Abstract:It is the fundamental caske of soil microbiology to expound the roles of microorganisms in organic matter decomposition and plant n utrient taransformation,their relations to soil fertility and plant growth,and microbial Function in the purification of polluted soil and other environments.Based on the history and present status of soil microbiology,this paper introduces and discusses some currently active research areas in the following seven aspects:(1) material cycling and its quantification in pedosphere and other ecosystems.(2) biodiversity of soils.(3) rhidosphere microorganisms.(4) symbiotic systems formed by microbes and plants.(5) microbial autecology in the soil.(6) role of soil microorganisms in the protection of the environment;and (7) applicatin of microorganisms benefical to agriculture.The author places emphasis on the importance of basic research for both the development of this discipline and the utilization of microbes in agriculture.

Abstract:The study carried out By the submerged incubation method and field experiments showed that the mineralization rate could be used as a charade ristic value onitrogen mineralization in paddy soils.The results obtained are summarized as follows:1.Effective accumulated temperature empirical model (Y=K[(T-T₀)D]ⁿ) obtained without deducting the dried soil effect during 12-week incubation period was better than that with deducting the dried soil effect.The empirical model without deducting dried soil effect had a higher precision,and its mineralization parameter K>0 and 0<n<1.2.The mineralization rate Y'(Y'=Kn[(T-T₀)D]^n-1) might be the charade ristic value of nitrogen mineralization.A highly positive correlation existed between the minera.lization rate at effective accumulated temperature of 105℃(Y₁₀₅') and mineralization power,and Y₁₀₅' was closely negatively related to the availability of mineralized N.The amount of IV mineralized during the last 4-weeks incubation period (effective accumulated temperature of 840-1260℃) was determined by Y₈₄₀'.The higher the Y₈₄₀',the more the N was mineralized in the late period.

Abstract:Influence of ammonium on release and fixation of potassium in soils was studiaied with eight soils derived from basalt,loess sediment etc.The increasing in availability of potassium in the soils was little by adding various amounts of ammonium under condition of submergence or alternate wetting and drying,but after wetting NH₄⁺ can prevent new fixation of K released from soil through airdried,thus keeping availability of potassium in the soil.For soils with mrca and illite as dominent clay minerals,K extracted with 1 mol/L boiling HNO₃ from soil added wish NH₄⁺ is 33-75 μg K/g less than that from soil without adding NH₄⁺.It indicates that NH₄⁺ can efficiently make potassium be occluded in the ditrigonal hole of 2:1 minerals,and the potassium will release difficultly.fertilizer K fixed in soils without leaching with NH₄⁺ and Ca⁺⁺ is 3.3-37.4%.After Ca⁺⁺ leaching,it has no more change compared with soils without leaching,except very few soils.The capacity of K fixation is greatly decreased in soils with NH₄⁺ leaching,only about 4% of fertilizer K is fixed.NH₄⁺ fixed in soils may dicrease the fixation of K from fertilizer and increase K fertilizer efficiency,but often ca uld cause leaching loss of K.Effects of NH₄⁺ and Ca⁺⁺ on K fixation in soils depend on the compsition of clay minerals in soil.The sequence of applying NH₄⁺ and K⁺ significantly influences the fixation of fertilizer K in soil.After 7 days of applying NHS followed by applying K,the fixation percentage of added K is the least,being 4.7-17.8%,and it is the highest,being 14.9-30.5%,when K⁺ was added 7 days befoxe applying NH₄⁺.When K⁺ and NH₄⁺ are added simultaneously,it is intermediate,being 4.7-24.1%

Abstract:In order to find out some endemic desease in relation to environmental selenium,the content and the regular distribution of Se in soils of selenium-rich area in Ziyang county have been studied,and the relationship between the soil available Se and soil properties has been discussed.The total Se contents of soils varied with the parent material and sail-farming condition,and the average content of total Se was 0.323 mg/kg,the water-soluble Se content ranged from 0.1% to 0.9%,and the KHzP04-extracted Se from 1.1 % to 3.8%.Selenium-rich rocks and soils were found to be only distributed in the limited areas.According to the geographical distribution of Se in soils of Ziyang county,Four areas could be distinguished follows:1.selenium-toxic area,2.high-selenium area,3.medium-stlenium area,and 4.low-selenaum area.The Se content of topsoil was the highest,and it decreased with the depth progressively in the soil profile.The degrees of seven soil factors affecting the KH₂PO₄-extracted Se:CaCO₃>silt>organic matter>clay>pH>free iron>CEC.The analytical results of the soils and plants have proved that the KH₂PO₄-cxtracted Se could reflect the situations of Se supplied by the soil.

