Yellow Cinnamon Soil Research Articles

Effects of nitrogen reduction rates on grain yield and nitrogen utilization in a wheat-maize rotation system in yellow cinnamon soil

<abstract> <p>Excessive nitrogen (N) fertilizer application severely degrades soil and contaminates the atmosphere and water. A 2-year field experiment was conducted to investigate the effects of different N fertilizer strategies on wheat-summer corn rotation systems in yellow-brown soil areas. The experiment consisted of seven treatments: no N fertilization (CK), conventional fertilization (FP), optimized fertilization (CF), reduced N rates of 10% (90% FP), 20% (80% FP), 30% (70% FP), and a combination of controlled release with conventional urea at 7:3 ratio (CRU). The results indicate that under the condition of 80% FP, both CF and CRU treatments can increase the yield of wheat and corn for two consecutive years. Compared with FP treatment, the wheat yield of CF and CRU treatments increased by 3.62–2.57% and maize yield by 3.53–1.85% with N fertilizer recovery rate (NRE) of crops by 46.2–37.8%. The agronomic N use efficiency (aNUE) under CF treatment increased by 35.4–37.7%, followed by CRU, which increased by 30.5–33.9%. Moreover, compared with FP treatment, both CF and CRU treatment increased the content of organic matter (OM), total N (TN), and hydrolyzed N (HN) in the topsoil layer, and 70% FP treatment significantly reduced the HN content. Both CF and CRU treatments significantly increased the NO<sub>3</sub> concentrations in the 0–20 cm soil depth during the wheat and maize season at maturity stages and decreased the residual inorganic N below the plow layer (40–60 cm). During the corn season, the CF and CRU treatments significantly reduced the NO<sub>3</sub> concentration in the 40–60 cm soil layer from seedling to jointing. Considering various factors, CRU treatment under 80% FP conditions would be the best fertilization measure for wheat-corn rotation in yellow-brown soil areas.</p> </abstract>

Biochar-induced variations in crop yield are closely associated with the abundance and diversity of keystone species

Biochar application has widely been used to improve crop yield, but its effectiveness is uncertain. Soil microbial communities may play critical roles, but we lack experimental evidences on the relationships between these communities and crop yield following biochar application. Here, we used cooccurrence networks to demonstrate the importance of ecological clusters (cooccurring taxa of soil microbes including bacteria and fungi) and to identify specific keystone species that were closely connected with the variations in crop yield in a pot experiment. The experiment included two soils (i.e., red soil and yellow-cinnamon soil) for wheat growth, with each soil receiving three biochar application rate. The grain yield in the red soil significantly increased while that in the yellow-cinnamon soil significantly decreased with the biochar application rate. Generally, the grain yield from the two soils showed close correlations with the relative abundance as well as with the diversity of keystone species within major clusters rather than with the soil properties and enzyme activities. This contrasting effectiveness was mainly associated with the enrichment of beneficial and suppression of detrimental keystone species in the red soil and the suppression of beneficial and enrichment of detrimental keystone species in the yellow-cinnamon soil. These species together mainly accounted for the variation in the relative abundance of keystone species within major clusters of each soil, suggesting their potential to affect crop yield following biochar application.

Dominance of archaeal ammonia-oxidizers in soil nitrification across different soil types and fertilities in North China plain

Microbially mediated soil nitrification process was largely limited by ammonia-oxidizing archaea (AOA) and bacteria (AOB), which further affect nitrogen (N) loss and retention with concomitant impacts on both crop productivity and environment. However, the spatial distribution of ammonia-oxidizers and their varying contributions to soil nitrification activity at provincial scale are poorly explored. 135 agricultural soils across different soil types and fertility conditions were collected from Henan province in North China Plain to draw the map of soil AOA and AOB abundance with quantitative PCR analysis. Soil nitrification potential (NP) and the relative contribution of AOA and AOB to NP that recovers after acetylene inactivation were essentially determined among the five major soil types. The abundance of ammonia-oxidizers, which was positively and significantly related with pH, was obviously predominated by AOA with AOA/AOB ranging 1.96–9.79 at provincial scale. AOA contributed more (at 60%–79%) to soil nitrification in acidic and neutral soils (Lime concretion black soil, Yellow-cinnamon soil, Paddy soil and Cinnamon soil) with significant relationships with its higher abundance, pH, soil organic carbon and ammonium nitrogen. On the contrary, the even contribution of AOB compared with AOA in alkaline Fulvo-aquic soil showed poor relationship with its abundance but was strongly affected by soil N availability. In summary, AOA even with lower abundance showed stronger function in acidic and ammonia-limited soil environments, but AOB with higher abundance tends to be the leader of soil nitrification in alkaline and substrate-rich soils of Henan province.

