Abstract:Three leaf stage seedlings were investigated for intake rates of potassium in each 11 genotypes of O.japonica O.indica and O.indica hybrid at different K⁺ levels according to ion depletion.Potassium utilization efficiencies at 3 leaf stage were compared with those at 5 leaf stage to screen efficient genotypes.The suitable potassium levels were 0.2mmo1/L for both O.japonica and O.indica and 0.4mmo1/L for O.indica hybrid.Five leaf stage was much better than 3 leaf stage for comparison of genotypic differences in K utilization efficieny.

Abstract:Salinity in soil or water presents a stress condition for growth of crops that are of increasing importance in agriculture.Crops differ greatly in their ability to survive and yield satisfactorily when grown on saline soils.Information on the relative tolerance of crops to a saline soil environment is of practical importance in planning cropping schedules for optimum returns.The relative salt tolerance of crops in the earlier growth period was investigated via pot culture tests with salinized light loam soil and four crop species in order to understand differences in salt tolerance of wheat,soybean,cotton and corn and its physiological mechanisms.The results obtained showed that cotton was the most salt-tolerant crop species and soybean was the most salt-sensitive one among four the crop species tested.Plant element analysis indicated that sodium concentration and sodium accumulation in all organs of crop plants increased sharply with the increase of soil salinity level.After absorbed by roots of wheat,soybean and cotton,sodium was transported to the aerial parts to certain extent.After absorbed by roots of corn,sodium was mainly accumulated there.It was only potassium accumulation but not potassium concentration in all organs of crop plants that decreased remarkably with the increase of salinity level in the media.Calcium concentration and calcium accumulation in all organs of crop plants decreased to certain extent with the increase of salinity level.After absorbed by roots of crop plants,potassium and calcium were mainly transported to the aerial parts.So potassium accumulation and calcium accumulation in the above-ground organs were more than those in the roots.K⁺/Na⁺ ratios in crop plants decreased with the increase of soil salinity.The large variations in responses of different crop species to salinity existed owing to difference in plant physiology,i.e.,difference in the ability to carry out special adaptive mechanisms.The results showed that cotton could absorb and accumulate more sodium in its organs under alkalinity level.Sodium could remedy the states of nutrition and water of cotton plant.So cotton was the most salt-tolerant crop species.After absorbed by roots of corn,sodium was mainly accumulated in the roots.Sodium concentration in the above-ground organs of corn was too low to suppress growth of corn plant seriously.

Abstract:The kinetic characteristics of NH₄⁺ adsorption-desorption for five major soils in shaanxi province were studied by using the continuous fluid flow method.NH₄⁺ adsorbing-desorbing equilibrium time and reaction rate,equilibrium adsorbing-desorbing capacity and adsorbing equilibrium constants changed with the soil clay content and CEC.Different kinetic models showed different fitting results to the data of experiment.First-order equation and Elovich equation were the best models for fitting to the data of NH₄⁺ adsorbing and desorbing reac-dons respectively.NH₄⁺ diffusion speed was the factor controlling the NH₄⁺ adsorbing and desorbing rates.NH₄⁺ desorbing rate increased significantly with raising temperature.

Abstract:Effects of combined application of organic manure and chemical fertilizers on crop yields,Soil fertility and nutrient balance were studied systematically according to the results of a 13-year located experiment.The results show that the basic productivity of lou soil in Guanzong could be kept in a shorter period of time.The amounts of soil nutrients supplied for corn were higher than those for wheat.So,the application of N and P in combination with organic manure would be an efficient way for raising crop fields and soil fertility in irrigated area.

Abstract:Self-diffusion coefficients of phosphate in four soils of different texture at varying water content and temperature were measured by the methods of diffusion half-cells and diffusion tube using ³²P-labelled KH₂PO₄ solution.The results showed that the apparent self-diffusion coefficient (D_a) in the water unsaturated soils increased with increasing soil water content (W) or decreasing soil water suction (S).The relationship between D_a and W or S could be described by the power equation of D_a=aW^b or D_a=aS^-b.The effect of soil texture on D_a value was closely related with moisture condition.Under the same water content,the lighter the soil texture the higher the D_a value,and a significant positive correlation of D_a value with clay content was observed.On the contrary,at equal water suction,a negative correlation between DQ value and clay content was found normally.The porous self-diffu-sion coefficient (D_p) in water saturated soil was higher 10²10³ fold than the D_a value of the soil,but there were no differences between the soils.The D_a or D_p value increased with the temperature,and every increase of temperature 10℃ within 5℃ to 45℃ caused the D" or D_p value to increase by about 10-50%,with an average of 30% or so.Moreover,nonlinear multiple regression analyses were used to investigate the relation between the interaction of soil moisture with temperature and the self-diffusion coefficient of phosphate in soil.The analytical results indicated that the interaction influenced the diffusion of phosphate clearly,and the influencing extent could be defined by the concepts of "water coeffeient" and "temnerature coefficient" advanced in this naner.

Abstract:Eight one Soil samples taken from the Hangzhou-Jiaxing-Huzhou plain were studied by the determination of the spore-pollen and micropaleontological fossils.Among those soil,41 samples had spore-pollen combination,and 13 samples had foraminifera.Based on spore-pollen combinations and foraminifera,four rinds of parent materials cauld be classified,including estuarine deposits,lagoon deposits.limnic deposits and plain-river deposits.The palaeogeographical environmental evolution of the plains from mid-Holocene epoch was also discussed.

