Abstract:In the famous eolian loess plateau of north China a number of paleosol layers were recognized early.Thirteen layers of buried paleosols can often be found in well preserved late Pleistocene Malan loess and middle Pleistoeene Lishi loess, that deposited during the Brunhes Normal epoeh.Among them,the fifth layer,counting from top to bottom,paleosol in Luoehuan locss section,Shaansi Province,is charaeterized by its greater thickness,red brown colour,and a well developed clay enriched horizons as well as carbonate eoneretions at the bottom.The reversed magnetization observed in samples from the top of soil section records short reversed event during the Brunhes epoch,corresponding to I Biwa reversed event in Japan.Thermolumi-nescence datiilg shows that this unit was formed between 212000-178000 years ago.The Luochuan fifth layer paleosol,with two closely related clay enriched horizons,consists of two thin layers paleosol.Large quantity of illuviation ferri-argillans observed in the soil section show that the elay had been transported and deposited.In addition,results of micropedology and soil magnetization studies,mechanical and chemical analyses prove that the fifth layer poleosol approach burozem type.It is a produet of bioelimatie belt between temperate deciduous-broadleaf forest and dry forest types.As a eonsequenee,the oceurrenee of fifth layer paleosol indicates that the climate in the loess plateau about 0.2 million Y.B.P.,is warmer and wetter than in Holocene at the same place,beeause the nature landscape in Holocene in Luochuan region belongs to steppe type.

Abstract:A tentative system for the classification of the peat distributed in northeastern and northern China is suggested.Present system is proposed for the purpose to see the possibility of this natural resource for agricultural utilization.

Abstract:The present paper deals with the fertility ehange of black soil after its cultivation from the virgin land in Heilongjiang province.Results obtained showed that under the influence of mechanical cultivation and current agricultural system,signifieant changes on the properties of black soil were brought by its cultivation.The development of soil fertility has been found in three stages—aetlvation,cultivation and restoratlon.It was observed tliat with the Increase of the time of cultivation,the thiekness of humus horizon,the oontente of humus,total N,hydrolyzed N and the value of C/N were decreased;at the same time, the soil aggregates were disintegrated gradually,the amount of soil microaggregate and its G₁-fraction,and the humus carbon and total N in both G₁ and G₂ fraction of microaggregate were depressed;the specific gravity and volume weight of soil were inoreased,whereas its porosity was deereased.The amount of available P and K inereased in varying extent following the developing of eultivation of the soil. The crop yield was higher in the first ten years after reclamation, and then a significant depression was found.

Abstract:The potential of phosphorus supply is higher in soil of plain region than those oecurring on hilly land in Liaonillg Provillce.The rate of response of crop yield to phosphatic fertilizer showed no definit correlation with the content of total phosphorus and organic phosphorus,but was highly correlated with the content of available phosphorus.The order of eontent of available phosphorus in neutral and weak acid soil is as follows:Meadow soil>Alluvial soil>Brown earth.As for tlle calcareous soils,the order is:Saline soil>Calcareous meadow soil>Cinnamon soil.

Abstract:Present investigations were carried out by soil column method in the greenhouse and by rainshed method under field conditions.The soil columns liave a cross section of 1m² and a height of 3.2m,provided with glass window in one side for the observation of root development.Movable rainsheds were used to oontrol the rainfall under field conditions.All field plots were isolated by cement Plate of 60 cm depth to prevent the watershed from nearby areas.Detailed treatments for both methods are given in Table 1 and Table 2.Water storage in soil before wheat sowing and water supply during the growing Period of wheat are detailed in Table 3.Table 4 reports the yield of wheat under different treatments.Table 5 and Table 6 analyse the water consumption of wheat plant at the rate of consumption at different growing periods.Coeffieients of the utilization of available water by wheat under field eonditions are presented in Table 8.Descriptions on the root development cnder various soil moisture status are given in Table 7 and Fig.5.Fig.2 illustrates the status of wheat growth by soil column method.Fig.1,Fig.3 and Fig.4 show the characteristics of soil water under various treatments.All explanations can be read in English translation from the Figures and Tables in the Chinese text of the present article,whieh come to the eonclusion that an adequate moisture content in deep soil layer before sowing has benefieial effects on the growth and yield of wheat plant in next year.

