Studies on the macropore morphology of grassland soil determined by X-ray and contrast media.

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The purpose of this study is to examine the morphology of macropores in the grassland soils. The morphology of macropores was studied on the universal of the pore formed by roots (rooted pore), the actual condition, the formative period of the pore formed by roots, and pore formed by particles and aggregates. Soil samples were collected from seven domestic and overseas soils. The macropore of particles and aggregates was from quartz sand, glass beads, grain of Andsol, aggregates of the Andsol, and aggregates of earthworm. The morphology of pores showed that the shap of almost all macropores is the rooted pore in the permanent grassland.The pores formed by particles and aggregates were consisted of inter-particles and inter-aggregates, that morphology was a globular form or a rod-shaped form. The Pores formed by aggregates of the earthworm were network structure of the spongy body. In the drainage and water-retention zone, the macropore was consisted of the rooted pore except under the influence of the earth-worm and weather. The morphology of the non-capillary pores observed the rooted pore in the dense and solid sur-face soil layr in Andosol, heavy clay, and steppe soil. The pore direction was in the horizontal and slant in rootmat of the sur-face soil layr, but the sub sur-face soil and subsoil layr is not clear in the steppe soil and brown forest soil in England. The morphology of the capillary pores was shaped by the rooted pore, inter-particles and inter-aggregates in the density and sandy each surface soil layr. The sub sur-face soil layr and subsoil layr were consisted all inter-particles and inter-aggregates in the sandy soil. In the clay soil, all the morphology of macropores was shaped by the rooted pore. The formative period of the rooted pore was for three years. The macropores of the grassland soil consisted mainly of the rooted pore formed by plant roots, that was universal phenomenon in the grassland soil.