Nature of Soil Acidity in Relation to Properties and Lime Requirement of Some Inceptisols

Some Inceptisols representing the Singla catchment area in Karimgaunge district of Assam, India, were studied for lime requirement as influenced by the nature of soil acidity. The electrostatically bonded (EB)-H+ and EB-Al3+ acidities constituted 33 and 67 percent of exchangeable acidity while EB-H+, EB-Al3+,exchangeable and pH-dependent acidities comprised 6, 14, 20 and 80 percent of total potential acidity. The pH-dependent acidity made a major contribution towards the total potential acidity (67%～84%). Grand mean of lime requirement determined by the laboratory incubation method and estimated by the methods of New Woodruff, Woodruff and Peech as expressed in MgCaCO3 ha-1 was in the order: Woodruff (15.6) ＞ New Woodruff (14.9) ＞ Peech (5.1) ＞ incubation (5.0). Correlations analysis among different forms of acidity and lime requirement methods with selected soil properties showed that pH in three media, namely water, 1 mol L-1 KCl and 0.01 mol L-1 CaCl2, had a significant negative correlation with different forms of acidity and lime requirement methods. Exchangeable Fe and Al showed significant positive correlations with EB-Al3+ acidity, exchangeable acidity, pH-dependent acidity and total potential acidity, and also lime requirement methods. Extractable Al showed positive correlations with different forms of acidity except EB-H+ and EB-Al3+ acidities. The lime requirement by different methods depended upon the extractable aluminium.Significant positive correlations existed between lime requirements and different forms of acidity of the soils except EB-H+ acidity and incubation method. The nature of soil acidity was mostly pH-dependent. Statistically, the Woodruff method did slightly better than the New Woodruff, incubation and Peech methods at estimating lime requirement and hence the Woodruff procedure may be recommended for routine soil testing because of its speed and simplicity.     

Soil Potassium‐Release Characteristics and the Correlation of its Parameters with Garlic Plant Indices

Abstract

Potassium (K)‐release characteristics (PRC) of soil play a significant role in supplying available K. Information about PRC in the Hamadan soils is limited. The objective of this research was to study the PRC in nine soils from the Hamadan province by successive extraction with 0.01 M CaCl₂ over a period of 2000 h. The correlation of kinetic equation rate constants with soil properties and garlic indices was also studied. The release of K was initially rapid. More than 60% of the total K released during the first 168 h. The amount of K released after 168 h varied among soils and ranged from 292.8 to 736.8 mg kg^?1. The amount of K released after 2000 h was significantly correlated with K extracted by 1 M HNO₃, 0.01 M CaCl₂, and 0.1 M BaCl₂, whereas it was not significantly correlated with other soil properties. Potassium‐release characteristics were evaluated using five kinetic equations. Statistical analysis showed that the Elovich equation described the K‐release kinetics. A plot of other equations shows a discontinuity in slope at 168 h. Thus, two equations were applied to segments of the total reaction time (2 to 168 and 168 to 2000 h). The release‐rate constants (slope) in segment 1 are higher than in segment 2. The release‐rate constant of the Elovich equation and the zero‐order equation in two segments were significantly correlated with 1 M HNO₃, 0.01 M CaCl₂, and 0.1 M BaCl₂. Rate constants of the other equations were not significantly correlated with soil properties. The release‐rate constants of the Elovich equation and release‐rate constants of the zero‐order equation in two segments were significantly correlated with garlic indices. Rate constants of other equations were not significantly correlated with garlic indices. The results of this research showed that the Elovich and zero‐order equations can be used to describe K‐release characteristics.     

