重粘土草地の乾燥期における根圏土層と下層土間の水フラックス

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Soil water flux between the root zone and subsoil in grasslands (orchardgrass, Dactylis glomerata L.) on heavy clay soils, Terrace Brown Forest Soil (Bf, Typic Dystrochrepts) and Haplic Gray Upland Soil (GrU, Typic Epiaquults), was investigated using the water balance method to analyze the role of upward soil water flux in grass growth during a dry period. The results are summarized as follows. 1) The downward soil water flux from the ropt zone (0 to 0.6 m) to the subsoil (below 0.6 m) showed an average rate of 2.1 mm d^<-1> for Bf and 1.9 mm d^<-1> for GrU during the wet period when the available soil moisture content was high. 2) On the contrary, the upward soil water flux from the subsoil appeared and water was supplied to the root zone throughout the dry period when the available soil moisture content was low. The average upward flux for GrU was estimated at 0.4 mm d^<-1> (20% of the evapotranspiration) and the values for GrU were smaller than those for Bf, 1.0 mm d^<-1> (55%). The difference in the upward soil water flux between Bf and GrU was due to the difference in the unsaturated conductivity between the subsoils. 3) The matric suction of the subsoils for both Bf and GrU increased during the period when the upward flux occurred. Stagnant water level in GrU also gradually decreased during the period of a month from early July, along with the appearance of the upward flux. 4) Soil water in the subsoil was important as a source of upward flux for both Bf and GrU. Stagnant water was also especially important for GrU. The presence of the upward flux in grasslands on heavy clay soils seemed to be one of the significant factors which control grass growth under drought conditions.
社団法人日本土壌肥料学会の論文
2001-02-05

重粘土草地の乾燥期における根圏土層と下層土間の水フラックス

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