Abstract:Studies on the distrinution of

Abstract:Albic,black,clernozem,and saline soils are main cultivated soils in Jilin.Albic soils are distributed over the east mountain and semi-mountain areas where there are higher relief,warm climate and more rainfall,and the soil is strongly eluviated.Chernozem and saline soils are dominated in the west plain where climate is dry,transporation is higher than precipitation and the sails are weak in eluviatiom.Black soils are Located in the central part of Jilin with transitianal climate regime between above two group of soils.The parent materials of these soils are mainly accumulative materials during different periods.Based upon some references,hydromica was dominant in the top layer of bath black soils and alhic soils,but the latter contained a small amount of kaolinite and amorphous materials.The authors considered that clay minerial components of soil are different due to the difference of environmental conditions although soils may be derived from the similar parent material or even belong to the same great group.The results show that clay(<0.002 mm) contents in the above mentioned four soils were albic soil (440 g/kg) black soil (314 g/kg)>saline soil (309 g/kg)>chernozem (119 g/kg).But when the cumulative-frenquency was 500 g/kg,a opposite sequence was found being albic soil (3.1 μm)2/Al₂O₃ molar ratio ranging 3.73 and 4.38.The higher SiO₂/Al₂O₃ molar ratio as compared with red soil and yellow soil means weak weathering and desilificanon process and more 2:1 clay minerals in these soils.

Abstract:Four typical profiles of albic soils from the maim distribution areas in China were collected to study for mechanical composition,chemical properties and geochemical elemental vanability of albic soils.The main results are summarized as follows:1.The particle size distribution of the non-clay fraction and soil TiO₂ content calculaced on the basis of >0.002 mm soil particles,the SiO₂/A1₂O₃ of soil and A1₂O₃(K₂O-I-MgO) of non-clay fraction proved that each profile has a uniform parent material 2.The mechanical composition of albic soil has a property of "double layers".The argillic horizon contains much more clay than the albic horizon.The ratio of clay in the argillic horizon to that in the albic horizon is >1.2.3.During the soil-forming process,clay moves from the albic horizon to argillic horizon,which,rather than the lithologically uncononuous deposition of parent material,results in the "doublo layersf9"double layers".4.The Properties of geochemical elemental variability are that SiO₂ and MnO were enriched in the albic horizon while FezOs in the argillic horizon;Fe₂O₃,MnO,TiO₂ and Al₂O₃ were enriched in caay,but SiO₂ in the non-clay fraction.

Abstract:The spatial variation of oxidation-reduction regime was expressed through the soils disributed an different reliefs,at differnt heights of mountains,the soil types and utilizacioa patterns.The common characteristics of oxidation-reduction regime in soils can be summarized as follows:There was a well negative correlation berween Eh₇ (intensive factor) and the concentration of reducing substances (capacity factor) in paddy soils and natural soils,with the correlation coefficients -0.905 and -0.745 respectively,implying that the factors were different in signilicance but closely interrelated.The natural soils any upland soils befonged ro oxidzzing soils,having Eh₇ of 410-590 mV and concentration of reducing substances corresponding to 0.16-5.0×10^-5 mol/L of Mn²⁺,without strongly reducing subsaances.Whereas under different water conditions,the paddy soils had a wider range of oxidation-reduction regimes as compared with natural soils and upland soils,with Eh₇ of 400-(-20) mV and ttae amount of reducing substances of 1.3-17.8×10-5 mol/L of Mne²⁺,which was considered as a true synzboi for the former soils differeat from the latter.

Abstract:This paper presents an analysis of the data from tlxe experiment on potential productivity of rainfed wheat field carried out contin uously for five years an a flat field of 66 m×100 m in Fengqiu.The results showed that under the condition of sufficient fertilizer supply,the potential productivity of the rainfed wheat field ranged from 3450 kg/ha to 5625 kg/ha,with a confidence of 74.8% obtained by the statistic analyses of water charactristics for the five wheat seasons and of the distribution of water in Fengqiu for all the previous years.The correlation between the wheat yield and the total water consumption was not obvious (r=0.67).In addition,it is worthwhile to mzntion that the water utilization rate of ≥0.75 kg/mu·mm for the five wheat seasons was remarkably higher than that in Fengqiu region (0.475 kg/mu·mm) and that in Huang Huai Hai region (0.46kg/mu·mm).This implies that the increases of fertilizer supply is also an effective approach to increasing water utilization rate of the farmlands.