Evaluation of the Migration Capacity of Zn in the Soil–Plant System

The mobility and migration capacity of Zn in the soil-plant system were studied in a series of pot experiments with barley as a test plant. The parameters of Zn accumulation depending on the metal concentrations in soils and soil solutions were estimated by soil and water culture methods. Experiments with barley in water culture were performed on a nutrient (soil) solution extracted from soddy-podzolic soil (Albic Retisol (Loamic, Ochric)) to which Zn²⁺ was added to reach working concentrations increasing from 0.07 to 430 μM. Different responses of barley plants to changes in the concentration of Zn in the studied soil were identified. Ranges of the corresponding concentrations in the soil and aboveground barley biomass were determined. Parameters of Zn accumulation by test plants were determined depending on the metal content in soddypodzolic soil and the soil solution. A new method was proposed for evaluating the buffer capacity of soils with respect to a heavy metal (Zn) using test plants (BCS(P)_Zn). The method was used to evaluate the buffering capacity of loamy sandy soddy-podzolic soil. The considered methodological approach offers opportunities for using data obtained during the agroecological monitoring of agricultural lands with heavy metals (HMs), including the contents of exchangeable HMs and macroelements (C and Mg) in soils and concentrations of HMs and (Ca + Mg) in plants, in the calculation of the buffering capacity of the surveyed soils for HMs.     

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.     

Mechanisms for the Movement of Fe,Mn,Cu and Zn to Plant Roots in Loessal Soil and Lou Soil

The pot experiments were conducted in the artificial climate laboratories to determine the relative importance of mass flow and diffusion in supplying ,Fe,Mn,Cu,and Zn to wheat,soybean and maize plants growing in loessal soil and lou soil.It was found that the calculated relative contribution of mass flow of iron,manganese,copper and zinc to plant uptake varied from 5% to more than 100%,depending on the crop species and soil types as well as plant growth stage,soil moisture,atmosphere humidity,etc.The results also showed that the major transportation mechanisms of these micronutrients in soil-root system varied with the crop and its growth,climate and soil,singnificantly,In general,mass flow was more important for Cu and Zn and diffusion was more significant for Fe and Mn at the seedling stage.     

Effect of Organic Manure Application on Physical Properties andHumus Characteristics of Paddy Soil

Long-term field experiment was established in 1978 on a coastal paddy soil to determine the effect of application of pig manure, rice straw and chemical N fertilizer on the physical property and humus characteristics of soil. Results showed that the porosity, the microstructural coefficient, the reactivities of organic C and N, the OlogK value, the degree of oxidation stability, the contents of o-alkyl C and alkyl C, and the ratio of aliphatic C to aromatic C of humic acid from soils received organic manure increased; whereas, the ratio of<10μm to >10μm of microaggregates, the humification degree of humus, the degree of organo-mineral complexation, the number-average molecular weight, the C/H ratio, the contents of carboxyl and aromatic C of HAs in them decreased. These results indicated that the application of organic manure not only improved the physical property of the paddy soil but also made the HA more aliphatic in structure and younger in origin.     

Contribution of Iron and Aluminum Oxides to Electrokinetic Characteristics of Variable Charge Soils in Relation to Surface Charge

The contribution of iron and aluminum oxides to electrokinetic characteristics of variable charge soils was studied through determination of electrophoretic mobilities of the red soils treated with either removal of iron oxides or coating of aluminum oxides,and of those deferrated under natural conditions.After removal of the iron oxides,zeta potentials of the latosol and the red earth decreased obviously with a shift of IEP to a lower pH,from 6.4 to 5.3 and 4.1 to 2.4 for the former and the latter,respectively,and the electrokinetic change for the latosol was greater than for the red earth.Zeta potentials of the kaolinite sample increased markedly after coated with iron oxides.The striking effect of iron oxides on electrokinetix properties of the soils was also demonstrated by the electrokinetic differences between the samples from the red and white zones of a plinthitic horizon formed naturally,and between the samples from the gley and bottom horizons of a paddy soil derived from a red earth.The coatings of aluminum oxides on the latosol and the yellow earth made their zeta potentials rise pronouncedly and their IEFs move toward higher pHs,from 6.2 to 6.8 and 4.3 to 5.3 for the former and the latter,respectively.The samples with different particle sizes also exhibited some electrokinetic variation.The experiment showed that the effects of iron and aluminum oxides were closely related to the pH and type of the soils.     

