Abstract:The state of orgsno-mineral complex in soils under the rotation of paddy and upland Crops was studied. Soils used in experiment were yellow brown earth derived from siashu loess and grey fluro aquic soil as well as their corresponding paddy soils. 1. A change from paddy field to dryland was advantageous to promote the complexing process and increase the amount of organomineral complex in soils. However, a change from dryland to paddy field could increase the quantity of free organic matter and was advantagenus to the accumulation of soil organic matter. The rotation of paddy and upland crops could improve the state of organomineral complex of soils by accelerating the transformation of organtc matter.2. After a change from paddy field to dryland, the content of tightly combined humus was comparatively increased, it was favorable to improve soil structure. Simultaneously, the liable oxidizing parts of loosely combined and tightly combined humus were increased and it could promote the oxidation and regeneration of combined humus. While a change from dryland to paddy field, the content of loosely combined humus was comparatively increased, it was advantageous to activation of soil humus. 3. The rotation of paddy and upland crops could caused the difference in fractionation end composition of soil humus. The increase of ratio HA-B/FA-B and the decrease of ratio HA-A/FA-A after the change from paddy field to dryland indicate that the laible mineralizable fraction of soil humus was increased and it might be promote to release soil nutrients.4. The contents of C, N, P and S in soil complexes were enhanced with the reduce of Sod complex particle sizes except silty complexes. The change of C, N, P and S contents in soil complexes of different particle sizes under the rotation of paddy and upland crops showed that a change from paddy filed to dryland was favourable to shorten the cycle period of C, N, P and S in sails and make them to be mineralizaed easily.

Abstract:Two series of 0.001 M Fe(NO₃)₃ solutions, having NaOH/Fe molar ratios ranging from 0 to 3.1, were prepared by diluting a 0.5 mol/L Fe(NO₃)₃ stock solution with water and then hydrolyzed at 70℃. The preparation differed only in the initial temperature of the water for dilution; but the final products were very different in particle size, morphology and crysrallinity. In Series I solutions, prepared with 70℃ water the reaction products were amorphous, structureless masses initially, but became well crystallized goethite and/or hematite in the shape of rods or plates shortly afaer being aged at 70℃. In Series Ⅱ solutions, prepared with room temperature water, the hydrolyzed products were tiny spheres havin a well-defined outline and homogeneous size throughout the experimentation. They were very poorly crystallized goethite and/or hematite even after, 248 d of aging at 70℃ and could be detected only with a high power Rigaku rotating anode x-ray diffractometer. The results suggested that the temperature of water for solution preparation plays a key role in the size and nature of the initial hydrolytic product which, in turn, plays a key role in the rate of redissolution and recrystallization.

Abstract:The electrical conductivity of the clay fraction of three red earths in suspension was measured with alternating current at different frequencies and direct current. The results Showed that the magnitude of conductivity dispersion suspension varied with the types of soil. It was strongest for red earth, stronger for lateritic red earth and weak for latosol. The frequency necessary for inducing a distinct conductivity dispersion was about 10 KHz for red earth and lateritic red earth, and nearly 100 KHz for latosol. The effect of the type of soil on conductivity dispersion was closely related to the sum of positive and negative charges carried by clay particles. For a given clay, the relative conductivity (the ratio of conductivity at a given frequency to that at 300 Hz) in suspension increased with the increase in clay concentration.The curves of the plot of conductivity dispersion in suspension vs. frequency in various electrolyte solutions were of different shapes. The line was nearly linear when KCl was present and concave when Ca(NO₃)₂ or CaCl₂ was present. Between 1 and 100 KHz, the magnitude of conductivity dispersion was of the order: KCl>Ca(NO₃)₂>CaCl,. The frequency necessary for inducing a distinct conductivity dispersion was about 1 KHz with KCl and nearly 10 KHz with Ca(NO₃)₂, and up to about 100 KHz with CaCl₂. At a given frequency, the relative conductivity of the clay fraction of red earth in suspeusion decreased with the increase in KCl concentration (10^-5-10^-3mol/L).

Abstract:Mössbauer spectroscopy and X-ray diffraction were used to characterize iron oxide mineralogy and AL-substitution of goethite in clays of paddy soils derived from red earth and their original soils (red earth). The results showed that the types and properties of iron oxide minerals in paddy soils derived from red earth were obviously different from those of their parent soils. The main iron oxide minerals of red earth were hematite and high Al-substitutcd (>20 mol%) goethite, but the environments of paddy soil were unfavourable to the formation of hematite which might be transformed to low Al-substituted goethite or other forms of iron oxide after rice planting. The amount of Al-substitution in goethite in P horizon clays of percogenic paddy soil.was higher than that of other diagnostic horizon clays of paddy soil. Small particle, low-substituted(<15 mol%) goethite was the main iron oxide mineral in clays of W horizon in periodically water-logged paddy soil and in G horizon of gleyed paddy soil, no hematite was detected in these clays.The main type of iron oxide minerals and the change of Alsubstitution in goethite of paddy soils derived from red earth reflect the conditions and characteristics of paddy soil, Which are very signnificant for paddy soil classification.

