Abstract:The mineral composition.of clay fraction(<2μ) of about sixty representative paddy soils was studied by X-ray diffraction,differential thermal analysis and chemical methods.It was found Chat in most paddy soils,the mineral composition resembled to the parent soils on which they had developed.For example,both the red soils derived from quartermary red clay and the corresponding rice paddy soils in the subtropic zone of central China possess kaolinite and illite as the predominant clay minerals with comparatively smaller quantities of quartz and montimorillonite."De-potassication" and "De-silication" are the manifest change of clay minerals during the development of paddy soil,where the illite-type clays are partially transformed into montimorillonite and further into kaolinite especially in soils rich in potassium-bearing minerals.

Abstract:The mineralogical constituents of the clay fraction(<1μ) of drab soils,including brown-drab soils,leached drab soils,typical drab soils,yellowish drab soils,and meadow drab soils were investigated by chemical analysis,cation-exchange capacity determinations,X-ray diffraction and differential thermal analysis.Data of chemical analysis show relatively higher contents of Fe₂O₃ and Al₂O₃ in these soils,as compared with the contents of the brown forest soils.The characteristic clay minerals of the drab soils as shown by X-rah diffraction patterns and thermo-differential curves are illite and vermiculite,with kaolinite and montimorillonite as minor constituents.The amount of vermiculite tends to increase from lower horizons to the upper.The soils possess a silica-sesquoxide ratio of 2.5-3.1,K₂O content 2.2-2.6,and canon-exchange capacity 45-60 m.e./100g.Characteristics of mineralogical constituent of drab soils are closely related to their parent materials and also to their environments of soil formation.Soils developed on the lossal deposits contain montmorillonite,but no interstratified clay minerals,whereas soils developed on the weathering products of metamorphic rocks apparently contain ractoriteillite interstratified clay minerals (11.4Å).

Abstract:Field practice has long proved that the application of straw ash on newly reclaimed paddy soils derived from the lacustrine deposit in the flooded areas of Li-Shia-Ho,Kiangsu,greatly increases the yields of wheat,barley and other upland crops.Field experimenter were conducted to compare the effect of superphosphate with straw ash as basic dressings at a same level of phosphate fertilizer.Results revealed that superphosphate has a similar effect as straw ash.Laboratory investigations gave evidences that fixation of available soil phosphorus takes place as the flooded soil dried out through reclamation and drainage.

Abstract: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.

Abstract:Почвы(дерново-коричневые и светлые лутовые) для исследования находятся в провинции Хзнани и в пригороде Пекина.

Abstract:(1) Soil "baking" induced sharp changes of the regimes of water,air and warmth of the rice-field soils,and hence also induced sharp changes in amount and composition of microorganisms.Experimental data shew that there were significant increases in total count,bacteria,actinomycetes and fungi.The ratio of aerobic to anaerobic microorganisms also significantly changed,aerobes increased in number while anaerobes decreased.Obviously,these changes were beneficial to the mineralization of organic N and P,raising up the regimes of N and P nutrients.

Abstract:The majority of citrus trees in Hwangyen district,Chekiang province,are planted on the alluvial soils.These soils are partially in poorly drained condition.Citrus trees occur also on yellow earth and red earth of the same district with a comparatively higher elevation.Microelements in the soils have been determined by polarographic and colorimetric methods.Results show that they contain Cu 1.1-4.1 ppm.,Zn 1.7-64.0 ppm.,Ma 5.6-260 ppm.,Mo 0.02-0.08 ppm.and B 0.4-3.3 ppm.