Abstract:The calcified paddy soils in China cover an area of more than 270 thousand hectares.The content of CaCO₃ varies from 10-20% and the ratio of CaCO₃/MgCO₃ from 10-30%.The soils are compact in texture with calcarous concretions and, sometimes, calcareous hard-pan in profile. The soils are deficient in P, K, available B, Zn, Mo and Mn.The calcium in the calcified paddy soils mainly results from liming and irrigating water with high Ca content from karst caves. The conditions of calcium carbonate accumulation in the soils are the high pH value, low partial pressure of CO₂ and poor water permeability of the soils.On the basis of the content of CaCO₃ and estimation by ¹⁴C dating method, the formation of calcified paddy sail has a history for at least more than three hundred years.Because liming is one of the factors resulting in the deterioration of the soils, it is recom mended that more organic manure should be ahp1ied father than liming on the soils, at the some time microelement such as Zn, B, Mo,etc should also be applied.

Abstract:The albic soils (baijiantu) is develop.nent under semi-humid climate of temperate none in this country. They are commonly derived from Quaternary deposits. Due to periodically stagnancy of water under conditions of alternate seasonal wetness and dryness, the iron and manganese are reduced and leached off, the clay fraction is also leached downward, its amount apparently decreases in A and SB horizon, but increases in the B horizon. Silicon-iron, silicon-aluminium, and silicon-iron-aluminium ratios change insignificantly in the entire soil profile.The soil acidity is stable, the base saturation is high generally around 70-90%.

Abstract:The fixed ammonium content and the NH₄⁺-fixing ability of the main types of paddy soils in Taihu lake region were determined and the availabilify of the fixed ammonium was studied under greenhouse conditions. It was found that both the fixed NH₄⁺ content and the NH₄⁺-fixing ability of soils varied with the parent materials, they decreased in the order:Yangtze River alluvium>loess-like material>Quaternary red clay. About 18% of the total N in the soil layer of 0-20 cm and 34% of that in the soil layer of 0-100 cm were in the form of fixed NH₄⁺-N.The availability of ehe "native" fixed ammonium was rather low,and varied considerabiy in diferent horizons, ranging from 0 to 13%, while that of the newly fixed NH₄⁺ was very high, berg nearly 100%. There was no evidence showing the effect of waterlogging on the availability of the fixed NH₄⁺. The significance of NH₄⁺-fixation in soil N,fertility is discussed, arid it is suggested that the values obtained by the submerged incubation method were not only lower than the real ones but also incomparable.-due to the presence of NH₄⁺-fixation and difference in NH₄⁺-fixing ability among various soils.

Abstract:The biological potash fertilizers (bio-K fertilizers) are the plants which can strongly absorb potassium from soil and accumulate K relatively high in its tissue. To investigate the mechanism of K-enriching carpacity of bio-K fertilizer and its influence on crop yield, three xypical plants-rice straw sunflower (fresh plant) and Alterndntherd philoxeroides (Mart) Griseb were used in pot and field experiments.It was found that the yield increased significantly by applying the bio-K fertilizers to potassium deficient soils. The average percentage increased was 17.5±8.2% for rice grain and 11.7% for lint cotton as compared with control However, at equal amount of K level applied,there was no significant difference in yield among all treatments of potassium chloride and bio-K fertilizers, it indicates that the K-supplying capacity of bio-K fertilizers is similar to that of KCl. In the terms of absorption rate of nonexchangeable-K by plants tested, the capacity of K accumulation waS high during its growing stage. Based on the total potassium absorbed, 68-76% of nonexchangeable-K was taken up by rice plant and 40-62% of that by sunflower (seedlings, 57 days). As to Alzernantlzera philoxeroides, the K⁺ concentration both in higher and lower solution can be recovered by 97% and 71-90% respectively, it seems that the roots of Alternanther a philoxeroides have a strong affinity to K⁺.The K⁺ in soil could be mantained by organic matter supplied as bio-K fertilizers. As a result, the loss of K⁺ from soil was decreased by 40%, this benefit was more markedly for sandy soils.Data from long-term experiment for four years showed that the K in soil appeared to be somewhat depleted, as compared with its origin content, this unbalance is mainly due to the K removed by crops excessing the K supply (90 kg K₂O/ha per year). However, the K consumed could be partly returned to soil by the use of bio-K fertilizers.

