Fractionation of Zinc in Paddy Soils of China

The rice fields in China amount to 25.4 million hectares of which low yield paddy soils areabout 26％(Xu,1981;Xiao,1981).One of the most important causes of low yield is the defi-ciency in nutrients including zinc.Zinc deficiency usually occurs in calcareous paddy soils withpH>6.5(Zhu and Liu,1981).And the availability of zinc in calcareous paddy soils is lowerthan that in neutral and acid paddy soils.     

Transformation of Fertilizer-N in Rhizosphere Soils of Wheat

INTRODUCTION There is a close relationship between the transformation of fertilizer-N and the statusof nitrogen nutrition in rhizosphere soils.Previously,Harmsen and Jager(1962)made ananalysis of N and C contents in the rhizosphere soils of upland crops and found thatclose to the root zone there was an enrichment of these substances.     

Size of Microbial Biomass in Soils of China

The microbial biomass C,N and P of soils all over China were determined in this study to study their affecting factors.The results,about 100-417 mg C kg^-1 soil,18-51 mg Nkg^-1 soil and 4.4-27.3mg P kg^-1 soil,showed the biomass C,N and P in linear relationship with the soil total organic C,toal N and soil organic P.The ratios of C:Nand C:P,ranging from 5.6 to 9.6 and from 11.2 to 48.4 respectively,were affected by soil pH.texture,crop rotation,macroclimate etc.The ratio of C:N in soil biomass increases gradually from the north to the south in China.     

Prediction of Chemical Element Contents in Soils

Assuming that the regularity for the dynamic changes of the chrono-sequences of chemical element contents in tree rings follows a k-order constant coefficient differential equation and substituting the differential with the difference,we could obtain the inferred value ym k 1 by the formula:ym k 1=c1ym 1 c2Ym 2 …ckym kEach coefficient ci in the formula may be ascertained by use of the measured data in the chrono-sequences,Extending the chrono-sequences on the assumption that the regularity of dynamic changes wouldn‘t change in the near future,the contents of chemical elements in the soils may be predicted in terms of a logarithmic linear correlation model.Also,this extension method could be used for the reproduction of the contents of chemical elemets in soils during different periods of time in the past.     

Water Budget Analysis of Red Soils in Central JiangxiProvince, China

The daily soil water budgets in the red soil areas of central Jiangxi Province, southern China, were investigatedwith a large-scale weighing lysimeter and runoff plots. From 1998 to 2000, peanuts (Arachis hypogaea L.) and rape(Brassica napus L.) were planted in the lysimeter and in 1999, peanuts were planted in the runoff plots. The soil waterbudget components including rainfall, runoff, percolation and evapotranspirat.ion were measured directly or calculated by Richards‘ equation and water balance equation. The results showed that most rainfall, including rainstorms, occurredfrom March to July, and induced the greatest soil water percolation during the year. The evapotranspiration was stilllarge from July to September when rainfall was ininimal. Thus, the lack of synchronization in soil water inputs and losseswas disadvantageous to crops growing in this region. Among the soil water losses, percolation was the largest, followed byevapotranspiration, and then soil runoff. Runoff was very small on farmland with crops. It was significantly different, fromthe uncultivated uplands where large-scale runoff was usually reported. The soil water storage fluctuated sinusoidally,with a large amplitude in the rainy season and a small amplitude in the dry season.     

Characteristics of Humic Substances in Paddy Soils

In the present paper,the composition of humus and the charateristics of humic acid from seven paddy soils were compared with those of upland (and/or natural) soils.Results show that:(1) in each group of the soil samples for comparison the HA/FA ratio of the humus of a paddy soil,in most cases,was appreciable higher than that of adjacent upland(and/or natural) soil derived from the same parent material;(2) the humic acid extracted from the paddy soils was characterized by a higher C/O ratio,a higher content of methoxyl groups,and a lower content of carboxyl groups than those from the corresponding upland (and/or natural) flooded soils,implying that the humic acid formed under rice cultivation is in a lower degree of humification than that formed under upland(and/or natural) conditions;and (3) the humic acid of paddy soils,however,was not always characterized by a lower aromaticity than that of the corresponding upland(and/or natural) soils.     

Factors Affecting Diffusion of Ions in Soils

In this work the diffusion coefficients of Na+, K+, Ca2+, NO3- and Cl- ions were estimated in terms of measuring apparent direct current (DC) conductivities of latosol, red soil and yellow-brown earth containing, respectively, NaNO3, KCI, and CaCl2 of different concentrations (0.005, 0.05, 0.10, and 0.15 mol/L) in the case of moisture contents ranging from wet to water saturation. The results showed that when bulk density, moisture content, and electrolyte concentration were constant, the diffusion coefficients of cations were in the order Na+> K+> Ca2+ except for Na+ and K+ in latosol, while the order for anions was NO3- > Cl-. The diffusion coefficients (Di) of cations and anions were linearly proportional to volumetric moisture content (θ) as electrolyte concentration and bulk density were unchanged. When moisture content and bulk density were constant, the diffusion coefficients of cations decreased, to varying extents, with the increase of electrolyte concentration, and the decrement in differen     

