[Changes in Soil Nitrogen Components and Their Relationship with Environmental Factors with Different Tea Plantation Ages]

Changes in soil nitrogen components in tea gardens affect the soil nitrogen supply capacity and nitrogen cycle. In this study, soil samples were collected from forest land, cultivated land, and tea gardens with different plantation ages (30, 50, and 70 years) to explore the changes in soil nitrogen components and their relationship with physicochemical properties and enzyme activities. The results showed that:① with the increase in tea plantation age, the silt, total phosphorus, and urease and catalase activities gradually increased, whereas the sand, clay, pH, electrical conductivity, soil organic carbon, and the activities of invertase gradually decreased. The alkaline phosphatase activity increased first and then decreased with the increase in tea plantation age, and no significant differences were observed in soil water content and acid phosphatase activity. ② With the increase in tea plantation age, the contents of acid ammonia nitrogen, amino acid nitrogen, and nitrate nitrogen (NO3--N) increased significantly, and the contents of total nitrogen, acid ammonia nitrogen, hydrolyzable unknown nitrogen, and non-hydrolyzable nitrogen in tea gardens were significantly higher than those in forest land. ③ The total phosphorus, alkaline phosphatase, and urease were the main factors affecting soil nitrogen components. Among them, organic nitrogen components were significantly correlated with total phosphorus and alkaline phosphatase, and inorganic nitrogen components were significantly correlated with alkaline phosphatase, whereas total nitrogen had significant correlations with sand, silt, total phosphorus, urease, and alkaline phosphatase.

The Effects of Partial Substitution of Fertilizer Using Different Organic Materials on Soil Nutrient Condition, Aggregate Stability and Enzyme Activity in a Tea Plantation

Fertilization plays a crucial role in enhancing tea production. However, it has been demonstrated that the long-term single application of chemical fertilizer will reduce soil nutrient content and the formation of soil aggregates, which is not conducive to the sustainable development of soil and agriculture. Many studies have shown that partial substitution of chemical fertilizer with organic fertilizer can improve soil physicochemical properties and soil nutrient content. This study compared the effects of different organic materials as substitutes for chemical fertilizer. We partially replaced chemical fertilizer with rabbit manure, wine lees and rapeseed cake, amounting to 30% of the total annual nitrogen application in the field experiment, and we set nine different fertilization methods to assess and analyze the soil nutrient condition, aggregate stability and enzyme activity. The results showed that the experimental soil aggregate mean weight diameter (MWD) and geometric mean diameter (GMD) were significantly increased compared with control (p < 0.05); the aforementioned fertilization methods also decreased the soil aggregate fractal dimension (D), disruption rate (PAD), average weight-specific surface area (MWSSA) and soil erodibility factor (K). The application of the fertilizer containing organic materials and microbial agent increased soil organic carbon (SOC) by 20.7% to 22.6% and total nitrogen (TN) by 34.6% to 38.1%; it also significantly promoted sucrase, urease and protease activities in all aggregate sizes (p < 0.05) and increased the 2-5 mm aggregate content. The correlation coefficients between the SOC and the enzyme activities were 0.18-0.95, and most of them showed an extremely significant positive correlation (p < 0.01). In conclusion, the application of fertilizers containing organic materials and microbial agents can improve soil aggregate stability, aggregate enzyme activity and soil structural stability.

Improvement of soil acidification and ammonium nitrogen content in tea plantations by long-term use of organic fertilizer

Soil acidification is common in some Chinese tea plantations, which seriously affected growth of tea trees. Hence, it is essential to explore soil remediation in acidified tea plantations for sustainable development of the tea industry. We sought to determine how different fertilizers affect acidified soil and their N transformation in tea plantations. Different fertilizers were used on acidified tea plantation soils for 4 years (2017-2021), and changes in soil pH, indices related to soil N transformation and tea yield were analysed to construct interaction networks of these indices and find which had the largest influence on fertilization. Long-term use of sheep manure reduced soil acidification, increased soil pH, enhanced the number and intensity of N-fixing and ammonifying bacteria, urease, protease, asparaginase and N-acetamide glucose ribosidase activity and nifH gene expression. This treatment reduced the number and intensity of soil nitrifying and denitrifying bacteria, nitrate reductase and nitrite reductase activity, while the expression of amoA-AOA, nirK, nirS, narG and nosZ in turn increased ammonium N content of the soil, reduced nitrate N content, and enhanced tea yield. Topsis index weight analysis showed that ammonium N content in the soil had the largest impact among fertilization effects. Long-term use of sheep manure was beneficial in restoring the balance of the micro-ecosystem in acidified soil. This study provides an important practical basis for soil remediation and fertilizer management in acidified tea plantation soils.