Abstract:This gager deals with the characteristics of persistance and bound residue of trifluralin in two soils.The results show that (1) dynamics of trifluralin persistent in soils under the tested conditions basically followed the first-order reaction equation(C=C₀^-kr) with a half-life (t) of 15-40 days.The most important facter affecting trifluralin degradation was mtcrobial activity in soil.The water conditions of tested soils would markedly affect persistence of the herbicide as well.In general,the rate of degradation of trifluralin in waterlogged soil was much faster than in aerobic soil.(2) Three metaholites,which were detemined by GC/MS as dealkylative and reductive derivatives of parent,were detected after incubation about two weeks in waterlogged red soil.(3) It was found that trifluralin could be bound by soils in considerable amounts.The capacity of soil binding this chemical varied with soil organic matter content the black soil rich in organic matter coold bind more residue than did the red soil.Waterlogged condition was more favourable to the formation of bound residue than aerobic condition in case of the same soil.(4) GC of the distillation products of soil samples containing boand residues by the high temperature distillation technique show that besides small amount of parent compound,they were mainly composed of metabolites.It seems that this herbicide bound residue in soil was mainly formed through the incorporation of the lowly steric hindered reductive derivatives of parent into soil.

Abstract:band flexibility means how many types of crop can be selectively and productively grown in a land.It is an important index of the land productivity and land capability.Pvesearch in this field is still in its starting stage.This article introduced and proposed a mathematic model for calculating the Land flexibility index.The model was used to calculate and analyse the land flexibility indices of some representative land units under different conditions of climate and other soil-forming factors in Canada.The results indicated that the model was reasonable and applicable.furthermore,it was also used to calculate and analyse the land fixibility indices for whole Canada (755 map units in all),especially for the three prairie provinces in Canada.The results accorded with the actual situations of both whole Canada and the prairies.This research also showed that this madel could be taken as a quick way to search and evaluate agricultural lands in a province or in a nation,and could be used to macroscopically master the potentials,over-reclamation or under-reclamation of lands in a province or in a nation.So it is an adrnin.istering tool for readjusting and realigning lands in a country-wide scope.Moreover,this research also revealed that establishing a soil information system and bringing it into full play would be very important and urgent.

Abstract:In the agricultural areas of Langqin Zhangbu and Maji Zhangbu valleys in northern foot of the western Himalayas, warped irrigated soils are a primary type of cultivated soils. Warped.irrigated soils in Tibet generally have three typical genetic horizons: 1) plough horizon with a thickness of 17 cm or so,an average organic matter content, of 3.24%, whieh is 2-10 time as much as that of original soil, higher fertility and higher contents of N, P and K; 2) old trrigated and cultivated horizon with a thickness of 50-80 cm, more carbon residues, few pieces of pottery and sheets of iron and an organic mater content of 0.8%-1.0%, being an important genetic horizon distinguished from other cultivated soil.sy and 3) original soil horizon with a burial depth of more than 1 m, being haplo-desert soil in ,Langqing Zhangbu Valley and being cryocalic scil in Majia Zhangbu Valley. In these proffiles of warped irrigated soils, there are neither depasition or surface accumulation CaCO₃ occurring in the original soils nor double mellow horizon.

Abstract:土壤氮素作为作物的主要营养元素是土壤农化工作者研究得最多一个领域。提高氮素利用率是土壤氮素研究中的一个中心问题。为此,除应了解不同作物的吸氮规律外,还必须搞清施入的氮肥在土壤中的转化过程的特点。对有机肥而言,过去的研究多集中在不同C/N比的有机物质施人土壤后的转化方面,而土壤性质对含氮有机物转化的影响研究较少。我国土壤类型众多,性质差异较大,在当前大力提倡施用有机肥和绿肥的情况下,加强这方面的研究无疑是有一定意义。本文是作者研究的初步实验结果,以供参考。

Abstract:丘陵红壤是江西省柑桔生产重要基地。1986年全省植桔总面积4.7万公顷,60%分布在红壤区。据有关统计从1952至1984年的30多年里全省植桔面积扩大18倍,而产量仅增2.8倍。河流两岸冲积土柑桔老产区产量较高,低产桔园主要分布在红壤。其低产原因较多,但移植时只将表土和草皮返穴,缺少基肥,因而红壤膺酸板旱成了影响柑枯生生产和产量的重要原因之一。除其他措施外,上壤改良对红壤区柑桔的发展和高产优质具有重要意义。刘家站垦殖场1984年开始进行低产桔园上壤改良工作,三年实践证明,改土培肥迅速改变柑桔生产停滞状况,社会和经济效益显著,栽后6年未结果的桔树经土壤改良并配合其他措施,次年每树实产7.5-10kg。三年后投产面积增加近1倍。总产从5.3万kg增至31万kg。社会盈利从49多增至300并。