Tea Plantation Soil Research Articles

Assessing heavy metal pollution and potential ecological risk of tea plantation soils

Accumulation of heavy metals in agricultural soils tends to increase crop uptake of heavy metals, and can adversely impact human health through food chains. This study assessed the heavy metal pollution status and the potential ecological risk of tea plantation soils in southern Shaanxi Province, China. A total of 330 topsoil samples were collected to analyze the concentrations of seven heavy metals (Pb, Zn, Cu, Cr, Hg, As and Cd) and the pH level. The Hakanson potential ecological risk index was used based on the background levels of soil heavy metals in Shaanxi. Results showed that the averaged concentrations of soil Pb, Zn, Cu, Cr, Hg, As, and Cd were 10.0, 87.6, 16.4, 12.4, 0.2, 6.9 and 0.1 mg/kg, respectively. Cd and Hg concentrations exceeded level II of China’s Soil Environment Quality Standard (GB 15618–2009) in 9.3% and 7.0% of the total samples, respectively. The coefficient of variation ranged from 29.2% to 52.2% for different elements, and was 49.3% for Cd and 48.6% for Hg. The averaged comprehensive potential ecological risk index was 95.4, and the overall potential ecological risk was low, with 82.4% of the total samples at a low level of potential ecological risk. Cd and Hg contributed most to the potential ecological risk (35.5% and 46.5%, respectively), and the risks associated with other elements were relatively minor. This study suggested that soil Cd and Hg pollution should be controlled to ensure the safe production of tea in the study area. Keywords: ecological risk, heavy metal, soil pollution, tea plantation DOI: 10.25165/j.ijabe.20191206.4363 Citation: Zhao Z P, Yan S, Duan M, Fu J, Wang Q, Liu Z F, et al. Assessing heavy metal pollution and potential ecological risk of tea plantation soils. Int J Agric & Biol Eng, 2019; 12(6): 185–191.

Assessing heavy metal pollution and potential ecological risk of tea plantation soils

Assessing heavy metal pollution and potential ecological risk of tea plantation soils

Effect of tea plantation age on the distribution of glomalin-related soil protein in soil water-stable aggregates in southwestern China.

Glomalin-related soil protein (GRSP) is crucial for the accumulation of soil organic carbon (SOC), and contributes to the formation of soil aggregates. However, it remains unclear whether GRSP is involved in altering the stability of soil aggregates in the long-term tea planting process. The relationship between the distribution of GRSP and soil aggregates in tea plantations is poorly studied. We compared the distribution of SOC and GRSP in aggregates in tea plantations of different ages (18, 25, 33, and 55years) and those in an abandoned land and investigated their potential contribution to the soil aggregate stability. Tea plantation was found to be beneficial for the accumulation of SOC and GRSP compared to the abandoned land. The content of SOC significantly increased after tea plantation, especially in surface soil (0-20cm), and the increase range was 21.79%-46.51%, due to the centralized management of tea plantations. The content of total glomalin-related soil protein (T-GRSP) and easily extractable glomalin-related soil protein (EE-GRSP) varied with the increasing tea plantation age. The T-GRSP content was higher in 25-year-old tea plantation, while EE-GRSP was gradually decreased with the increasing age of the tea plantation, and T-GRSP had better correlation with SOC than EE-GRSP. Long-term tea plantation (after 33years) was not conducive to the preservation of GRSP. The distribution of GRSP in the tea plantation soils differed greatly among the aggregates, with the 0.25-1-mm aggregate having less GRSP, which might be related to the distribution of soil fungi in the aggregates. There was a significant correlation between T-GRSP and mean weight diameter (MWD; P < 0.05) in the whole soil, whereas EE-GRSP had no correlation with the MWD of the aggregates. The T-GRSP content was correlated closely with the stability of soil aggregates in the tea plantations, and their relationship was dependent on the aggregate scale. Our results show that the T-GRSP content in the tea plantation soils has important effects on the formation and stability of aggregates in this region, which was one of the factors affecting the structure and quality of tea plantation soil. Improving GRSP is an effective way for the both SOC sequestration and soil health after long-term tea plantation.

