Tea Garden Soil Research Articles

Sensitivity of simulated hillslope subsurface flow to rainfall patterns, soil texture and land use

AbstractKnowledge of the generation of subsurface flow for hillslopes is important for controlling agricultural nonpoint nutrient losses. This study used a physically based hillslope hydrologic model HYDRUS‐2D to assess the sensitivity of simulated subsurface flow to the interactions between precipitation, soil texture and land use. Soil moisture data from 1 January 2013 to 23 August 2014 at two monitoring sites on a tea plantation hillslope were used to calibrate the van Genuchten–Mualem hydraulic parameters for this model. For six different textural classes (loamy sand, loam, silt, silt loam, clay loam and clay) and four land‐use types (tea garden, forest, grassland and bare soil), scenario‐based simulations were carried out for varied precipitation intensities (6.0, 15.0, 30.0, 45.0, 60.0 and 76.0 mm/day) and frequencies (time intervals of 1, 5, 10, 15, 20 and 25 days). Results indicated that the hillslope run‐off was dominated by subsurface flow, which was influenced by precipitation and antecedent moisture conditions. A threshold value of 0.18 m3/m3 of mean hillslope soil moisture was observed for the initiation of subsurface flow. High precipitation intensity (i.e. 75.0 mm/day) substantially increased subsurface flow for all soil textures. In addition, the sensitivity of the bare soil hillslope to rainfall patterns was more than two times higher than that of the vegetated (i.e. grassland, tea garden and forest) hillslope. These findings suggest that extreme precipitation events and land‐use change will increase the risks of subsurface flow on hillslopes. Therefore, optimal fertilizer application strategy and land‐use planning should be proposed for controlling the hillslope nonpoint nutrient losses.

Simultaneous Determination of β-Cypermethrin and Its Metabolite 3-Phenoxybenzoic Acid in Microbial Degradation Systems by HPLC-UV.

The wide use of pesticides in agriculture is necessary to guarantee adequate food production worldwide. However, pesticide residues have caused global concern because of their potential health risk to consumers. In this study, we could identify β-cypermethrin (β-CY) and its degradation product 3-phenoxybenzoic acid (3-PBA) by liquid chromatograph-mass spectrometry. Few studies on the simultaneous determination of β-CY and its metabolites have been carried out so far; hence, we established a high-performance liquid chromatography method to determine the concentrations of both β-CY and 3-PBA simultaneously in microbial degradation systems. In this study, a novel β-CY degrading strain, Bacillus licheniformis B-1, was isolated from a tea garden soil, utilizing β-CY as a growth substrate. Good linear relationships between β-CY and 3-PBA were observed and the concentrations of reference solutions were between 0.50 and 60.00 µg/mL. Satisfactory stability and intra- and interday precision were obtained. The limits of detection were 0.06 and 0.13 µg/mL for β-CY and 3-PBA, respectively, and the corresponding limits of quantification were 0.21 and 0.34 µg/mL, respectively. Spiking recoveries for β-CY varied from 98.38 to 105.80%, with relative standard deviations (RSDs) varying from 1.49 to 3.93%. Spiking recoveries for 3-PBA varied from 99.59 to 101.20%, with RSDs varying from 0.58 to 3.64%. The proposed method has advantages of simplicity, rapidity, high accuracy, good separation and reproducibility; thus, it is ideally suitable for simultaneous determination of β-CY and 3-PBA in microbial degradation systems.

Microbial decontamination of gamma irradiated black tea and determination of major minerals in black tea, fresh tea leaves and tea garden soil