Influence of Rhizosphere Bacteria on the State of Heavy Metal Сompounds in the Soil–Plant System

Eurasian Soil Science - The results of a greenhouse experiment with the humus horizon of a sandy loamy soddy-podzolic soil are presented. It was contaminated with heavy metals added with sewage...     

Investigation of Soil Concentrations of Persistent Organic Pollutants, Trace Elements, and Anions Due to Iron–Steel Plant Emissions in an Industrial Region in Turkey

The spatial distribution of several air pollutants emitted from iron–steel industries in Hatay-Iskenderun industrial region in Turkey was investigated by measuring their concentrations in soil. Collected soil samples (n?=?20) were analyzed for persistent organic pollutants (POPs; i.e., polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polybrominated diphenyl ethers, and polychlorinated naphthalenes), anions, and trace elements. Generally, all measured POP concentrations and marker trace elements for iron–steel industry (Zn, Pb, and Cu) were high relative to those reported previously for rural and urban areas around the world, and they were comparable to those measured recently in a similar industrial region (Aliaga, Izmir, Turkey). For all investigated POPs, elements, and anions, the highest concentrations were measured at points located north of the iron–steel industries where their emissions are transported by the prevailing southerly winds. The spatial distribution and levels of POPs, elemental, and anionic concentrations indicated that the iron–steel plants in Hatay-Iskenderun region are important sources for these pollutants. Statistically significant relationships between several organic and inorganic pollutants further confirmed that they are emitted by common sources (iron–steel plants).     

Application of Ground Phosphate Rock to Dimmish the Effects of Simulated Acid Rain on Soil Properties

The effects of simulated acid rain retained in soil on the properties of acid soil and its diminishing by application of ground phosphate rock were investigated by using the sorption method.Results show as follows:(1)For yellow brown soil,the effect of simulated acid rain on the properties of soil with a pH value of 5.9 was relatively small,except a great quantity of acid rain deposited on it.(2) for red soil,the effect of simulated acid rain on the properties of soil was significant.With the increase of the amount of acid deposition,the pH value of soil was declined,but the contents of exchangeable H^ ,Al^3 and Mn^2 and the amount of SO4^1- retention were increased.(3) Many properties of acid soils could be improved by applying ground phosphate rock.For example,pH value of soils and the amounts of available P and exchangeable Ca^2 and Mg^2 were increased,and the amounts of exchangeable H^ and Al^3 and SO4^2- retained was reduced.The application of ground posphate rock could effctively diminish the pollution of acid rain to soil.     

Effect of Amorphous Silicon Dioxide on Cadmium Behavior in the Soil–Rice Plant System

The effect of amorphous silicon dioxide (SiO₂) on cadmium behavior in the soil–plant system was studied in a field experiment on a flooded paddy soil slightly contaminated by cadmium. The application of amorphous SiO₂ results in a 1.3- to 1.8-fold smaller cadmium accumulation in the aboveground organs of rice and a 1.8- to 2.6-fold decrease in the content of its available compounds, which can be explained by metal sorption on the surface of applied silicon dioxide and by the reaction of monosilicic acid, which forms in the SiO₂ solution, with cadmium. The decrease in cadmium availability is most intensive in the first 2 weeks after SiO₂ application. Amorphous silicon causes a 26.6% increase in rice productivity in the first season and 72.9% in the second. The data obtained testify to the fact that the application rates of traditional mineral fertilizers can be decreased without risk to rice productivity if silicon compounds are used. They should become an integral and important part of implementing the 4R-STRATEGY for fertilizer application and plant nutrition optimization.     

Methods to Estimate Aggregate Protected Soil Organic Carbon, 2: Does the Grinding of the Plant Residues Affect the Estimations of the Aggregate Protected Soil Organic Carbon?