Research on the Influence of Typical Soil Parameters on Critical Breakdown Field Strength and Residual Resistivity Based on Discharge Topography

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil.

Effects of various phosphorus fertilizers on maize yield and phosphorus uptake in soils with different pH values

ABSTRACT The performance of fertilizers may differ significantly in different soils. Here, we quantify effects of various phosphorus (P) fertilizers on maize yield and P uptake in soils with different pH values, using a pot experiment. Five P fertilizers were used; monoammonium phosphate (MAP), diammonium phosphate (DAP), calcium superphosphate (CSP), calcium magnesium phosphate (CMP) and, ammonium polyphosphate (APP). Two soils were neutral fluvo-aquic soil (pH 7.2) and acidic yellow cinnamon soil (pH 5.0). Generally, acidic soil restricted the root activity, dry matter accumulation, P uptake, and yield of maize. The effects of P fertilizers were inconsistent in the different soils. In neutral soil, the effects were the highest for DAP and lowest for CMP. However, in acidic soil they were highest for CMP, followed by DAP, and lowest for MAP. In neutral soil, DAP treatment showed higher P uptake efficiency (PUpE) and partial factor productivity (PPFP), while CMP treatment showed higher P harvest index (PHI) and utilization efficiency PUtE. In acidic soil, the PUpE and PPFP of CMP and DAP treatments were higher than in other treatments. Therefore, choosing the right P fertilizer based on soil acidity can significantly improve maize yield, P uptake, and P utilization to optimize P management.

Soil nematode community and crop productivity in response to 5-year biochar and manure addition to yellow cinnamon soil

BackgroundManure and biochar soil amendments have shown many benefits to soil quality and crop productivity. This study aimed to reveal the effects of biochar and manure applications on soil fertility improvement and crop productivity in yellow cinnamon soil.ResultsThis study based on a 5-year field experiment. Four treatments were designed, included the control (CK), biochar amendment, manure amendment, and both biochar and manure amendment (BM). The results showed that: after five years, both biochar and manure treatment improved soil structure by increasing soil mean weight diameter (MWD), and soil water and nutrient supply was also increased by increasing the contents of water content, available potassium and available phosphorus. The productivity was also enhanced as wheat yield under the biochar, manure, and BM treatments increased by 3.59–11.32% compared with CK. In addition, biochar and manure treatment increased soil microbial biomass carbon (MBC) by > 15%, and soil total nematode abundance was significantly increased. Furthermore, the nematode community structure was significantly affected by biochar and manure treatment, dominant trophic group in CK was herbivores, but bacterivores were dominant in the biochar and manure treatments. The distribution of nematode genera was closely related to soil chemical properties and microbial biomass. Increases in the Shannon's diversity index, and decreases in the dominance index and summed maturity index after the 5-year treatment indicated a sustainable soil ecosystem after the biochar and manure applications.ConclusionsThese findings indicate that biochar and manure result in better soil quality and increased productivity in yellow cinnamon soil.

Soil diatom communities and their relation to environmental factors in three types of soil from four cities in central-west China

Diatoms constitute a major part of microbial biomass and species richness in soil habitats. However, in spite of a growing interest on soil diatoms, variations in soil diatom communities across different types of soil are poorly known. We hypothesize that diatom communities are different in distinct soil types and can serve as a potential bioindicator for soil environmental assessment. Thirty-four soil samples were collected from Wuhan (yellow brown soil, n = 11), Xi'an (yellow cinnamon soil, n = 10), Korla and Karamay cities (brown calcic soil, n = 13) in central-west China. Diatom flora and thirteen environmental variables were analysed in these soil samples. In total, 66 taxa belonging to 30 genera were identified. Analysis of similarity (ANOSIM) revealed that diatom communities are significantly different among the three types of soil. The indicator species of yellow brown soil in Wuhan City included Pinnularia microstauron, Nitzschia amphibia, Sellaphora nigri, Pinnularia borealis and Humidophila contenta. Brown calcic soil in Korla and Karamay cities was characterized by Luticola suecorum, Luticola cohnii, Luticola nivalis and Luticola mutica. Yellow cinnamon soil in Xi'an City was featured by Stauroneis lundii and three unidentified Luticola species. Results of RDA showed that diatom communities were significantly correlated with magnesia, total phosphorus, organic phosphorus and conductivity, suggestive of the effects of nutrients and ionic strength on soil diatom distribution. Our results reveal high diatom diversity in soil habitats and highlight the potential of diatoms as a bioindicator for soil environmental assessment.