The purpose of this research was to establish an effective dose of gamma irradiation to eliminate any possible bacterial contamination as well as assess the levels of essential major elements [sodium (Na), potassium (K), calcium (Ca), magnesium (Mg) and iron (Fe)] present in black tea. The samples were compared to fresh tea leaves and soil from the tea gardens of two distinct tea cultivating regions (Sylhet and Moulvibazar) in Bangladesh. Maximum coliform bacterial contaminants (4.0 × 102 cfu/g) were completely eliminated following an irradiation dose of 2.5 kGy, whereas a viable bacterial load of 9.0 × 103 cfu/g was completely eliminated at 5.0 kGy. Major elements were present at higher concentrations in black tea samples originating from Sylhet compared to those from Moulvibazar. Among the analyzed elements, only Na and Fe were present at higher concentrations in the fresh tea leaves from Sylhet, whereas K, Ca and Mg were observed at higher concentrations in the tea leaves from Moulvibazar. The amount of each mineral in the black tea is acceptable for daily intake and is safe for consumption. It is concluded that black tea from Bangladesh is a rich source of minerals and could be free of microbial contamination after receiving 5.0 kGy of gamma radiation.

Effect of synthetic pyrethroid insecticides on N2-fixation and its mineralization in tea soil

Microorganisms degrade a great variety of chemical substances including pesticide residues in soil. By virtue of low persistence and broad-spectrum efficacy, pyrethroid insecticides are sometimes used in tea garden to combat insect pests but the residual effects of these chemicals on microbial activities in soil have rarely been studied. The present experiment has been conducted under laboratory conditions to investigate the effect of four synthetic pyrethroid insecticides, viz. cypermethrin, deltamethrin, fenvalerate and permethrin at their field application rates (225, 200, 225, 210 g a.i. ha−1, respectively), on growth and activities of microorganisms in relation to non-symbiotic N2-fixation and N mineralization in a tea garden soil of the Himalayan terai (at the lower base) region of West Bengal, India. Application of insecticides, in general, decreased growth and activities of ammonifying and nitrifying bacteria but increased proliferations of non-symbiotic N2-fixing bacteria, resulting in greater fixation of atmospheric N2, more so with permethrin (7.8%) followed by cypermethrin (5.2%). Most of the insecticides had a deleterious effect on the accumulation of oxidizable organic C and total N, more pronounced with fenvalerate and permethrin. The availability of exchangeable NH4+ was also significantly reduced, more prominently with fenvalerate (15.6%) followed by deltamethrin (11.2%), while permethrin followed by cypermethrin accentuated greater accumulation of soluble NO3− in soil. Therefore, the effects of synthetic pyrethroid insecticides on microbial activities in relation to non-symbiotic N2-fixation and its mineralization in tea soil of West Bengal can not be generalized, rather in most cases the effects were inclined more towards detrimental than a few stimulative one.

Surface Amendments Can Ameliorate Subsoil Acidity in Tea Garden Soils of High-Rainfall Environments

Strongly acidic soils (pH < 5.0) are detrimental to tea (Camellia sinensis) production and quality. Little information exists on the ability of surface amendments to ameliorate subsoil acidity in the tea garden soils. A 120-d glasshouse column leaching experiment was conducted using commonly available soil ameliorants. Alkaline slag (AS) and organic residues, pig manure (PM) and rapeseed cake (RC) differing in ash alkalinity and C/N ratio were incorporated alone and in combination into the surface (0–15 cm) of soil columns (10 cm internal diameter × 50 cm long) packed with soil from the acidic soil layer (15–30 cm) of an Ultisol (initial pH = 4.4). During the 120-d experiment, the soil columns were watered (about 127 mm over 9 applications) according to the long-term mean annual rainfall (1 143 mm) and the leachates were collected and analyzed. At the end of the experiment, soil columns were partitioned into various depths and the chemical properties of soil were measured. The PM with a higher C/N ratio increased subsoil pH, whereas the RC with a lower C/N ratio decreased subsoil pH. However, combined amendments had a greater ability to reduce subsoil acidity than either of the amendments alone. The increases in pH of the subsoil were mainly ascribed to decreased base cation concentrations and the decomposition of organic anions present in dissolved organic carbon (DOC) and immobilization of nitrate that had been leached down from the amended layer. A significant (P < 0.05) correlation between alkalinity production (reduced exchangeable acidity – N-cycle alkalinity) and alkalinity balance (net alkalinity production – N-cycle alkalinity) was observed at the end of the experiment. Additionally, combined amendments significantly increased (P < 0.05) subsoil cation concentrations and decreased subsoil Al saturation (P < 0.05). Combined applications of AS with organic amendments to surface soils are effective in reducing subsoil acidity in high-rainfall areas. Further investigations under field conditions and over longer timeframes are needed to fully understand their practical effectiveness in ameliorating acidity of deeper soil layers under naturally occurring leaching regimes.

