Chemical analysis of seperate plant organs of green manures at various stages of growth collected from representative districts of Central China showed that the accumulation of green mass and the absorption of nutrients chiefly occurred during the last 30 to 45 days before plowing-under.Astragalrts sttzicrrs,the principal leguminous green manure in central China,showed some correlation in P and K contents with soil fertility,whereas the nitrogen content remained practically constant regardless the nutritive status of the soil.It was estimated that the nodular bacteria of Astragalus sinicus assimilated about 105 kg of nitrogen per hectare at the yield of 37,500 kg of green mass.Green-house experiments revealed that manure crops possessed a stronger power in assimilating their phosphgrus from rock phosphate and magnesium from serpentine compared with winter wheat.Laboratory experiments with exciled root also demonstrated that the root systems of manure crops have a stronger absorption power,greater canon-exchange capacity,larger absorbing surface area and more intensive rate of respiration than that of the wheat.Among the tested manure crops,Rapharaus sativus,a cruciferous plant widely planted on infertile soils,has been proved the best variety.