[Effects of Fertilizer Application Strategy Adjustments on Nitrogen and Phosphorus Loss from Typical Crop Systems in Taihu Lake Region]

The intensity of crop farming fertilizer input is generally high in the Taihu Lake Region, with chemical fertilizer as the main form. Due to inappropriate fertilizer application, nitrogen and phosphorus loss have occurred, causing serious agricultural non-point source pollution. The Ministry of Agriculture and Rural Affairs of China has launched the "zero-growth action for chemical fertilizer use" and "replacement action with organic fertilizer" ("two actions" for short) campaigns since 2015. Local agricultural sectors adjusted fertilizer application strategies of crop farming to respond to the call of two actions. However, the current research is still focusing on reducing the total amount of fertilizer application and increasing the area of organic fertilizer application, which is mainly based on grain crops. The study of agricultural environment problems is still lacking, especially in vegetable, orchard, and tea systems. Therefore, a study was carried out in the typical agricultural area of Suzhou City Wuzhong District from 2019 to 2021. Based on the data of the amount of nitrogen and phosphorus removal by harvest crops and soil nitrogen and phosphorus residual in paddy, vegetable, orchard, and tea systems, the loss was estimated. The responses of nitrogen and phosphorus loss from typical crop systems to fertilizer application strategy adjustments were studied through analysis of different factors. The results showed that fertilizer application rate was the key to control nitrogen and phosphorus loss. Additionally, the suitable replacement ratio of organic fertilizer could further reduce the loss risk. It should be noted that the urgent demand for nutrients in crop growth should be considered to determine the timing of organic fertilizer application, and agricultural machinery should be used to assist organic fertilizer application to reduce labor output if possible. Fertilizer efficiency was the core of environmental friendliness and economic benefits of crop farming. Hence, improving fertilizer efficiency should be the guidance of fertilizer application strategy adjustment. Our suggestions on the adjustment of fertilizer application strategy in different crop systems in the study area are as follows:attention should be paid to the nitrogen, phosphorus, and potassium input ratio in paddy systems to further reduce nitrogen and phosphorus loss. Planting structure adjustment should be emphasized in vegetable systems to promote fertilizer efficiency. The strategy to satisfy both tea and orchard growth from a composite system perspective would help to build crop systems that meet the needs of green agricultural development.

Reasonable deep application of sheep manure fertilizer to alleviate soil acidification to improve tea yield and quality

Soil acidification in Chinese tea plantations is widespread, and it has significantly affected the growth of tea trees; it was important to explore soil remediation of acidified tea plantations in depth for the sustainable development of tea industry. In this study, the effects of sheep manure fertilizer with different application depths on soil acidification, tea yield and quality, and soil nitrogen transformation in tea plantations were analyzed for five consecutive years from 2018 to 2022. The results showed that long-term use of sheep manure fertilizer significantly reduced soil acidification (P< 0.05) in tea plantations, improved soil pH and soil ammonium nitrogen content, enhanced root activity and root nitrogen uptake capacity of tea trees, and thus improved tea yield and quality. The effect of different application depths of sheep manure fertilizer on tea yield and quality was mainly reflected in the transformation ability of soil ammonium nitrogen and nitrate nitrogen, which showed that high transformation ability of soil ammonium nitrogen and high ammonium nitrogen content were beneficial to high tea yield and vice versa, and the best effect was achieved when sheep manure was applied at a depth of 50 cm and 70 cm. The topsis analysis confirmed that sheep manure fertilization had a greater effect on root activity, ammonium nitrogen, ammonia intensity, and nifH gene. This study provided an important practical basis for the restoration of acidified tea plantation soil through sheep manure fertilizer management.