Abstract:The present paper deals with the effect of the components of soils on the specific adsorption of copper ion and its characteristics. Latosol, red earth and paddy soil (neutral) were used in this paper. The specific adsorption of Cu²⁺ ion was determined in the presence of 0.5 M NaCl as supporting electrolyte, and the initial pH of solution was 4.00.The results showed that Cu specific adsorption isotherms of tested soils followed the Langmuir equation (Table 2). The specific adsorption of Cu by latosol and paddy soil was greater than that of red earth. By comparison of maximum adsorption, the specific adsorbed Cu of latosol and paddy soil was about 3.1 times and 3.0 times the amount of adsorbed Cu of red earth respectively.Desorption experiments reveled that there existed two types of specific adsorbed Cu, one was with a low bonding energy and could be desorbed by 1 N NH₄Cl (pH 5.0) and the other was with a high bonding energy and could only be desorbed by 0.1 N HCl, corresponding to the loosely bonding and tightly bonding fractions of copper respectively.The tightly bonding Cu was independent of the concentration of Cu added, once the specific sites were filled with this fraction of copper (Fig. 3, 4, 5), it had greater affinity with the specific sites. The loosely bonding Cu increased with increasing concentration of copper added, and followed the Langmuir equation (Fig. 3, 4, 5). Thus there must be a fixed number of specific sites at a given pH from which copper is less readily desorbed (tightly bonding Cu), and with increasing concentration of copper added, there will be an increasing proportion of the adsorbed Cu at that pH which can be readily desorbed (loosely bonding Cu).At lower concentration of copper added, tightly bonding Cu was more than loosely bonding Cu for latosol and paddy soil, and vice versa. Loosely bonding Cu dominated in specific adsorbed Cu for red earth. The amount of tightly bonding Cu in soils was in the order: latosol>paddy soil>red earth; while that of loosely bonding Cu in soils was in the order: paddy soil>latosol>red earth. This distinct difference in specific adsorbed Cu for the tested coils is probably related to the different content and properties of hydrous oxides, organic matter and composition of clay minerals of soils.

Abstract:For evaluating the effect of puddling on crop growth, comparative experiments have been carried out. Soils used in experiments were two paddy soils in Taihu Lake Region. Results obtained showed that puddling of clayey paddy soil, especially, of the soil with poor structure was beneficial to rice growth under pot experimental condition of no leaching: but she advantage of puddling disappeared under field condition. This may be due to that the efkct of puddling is concealed by leaching, fertilization, etc. of the soil under field condition. It was also found that the main reason affecting the growth of upland crop was the unharmonic regime among moisture, air and mechenical strength of puddled soil, which could not improved by mechenical approach when the soil water content was above plastic limits. It is suggested that drainage of the soil should be the only way to accelerate the aeration of the coil under this condition.

Abstract:In order to predict the variation of soil moisture content and adopt effective measures in time, a forecast model for soil moisture was studied and developed on the basis of the model of Xinanjiang according to the meteorological data of the Three-River Plain region. The model was tested with the data of 1979-1984. A comparison between the calculated values and the practically measured values was made, and their correlations were analyzed. According to the meteorological data of the region in spring of 1985, Prediction of moisture content of soils in Baoqing County was made with the model, the results is recorded in the table 3.

Abstract:The total K content of the hilly upland soils in Zhejiang Province ranged from 0.57% to 3.13% and increased with increasing contents of the feldspar and mica in parent rock. The contents of readily available K and slowly available K were 33-216 ppm and 80-838 ppm respectively which were correlated with the relative contents of kaolinite and illite in the soil clay.By means of chemical successive extraction, electro-ultrafiltration (EUF) and quantity-intensity (Q/I) studies, it was found that the potential bufferring capacity (PBC) and supplying power of potassium were lower in those soils with clay minerals dominated by kaolinite, bw higher in the soils dominated by illite. The ryegrass pot experiments revealed that the soil potassium supplying power was more important than the reserve of the available K.