浉河区茶园土壤性状与茶叶品质相关性研究

为明确浉河区茶园土壤性质和茶叶品质的现状及其之间的相关性，通过对浉河区茶园所采土壤和茶叶样品的测定，明确茶园土壤性状和茶叶品质现状，并对其进行偏相关性分析。结果表明：供试浉河区茶园土壤pH值在4左右，低于茶树最适宜的最低pH值4.5~5.5；土壤有机质、全氮、碱解氮、有效磷含量丰富，均能够满足茶叶生长所需，有效磷的含量变异系数较大；董家河镇的速效钾含量相对较低。施用有机肥可增加茶园土壤细菌群落的丰度和生物多样性。所采茶叶样品的茶叶品质中，茶水浸出物、咖啡碱和氨基酸含量都满足优质茶叶的标准，茶多酚的含量偏低。茶叶百芽头重、水浸出物和咖啡碱含量都与土壤全氮量的偏相关性更为显著，茶多酚与土壤有效磷的偏相关性更为显著。 In order to clarify the soil nutrient and tea quality in the tea plantation of Shihe District in Xinyang, soil samples and tea samples were tested and the quality as well as the partial correlation between them were analyzed. The results showed that: pH value of the soil tested was at about 4, which was lower than the minimum pH of 4.5 - 5.5 that tea plant is the most suitable. The content of soil organic matter, total nitrogen, alkali-hydrolyzable-N and available phosphorus were rich, which were able to meet the growth of tea. The variation coefficient of available phosphorus content was larger. The content of available potassium was relatively lower in Dongjiahe Town that was a new tea region developed by Xinyang City. It could increase the abundance and biodiversity of bacterial community in tea garden soil to apply organic fertilizer. In the tea quality of tea samples taken, the content of tea-polyphenols was low, and the content of water extractives, theine and amino acids were to meet the standards of high-quality tea. The partial correlation between the content of one-hundred-bud weight, water extractives and theine and total nitrogen in soil was more significant, and there was more significant partial correlation between tea- polyphenols and available phosphorus in soil.

Ultraviolet-visible and Infrared Spectroscopic Studies of Soil Humic Acids

Structural characterization of humic acids extracted from surface, below 15 cm depth and 30 cm depth tea garden soils have been studied here. Instrumental analysis of the organic substances were carried out using UV-Visible and IR spectroscopies. The results reveal low level of humification of the humic acids occurring in the soil samples and low condensation of these molecules. The predominant aliphatic characters of the humic acid molecules are evident from this study. The occurrence of hydrogen bonded oxygen containing groups, e.g., hydroxyl, carboxyl, etc., have been observed. The presence of nitrogen containing organic compounds as well as unleachable (in acid and alkali treatments) metal-bonded oxygen and nitrogen species are also indicated. The results obtained in this study would be quite helpful for structural understanding of soil organic matters.

Effect of Nitrogen Fertilizer on Combined Forms and Transformation of Fluorine in Tea Garden Soil

Effect of Nitrogen Fertilizer on Combined Forms and Transformation of Fluorine in Tea Garden Soil

Soil Characteristics and Nutrients in Different Tea Garden Types in Fujian Province, China

Abstract: Anxi is the largest producing area of Tie Guanyin tea in China. “The cultural system of Tie Guanyin tea in Anxi” was selected as “Nationally Important Agricultural Heritage Systems” (China-NIAHS) in 2014. Tea gardens in this region are organic, ecological or non-ecological. After sampling the soil in these three kinds of tea gardens, we compared soil properties and nutrient content at different soil depths using physical and chemical analyses. Our aim was to provide a scientific basis for the management of tea plantations. We measured and analyzed soil in two organic, three ecological and one non-ecological tea gardens at depths of 0–10 cm and 10–20 cm in Anxi County. According to Duncan multiple comparisons and t tests, soil nutrients differed between organic and ecological or non-ecological tea gardens at 0–10 cm. Organic matter and total nitrogen differed between organic and nonecological tea garden soils at 10–20 cm. In organic tea gardens, soil bulk density, porosity, relative water content...

