreased abruptly when osmotic potential increased more than 2 kPa. If the matric and osmotic potentials were low, the stem flow rates became a maximum at 6 hours later after light period started. However, as the matric and osmotic potentials increased, the daily stem flow decreased and the peak of stem flow rate did not become clear.