Food-Security Indexes Related to Combined Pollution of Chromium and Phenol in Soil-Rice Systems

The pot-culture method combined with chemical and statistical analyses was used to get basic data for determination of the food-security indexes related to combined pollution of Cr and phenol in soil-rice systems.Regression analyses according to the experimental result indicated that the critical concentrations of Cr andphenol in brown rice were 0.37 and 0.33 mg kg-1, respectively, under the condition of Cr-phenol combined pollution.

Influence of Organic Manure on Organic Phosphorus Fraction in Soils

The transformation of organic P(Po) from organic manures in two types of soils (ultisol and entisol) and the influences of external addition of organic substance or inorganic P(Pi) on Po under the condition of the 60% maximum water capacity were investigated.The results obtained from Po fractionation experiments indicated that all the Po fractions except for the highly resistant Po fraction decreased during incubation.Application of pig feces and cow feces could largely increase each fraction of Po in the soils.Immediately after application of organic manure into the soils a large part of labile and moderately labile Po from organic manure was transferred into moderately resistant Po,which might be due to the fact that Ca-or Mg-inositol P was precipitated into Fe-inositol P.However,the availability of Po from organic manure in the soils would increase again after incubation because of the transformation of moderately labile and resistant Po fractions into labile Po fractions.Addition of cellulose or Pi into the soils showed a good effect on increasing all the Po fractions except for the highly resistant Po,and this effect was much more pronounced when cellulose was applied in combination with Pi.Therefore,in view of the effect of organic manure on improving P nutrition to plant,attention should be paid to both the Po and the organic substances from organic manure,It is suggested that application of Pi fertilizer combined with organic manure may be referred to as an effective means of protecting Pi from chemical fixation in soil.

Species of Inorganic Phosphate Solubilizing Bacteria in Red Soil and the Mechanism of Solubilization

INTRODUCTION The insoluble phosphates which can not be directly absorbed by plants are the mai forms of inorganic phosphate in soil. These kinds of phosphates can be solubilized by several species of bacteria which are widely spread in soil especially in rhizosphere where70% of the bacteria are capable of solubilizing inorganic phosphate. Many researchers re-

Effects of Organic Anions on Phosphate Adsorption and Desorption from Variable-Charge Clay Minerals and Soil

Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite, goethite, amorphous Al-oxide and Ultisol were studied. P adsorption was significantly decreased as the concentration of the organic anions increased from 10-5 to 10-1 M. At 0.1 M and pH 7.0, tartrate decreased P adsorption by 27.6% - 50.6% and citrate by 37.9 - 80.4%, depending on the kinds of adsorbent. Little Al and/ or Fe were detected in the equilibrium solutions, even at the highest concentration of the organic anions. Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given conditions.Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KC1 solution alone. However, for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P. The effect of organic anions on phosphate desorption arises primarily from ligand exchange.

Sterility of Rice Plants with Relation to Copper Deficiency Under Field Conditions

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Study on "Blind-Ear"——Copper Deficiency Symptom in Wheat on Subtropic Hill Soils

The “blind-ear” as a Cu deficiency symptom in wheat on upland soils in the hilly area of Zhejiang Province was discussed in this paper.Through 3 years of field experiments,it was elucidated that “blind-ear” in wheat plant appeared due to the low level of available Cu in the soils,and the critical value 3 mg/kg for total Cu in the plant at grain filling stage and 1 mg/kg for available Cu(0.1 M HCl)in the soils.A basal dressing of 30 kg/ha of Cu sulfate to the soils could completely eliminate Cu deficiency symptoms,obtain normal grain yield and have residual effect for at least 3 years.

Effect of Anions on Toxicity of Cadmium Applied to Microbial Biomass in Red Soil

A laboratory incubation experiment was conducted to elucidate the effects of associated anions on toxicity of cadmium applied to microbial biomass in the red soil. Cadmium was applied at six different levels, i.e., 0 (background), 5, 15, 30, 60 and 100 μg-1 soil in the form of either cadmium acetate or cadmium chloride.Application of cadmium as cadmium acetate markedly reduced the soil microbial biomass carbon compared to cadmium applied as cadmium chloride at all the tested levels. Similarly, organic carbon to biomass carbon ratio in the soil was markedly increased by increasing the level of the cadmium in the soil as cadmium acetate,while the change was much smaller in the case of cadmium chloride at the same cadmium levels. The results suggested that due consideration should be given to the source of cadmium while deciding the cadmium levels in experiments.

Effect of Organic Manure on Phosphorus Adsorption－Desorption and Availability in Paddy Soil Derived from Red Earth

A field test with the traditional rotation of paddy rice/upland crop (wheat) was carried out on a paddysoil derived from red earth to elucidate the effect of organic manure on the phosphorus adsorption-desorptionby soil and its P availability Soil samples were taken from different treatments at rice harvesting stage andanalysed. The isothermal adsorption of P by the samples fitted very well with Langmuir equation, and hence,the parameters in the equation, i.e., maximum adsoaption (qm), constant related to bonding energy (k) andtheir product (k x qm) could be used as a comprehensive index to characterize the potential P adsorptivityof the soil.Organo-inorganic fertilization and organic manuring conld decrease qm and k, while mineral P appli-cation had little effect on them. The isothermal desorption of P was significantly correlated with initiallyadded and isothermally adsorbed P. Part of P added was fixed, which represented the P fixation capacityof soil, and organic manuring could obviously lower the P fixation. The content of soil available P had asignificant negative correlation with qm, k and fixed P. It is concluded that organic manure could increase theP availability of paddy soil derived from red earth by decreasing qm, k, maximum buffering capacity (MBC=k x qm) and fixation capacity.