Characterization of biochar from fast pyrolysis and its effect on chemical properties of the tea garden soil

The characteristics and application of biochar from conventionally slow pyrolysis have been studied a lot, but biochar, as a byproduct in the bio-oil production process, produced by fast pyrolysis was rarely studied. This work assessed the characterization and utilization of biochars derived from rice husk (RH) and elm sawdust (ES) by fast pyrolysis. Incubation experiment of rice husk biochar (RHB) and acid soil in a controlled cabinet was carried out to test the effect of biochar on soil available elements. The volatile and fixed carbon was 2.2 and 1.7-fold respectively higher in elm sawdust biochar (ESB) than those in RHB, but the ash content was 4.2-fold higher in RHB than that in ESB. Although the C, H, N, and O contents were significantly varied in two biochars, the ratio H/C and O/C were nearly the same. The Fourier Transform Infrared Spectroscopy (FTIR) results revealed that RHB had more functional groups than ESB. More surface area was found in RHB (78.15m2g−1) than ESB (0.22m2g−1) by BET test. Incorporation of the biochar improved the quality of acid soil properties. The levels of soil pH, K, Ca, Mg, Na and total C and N increased while the Al and Pb contents decreased. Total carbon and potassium increased by 72% and by 6.7-fold respectively over the control at 4% of rice husk biochar adding level.

Effects of Phosphate Fertilizers on Bioavailable Lead in Tea Garden Soil and Lead Absorption and Accumulation by Tea Plants

Tea is a widely consumed beverage in the world and an important economic crop in China. However in recent years tea gardens were increasingly contaminated by heavy metals such as lead (Pb). Root uptake of Pb could contribute significantly to Pb accumulation in tea leaves due to the strong acidity of tea garden soils. To reduce the Pb bioavailability and absorption by tea plants, a pot experiment was conducted to evaluate the effects of 3 phosphate fertilizers separately with a normal application rate in the field of 0.2 g (P2O5) ·kg-1soil and a high application rate of 0.5 g (P2O5) ·kg-1soil on bioavailable Pb in tea garden soil and Pb absorption and accumulation by tea plants. Results showed that application of calcium magnesium phosphate significantly increased soil pH by up to 0.6 units from 3.50 to 4.13. Phosphate fertilizers resulted in an increase of bioavailable Pb concentration in tea garden soil under our experimental conditions. Pb concentration in tissues of the tea plants under different phosphate fertilizer treatments followed the order of root&gt;stem&gt;leaf. Calcium magnesium phosphate with a high application rate of 0.5 g P2O5·kg-1soil decreased Pb concentrations of roots, stems and leaves of tea plants significantly. For one phosphate fertilizer, Pb absorption in tea plants under high application rate was much lower than it under normal application.

English

An acidity-tolerant, aluminum resistant bacterium was isolated from tea soils in Kagoshima Experimental Station (Japan). Based on the morphological, physiological and biochemical characteristics and 16S rDNA nucleotide sequence analysis, the bacterium was identified as Bacillus sp. An 3 (DQ234657) in Bacillus cereus group. The bacterium was able to grow on S-LB plates (pH 3.7) with 1.0 g/L Al and survived in LB broth even at 10 g/L Al (pH 2.0). While cultured, the growth of the bacterial strain in LB liquid medium containing increasing concentrations of Al (0, 100 and 200 ppm), was inhibited by the presence of Al, especially at concentration of 200 ppm. The pH of culture medium without Al increased steeply and reached pH 7.0 after 10 days, meanwhile it was almost constant in the other cases. The elimination of Al from culture medium by the bacterium was also affirmed and it was more conspicuous at 100 ppm Al. Due to their tolerance to high acidity, resistance to and removal of a substantial amount of Al, the bacterium might be applicable in restoring acidic soils, particularly acidified tea garden soils. Key words: Tea garden soil, acidity-tolerant bacterium, aluminum-resistant bacterium.