Abstract:In the system of NH₄C1-CaCO₃, the pH of solution with aeration was lower than that without aeration, whereas the reverse was found for solution Ca²⁺ concentration. In the system of K₂HPO₄-CaCO₃ no significant differences in P sorption by CaCO₃ were observed between aeration and nonaeration during the entire reaction period of 24 hours. The effect of NH₃ volatilization on P sorption by CaCO₃ gradually diminished during 24 hour reaction time as solution pH increased in the system of DAP-CaCO₃. (diammonium phosphate) In the calcareous soil, very little NH₃ volatilization was found in the treatments of urea+ISSP or urea alone. On the other hand, approximately 56% of DAP-N initially applied was lost as NH₃ from the soil after 6 days. The amount of water soluble P in the soil treated by DAP without aeration was higher than that with aeration, whereas no significant difference was mbserved between treatments of urea+SSP with aeration and without aeration. Furthermore,the amount of water-soluble P in the soil was about the same in the treatments with urea-I-SSP or with SSP alone. All these. observation suggest that NHa volatilization, if it occurs, can enhance P sorption by CaCO₃ in calcareous soils, while the P sorption also enhance the NH₃ volatilization. Thus the NH₃ volatilization and P sorption are promoted and affected by each other.

Abstract:Contributions and influence of meth anical composition, specific surface, variable and permanent charges, organic matter coptenf and cotnplexing degree and forms of mineral fraction on exclla.nge capciey of light cinnamon soils iri-central Shanxi were studied. Results from path analysis indicate that although the organic matter content was much lower than that of mineral particles in the soil, the effect of organic matter was more-significant-than the mineral fraction of the soils, it was espically so in the soil with lighter mxture.

Abstract:Micromorphological characteristics of the scnls under simulation of intensive cropping system for four years were investigated by means of the thin section and scanning electron macrostopic techniques. The micromorphological observation showed that porosity of clayey soil increased with the organic materials applied in soil, in the soil applying organic material, not only the rnacropores occured among the aggregates, but the medium and micropores also exsisted in the aggregates, which formed a network of pathways beneficial for the movement of both air and water in soil. This structure in soil, consequently, is also favorable for the field cultivation and sowing of upland crops after harvesting rice crop in intensive farming system.Directly applying rice straw in soil promoted soil aggregation and increased soil porosity. Under treatment of directly applying rice straw,iron coatings were formed on the wall of soil pores, which stabilizes the network of pathways in soil. Due to tight arrangement and formation of massive structure resulted from puddling, few soil pores and no iron coating on the wall of pores were observed in the thin section of the soil. Iron streaks, however,was found in the soil matrix. The morphology of soil. structure varied with different flooding duration of soil. It is indicaxed that the flooding condition of soil under double.cropping rice is a factor to result in the cotnpactian and lack of pores in soils.

Abstract:Results from the experiment on sandy-loam soil with different bulk densities showed that there was a linear relation of quadratic curve between wheat yield and bulk density of soil, the highest yield occured on the soils with the bulk densities of 1.23-1.31 g/cm³. When the bulk density was larger than 1.5 g/cm³ and the penetration resistance for root was 25 kg/cm³,the root growth was hindered seriously.The experiment also proved that the soil nutrients was more in upper layer and less in lower layer, showing a T-type distribution. This is consistent with the character of the root system-growing, more in the upper and less in the lower. And therefore, keeping the original state of the soil layers and the feritility distribution is advantageous to coordination of the supply and demand of soil nutrients.