Transformation and Availability of Various Forms of Zinc in Soils

The transformation and availability of various forms of Zn applied into a cinnamon soil and a carbonate meadow soil as well as the effects of fertillizer-P on them were studied by using the field experiment method and chemically sequential extraction procedure.Zn added into the soils was found to be rapidly transformed into the various forms. In the cinnamon soil,the amount of Zn transformed into the carbonate bound form was the highest,and the carbonate bound form was proven by the analyses of intensity factor and capacity factor to be the primary available Zn pool.But in the carbonate meadow soil,the Zn transformed was relatively homogeneously distributed in the various forms though the amount of Zn transformed into the Mn-oxide bound form was relatively high,and the organically bound,Mn-oxide bound and amorphous Fe-oxide,bound forms were found to be the main available Zn pool.Fertilizer-P took part in the regulation and control of available Zn in the soils to a certain degree.In the carbonate meadow soil,application of P fertilizer probably aggravated Zn deficiency at low Zn rate,while it was favorable to the storage of available Zn in the case of high Zn rate.     

Surface Chemical Properties of Colloids in Main Soils of China

Surface chemical properties of soil colloids are the important factor affecting soil fertility and genesis.To provide scientific basis for soil genetic classification,promotion of soil fertility and reasonable fertilizqation,the specific surface area and electric charge of soil colloids in relation to clay minerals and organic matter are further discussed on the basis of the results obtained from the studies on surface chemical properties of soil colloids in five main soils of China.Results from the studies show that the effect of clay minerals and organic matter on the surface chemical properties of soil colloids is very complicated because the siloxane surface,hydrated oxide surface and organic matter surface do not exist separately,but they are always mixed together and influenced each other.The understanding of the relationship among clay minerals,organic matter and surface chemical properties of soil colloids depends upon further study of the relevant disciplines of soil science,especially the study on the mechanisms of organo-mineral complexes.     

Distribution of Chemical Forms for Co, Cr, Ni and V in Typical Soils of China

Co,Ni,Cr and V in 25 typical soils of China were fractionated into exchangeable,carbonate bound (calcareous soils),Mn oxide bound,organically bound,amorphous Fe oxide bound,crystalline Fe oxide bound and residual forms using a seven-step sequential extraction procedure,so as to study the distribution of chemical forms of these metals as well as the effects of soil proiperties on the distribution.The results showed that most of soil Co,Ni,Cr and V were present in residual forms,and the distribution ratio averaged 48.2% for Co,53.0% for Ni,81.5% for Cr and 68.7% for V.The speciation of heavy metals was greatly influenced by soil physico-chemical properties and the chemistry of elements.The results also indicated that the recovery of metal elements by the sequential extraction procedure was satisfactory,with the relative difference between the sum of seven forms and the total content in soils averaging 9.5% for Co,12.8% for Ni,6.6% for Cr and 7.2% for V.     

Assessment of Cd–Pb Pollution in Soils of the Youjiang River Basin,South China

Eurasian Soil Science - To determine the distribution, migration, and accumulation characteristics of heavy metal pollution in the Youjiang River basin in South China, 71 shallow soil samples were...     

Evaluation of Nutrient Release in Salt‐Saturated Soils

Abstract

The effects of irrigating with saline water on native soil fertility and nutrient relationships are not well understood. In a laboratory experiment, we determined the extent of indigenous nutrient [calcium (Ca), magnesium (Mg), potassium (K), manganese (Mn), and zinc (Zn)] release in salt-saturated soils. Soils were saturated with 0, 75, and 150 mmolc L^?1 sodium chloride (NaCl) solution and incubated for 1, 5, 10, and 15 days. The saturation extracts were analyzed for pH, ECe, and water‐soluble Ca, Mg, K, Mn, and Zn, and the remainder soil samples were analyzed for exchangeable forms of these elements. In a subexperiment, three soil types (masa, red‐yellow, and andosol) were saturated individually either with 100 mmolc L^?1 of NaCl, sodium nitrate (NaNO₃), or sodium sulfate (Na₂SO₄) salt. These salts were also compared for nutrient release. Soils treated with NaCl released higher amounts of water‐soluble than exchangeable nutrients. Except for Zn, the average concentrations of these nutrients in the soil solution increased significantly with time of incubation, but concentrations of the exchangeable forms varied inversely with time of incubation. The masa soil exhibited the highest concentrations of Ca and Mg, whereas K was highest in andosol. The extract from soils treated with NaCl contained greater amounts of soluble cations, whereas soils treated with Na₂SO₄ produced the lowest concentration of these elements irrespective of the type of soil used.     