Strategical isolation of efficient chicken feather-degrading bacterial strains from tea plantation soil sample.

Chicken feather waste is generally insufficiently utilized despite its high content of protein, constituting an environmental issue. Biodegradation of the waste with enabling microbes provides an advantageous option among the available solutions. In this study, an efficient whole feather-degrading strain was strategically isolated from a soil sample taken from a local tea plantation that has little or nothing to do with feathers. The strain was identified as Bacillus thuringiensis (designated as FDB-10) according to the cloned complete 16S rRNA sequence. The FDB-10 could efficiently degrade briefly heat-treated whole feather (102°C, 5min; up to 90% of a maximum concentration of 30g/L) in a salt medium supplemented with 0.1g/L yeast extract within 24h (37°C, 150rpm). Addition of carbon sources (glycerol, glucose, starch, Tween 20, Tween 80, 1.25g/L as glycerol) to the fermentation medium could improve the degradation. However, significant inhibition could be observed when the added carbon source reached the amount usually adopted in the investigation of carbon source preference (1%). Nitrogen source (NH4Cl, (NH4)2SO4, peptone) adversely influenced the performance of the strain. When the molar concentrations of NH4+ were equal for the two salt, the inhibitory effect on degradation of whole feathers was similar. Entirely different from other reported feather-degrading strains showing a preference to melanin-free feather substrates, the strain isolated in this study could degrade melanin-containing feather equally efficiently, and higher protease activity could be detected in the digest mix. As a plus, the strain could degrade feathers in rice wash produced in daily cooking, indicating its potential use in the simultaneous treatment of rice cooker wastewater produced by a rice processing plant. All these results imply that the FDB-10 is a strain with great potential in the biodegradation of feather waste.

Rapid evaluation of soil fertility in tea plantation based on near-infrared spectroscopy

An efficient soil analysis technique was developed to monitor soil fertility and perform precise soil management in tea plantations. In this study, near-infrared spectroscopy combined with chemometric methods was utilized to determine the organic matter and total nitrogen content and evaluate fertility of tea plantation soils. First, photometric precision and subtractive spectroscopy were used as indicators in identifying optimal sample preparation condition. Spectral reproducibility reached an optimum with powder particle size of 100 mesh (0.149 mm). Second, after comparing the combinations of the partial least squares method with three different characteristic wavelength extraction methods, the genetic algorithm and competitive adaptive reweighted sampling quantitative discrimination models were determined to be optimal for organic matter and total nitrogen contents, with prediction correlation coefficients of 0.9102 and 0.8763, respectively. Third, classification models for soil fertility level using linear discriminant analysis, support vector machine, and extreme learning machine were established based on a full spectrum and successive projections algorithm separately. The successive projections algorithm-extreme learning machine model was deemed superior with a correct classification rate of 84.38%. Our findings demonstrate that the proposed near-infrared spectroscopy calibration models successfully achieve the nondestructive and rapid evaluation of organic matter and total nitrogen contents, as well as the classification of soil fertility levels, in tea plantation soils. The results provide a basis for the development of internet-of-things sensors in the construction of a high-yield and high-quality tea plantation.

Linking N2O Emissions from Biofertilizer-Amended Soil of Tea Plantations to the Abundance and Structure of N2O-Reducing Microbial Communities.

Nitrous oxide (N2O) contributes up to 8% of global greenhouse gas emissions, with approximately 70% from terrestrial sources; over one-third of this terrestrial emission has been linked to increased agricultural fertilizer use. Much of the nitrogen in fertilizers is converted to N2O by microbial processes in soil. However, the potential mechanism of biofertilizers and the role of microbial communities in mitigating soil N2O emissions are not fully understood. Here, we used a greenhouse-based pot experiment with tea plantation soil to investigate the effect of Trichoderma viride biofertilizer on N2O emission. The addition of biofertilizer reduced N2O emissions from fertilized soil by 67.6%. Quantitative PCR (qPCR) analysis of key functional genes involved in N2O generation and reduction ( amoA, nirK, nirS, and nosZ) showed an increased abundance of nirS and nosZ genes linked to the pronounced reduction in N2O emissions. High-throughput sequencing of nosZ showed enhanced relative abundance of nosZ-harboring denitrifiers in the T. viride biofertilizer treatments, thus linking greater N2O reduction capacity to the reduced emissions. Our findings showed that biofertilizers can affect the microbial nitrogen transformation process and reduce N2O emissions from agroecosystems.