A method to estimate the amount of soil organic carbon (SOC) physically protected within macroaggregates (>200 μm) consists of crushing soil samples and measuring the following SOC mineralization increase. This study investigated the effect of grinding the plant residues during soil crushing on the calculated amount of the protected SOC on two tropical soils (Arenosol and Ferralsol). Incubations of crushed and uncrushed soil samples amended with ground or unground plant residues were conducted. Our results showed that soil crushing increased SOC mineralization and that the presence of plant residues enhanced soil respiration also. The plant residues of the two soils had different decomposition rates, but grinding plant residues did not increase the amounts of cumulative carbon (C) mineralized after the 28 days of the experiment. We propose that the extra C mineralized after soil crushing is due to the breakdown of the soil structure and not to the grinding of plant residues.     

Screening of Seven Plant Species for Short‐Term Improved Fallows in the Humid Forest Zone of Cameroon

Seven short‐fallow plant species were evaluated for their aboveground biomass production, nutrient accumulation, and weed suppression potential in Nkolbisson, Cameroon. The fallow species included Arachis pintoi, Vigna radiata, Desmodium intortum, Centrosema pubescens, Indigofera hirsutus, Indigofera spicata, and Pueraria phaseoloides. The experimental design was a randomized complete block with four replications and seven treatments (fallow species). Twelve months after planting, highly significant differences (p < 0.01) were observed among fallow species for phosphorus (P), potassium (K), calcium (Ca), and magnesium (Mg) concentrations, respectively, in plant tissue. Similarly, highly significant differences (p = 0.0013) occurred among fallow species for aboveground biomass production, which ranged between 3.12 t ha^?1 (I. spicata) and 9.16 t ha^?1 (A. pintoi). Potassium only showed highly significant differences among plant species for nutrient accumulation (p = 0.0001). However, A. pintoi, C. pubescens, I. hirsutus, and P. phaseoloides yielded substantial amounts of recycled N (>100 kg ha^?1 year^?1) that can benefit the subsequent crop. For small‐scale producers, these species are likely to supply adequate nitrogen for cereal crops. A total of 26 weed species belonging to 15 botanical families were encountered in the various plots. Weed dry weight differed significantly (p = 0.02) among the fallow plots and ranged from 0.12 t ha^?1 (in P. phaseoloides plots) to 2.32 t ha^?1 (in A. pintoi plots). Results of this study suggest that there are a wide range of plant species that could be used in improved fallow technologies aimed at improving nutrient‐degraded soils and suppressing weeds.     

Evaluation of Soil Tests for Plant‐available Mercury in a Soil–Crop Rotation System

A reliable soil test is needed for estimating mercury (Hg) availability to crop plants. In this study, four extraction procedures including 0.1 M hydrochloric acid (HCl), 1 M ammonium acetate (NH₄OAc) (pH 7.0), 0.005 M diethylenetriaminepentaacetic acid (DTPA), and 0.1 M calcium chloride (CaCl₂) (pH5.0) were compared for their adequacy in predicting soil Hg availability to crop plants of a rice–cabbage–radish rotation system. The amounts of Hg extracted by each of the four procedures increased with increasing equilibrium time. The optimal time required for extraction of soil Hg was approximately 30 min, though it varied slightly among the four extractants. The amounts of Hg extracted decreased with increasing soil/solution ratio, and a soil/solution ratio of 1:5 appeared to be adequate for soil Hg availability tests. The amounts of Hg extracted increased in the order of NH₄OAc < CaCl₂ < DTPA < HCl in silty loam soil (SLS) soil, and the order was NH₄OAc < CaCl₂ ≈ DTPA < HCl in yellowish red soil (YRS) soil. Significant positive correlations among the four extractants were obtained in SLS soil. In contrast, the correlations were poor in YRS soil, especially for HCl. There were significant correlations between concentrations of Hg in edible tissue of three plants and the amounts of soil Hg extractable to the four extractants for soil–rice system and soil–radish system, but not for soil–Chinese cabbage system. The 0.1M HCl extraction overall provided the best estimation of soil‐available Hg and could be used to predict phytoavailability of Hg in soil–crop systems.     