Micronutrient Contents of Citrus Orchard Soils in Southern China

Investigations were carried out on the micronutrient contents,of major citrus orchard soils (involving seven soil great groups in 8 provinces and an autonomous region of southern China),and an evaluation on the abundance and deficiency of available micronutrients in these soils was made in this paper.In southern China,citrus orchard soils derived from sandstone,sandy shale,Quaternary red clay,diluvial deposit,granite gneiss and neritic deposit were deficient in available Mo and B and low in Zn.Those developed on purple sandy shale,limestone and slope deposit were all in short supply of available Zn,B and Mo.Coastal solonchak was fairly abundant in B,but its available Fe,Zn and Mo contents were rather low.     

Chemical Behavior of Chromium in Soils: Ⅲ. Mechanism of Cr(Ⅵ) Adsorption by Soils

An analysis of Cr (Ⅵ)-sorbed surface of the soils by using a scanning electron microscope and an electron probe microscope has proved that aluminium is the chief element affecting Cr (Ⅵ) adsoption. As the ionic strength of the solution increased, the amounts of Cr (Ⅵ) adsorbed by goethite and soils decreased. Cr (Ⅵ) adsorption was greatly depressed in the presence of SO₄^2-, WO₄^2-, MoO₄^2-, HPO₄^2- and H₂PO^4- which competed for anion adsorption sites. The depressing extent of these anions was found to follow the sequence: HPO₄^2-, H₂PO^4->MoO₄^2->WO₄^2->SO₄^2->>Cl^-, NO^3-. The amounts of Cr (Ⅵ) desorption varied with different extractants.     

Comparison of Kinetic Models for Boron Adsorption in Alluvium‐Derived Soils of Punjab,India

Abstract

The understanding of the boron (B) adsorption mechanism on soil materials is vital because plants respond primarily to the B activity in soil solution. Batch studies were conducted to investigate the adsorption behavior of B in 21 surface soils representing major soil series of Punjab. The soils varied widely in their properties. Six mathematical models (viz., zero order, first order, second order, Elovich, power function, and parabolic diffusion) were used to describe B adsorption. The B adsorption pattern was characterized by an initial fast reaction followed by a slow process, and it was complete in 24 h of equilibrium. The B equilibrium concentration was negatively correlated with clay content (r=?0.911**), organic carbon (OC) (?0.541*), and cation exchange capacity (CEC) (?0.540*) and positively with sand content (r=0.706**). The Elovich equation was best to describe the rate of B adsorption followed by the power function.     

Investigation of Aluminum‐Tolerant Species in Acid Soils of South China

Abstract

The low‐hilly regions in South China are mainly covered with Ultisols and Alfisols with a pH of 4.5–6.0. The major factor limiting crop performance is soluble aluminum (Al) in acid soils, resulting in phytotoxicity in susceptible species. An investigation in Jiangxi and Zhejiang provinces in South China showed that many plants including some native plants and cultivated crops (total of 27 species) could grow well in acid soils of these areas. The Al‐accumulating capacity in leaves varied greatly from species to species. Camellia oleifera Abel accumulated more than 13,500 mg kg^?1 Al in old leaves; Camellia sinensis (L.) O. Kuntze, Fagopyrum esculentum Moench, and Dicranopteris pedata (Houtt.) Nakaike accumulated more than 1000 mg kg^?1 Al in leaves; and Oryza sativa L., Eucalyptus globulus Labill., Citrus reticulata Blanco, and Brassica chinensis L. accumulated less than 200 mg kg^?1 Al in leaves. This investigation provides an important basis for further exploring Al accumulation and resistant mechanisms in plants.     

Quantification of Organic Matter in Agricultural Soils from the Central Region of Paraná State,Brazil

The organic matter (OM) quantity in soils is of fundamental importance for agriculture. The indirect determination of the OM through the Total Organic Carbon (TOC) quantity is performed by most soil laboratories in Brazil using the Walkley–Black (WB) method. This procedure involves oxidation with potassium dichromate which is a cancerous reagent. The objective of this study is to optimize the parameters for OM determination by the gravimetric method and to estimate the van Bemmelen factor for the studied soil. The studied region is the second and third plateau of Parana State, Brazil, from which 50 agricultural soil samples were analyzed. The temperature and exposition time in muffle were determined after a thermal analysis. The optimized parameters for the gravimetric method were 3 h at 420°C in the muffle furnace. The results for WB and gravimetric methods presented a good correlation and the van Bemmelen factor for the studied soil was 4.37.     

Transformation of Phosphate Fertilizers with Different Solubilities in Calcareous Soils

In this research work,the authors,using the recently developed method of fractionating the forms of inorganic phosphorus in calcareous soils,have studied the transformation processes of inorgnic phosphorus in three different phosphate fertilizers,i.e.,superphosphate,diammonium phosphate and calcium magnesium phyosphate,being commonly used in China,during a period of 3 years after their application to calcareous soils,and based on the experimental results obtained,some problems in current use of phosphate fertilizers are discussed.