Abstract:The fate of nitrogen in wheat stubble incorporated with soil or mulched on soil surface was studied by ¹⁵N tracer technique.Pot experiment in which millet was sown and harvested after 87 days was conducted at cinnamon soil Beijing Drab Soil. The results arc as follows: 1. The applied nitrogen recovery in straw and grain of millet was 28.3% and 15.2% respectively under wheat stubble mulch as compared to that of 20.6% and 12.0% by incorporation with soil. 2. After 87 days of millet grown, 28.3 % of the N of wheat stubble applied on soil surface was in millet plant, 16.5% in humus, 8.5% leached off by percolating water, 3.1% lost ny volatilization and about 51.6% remained in soil, whil 20.0% of that incorporated with coils was in millrt plant, 14.8% in humus, 0.2% leached off, 11.5% lost by volatilization and 53.1% remained in soil.

Abstract:The enzyme activities of straws, animal manures, composts and other organic materials widely used in Huang-Huai-Hai region were studied. Among all tested materials, straws showed stronger activities of invenase and amylase than other organic manures. Except some cases, urease and protease activities in animal manures were stronger than those in other organic manures. Soybean straw was proved to be the best one with enzyme activities, but sludge was worse than other organic manures. Under laboratory conditions, straws and animal manures could strengthen the activities of invertase, phosphatase and urease in fhtvo-aquic soil to varying degree. Field test showed that urease and phophatase activities, in soil applied with more wheat straws were stronger and those in soil applied with less ones were weaker. Organic manures not only strengthened enzyme activities, but also had great effects oa soil N and P transfomations.

Abstract:This article deals with numbers, compositions and enzyme activities of denitrifiers in paddy soil in Taihu Lake district. The results obtained are as follows. 1. The amount of denitrifiers teas rather numerous in paddy soil in this region, generally, more than million per gram of dry soil. Numbers of denitrifiers in soil with higher fertility were larger than that with lower fertility. In all the paddy soils, there was significant positive correlation between numbers of denitrifiers and bacteria. 2. The species in genus Bacillus and Pseudomonas were the predominant denitrifying bacteria in paddy soils in Taihu Lake district. The highest occurrence frequency of Bac. megotherium and Pseu. fluorecens has been found in these soils, they even constituted 10-50% of the total denitrifiers, while the frequencies of Bec. licheniformis and Bac. firmus were much lower than the former. 3. The enzyme activities of denitrifiers have been determined by means of GC-technique. The amount of the strains reducing NO₃^- to N₂O and those reducing N₂O to N₂ constituted 67% and 56% of the strains tested, respectively. The amount of denitrifiers being able to reduce ¹⁵NO₃^- to ¹⁵NH₄⁺ through dissimilatory reduction pathway constituted 92% of the strains tested. The dissimilatory reduction ability of Bac. cereus and Bac. licheniformis were vigorous.

Abstract:The Brown red earths on hilly lands east and west of Dongting lake wire studied, thr rcesuits obtained are summarized as follows: 1. In comparison with red earth, the main characteristics of formation for brown red rearth are weak in desilicificarion and allitic processes (the content of Fe₂O₃ is lower, Al₂O₃ is higher; the silica sesquoxide ratio is about 2.7-3.0), weaker in eluviation prqeess (the content of alkali metals and alkali earth metayls is as 1.18-3 times as red earth; the coefficiem of weathering and eluviation process. (the content of alkali metals and alkali earth metals is as 1.18-3 times as red earth; the.coefficient of weathering and eluviation is more than 0.3). The dominant clay minerals are illite and kaolinite; the content of free iron oxide is more than 2% and the degree of its segregration is 50-60%. 2. The properties of brown red earth are reddish yellow and dark reddish brown in color with the silt/clay and sand/clay ratios of less than 1 the clayization value of larger than 1;pH of 4.8-5.8, CEC 8-14 m.e/100 g soil, and a base saturation about 40-60%. 3. According to the indexes mentioned above, parcni materials and characteristics of the region, the soil families of typic brown red earth, granite brown earth, slate-cheer brown red earth, sandstone brown red earth are classified.

Abstract:生物残体是由活的生物(包括动物和植物)死亡后形成,如森林砍伐后遗留的树桩,温带森林中每年一度集中产生的枯枝落叶,森林和草原中大型动物死亡遗留的尸体,这些生物残体一般都独自形成一个实体,不与土壤进行均匀的混合,它们的分解,一般主要不是依靠贮积在土壤中的酶或微生物的作用,它们的分解要经过一个在残体内重新滋长微生物的过程,使残体逐渐腐烂变质,进行分解。因此,生物残体的分解,与其说是分解过程,还不如说是一个微生物的培养过程,或者说是这两个过程相互交错,一方面是微生物种群的增长,另一方面是残体中有机物质被微生物分解、转化、利用和复合成新的有机体,对于这样一个复杂的过程,通常适用于土壤有机质分解过程的Stanford-Smith方程^[2]就不适用了,而建立在营养动力学基础上的单种群模型(崔-Lawson方程^[3-5])却可加以转化用来描述这个过程。