Returning Tea Pruning Residue and Its Biochar Had a Contrasting Effect on Soil N2O and CO2 Emissions from Tea Plantation Soil

A laboratory incubation experiment is conducted for 90 days under controlled conditions where either pruning residue or its biochar is applied to determine which application generates the lowest amount of greenhouse gas from tea plantation soil. To study the effect of incorporation depth on soil N2O and CO2 emissions, experiment 1 is performed with three treatments: (1) control; (2) tea pruning residue; and (3) residue biochar mixed with soil from two different depths (0–5 cm and 0–10 cm layers). In experiment 2, only the 0–10 cm soil layer is used to study the effect of surface application of tea pruning residue or its biochar on soil N2O and CO2 emissions compared with the control. The results show that biochar significantly increases soil pH, total C and C/N ratio in both experiments. The addition of pruning residue significantly increases soil total C content, cumulative N2O and CO2 emissions after 90 days of incubation. Converting pruning residue to biochar and its application significantly decreases cumulative N2O emission by 17.7% and 74.2% from the 0–5 cm and 0–10 cm soil layers, respectively, compared to their respective controls. However, biochar addition increases soil CO2 emissions for both the soil layers in experiment 1. Surface application of biochar to soil significantly reduces both N2O and CO2 emissions compared to residue treatment and the control in experiment 2. Our results suggest that converting pruning residue to biochar and its addition to soil has the potential to mitigate soil N2O emissions from tea plantation.

Potassium solubilization, plant growth promoting substances by potassium solubilizing bacteria (KSB) from southern Indian Tea plantation soil

Abstract A study was undertaken to identify indigenous potassium solubilizing bacteria in southern Indian tea plantation soils. The samples were analysed for various soil edaphic parameters such as pH, Ec, water holding capacity, organic carbon, nitrogen, available phosphorous, exchangeable potassium, exchangeable calcium, sodium and magnesium and potassium solubilizing bacteria were identified. The study revealed that the population density was found to be more in Valparai soils (18.20×104/g of soil) followed by Gudalur and least in Koppa region (5.90×104/g of soil). The population density of KSB in soils of different cultivars of tea plants revealed that higher population was achieved with China hybrids especially UPASI-9 followed by ATK-1, SMP-1 and SA-6.The results indicated that existence of clonal preference by KSB and rhizosphere effect with very good bonding pattern of root systems. About six efficient KSB strains were selected based on its solubilization efficiency in agar and liquid medium. The strains were characterized and identified through biochemical and molecular level. Higher K solubilization (41.91 mg/l) was observed in the KSB strain isolated from Valparai region. In addition solubilization was more when MOP used as K source followed by SOP and Montmorillonite at 5th day of incubation period. Least K solubilization was recorded with GKSB6 (20.31 mg/l). They also proved to produce plant growth promoting substances. These potent indigenous potassium solubilizers were could be used as bioinoculants in tea plantation inturn reduces the usage of chemical fertilizers and improve soil fertility.

Dynamics of soil organic carbon mineralization in tea plantations converted from farmland at Western Sichuan, China.