Abstract:Effect of organic matter, free iron oxide and amorphous Si and Al on the Cd adsorption and desorption of colloids of lime concretion black soil (IBC), yellow brown earth (YBC),red earth (RC) and latosol (LC), which are the typical soils in South and Southeast China,was studied with selective dissolution method. Results showed the decrease of Cd adsorption by colloids of the soils after removal of OM might be due to the decrease of exchangeable adsorption by the soil colloids. Removal of free Fe₂O₃ resulted in significant decrease of Cd adsorption by the colloids of YBC, RC and LC, which indicates the significance of specific adsorption of free iron oxide in these soils. Cd adsorption decreased with increasing of amorphous Al content in soil colloids, which might be due to the high energy exchange sites being occupied by Al ions.The Cd desorption percentage by the soil colloids after different treatmems was in the order: that removing amorphous Si, Al> that removing free Fe₂O₃>that removing OM>the original soil colloids, however, the order differed slightly for different soils under different pH.

Abstract:Degradation of styrene by soil microbes in Changzhou region, Jiangsu Province was studied. Experiments were carried out under conditions.simulated to those of submerged and upland soils. Styrene was addied at concentration of 800 ppm. The amount of residual styrene was determined by gas chromatography.The styrene could be degradated by microbes at 300C in both soils metioned above. The kinetic equation of degradation was of the first order. In submerged soil the kinetic regression equation wsa Ĉ=1.03C₀e^-3.46×10-3t while in upland soil Ĉ=0.99C₀e^-2.33×10-2t wheze C₀ is the original concentration of styrene in the soil, Ĉ residual concentration calculated, t degradation time (day). The degradation rate in both soils were compared statistically with each other. In upland soil it was 6.7 times higher than that in submerded soil.styrene coexisted with chlorobenzene, P-dichlorobenzene and m-dichlorobenaxne, its degradation rate was accelerated.Four bacteria strains capable of degradating styrene and using it as a sole source of carbon were isolated from the experimented soil. Identification indicated that two of them were Pseudomonas sp., the other two were Corynebaczeriaam sp. and Arthrobacter sp.

Abstract:Investigation showed that BHC residue in soil was characterized by higher persistence in upland soil than in paddy soil, greater ratio of β-isomer γ-isomer of BHC residue in soil and lower residue of BHC in paddy soil. These characteristics resulted from the higher rate of BHC degradation in paddy soil and higher stability of β-BHC in comparision with γ-BHC in soil. Expei-iznent results alsp showed that the amount of BHC residue absorbed by various crops was different. No significant correlation was found between the content of BHC in rice plant and its residue in soil during harvest. However, the content of BHC in peanut was significantly correlatal with BHC residue in soil during harvest (r=0.64,n=21). The degradation of SHC in soil was related to.soil moisture, temperature and organic matter. It was observed that the degradation rate of BHC was increased with the increase of moisture and temperature in soil;appropriate amoant of organic matter promoted degradation rate of BHC in soil.The possible pathway of degradatian of BHC in soil is discussed in this paper.

Abstract:Trace elements including Si, Fe, Mn, Cu, Zn, etc.in 6 purple rocks and soils derived from the rocks in Sichuan were studied. Data obtained revealed the despersion and enrichment characteristics in the process of rock formation and soil genesis and the inconformity of the total content to the available contents of the elements. It is suggested that the geochemical gradation of these elements in the soils based on thfir available contents may be used as the indexes for trace element fertilization.

Abstract:土壤中的氮素主要以有机态的形式存在,大部分有机氮通过矿化作用成为无机态氮供植物利用;小部分有机氮可直接为植物所吸收。土壤中还含有微量的有机氮化物,如核酸及各种维生素等,这类物质对植物、微生物的生长有着特殊的作用^[l.14]。研究土壤中有机氮化物的组成和性质,是土壤有机质本性研究的一部分,它对于进一步调节氮素的转化、提高土壤的供氮能力、以及制定合理的施肥制度都有着重要的意义。本文对我国几种土壤中的氮素形态、组成和分布进行了研究,现简报如下。