Effects of tannic acid on active aluminum forms distribution in tea garden soils with different pH

采集云南省普洱市和江西省南昌县两地典型的茶园土壤, 通过添加HCl和Ca(OH)2调节土壤pH, 研究不同pH(3.0、3.5、4.0、4.5)茶园土壤添加0.4 mmol·kg^-1、2.0 mmol·kg^-1、4.0 mmol·kg^-1、8.0 mmol·kg^-1、12.0 mmol·kg^-1单宁酸后, 活性铝形态交换态铝(Al³⁺)、单聚体羟基铝[Al(OH)²⁺、Al(OH)₂⁺]、酸溶无机铝[Al(OH)₃⁰]和腐殖酸铝[Al-HA]的分布特征。结果表明: 单宁酸添加量为0~0.4 mmol·kg^-1和0~2.0 mmol·kg^-1时, 江西南昌和云南普洱茶园土壤中交换态铝随土壤pH的增加呈明显下降趋势, 而羟基态铝、酸溶无机铝和腐殖酸铝呈逐渐上升趋势; 当单宁酸浓度增至2.0 mmol·kg^-1以上时, 随土壤pH的增加, 单宁酸对活性铝释放的抑制作用增强, 各形态活性铝含量都较低, 且不同pH处理土壤间的差异不显著。0~20 cm土层土壤与20~40 cm土层土壤变化规律大致相似, 总体上看, 下层土壤活性铝总量高于上层。云南普洱茶园土壤活性铝总量明显高于江西南昌的茶园土壤。相关分析表明, 0~20 cm土层土壤中, pH与羟基态铝、腐殖酸铝、土壤酸碱缓冲容量(<i>pHBC</i>)呈正相关(<i>r</i>=0.796,<i> P</i><0.01;<i> r</i>=0.960, <i>P</i><0.01; <i>r</i>=0.852, <i>P</i><0.01); <i>pHBC</i>与交换态铝、羟基态铝呈负相关(<i>r</i>= 0.904, <i>P</i><0.01;<i> r</i>= 0.645,<i> P</i><0.05), 而与腐殖酸铝呈正相关(<i>r</i>=0.795,<i> P</i><0.01)。同时, 单宁酸加入浓度为0~0.4 mmol·kg^-1时, 土壤pH明显上升, 之后随着单宁酸加入浓度的增加土壤pH持续下降, 土壤pH(Y_pH)与单宁浓度(CDN)在此阶段基本符合方程: Y_pH= 0.04CDN+3.82 (<i>R</i>²=0.95,<i> P</i><0.01)的线性变化趋势, 在单宁酸浓度达到8.0~12.0 mmol·kg^-1时, 土壤pH基本不再变化。

Effect of crop residue biochar on soil acidity amelioration in strongly acidic tea garden soils

AbstractStrongly acidic soil (e.g. pH &lt; 5.0) is detrimental to tea productivity and quality. Wheat, rice and peanut biochar produced at low temperature (max 300 °C) and differing in alkalinity content were incorporated into Xuan‐cheng (Ultisol; initial pHsoil/water = 1/2.5 4.12) and Ying‐tan soil (Ultisol; initial pH soil/water = 1/2.5 4.75) at 10 and 20 g/kg (w/w) to quantify their liming effect and evaluate their effectiveness for acidity amelioration of tea garden soils. After a 65‐day incubation at 25 °C, biochar application significantly (P &lt; 0.05) increased soil pH and exchangeable cations and reduced Al saturation of both tea soils. Association of H+ ions with biochar and decarboxylation processes was likely to be the main factor neutralizing soil acidity. Further, biochar application reduced acidity production from the N cycle. Significant (P &lt; 0.05) increases in exchangeable cations and reductions in exchangeable acidity and Al saturation were observed as the rate of biochar increased, but there were no further effects on soil pH. The lack of change in soil pH at the higher biochar rate may be due to the displacement of exchangeable acidity and the high buffering capacity of biochar, thereby retarding a further liming effect. Hence, a significant linear correlation between reduced exchangeable acidity and alkalinity balance was found in biochar‐amended soils (P &lt; 0.05). Low‐temperature biochar of crop residues is suggested as a potential amendment to ameliorate acidic tea garden soils.