Climate warming and land use change are some of the drivers affecting soil organic carbon (SOC) dynamics. The Grain for Green Project, local natural resources, and geographical conditions have resulted in farmland conversion into tea plantations in the hilly region of Western Sichuan. However, the effect of such land conversion on SOC mineralization remains unknown. In order to understand the temperature sensitivity of SOC decomposition in tea plantations converted from farmland, this study considered the different years (i.e., 2–3, 9–10, and 16–17 years) of tea plantations converted from farmland as the study site, and soil was incubated for 28 days at 15°C, 25°C, and 35°C to measure the soil respiration rate, amount, and temperature coefficient (Q10). Temperature and land use type interactively affected the SOC mineralization rate, and the cumulative amount of SOC mineralization in all the plots was the largest at 35°C. SOC mineralization was greater and more sensitive to temperature changes in the farmland than in the tea plantations. Compared with the control, tea plantation soils showed lower SOC mineralization rate and cumulative mineralization amount. The 16–17-year-old tea plantation with a low SOC mineralization amount and high SOC content revealed the benefits of carbon sequestration enhancement obtained by converting farmland into tea plantations. The first-order kinetic equation described SOC mineralization dynamics well. Farmland conversion into tea plantations appeared to reduce the potentially mineralizable carbon pool, and the age of tea plantations also had an effect on the SOC mineralization and sequestration. The relatively weak SOC mineralization temperature sensitivity of the tea plantation soils suggested that the SOC pool of the tea plantation soils was less vulnerable to warming than that of the control soils.

Abundance and diversity of carbon monoxide dehydrogenase genes from BMS clade bacteria in different vegetated soils

Carbon monoxide (CO)-oxidizing bacteria are active consumers of atmospheric CO, undergoing a CO oxidation process that is catalyzed by carbon monoxide dehydrogenase (CODH). Little is known about the phylogeny of a group of bacterial CO-oxidizers known as the BMS clade, which possess putative CODH genes, or their abundances in soils. In this study coxL genes indicative of bacteria belonging to the BMS clade were amplified from DNA directly extracted from four vegetated soils: paddy rice (PR) soil, maize cropland (ML) soil, tea plantation (TP) soil, and natural forest (NF) soil. Quantitative PCR (qPCR) analysis showed that BMS coxL gene copy numbers ranged from 1.47 × 107 to 7.40 × 108 copies g−1 dry soil and differed significantly among PR, ML, TP, and NF soils (P < 0.05). CoxL gene abundance appeared to be linked to total P and Olsen P concentrations, as revealed by correlation analysis (P < 0.05). Phylogenetic analysis of BMS coxL sequences indicated a diverse clade of BMS CO oxidizers closely related to Bradyrhizobium sp. ARR65, Rhizobiales GAS188, Paraburkholderia phytofirmans, and Tistlia consotensis. However, the community compositions of BMS coxL-containing bacteria differed among soils. Collectively, these results indicate a high abundance and diversity of BMS clade CO oxidizers in a wide variety of vegetated soils.

Diversity and functional properties of acid-tolerant bacteria isolated from tea plantation soil of Assam.

In this study, we report on the bacterial diversity and their functional properties prevalent in tea garden soils of Assam that have low pH (3.8-5.5). Culture-dependent studies and phospholipid fatty acid analysis revealed a high abundance of Gram-positive bacteria. Further, 70 acid-tolerant bacterial isolates characterized using a polyphasic taxonomy approach could be grouped to the genus Bacillus, Lysinibacillus, Staphylococcus, Brevundimonas, Alcaligenes, Enterobacter, Klebsiella, Escherichia, and Aeromonas. Among the 70 isolates, 47 most promising isolates were tested for their plant growth promoting activity based on the production of Indole Acetic Acid (IAA), siderophore, and HCN as well as solubilization of phosphate, zinc, and potassium. Out of the 47 isolates, 10 isolates tested positive for the entire aforesaid plant growth promoting tests and further tested for quantitative analyses for production of IAA, siderophore, and phosphate solubilization at the acidic and neutral condition. Results indicated that IAA and siderophore production, as well as phosphate solubilization efficiency of the isolates decreased significantly (P≤0.05) in the acidic environment. This study revealed that low soil pH influences bacterial community structure and their functional properties.

Influence of land use on bacterial and archaeal diversity and community structures in three natural ecosystems and one agricultural soil.