Effect of Land Use History on Methane Emission and Methanogenic Flora in Flooded Soils

The characteristics of methane emission were compared among six types of upland and paddy soils developed from different parent materials with distinct physics and chemical properties after planting rice. The fluxes of methane emission in submerged soils from the upland were obviously lower than those from the paddy rice field. The flux of methane emission in the paddy soil developed from fluvo-aquic soil was the largest among all the types of soils. Planting of rice was helpful to emission of methane in soils. The amounts of various groups of methanogenic flora were conformed with the deferences among the fluxes of methane emission in various types of soils. Methane formation was observed in each type Of air-dried soils stored for a long time after addition of water and incubation at 35℃.

Biological Characteristies of Methane Emission of Oryzasativa，Panicumcrus－galliand Cyperusdif for misGrown on PaddySoil

Biological characteristics of methane emission were compared among Oryza sativa, Panicum crus-galli andCyperus difformis grown on paddy soil. The order of the amounts of methane emitted was P. crus-galli > O. sativa >C. difformis, with the former two 11 and 8 times as much as that of the latter, respectively. And it was just opposite tothat of the methane-forming activities of roots of the three plants. The diurnal changes of methane emission of thethree plants were relatively consistent with valleys during 11:00-14:00 and midnight and peaks during 8:00-11: 00,14:00- 20:00 and about 5:00 early morning. The methanogenic activites in rhizospheric soils were higher than those innonrhizospheric soils with P. crus-galli and O. sativa, but not with C. difformis. The pathways of methane release ofP. crus-galli and O . sativa were probably through the top gaps near the junctions of nodal plate and leaf sheath, how-ever in C. difformistopgaps from which methane could escape into atmosphere were not found.

Effect of Cl￣ on Behavior of Fertilizer Nitrogen, Nnmberof Microorganisms and Enzyme Activities in Soils

Pot experiments were conducted to study the effect of Cl￣- on transformation of fertilizer N, number ofmicroorganisms and enzyme activities in soils. It is indicated that Cl￣- did not show significant influenceon total number of bacteria, actinomyces and fungi, but significantly reduced the number of nitrosobacteria,which led to decrease of NO content in the soil. Application of Cl￣- to soil could significantly enhance theactivities of phosphatase and urease in the coastal saline soil and orthic aquisols. In hilly red soil, however,the application of Cl￣- at the rate of 500-1000 mg Cl￣- kg￣(-1) soil significantly decreased the activity of thetwo enzymes mentioned above.

An Integrated Planning for Rense and Wetland Strategyof Waste Water from Rural Enterprises: A Case Stndy

A waste water reuse engineering was designed and then operated in Hongshan, a small town in ZhejiangProvince, China, in order to solve pollution and shortage of water resources due to the development of ruralenterprises. The results showed that series-structure design and cycling model were two effective modes ofsaving water and decreasing pollutants into environment, and wetland strategy should be a component partof the integrated planning for waste water reuse of rural enterprises. This case study could provide a basisfor the optimum utilization and pollution avoidance of water resources.

Effect of Liming on Cadmium Forms and Its Toxicity in Red Soils

The effect of liming 4 soils developed from Quaternary red clay and red sandstone on the cadmium forms and its toxicity were investigated.Liming the acid red soils could greatly reduce Cd toxicity to plants because the soluble Cd and organic Cd in the soils decreased significantly while Cd bound to minerals/oxides and residual Cd increased markedly with increasing lime rates(pH).

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 SO42-, WO42-, MoO42-, HPO42- and H2PO4- which competed for anion adsorption sites. The depressing extent of these anions was found to follow the sequence: HPO42-, H2PO4-> MoO42-> WO42-> SO42-> > Cl-, NO3-. The amounts of Cr (Ⅵ) desorption varied with different extractants. 0.5 M NH4F and 0.1 M KH2PO4 could be regarded as the best extractants for Cr (Ⅵ) sorbed in the soils. The mechanism of Cr (Ⅵ) adsorption by goethite and soils seemed to be similar to that of phosphate. Basically, Cr (Ⅵ) was adsorbed through specific adsorption and could not be desorbed by Cl- and NO3-. Cr (Ⅵ) adsorption on goethite released OH-. There was a significant correlation between the amounts of Cr (Ⅵ) adsorbed and pH variation in goethite suspension.