Subsoiling Improves the Photosynthetic Characteristics of Leaves and Water Use Efficiency of Rainfed Summer Maize in the Southern Huang-Huai-Hai Plain of China

In the southern Huang-Huai-Hai (HHH) region, China, maize production is frequently threatened by waterlogging at the seedling stage and by drought at the big flare stage. A two-year field experiment was performed to explore whether subsoiling (SS) in the winter wheat season could improve the photosynthetic capacity and increase the water use efficiency (WUE) of summer maize using the variety, Luyu9105. A split design was adopted in the experiment. The main plots used tillage practices, including SS and rotary tillage (RT). The subplots consisted of two irrigation methods, i.e., applied supplemental irrigation at the big flare stage (I) and no irrigation at the big flare stage (NI). The results showed that the SS treatment significantly increased soil water content (SWC) in the 40–60 cm soil layer. The SS treatment improved green leaf area index (gLAI) by 15.1%–30.2%, and enhanced the ear-leaf net photosynthetic rate (Pn), stomatal conductance (gs), intercellular CO2 concentration (ci) and transpiration rate (Tr), and was accompanied by an increase in the grain-filling duration (T) by 5 days and the mean grain-filling rate (Va). The SS treatment decreased the stomatal limitation (Ls), indicating that RT treatment, which was under lower SWC, led to a decrease in Pn. Applied supplemental irrigation under RT treatment was able to compensate for the growth of leaves, but could not reverse the decreasing trend in the gLAI. Ultimately, the SS treatment improved WUE by 9.1%–9.9%, and increased grain yields by 10.0%–29.3%. Therefore, this study showed that in the southern Huang-Huai-Hai Plain, which has a yellow cinnamon soil type, the practice of SS can improve the photosynthetic characteristics of leaves and WUE of rainfed summer maize.

Sorption of vanadium (V) on three typical agricultural soil of the Loess Plateau, China

ABSTRACTSelected three soil (yellow cinnamon soil, manual loessial soil and aeolian sandy soil) to study the kinetics and isotherms sorption of V(Ⅴ), and further explore the differences in the adsorption mechanism caused by initial V (V) concentration, ionic strength (IS), pH and different reaction times. It was observed that V(Ⅴ) adsorption onto the soil had three processes and completed rapid adsorption in 60, 100 and 120 min. The maximum adsorbing capacity of V(Ⅴ) on yellow cinnamon soil, manual loessial soil and aeolian sandy soil reached stable in pH range from 4 to 8. The adsorption capacity decreased with the increase of IS. V(Ⅴ) adsorption onto soil varied greatly with mineralogy and properties of soil, the surface area, soil organic carbon content and composition of particulate matter. This research enhanced the understanding of how soil properties affect vanadium (V) sorption onto agricultural soil.To investigate the reaction mechanism between vanadium (Ⅴ) and soil, and further explore the differences in the adsorption mechanism caused by initial V(V) concentration, ionic strength, pH and different reaction times. Selected three soil (yellow cinnamon soil, manual loessial soil and aeolian sandy soil) which are the typical agricultural soil from Shaanxi province to study the kinetics and isotherms sorption of V(Ⅴ). SEM study is used to probe the morphological features of the soil in the presence of vanadium and to investigate the change of surface functional groups on the three soils after adsorption by the FTIR spectra. It was observed that V(Ⅴ) adsorption onto the soil had three processes and completed rapid adsorption in 60 min, 100 min and 120 min. The maximum adsorption concentration of V(Ⅴ) derived from experimental data for the yellow cinnamon soil, manual loessial soil and aeolian sandy soil were 1124.6mg kg, 854.4mg kg and 748.6mg kg, respectively. The maximum adsorbing capacity of V(Ⅴ) on yellow cinnamon soil, manual loessial soil and aeolian sandy soil reached stable in the pH range from 4.0 to 8.0. The adsorption capacity decreased with the increase of ionic strength. V(Ⅴ) adsorption onto soil varied greatly with mineralogy and physical–chemical properties of soil, the BET surface area, soil organic carbon content and composition of particulate matter. This research enhanced the understanding of how soil properties affect vanadium (V) sorption onto agricultural soil.