Studying shifts in microbial communities under different land use can help in determining the impact of land use on microbial diversity. In this study, we analyzed four different land-use types to determine their bacterial and archaeal diversity and abundance. Three natural ecosystems, that is, wetland (WL), grassland (GL), and forest (FR) soils, and one agricultural soil, that is, tea plantation (TP) soil, were investigated to determine how land use shapes bacterial and archaeal diversity. For this purpose, molecular analyses, such as quantitative polymerase chain reaction (Q-PCR), 16S rRNA gene sequencing, and terminal restriction fragment length polymorphism (T-RFLP), were used. Soil physicochemical properties were determined, and statistical analyses were performed to identify the key factors affecting microbial diversity in these soils. Phylogenetic affiliations determined using the Ribosomal Database Project (RDP) database and T-RFLP revealed that the soils had differing bacterial diversity. WL soil was rich in only Proteobacteria, whereas GR soil was rich in Proteobacteria, followed by Actinobacteria. FR soil had higher abundance of Chloroflexi species than these soils. TP soil was rich in Actinobacteria, followed by Chloroflexi, Acidobacteria, Proteobacteria, and Firmicutes. The archaeal diversity of GL and FR soils was similar in that most of their sequences were closely related to Nitrososphaerales (Thaumarchaeota phylum). In contrast, WL soil, followed by TP soil, had greater archaeal diversity than other soils. Eight different archaeal classes were found in WL soil, and Pacearchaeota class was the richest one. The abundance of bacterial and archaeal 16S rRNA gene copies in WL and GL soils was significantly higher than that in FR and TP soils. Redundancy analysis showed that bacterial diversity was influenced by abiotic factors, e.g., total organic carbon and pH, whereas total nitrogen, pH, and cation exchange capacity (CEC) significantly affected archaeal community composition. Pearson correlation analysis showed that bacterial and archaeal 16S rRNA gene abundance had the highest correlation with clay content (r > 0.905, P < 0.01), followed by total-P, CEC, pH, and silt (%). These results will lead to more comprehensive understanding of how land use affects microbial distribution.

Rates of soil acidification in tea plantations and possible causes

Soil acidification has threatened the sustainability of agricultural systems. Organic manures have been reported to alleviate soil acidification in tea (Camellia sinensis) plantations. However, little is known about the pH status at different soil depths in these plantations. Whether the downward movement of acid contributes to subsurface soil acidification and the magnitude of the movement are unknown. We took soil samples from tea plantations that were 5, 10, 20, 33, and 56 years old at depths up to 120cm in the soil profile. We examined the soil pH, Fe, Al, nitrate N (NO3-N), ammonium N (NH4-N), and organic carbon (OC) in every 20-cm soil layer, and observed the downward movement of H+, NH4-N, and OC using undisturbed soil column experiments. The results show that organic manures and plant residues increased the topsoil pH, but did not reduce soil acidification below 80cm. At a planting density of 10,000 plantsha−1 and with the application of organic manures at 6000kgha−1a−1, the soil acidification rates (decrease in pH) were −0.0161 and −0.0245 per year at depths of 80–100 and 100–120cm, respectively. The soil pH increased by 0.0158 and 0.0140 per year at depths of 0–20 and 20–40cm, respectively. The downward movement of acid is one cause of topsoil alkalization and deeper soil acidification in cultivated tea plantations. No-till farming and increased vegetation coverage to reduce the downward movement of H+, NH4-N, and OC are effective measures to alleviate deep-soil acidification. Planting density also affects soil acidification; tea trees excrete less H+ into the rhizosphere at a lower planting density than at a higher planting density. Tea plantation soil is not acidified at a lower planting density of 5000plantsha−1.

Paraburkholderia caffeinitolerans sp. nov., a caffeine degrading species isolated from a tea plantation soil sample.