Amelioration Effects of Crop Residues with Different Chemical Components on an Acidic Tea Garden Soil

Various crop residues were applied to a strongly acidic tea garden soil to investigate their performance in ameliorating soil acidity. A laboratory study found the performance of crop residues on soil acid amelioration was mainly determined by the combined effect of nitrogen (N) transformation, cation exchange, and ash alkalinity. Nitrogen transformation was varied for different crop residues added, but followed N regulation, resulting in an adverse liming effect. It was assumed that during the release of ash alkalinity, cations replaced soil exchangeable acidity in soil solution, which largely diminished the liming effect of ash alkalinity. That was why soil pH was highly correlated with N transformation process. Furthermore, soil pH was positively correlated with carbon (C)/N ratios of crop residues both in low-level treatment (R 2 = 0.955) and in high-level treatment (R 2 = 0.981). Therefore, crop residues with relative high C/N ratios were considered to be more suitable for long-term pH adjustment of tea garden soils.

Humus Characterization of Humid Tropical Forest, Tea Garden, and Field Crop Soils of West Bengal, India: Chemical, Potentiometric, and Spectroscopic Methods

Humic acids (HA) and fulvic acids (FA) were extracted from tropical humid forest, tea garden, and field crop soils, and their chemical, potentiometric, and spectrophotometric properties were measured. There was less HA than FA in the cultivated soils. The HAs contained more carbon (C) and nitrogen (N) and had greater C/H ratios but lower O (oxygen)/H (hydrogen) ratios than FAs. Cultivated soils had greater total acidity than the forest soil generally because of both —COOH and phenolic-OH. Molecular weights of HA an FA, estimated from intrinsic viscosities, revealed that cultivation had reasonably reduced the molecular weights. The difference in pH (ΔpH) values, corresponding to three-fourths and one-fourth of the pH at final inflexion point showed that they were polyprotic. The longer time required for stability of greater pH of HAs was related to greater degree of stable coiling. The (E4/E6), in general, revealed a greater amount of aliphatic moiety rather than aromatic moiety.

Estimation of N2O emission from tea garden soils, their adjacent vegetable garden and forest soils in eastern China

The objective of this study was to investigate nitrous oxide (N2O) emissions from different land-use types in eastern China. The dynamic changes of N2O emissions were investigated in tea gardens with different nitrogen application rates, their adjacent vegetable garden and forest soils from June 2009 to May 2010. The results showed that high nitrogen application in a tea garden significantly increased soil N2O emissions. Lower N2O emission and percentage of N2O–N to the applied N were observed in a tea garden with low N application than that from vegetable garden, indicating reasonable control of N application can efficiently decrease N2O pollution in tea gardens. Both air and soil temperature had significant and positive impact on N2O emissions, but little effect of precipitation was observed. Therefore, N application rate and environmental temperature are the most essential factors in influencing N2O emission and should be taken into consideration in the field management of tea production.

Combined Use of Alkaline Slag and Rapeseed Cake to Ameliorate Soil Acidity in an Acid Tea Garden Soil

Rapeseed cake (RC), the residue of rapeseed oil extraction, is effective for improving tea (Camellia sinensis) quality, especially taste and aroma, but it has limited ability to ameliorate strongly acidic soil. In order to improve the liming potential of RC, alkaline slag (AS), the by-product of recovery of sodium carbonate, was incorporated. Combined effects of different levels of RC and AS on ameliorating acidic soil from a tea garden were investigated. Laboratory incubations showed that combined use of AS and RC was an effective method to reduce soil exchangeable acidity and Al saturation and increase base saturation, but not necessarily for soil pH adjustment. The release of alkalinity from the combined amendments and the mineralization of organic nitrogen increased soil pH initially, but then soil pH decreased due to nitrifications. Various degrees of nitrification were correlated with the interaction of different Ca levels, pH and N contents. When RC was applied at low levels, high Ca levels from AS repressed soil nitrification, resulting in smaller pH fluctuations. In contrast, high AS stimulated soil nitrification, when RC was applied at high levels, and resulted in a large pH decrease. Based on the optimum pH for tea production and quality, high ratios of AS to RC were indicated for soil acidity amelioration, and 8.0 g kg−1 and less than 2.5 g kg−1 were indicated for AS and RC, respectively. Further, field studies are needed to investigate the variables of combined amendments.