Exploring the Distribution of Zn2+ in Inner and Outer Helmholtz Planes of the Electrical Double Layer of Soil based on Wien Effect

Core Ideas Wien effect measurements assess adsorbed cations distribution over the Helmholtz planes of the electrical double layer. Assessing cation distributions in the electrical double layer improves bioavailability predictions for plant nutrients and pollutant metals. Most of the zinc adsorption takes place in the inner Helmholtz plane layer and occurs via chemical interactions. The classical electrical double layer (EDL) theory explains the interaction between ions and charged soil colloidal particles, playing an importance role in the bioavailability and toxicity of ions in soils, which are of agricultural and environmental concern. A new approach based on extrapolating measurements of suspension Wien effect is suggested to determine the adsorbed ions distribution in the different compartments of the EDL. The new approach was applied to assess Zn2+ distribution in the EDL of Zn‐saturated soil colloids. The results showed that more than 84% of Zn2+ was adsorbed via chemical interactions and located in the inner Helmholtz plane layer. The remaining Zn2+ fraction was electrically adsorbed and distributed in the outer Helmholtz plane layer (0.3 to 2.1%) and in the Gouy–Chapman diffuse layer (7.4 to 15.0%). Independently, the results of linear combination fitting of extended x‐ray absorption fine structure (EXAFS) spectra indicated that the contents of outer‐sphere Zn in one paddy soil and the boggy soil were consistent with the proportions of Zn2+ electrostatically interacting with the soil colloids based on the extrapolation of the suspension Wien effect method, while the contents of outer‐sphere Zn in a second paddy soil, the yellow cinnamon soil, and the yellow brown soil was overestimated by the EXAFS method. The approach proposed in this paper to assess specific and electrostatic adsorption deepens our understanding of metal sorption processes in soils and reinforces the adequacy of the Grahame–Stern–Gouy–Chapman model of the EDL to describe the ion distribution in the solid‐water interface.

Effects of rice (Oryza sativaL.) cultivation and soil type on potassium mobilization and transformation behavior

To understand the chemical behavior of potassium (K) in soil, rhizobox experiments were conducted to study the effects of K uptake by cultivated rice and soil type on K migration and transformation in soils. The aim of this study was to guide reasonable application of K fertilizer in different soil types. The results showed that at the maximum tillering stage, the migration distances of water-soluble K (Sol-K) were 6 and 5 cm, the depletion of exchangeable K (Ex-K) was 7 and 4 cm, and depletion of nonexchangeable K (Nonex-K) was 1 and 5 cm, respectively, in yellow cinnamon soil (YCS) and fluvo-aquic soil (FS). With the growth of rice, the migration distances of Sol-K showed little difference between YCS and FS. Throughout the season, the contributions of Sol-K, Ex-K, and Nonex-K to K uptake in YCS were 12.0%, 40.0%, and 48.0%, respectively, whereas their contributions in FS were 25.7%, 25.8%, and 48.5%, respectively. K uptake by rice was linearly related to the concentration of different forms of K in soils (R2 = 0.687*). In conclusion, soil type significantly affected K mobilization and transformation behavior. This indicated that the location of K fertilizer addition in the root zone should differ with soil type.

Comparison of Archaeal Populations in Soil and Their Encapsulated Iron-Manganese Nodules in Four Locations Spanning from North to South China