Distribution of Polycyclic Aromatic Hydrocarbons in the Soil–Plant System as Affected by Motor Vehicles in Urban Environment

Eurasian Soil Science - The paper focuses on the interactions among the components of urban natural complex (surface soil layer, rhizosphere, and aboveground phytomass of herbaceous plants)...     

Modeling the Nutrient Balance of the Soil–Plant System using the 4M Simulation Model

Development of the Hungarian ecological systems model 4M was initiated because the conditions and methods of Hungarian applications are different from the ones that appear in international crop simulation software packages. Because the majority of ecological systems models, just like the CERES model that was used during the development of 4M, do not have phosphorus and potassium modules, 4M initially was incomplete. Based on the work of Hungarian and foreign experts, a nutrient module was developed and was incorporated into the 4M model. The new module was calibrated and validated for phosphorus and potassium using the results of Hungarian aftereffects and long-term experiments. In principle, the nutrient module can be made suitable for simulating the turnover of any kind of nutrient by giving adequate values to the parameters.     

Spatial Characteristics of Soil Organic Carbon Storage in China＇s Croplands

The soil organic carbon （SOC） pool is the largest component of terrestrial carbon pools. With the construction of a geographically referenced database taken from the second national general soil survey materials and based on 1546 typical cropland soil profiles, the paddy field and dryland SOC storage among six regions of China were systematically quantified to characterize the spatial pattern of cropland SOC storage in China and to examine the relationship between mean annual temperature, precipitation, soil texture features and SOC content. In all regions, paddy soils had higher SOC storage than dryland soils, and cropland SOC content was the highest in Southwest China. Climate controlled the spatial distribution of SOC in both paddy and dryland soils, with SOC storage increasing with increasing precipitation and decreasing with increasing temperature.     

Soil‐Applied Selenium Effects on Tissue Selenium Concentrations in Cultivated and Adventitious Grassland and Pasture Plant Species

Abstract

According to international nutritional standards, plant selenium (Se) concentrations in Belgium are too low. To correct this situation, adding Se in fertilizers for pastures and grasslands is suggested, similar to activities in Finland. However, there is a lack of data on meadow plant species' ability to absorb Se. Therefore, a pot experiment was initiated using 24 meadow plant species cultivated on a Belgian cambisol receiving standard fertilizer treatment, with or without the addition of 9 g Se ha^?1 yr^?1 as sodium selenate. Soil Se analysis confirmed the low Se status of the native soil. Mean foliar Se concentration in the control group was 0.05 mg kg^?1. Because plant deficiency may occur at levels less than 0.10 mg Se kg^?1, data provided further evidence for Se deficiency in Belgium plant production. When grown with Se, plant species showed wide variations for Se concentration, ranging from 0.08 to 0.49 mg Se kg^?1. All values were less than 2 mg Se kg^?1, the suggested threshold toxicity level for dairy cattle. There were two different types of plants in terms of response to Se fertilization. Most of the tested plants were known as nonaccumulators. There were also two probable secondary accumulators: Sinapis arvensis and Melilotus albus. Finally, one has to question the reliability of plant Se enhancement using this method when floristic composition is poorly controlled.     

Effect of Pig Manure Application on Structural Characteristics of Humic Acids in Brown Soil

The effect of application of pig manure (PM) on the structural characteristics of humic acids (HAs) of brown soil was studied in field and incubation experiments.The results showed that the number-average molecular weights (Mn),the ratios of C/H,C/H and O/C,the contents of carboxyl and phenolic hydroxyl groups,the content of aromatic C,the values of E2,E4 and λExmax of HAs all decreased;whereas,the contents of alkyl C and O--alkyl C,the ratio of carboxyl to phenolic hydroxyl groups,the degree of oxidation stability,te absorption intensity at 285mμ (UV),and 2920cm^-1 of HAs increased after the application of PM.The above results indicated that the molecular structure of HAs tended to be more aliphatic and simpler after the application of PM.