Analysis of nutrient and microbial Biolog function diversity in tea soils with different planting years in Fujian Anxi

茶园提早衰老退化是制约茶叶经济效益的一个关键性问题。以1年生、6年生与20年生茶树土壤为研究对象, 对不同年限的茶树土壤养分与微生物多样性进行研究。结果表明: 根据《茶叶产地环境技术条件》(NY/T8 53-2004)的pH和各项肥力指标, 1年生茶树土壤的pH为 4.73, 处于Ⅱ级水平, 6年生茶树土壤的pH为4.41, 接近Ⅱ级水平, 都符合优质、高效、高产茶园土壤的酸碱指标; 20年生茶树土壤pH为4.15, 接近4.0, 呈酸化。6年生茶树土壤的有机质、碱解氮和速效磷都达到肥力Ⅰ级, 速效钾处于肥力Ⅲ级, 整体肥力水平最好; 1年生茶树土壤的速效磷丰富, 达到肥力Ⅰ级, 碱解氮达到肥力Ⅱ级, 有机质和速效钾处于肥力Ⅲ级, 肥力处于中等水平; 20年生茶树土壤的有机质达到肥力Ⅱ级, 碱解氮、速效磷和速效钾都处于肥力Ⅲ级, 整体肥力水平最差。基于Biolog平板法的微生物功能多样性研究表明, 6年生茶树土壤的微生物群落利用碳源的能力最好, 20年生茶树土壤微生物对6类碳源的利用程度都不高, 1年生茶树土壤微生物对6类碳源的利用处于中等水平。多样性指数分析表明, 6年生茶树土壤微生物群落的Shannon、Brillouin、均匀度、丰富度指数均最高; 20年生茶树土壤最低。总之, 与6年生和1年生茶树土壤相比, 20年生茶树土壤呈现较强酸化, 有机质含量比6年生茶树土壤下降47.81%, 微生物群落的生理活性最低, 生理功能多样性急剧减少。

Influences of charcoal and bamboo charcoal amendment on soil-fluoride fractions and bioaccumulation of fluoride in tea plants

High levels of fluoride in tea plants pose a potential health risk to humans who drink tea. It has been demonstrated that tea plant fluoride is closely related to the available fluoride in soil. But approaches that could be used to regulate the availability of fluoride in soil have been rarely seen. This study aims to investigate how the addition of charcoal and bamboo charcoal affected soil fluoride availability and bioaccumulation of fluoride in tea plants. In a microcosm experiment, tea plants were grown in the tea garden soil mixed with different amounts of charcoal and bamboo charcoal [that is, 0.5, 1.0, 2.5, and 5.0% (w/w)]. Soil-fluoride fractions and fluoride accumulated in tea plants were determined using the sequential extraction and ion selective electrode method. Obtained results showed that both charcoal and bamboo charcoal additions significantly enhanced the concentrations of Fe/Mn oxide-bound fluoride, but significantly reduced the concentrations of water-soluble and exchangeable fluoride (p<0.05) in soil. Charcoal and bamboo charcoal additions also significantly decreased the amounts of fluoride in tea roots and tea leaves (p<0.05). However, the additions of charcoal and bamboo charcoal had no impacts on the tea quality, as indexed by the concentrations of polysaccharides, polyphenols, amino acids, and caffeine in tea leaves. These results suggested that application of charcoal and bamboo charcoal may provide a useful method to reduce the availability of fluoride in soil and the subsequent fluoride uptake by tea plants.