ABSTRACTTo characterize the archaeal community composition in soil originating iron-manganese nodules, four types of soils—brown soil, yellow-cinnamon soil, yellow brown soil and red soil—and their associated iron-manganese nodules were collected from Queyu (QY), Zaoyang (ZY), Wuhan (WH) and Guiyang (GY), China, respectively, and subjected to quantitative polymerase chain reaction, cloning and sequencing analyses. The results showed that the archaeal 16S rRNA gene copy numbers in nodules, ranging between 3.59 × 102 and 4.17 × 103 copies g−1 dry nodule, were about 50–1000 times lower than those in their corresponding soils (1.87 × 105 to 1.08 × 106 copies g−1 dry soil), correlating with the low organic matter in the nodules, while archaea accounted for a relatively higher proportion of total prokaryote in nodules than in soils. Community composition analysis suggested that the archaeal diversity in both soils and nodules were much lower than bacterial, but archaeal community structures were similar to each other among the soils and nodules from the same location but varied among four locations, converse to the previous observation that bacterial community shifted markedly between nodules and soils as the result of habitat filtering. The archaeal communities in both soils and nodules were predominated by Thaumarchaeota Group I.1b with the relative abundance ranging between 73.88 and 94.17%, except that Euryarchaeota dominated the archaeal community in one nodule sample (WHn) developed from lake sediment. The finding shed new light on the archaeal diversity and their ecophysiology in different habitats, and further supported the opinion that archaea are more adaptable to stress and unfavorable conditions.

Potassium Fixation and Release Characteristics of Several Normal and K-Exhausted Soils in the Middle and Lower Reaches of the Yangtse River, China

Potassium (K) fixation and release in soil are important factors affecting K availability to plants and the utilization efficiency of K fertilizer. Three typical soils (red soil, yellow cinnamon soil, and alluvial soil) were collected from the middle and lower reaches of Yangtse River, China, to study the K-fixation and K-release characteristics of the normal and K-exhausted soil. Results showed that K fixation of added K in K-exhausted soils were significantly (P < 0.05) greater than that of the normal soils. There were significantly (P < 0.05) negative correlations among K-fixation capacity, concentration of soil-available K, and K+ saturation. Irrespective of soil K exhaustion, K fixation of added K was in the order of red soil > yellow cinnamon soil > alluvial soil, but the cumulative amount of K released from the three soils during successive extractions with 1.0 mol L−1 nitric acid (HNO3) was in the opposite order. The cumulative amounts of K released with 1.0 mol L−1 ammonium acetate (NH4OAc) and 1.0 mol L−1 HNO3 extraction increased with the increasing numbers of extractions. The K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was lower in K-exhausted soil than in normal soil. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.

Immobilization of soil exogenous lead using raw and activated phosphate rocks

Phosphate rock (PR) has been widely and successfully used in immobilization of lead in contaminated soils. However, application of oxalic acid‐activated PR (APR) in the immobilization of lead and particularly investigations about the lead form in the contaminated soils are limited. Exogenous lead (Pb) immobilization was studied by Tessier's sequential extraction procedures after applying raw PRs and oxalic acid APRs into the yellow cinnamon soil (S1) and latosol soil (S2) at four levels of 0 (CK), 50, 500, and 2000 mg P kg−1 soil. The PRs selected were Nanzhang PR (NPR) and Kaiyang PR (KPR), and their activation products were ANPR and AKPR. The results indicated that the content of exchangeable Pb in two soils decreased gradually with the rising PRs amount compared with the control, within 0–7.5 mg kg−1 in S1 and 0–64.1 mg kg−1 in S2. The content of carbonate‐bound Pb changed marginally in S1 while increased substantially in S2 with the increase of PR amount; the change of Fe–Mn oxide‐bound Pb content showed similar change as the carbonate‐bound Pb and organic compound‐bound Pb increased generally. The residue fraction of Pb changed a little for all treatments. To sum up, after applying the testing PRs in two soils, the content of exogenous exchangeable Pb decreased in all treatments and residual fraction augmented conversely in most treatments. Therefore, Pb had been immobilized effectively by PR in thetwo soils and a better fixation effect obtained in APR. ©2013 American Institute of Chemical Engineers Environ Prog, 33: 81–86, 2014

Effects of Simulated Acid Rain on Soil Chemical Properties of Potting Yellow Cinnamon Soil under Quercus Variabilis

Acid rain pollution is a serious environmental problem in the world. This study investigated the impacts of simulated acid rain on yellow cinnamon soil planted with seedlings of Quercus variabilis. The results showed that the acidity of simulated acid rain had complex impacts on the organic matter content of the studied soil. With the decrease of the acidity, available K increased but soil pH reduced. Rainfall of simulated acid rain also had impacts on available K and the soil pH, and produced the same trend as the acidity. In conclusion, we estimated that high intensity and large rainfall of acid rain could affect soil properties.