A Gram-stain negative, facultatively anaerobic, non-sporulating, non-motile and rod-shaped bacterium, designated CF3T, was isolated from a tea plantation soil sample and its taxonomic position was determined using polyphasic taxonomy. Strain CF3T displayed optimum growth at 25°C, pH 5.0 and in the presence of 0-1% NaCl. Comparative phylogenetic analysis of the 16S rRNA, recA and gyrB gene sequences showed that the isolate belongs to the genus Paraburkholderia, showing high levels of similarity with respect to Paraburkholderia oxyphila OX-01T (98.3, 95 and 93%, respectively) and Paraburkholderia sacchari IPT101T (98.2, 95 and 95%, respectively). The predominant ubiquinone was determined to be Q-8, and the polar lipids are phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unidentified amino-phospholipid, three unidentified amino-lipids and three unidentified polar lipids. The major fatty acids were found to be C16:0, C17:0 cyclo, summed feature 8 (C18:1 ω7c and/or C18:1 ω6c) and summed feature 3 (C16:1 ω7c and/or C16:1 ω6c). The DNA G+C content was found to be 63.8mol% and the DNA-DNA relatedness values between strain CF3T and its two close relatives P. oxyphila OX-01T and P. sacchari IPT101T was 41 and 40%, respectively. Based on phylogenetic analysis, phenotypic and genotypic data, it is concluded that the isolate represents a novel species of the genus Paraburkholderia, for which the name Paraburkholderia caffeinitolerans sp. nov. is proposed. The type strain is CF3T (=LMG 28688T=CGMCC 1.15105T).

Effect of tea plantation age on the distribution of soil organic carbon fractions within water-stable aggregates in the hilly region of Western Sichuan, China

Establishment of tea plantations (Camellia sinensis L.) could markedly change the pools of soil organic carbon (SOC) and labile organic carbon (LOC). However, the effects of different chronosequence phases on the quantity and quality of SOC in such plantations were poorly understood. In this study, we investigated SOC dynamics following farmland conversion to tea plantations of 16-, 23-, 31-, and >50years old in Zhongfeng Township of Mingshan County, Sichuan, which is in southwest China. We specifically examined the effects of the age of various tea plantations on the concentrations of SOC and LOC, including readily oxidizable carbon (ROC), water soluble organic carbon (WSOC), microbial biomass carbon (MBC), particulate organic carbon (POC), and mineralizable organic carbon (MOC) within soil water-stable aggregates. We found that the contents of very coarse fraction (>5mm) and very fine fraction (<0.25mm) dominated in the soil of the different tea plantations. Importantly, contents of water-stable aggregates at the size of >5mm and mean weight diameter (MWD) in 23year old tea plantation were seen to be higher when compared with >50years, indicating that maximum soil stability was within soil macro-aggregates. SOC, ROC, POC, MBC, and MOC contents were reduced with the decreasing of particle size except for WSOC. On the whole, the SOC concentrations in >50yr. of tea plantations at two soil depths were significantly lower than those of 23yr. In addition to WSOC, other LOC contents changed in trends parallel to SOC, demonstrating that tea plantation reaching up to about 23years contributed more to the soil quality than >50yr.

Characterization of the bioactive metabolites from a plant growth-promoting rhizobacteria and their exploitation as antimicrobial and plant growth-promoting agents.

A plant growth-promoting bacterial strain, PM 105, isolated from a tea plantation soil from the North Eastern region of India was identified as Pseudomonas aeruginosa through classical and 16S ribosomal DNA (rDNA) gene sequencing. Further studies with this strain confirmed broad spectrum antifungal activity against ten human and plant pathogenic fungal pathogens viz. Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus tubingensis, Candida albicans, Colletotrichum gloeosporioides, Fusarium oxysporum, Pencillium expansum, Rhizoctonia solani, Trichophyton rubrum besides growth-promoting property in cowpea (Vigna unguiculata) and pigeon pea (Cajanus cajan). However, no antibacterial property was exhibited by this strain against the four test bacterial pathogens tested in agar overlay method. The crude bioactive metabolites produced by this strain were isolated with three different solvents that exhibited significant antimicrobial and plant growth-promoting activity. Chloroform extract recorded significant antimicrobial and plant growth-promoting activity. Three major compounds viz. 1-hydroxyphenazine, pyocyanin, and phenazine-1-carboxamide were purified and characterized from crude extracts of this strain by various spectral data. The purified compounds recorded prominent antimicrobial activity but failed to establish the plant growth promotion activity in test crop plants under gnotobiotic conditions. Pyocyanin recorded significant antimicrobial activity, and best activity was recorded against T. rubrum (29 mm), followed by P. expansum (28 mm). These results suggest the use of PM 105 as plant growth-promoting agent in crop plants after successful field trials.