Abstract:An endemic heartdisease,which was called "Keshan Disease",has been noted in northeastern China.The soil associated with the disease which was described as the leaehed soil was mainly located on the rolling hills and mountains.In order to study the correlation between the selenium content of soil and "Koshan Disease" the content of trace element selenium in soils of this region was determined. It has been found that the total selenium content of soil in northeastern China varies from 0.015 to 0.540 ppm,with an average content of 0.108 ppm.The selenium content has a close relation with soil organic matter,the more the organic matter,the higher the selenium contains.

Abstract:"Low-tu" has long been recognized as a main soil type in China.This soil is oecurring on the loessial plateau of Shaanxi and Shanxi provinces of northwestern China and developed on drab soil after a long history of cultivation and manuring. Continuous deposition of loessial materials results the soil slightly ealcareous,with a thick and loose surface soil of silty loam texture,characterizing as the "Low-tu" horizon.This old cultivated horizon usually has a depth up to one meter,under which is a clay accumulated layer,subsequently a lime accumulated layer,and then the parent material of original drab soil.Pot culture experiments with corn plant were made separately for the soil samples of these four horizons.The soil and Plants were analysed and interaetions of P-Zn were explained.

Abstract:The available phosphorus waas extracted with 2% of citrie acid from 12 humate Phosphate fertilizer eomposed of different powdered coal^* and rock phosphate.The result obtained showed that most of the extractable phosphorus of the samples was of negative value, while the lowest value was only equal to 14% of the P₂O₅ of powdered rock phosphate.The change of the negative value of the extractable phosphorus significantly correlated with the content of calcium and magnesium in powedered coal. The result also showed that the mechanism of the negative value is mainly due to the secondary retention induced by the calcium and magnesium ions of the powdered coal. Based on the results mentioned above, the phenomenon of negative value can be eliminated by using potassium sulfate or sodium fluoride to control the activities of Ca and Mg ions in the extraction system. In this paper a mixed extractant composed of 2% of citric acid-2% of sodium fluoride-7% of potassium sulfate which can control the activities of calcium, magnesium, iron and aluminium is proposed for the extraction of available phosphate from humate-phosphates. Pot experiment with rice and millet showed that the mixed extractant can basically eliminate the negative value of extractable phosphorus from samples, and the quantity extracted by the mixed extractant is well correlated with absorbed phosphorus by plants from the humate-phosphates as compared with the extraction of 2% citric acid. It is proved that the mixed extractant may be more practical for extraction of available phosphorus from humate-phosphates.

Abstract:建湖县地处苏北里下河地区的东北部,是射阳河下游的水网圩区。全县耕地85万亩,除上冈、建阳两块高地约20万亩,其地面高程(废黄河零点,以下同)在2.0米以上外,其余耕地均为高程低于2.0米的低洼圩区。

Abstract:昆山县城北同心圩,地处太湖湖东阳澄低洼圩区,田面高程2.3-3.3米(吴淞基面),近半数农田在汛期常水位以下,土质粘重板结,通透性差。七十年代以来,随着双三制面积逐步扩大,使土壤渍水时间加长。

Abstract:在田间条件下,定量检测施用化学氮肥后土壤的氨气损失,往往需要很多设备,试验周期也较长^[3-6]。我们在研究碳酸氢铵、氨水在土壤中的扩散损失时,采用了J.H.Baker研究液氨的方法^[2]。

Abstract:我国华北平原土壤质地情况比较复杂,壤土剖面中,在不同部位上往往有不同厚度的粘土层^[6]。土壤中水盐运行的情况密切受土壤质地和地下水位的影响^[5]。如土壤剖面中有粘土夹层,它将在很大程度上影响剖面中水分的分布和运行。