Adsorption and desorption behavior of herbicide diuron on various Chinese cultivated soils

The adsorption-desorption behaviors of diuron were investigated in six cultivated soils of China. The effect of system pH and temperature were also studied. The data fitted the Freundlich equation very well. The adsorption K(F) values indicated the adsorption of diuron in the six soils was in the sequence of black soil (D)>yellow earth (F)>paddy soil (B)>yellow-brown soil (C)>yellow-cinnamon soil (A)>lateritic red earth (E). The adsorption K(F) and Freundlich exponents n were decreased when temperature was increased from 298 K to 318 K. However, the Gibb's free energy values were found less negative with the increasing temperature. Meanwhile, the extent of diuron adsorption on soil was at rather high level under low pH value conditions and decreased with increasing pH value. In addition, the desorption behavior of diuron in the six soils was in the sequence of lateritic red earth (E)>yellow-cinnamon soil (A)>paddy soil (B)>yellow earth (F)>yellow-brown soil (C)>black soil (D). At the same time, desorption hysteresis of diuron were observed in all of the tested soils. And the soil organic matter content may play an important role in the adsorption-desorption behavior.

The difference of potassium dynamics between yellowish red soil and yellow cinnamon soil under rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation

To increase the use efficiency of potassium (K) fertilizer, special attention was paid to the dynamics of soil K in the root zone and non-root zone. Difference in K dynamics between yellowish red soil and yellow cinnamon soil under rapeseed (Brassica napus L.)rice (Oryza sativa L.) rotation was studied using a rhizobox system. Results showed that soil water soluble K (Sol-K) and exchangeable K (Ex-K) in the root zone of both soils were reduced in the early stage of rapeseed growth. Along with plant growth and K uptake, soil Sol-K in the inner (0–20 mm to root zone), middle (20–40 mm) and outer (40–60 mm) compartments of the non-root zone of yellowish red soil migrated towards the root zone. As a result, soil Ex-K was transformed into Sol-K. The changes in soil Sol-K and Ex-K in the non-root zone of yellow cinnamon soil were similar to yellowish red soil, and soil non-exchangeable K (Nonex-K) in the root zone also decreased significantly. In the early stage of rice growth, waterlogging promoted diffusion of soil Sol-K from non-root zone to root zone and transformation of Ex-K into Sol-K. Along with the growth of rice and K uptake, soil Ex-K in each compartment of yellowish red soil decreased significantly. Soil Sol-K and Ex-K in the yellow cinnamon soil declined to a certain extent, and then remained unchanged, while soil Nonex-K kept on decreasing. It revealed that the plants first absorbed K in the root zone, of which K reserve was replenished by a gradual diffusion of K from the non-root zone. The closer to the root zone, the greater the contribution to K uptake by plants. Within one rotation cycle, Ex-K and Sol-K in yellowish red soil were the main forms of K available to the plants, and little Nonex-K could be absorbed. However, in the yellow cinnamon soil, Nonex-K was the main form of K available to the plants, followed by Ex-K and Sol-K.

Effect of Selected Organic Acids on Cadmium Sorption by Variable- and Permanent-Charge Soils

Batch equilibrium experiments were conducted to investigate cadmium (Cd) sorption by two permanent-charge soils, a yellow-cinnamon soil and a yellow-brown soil, and two variable-charge soils, a red soil and a latosol, with addition of selected organic acids (acetate, tartrate, and citrate). Results showed that with an increase in acetate concentrations from 0 to 3.0 mmol L −1, Cd sorption percentage by the yellow-cinnamon soil, the yellow-brown soil, and the latosol decreased. The sorption percentage of Cd by the yellow-cinnamon soil and generally the yellow-brown soil (permanent-charge soils) decreased with an increase in tartrate concentration, but increased at low tartrate concentrations for the red soil and the latosol. Curves of percentage of Cd sorption for citrate were similar to those for tartrate. For the variable-charge soils with tartrate and citrate, there were obvious peaks in Cd sorption percentage. These peaks, where organic acids had maximum influence, changed with soil type, and were at a higher organic acid concentration for the variable-charge soils than for the permanent charge soils. Addition of cadmium after tartrate adsorption resulted in higher sorption increase for the variable-charge soils than permanent-charge soils. When tartrate and Cd solution were added together, sorption of Cd decreased with tartrate concentration for the yellow-brown soil, but increased at low tartrate concentrations and then decreased with tartrate concentration for the red soil and the latosol.