The soil particle composition of grassland is affected slightly by the cover-degree and yield of grass in the loess Plateau.It is mainly affected by the distribution of soil zonality of soil zonality.The volume weighet and total porosity of grassland are affected by the cover-degree and yield of grass.When the cover-degree and yield are low

the soil volume weight is greater than or equal to 1.20g/cm2and the soil tatal porosity is around 55%;with the increase in them

the soil volume weight will become less than or equal to 1.20g/cm2 and soil total porosity become greater than or equal to 50%.When the cover-degree and yield are low

there phase ratio of solid

liquid and gas for grassland is 1∶0.10～0.19∶0.60～0.90;conversely

that raito become 1∶0.33～0.75∶1.15～1.76.The soil physical properties of grassland are correlated with litter layer and content of soil organic matter.The soil physical properties and the density of root system are keys to improve characteristics of soil hydraulics

to strength soil anti-scaurability and infiltraion

and to increase slope stability.