Effect of Bradyrhizobium sp. Inoculation on Biomass and Nodulation of Cowpea

Vigna unguiculata(L.) Walp (cowpea) is a tropical legume of very high nutritive and economic values. A laboratory experiment was conducted to evaluate the BNF (biological nitrogen fixation) efficiency of 4 strains of Bradyrhizobium sp. (VUXYI, VUIEI, VUMDSI and VUIDI). From the results obtained these strains were classified into efficiency groups, with VUIDI being the most efficient and VUXYI the least efficient.The effect of inoculation was tested on 2 cowpea varieties in a field experiment. Remarkable increases in nodulation biomass and crop yield were observed. An increase from 58% to 81% in dry seed was obtained for the two varieties. A significance test revealed a significantly positive correlation between nodulation and biomass.

Effect of Land Reclamation on Nutrient Distribution in Reclaimed Farmlands Overlying Xuzhou Underground Coal Mines *1

This research was carried out to evaluate the effect of the reclamation procedure with respect to soil fertility and nutrient distribution pattern in the reprecipitated reclaimed soil. Although there was an obvious indication of low levels of essential nutrients in the reclaimed farmlands (organic matter=0.32 g kg -1 ,total N=380.8 mg kg -1 , available P=4.7 mg kg -1 ), compared to the undisturbed farmlands (organic matter=2.5 g kg -1 , total N=1 220 g kg -1 , available P=20.8 mg kg -1 ), the uneven pattern of nutrient distribution was also shown to have been the major limitation to successful reclamation. Further improvement can be achieved through the integration of intensive eco farming systems using proper fertilizer field correction (PFFC) and organic manure for successful reestablishment and management of newly reclaimed farmlands overlying the Xuzhou coal mine subsidence.

Iron Oxides and Their Relations to Colors in Some Soilsof Southern China

Iron oxides from 33 samples of 25 soils derived from various parent materials in the southern China were studied using NaOH selective dissolution technique and X-ray diffraction (XRD). Goethite and hematite were the only two crystalline Fe oxides occurring in a significant quantity. The goethite / (goethite + hematie )ratios ranged from 0 to 1, being the highest in yellow soil, some yellow-red soils and saprolite samples and the lowest in soils derived from purple sandstone where only hematite was present. Al substitution in goethite ranged from 6.6 to 29.9 mol % with a mean value of 16.7 mol %, while substitution of Al in hematite ranged from 0 to 12.1 mol %. The values of Al substitution of hematite in coexisting goethite and hematite were closely related with corresponding values of goethite (r=0.7292, P<0.01, n=27). The redness rating of soils increased linearly with increasing amount of hematite (r=0.8109, P<0.01). It was suggested that redness rating could be used to crudely estimate hematite contents of soils.

Composition and Characteristics of Organo-Mineral Complexes of Red Soils in South China

The objective of the present study is to reveal the composition and characteristics of organo-mineral complexes in red soils (red soil, lateritic red soil and latosol) of south China in terms of chemical dissolution and fractional peptization methods. In the combined humus, most of the extractable humus could dissolve in 0.1 M NaOH extractant and belonged to active humus (H1), and there was only a small amount of humus which could be further dissolved in 0.1 M Na4P2O7 extractant at pH 13 and was stably combined humus (H2). The H1/ H2 ratio ranged from 3.3 to 33.8 in red soils, and the proportions of both H, and total extractable organic carbon (H1+H2) in total soil organic carbon and the ratios of H1 to H2 and H1 to (H1 +H2) were all higher in lateritic red soil and latosol than in red soil. The. differences of combined humus composition in various red soils were directly related to the content of Fe and Al oxides. In organo-mineral complexes, the ratio of Na-dispersed fraction (G1) to Na-ground-dispersed fraction (G2) was generally smaller than 1 for red soils, but there was a higher G1 / G2 ratio in red soil than in lateritic red soil and latosol. G1 fraction had a higher content of fulvic acid (FA), but G2 fraction had a higher content of humic acid (HA). The ratios of H1 to H2 and HA to FA were higher in G2 than in G1. The differences in the composition and activity of humus between G1 and G2 fractions were related to the content of free Fe and Al oxides. The quantities of complex Fe and Al, the Fe/ C and Al/ C atomic ratios were higher in G2 than in G1, and the ratio of Al/ C was much higher than that of Fe/ C. It may be deduced that aluminum plays a more important role than iron in the formation process of organo-mineral complexes in red soils.

Agronomic Effectiveness of Partially Acidulated Phosphate Rock

Laboratorial incubation and field experiments were conducted on soils ranging in texture from sandy loam toclay and in PH from 3 .6 to 9.0 to determine the agronomic effectiveness of single superphosphate (SSP), fused magne-sium phosphate (FMP)and partially acidulated phosphate rock (PAPR)on 8 field crops. The results showed that thepottern of available P released from SSP was fixing -releasing-fixing-steady state, while that of PAPR was shortlyfixing-slowly releasing-fixing-steady state And the PAPR . SSP and FMP were equally effective as judged by yield, Puptake by plants and extractable P in soils after crop harvesting. The PAPR used as basal fertilizer was more effectivethan that as top dressing, and its residual effect was also obvious.

Dynamics of ryegrass P in red soils

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