Abstract:The profile morphology,main physico-chemical properties and clay mineral composition of acid brown soil,grey brown soil are disscussed according to the natural conditions of the mountain soil formation in the west Hubei.The results show that both of the acid brown soil and grey brown soil belong to the forest soils formed in the middle and upper parts of subalpine and medium mountain areas in the subtropic climatic zone under cold and humid conditions.But their physico-chemical properties differed obviously with the same soil types in the northern China.The acid brown soils are distributed in the middle and upper parts of the medium altitude mountains,with an altitude higher than the dark yellow-brown soils,being the forest soils with the vegetations of bright conifer and broadleaf deciuous scrubs.Their distribution altitude is higher in the southwest Hubei than in the Northwest Hubei.Grey brown soil is the forest soil formed under colder and more humid conditions than the acid brown soil and located at a higher altitute than the acid brown soil about 2500m above the sea level in Shen nongjia region,and its vegetations are dark conifer forests.

Abstract:This paper deals maiilly with the relationship between Pb and Cd pollution and enayme activities of soil in wastewater irrigated area of Banding city.The results show that the contents of Pb and Cd in soils of wastewater irrigated area were higher than those in soils irrigated with fresh water and exceeded the standards of soil background values for some cities at home and abroad,and the contents of Pb and Cd in soils of wastewater irrigated area approched or reached the lightly polluted levels.There appeared a close relationship between heavy metal pollution and enzyme activity.The soil unease and catalase activities decreased evidently with increasing contents of Pb and Cd.According to the regressive fitting results there existed a very significant exponential negative correlation between soil unease and catalase activities and Pb and Cd contents with the maximum r² model equation of y=axe^-bx band the correlation coefficients (r) of -0.804^**,-0.795^** and -0.899^**,-0.852^**,respectively.It is feasible to use soil unease and catalase activities as primary biochemical indexes to evaluate Pb nd Cd pollution in soils of the wastewater irrigated area.

Abstract:This paper deals with the environmental factors and the damages of wind erosion occurring in sandy lands of shahe area of Yucheng County in Shandong Province.The practical resups showed that such techniques as water conservancy project,planting trees and grasses,biological mulching and stereoscopic farming measures could effectively stabilize sand surface,reduce wind velocity and increase the resistance to wind erosion,thus halting the wind-sand hazards.In addition,the paper also discusses the wind erosion mechanism and the laws of wind-sand activities,which may provi}le a basis for the agricultural development of sandy lands in the Huang-Huai-Hai plain.

Abstract:The soil agrochemical properties and microbiota of three degraded grasslands (Kobresia pygmaea meadow,Dasiphora fruticosa shrub and Festuca sinensis grassland) were studied.The main results are summarized as flliows:(1) There existed obvious vertical distribution of the contents of N,P,K,organic matters and pH value as well as microorganism numbers in the soils.Soil agrochemical properties were significantly correlated with soil microorganism numbers.(2) Soil fertility and the numbers of soil microorganisms,decreased with grassland degradation.(3) N and P were deficient but K and organic matter were rich in soils of the three degraded grasslands.And (4) The soil microbiota varied obviously with grassland degradation.Weakly degraded grassland had more soil microorganism genera than the strongly degraded one,and the microbiota were similar in the grasslands with the similar degradation degrees.

Abstract:The objective of this study was to examine the effects of tillage on soil microbial biomass carbon under a crop of corn(Zea mays L.) Soil microbial biomass carbon was measured every two weeks and every month in conventional tillage(CT),1-year no-tillage(SNT),and long-term(>15 years) no-tillage (LNT) plots using the chloroform fumigation-extraction technique.The plots are located near Guelph,Ontario,Canada on a Typic Hapludalf(loam) soil.Sampling sites were in the corn row,directly between corn rows(interrow),and half way between the row and interrow(quarter row).Systematic spatial differences in soil microbial biomass carbon within and between tillage treatments were observed throughout the entire growing season of crop.The major changes in the biomass occurred as a large increase between the time of planting and the time of Bilking and were correlated with predicted and expetted root growth.Spatial variations of LNT biomass carbon were significantly correlated to spatial variations in soil water content over the crop growth season.

Abstract:Based on the simulated experiment data of winter wheat and corn in growth boxes,the variability of hydraulic resistance in the soil-plant system was analysed from aspects of diurnal changes and long-term changes of transpiration rates in this paper.The results indicated that hydraulic resistances in the plant were relatively large at low transpiration rates,decreased as transpiration rates increased and approached a constant value at higher transpiration rates.The effect of effective soil water potantial on hydraulic resistances was also studied.

Abstract:在19和20世纪之交的前后约二、三十年间是土壤微生物学发展的黄金时代(Waksman,1952)^[19],研究工作在多方面取得显著成果,并在一些领域继续深人.当时已发现根系范围内的微生物对植物具有重要作用.慕尼黑大学上壤细菌学家和农学教授希尔特勒于1904年首次采用Rhizosphere一词来描述受豆科植物根系影响的土壤区((Soilzone),以强调这一区域中的微生物对植物营养和生长的密切关系(Hiltner,1904)^[10].

Abstract:我国南方广泛分布的潜育化水稻土,由于土壤过度渍水,通透性差,氧气供应缺乏,导致土壤处于强烈还原状态,有毒还原物质易于累积,因而水稻生长不良,产量低.碱土金属的过氧化物如CaO₂,MgO₂和BaO₂等,由于其分子结构中含有活性氧,它们与水作用时能缓慢释放出氧((2MO₂+2H₂O→2M(OH)₂+O₂^↑.