ISOLASI ACTINOMYCETES DARI TANAH KEBUN SEBAGAI BAHAN PETUNJUK PRAKTIKUM MIKROBIOLOGI

The objective of this study was to isolate actinomycetes from soil of tea plantations, Jamus ngawi as a microbiology lab manual chapter isolation and characterization of microbes. The medium used is the medium of MHA and MHB. Soil samples taken to a depth of 10-15 cm from the surface with capture location is about 07o 41'53,07 'S and 111o 37' 24.64 '' E. The isolates were obtained observed morphologic characters include colony shape, colony color, surface characteristics of colonies, colony growth, colony elevation, and the edge of the colony. Isolates of actinomycetes were successfully isolated are Streptomyces, Nocardia and Nocardiopsis. Actinomycetes isolates have been found that can be used as a collection of the microbiology laboratory.

Effects of organic and other management practices on soil nematode communities in tea plantation: a case study in southern China

AbstractFour major tea management practices (organic, pollution‐free, conventional, and semi‐natural) are employed in Chinese tea plantations at present. These practices can induce changes in the physiochemical parameters, microorganism community and enzyme activity in tea plantation soil. However, understanding of their effects on soil nematodes is still scarce. This study aimed to investigate whether and how different management practices affect the biodiversity, function, and structure of soil nematode communities in tea plantation habitats. The soil nematode community structures and ecological indices were determined from the soil samples collected more than 6 y after their respective farming practices were first applied, and different management practices did not greatly affect soil nematode community evenness or species diversity, but organic practice increased nematode trophic diversity, common species diversity, and species richness. Pollution‐free practice considerably increased fungivorous nematodes, and both pollution‐free and conventional practice decreased bacterivorous nematodes markedly in the subsurface layers of soil. Predator and omnivorous nematodes were found to be more abundant in semi‐natural plantation. Organic practice was more sustainable and suitable for tea cultivation, with the greatest biodiversity, best nutrient conditions, higher and more stable C/N ratio and lower interference in the food web.

Assessment of Selenium Bioavailability in Tea Plantation Soil to Bashan Tea Species (Wanyuan, Southwest China) Using Single Extraction Methods

Se concentration varies for different soil types, whether can be absorbed by plants is not related with the total amount of selenium, it is controlled by the bio-availability Se in soil. This paper is aim to look for the laws of the bio-availability Se in different soils, and find out an accuracy and effective method to extract the bio-available Se from different soil types. Digest the soil and tea leaves samples and used six methods (KH2PO4, NaHCO3, HAC, MgCl2, HCl, EDTA) to extract Se from the different soils, the result was measured by AFS. The mean values of total Se is 8.45μg/g in carbonaceous slates soil, 0.32μg/g and 0.41μg/g in malmstone soil, 0.78μg/g in shale soil. The maximum correlation coefficients (r) between the six extract methods and tea leaves about the extraction ratio of Se in four soils is 0.93188 with KH2PO4, 0.77097 and 0.83589 with NaHCO3, 0.84231 with HAC. So it can be indicate that the total Se contents is carbonaceous slates soil&gt;shale soil&gt;malmstone soil, the best extract method for carbonaceous slates soil, malmstone soil and shale soil are KH2PO4, NaHCO3, and HAC respectively.

Conventional to Ecological: Tea Plantation Soil Management in the Panchagarh District of Bangladesh

Conventional to Ecological: Tea Plantation Soil Management in the Panchagarh District of Bangladesh