Behavior of Nutrients in the Rhizosphere of Spinach Cultivated in Light-Colored Andosol Upland Fields

Abstract

The soils around the roots of various kinds of vegetables cultivated in upland fields were separated into three fractions, namely, rhizosphere soil (soil I), soil in root area (soil II) and soil out of root area (soil III). The water-soluble NO_3 and bases, and Truog P_2O_5, together with pH and EC, of the separated soil samples, and N and P contents of the spinach plant were determined. The nitrate contents of the soil samples were in the order of soil I ≧ soil II > soil III in the middle of growth of the vegetables. The Truog P_2O_5 contents of the soil samples from an Andosol field were soil I > soil II ≧ soil III, both in the middle of growth and at harvest of the vegetables, while no difference in Truog P_2O_5 content was observed among soil I , II and III from a Red-Yellow or Brown Lowland field. In the Andosol field, the total-P and Al-P contents of the soil I were higher than those of soils II and III. Soil I contained more water-soluble bases than soils II and III. The nitrate contents of soils I and II correlated well with that of spinach and yield, as did Truog P_2O_5contents of soils I and II did with yield and the P content of spinach in the middle of growth and at harvest.