CFD-based pesticide selection for a nozzle used in a six-rotor UAV in hover mode for tea spraying

BACKGROUND

A key challenge for unmanned aerial vehicle (UAV) spraying sometimes used in tea plantations is the downwash flow structure there stronger than in crops. In addition, the UAV spray is affected by the relationship between the nozzle design and the pesticide. However, there is little current research on this aspect. As a preliminary step this study focuses on the most appropriate pesticide for a designated nozzle in a six-rotor UAV according to the nozzle-pesticide relationship using a three-dimensional computational fluid dynamics model. This model considers the downwash flow structure effect and nozzle spray performance in hover. Nozzle FVP110-02, widely used in six-rotor UAVs, is used as a representative nozzle and bifenthrin and tea saponin water, commonly used in tea plantations, are used as the pesticides.

RESULTS

The downwash flow structure of the six-rotor UAV in hover was conveniently controlled by the flight height and rotational speed, thereby causing the turbulence to be more stable. For nozzle FVP110-02, bifenthrin was more appropriate than tea saponin water at the same concentration, whilst bifenthrin and tea saponin water at a concentration of 1:1000 showed the best performance under identical working conditions.

CONCLUSION

The numerical model developed here was shown to be effective for investigating the relationship between nozzle and pesticide. Our findings will help to not only improve UAV spraying for tea cultivation but also provide guidelines for pesticide selection in crops. Further work will address the comparison of the rigorous qualification of the numerical simulations with the measurements by the field test. © 2023 Society of Chemical Industry.

Nitrous oxide emissions from tea plantations: A review

Tea plantations are an important N₂O source. Fertilizer-induced N₂O emission factors of tea plantations are much higher than other upland agricultural ecosystems. According to the basic information on characteristics and knowledge of N₂O emissions from tea plantations around the world, we comprehensively reviewed N₂O emission characteristics, production process, influencing factors, and reduction measures from tea plantations. The global means of ambient N₂O emission and N₂O emission stimulated by nitrogen fertilizer application from tea plantations were (2.68±2.92) kg N·hm^-2 and (11.29±9.45) kg N·hm^-2, respectively. The fertilizer-induced N₂O emission factor in tea plantations (2.2%±2.1%) was much higher than the IPCC-estimated N₂O emission factor for agricultural land (1%). N₂O emission from tea plantation soil (a typical acid soil) were mainly produced during nitrification and denitrification, with denitrification being dominant. N₂O emission from tea plantations were significantly related to the amount of fertilizer application. Other factors, such as fertilizer type, could also affect soil N₂O emissions in tea plantations. The main reduction methods of N₂O emission from tea plantations included optimizing the amount and type of fertilizer, amending biochar, and rationally using nitrification inhibitors. In future, we should strengthen in-situ observations of soil N₂O emission from tea plantations at both temporal and spatial scales, combine lab incubation and field studies to elucidate the mechanisms underling tea plantation soil N₂O emissions, and use a data-model fusion approach to reduce uncertainties in the estimation of global N₂O emission. These would provide theoretical support and practical guidance for reasonable N₂O emission reduction in tea plantations.

Improvement of soil acidification in tea plantations by long-term use of organic fertilizers and its effect on tea yield and quality

Soil acidification in tea plantation seriously reduced the yield and quality of tea. It was an effective method to use organic fertilizer for acidified soil remediation to ensure tea yield and quality. In this study, different fertilizers were used to treat the acidified tea plantation soils for 4 consecutive years to analyze the remediation effect of different fertilizers on acidified soil and their effects on tea yield and quality. The results showed that during the period of 2017-2021, the soil pH value of tea plantation (S1) with long-term use of chemical fertilizer decreased continuously, from 3.07 to 2.82. In the tea plantation (S2), the soil pH value was stable between 4.26 and 4.65 in the combination of organic fertilizer and chemical fertilizer for a long time. The tea plantation (S3) with long-term use of organic fertilizer has a stable soil pH value between 5.13 and 5.33, which is most suitable for the growth of tea trees. The analysis results of tea yield and quality indicators (tea polyphenols, theanine, amino acids, caffeine, catechin components) showed that after long-term use of chemical fertilizer in S1 tea plantation, soil pH value decreased continuously, soil acidification intensified, tea tree growth was hindered, and tea yield and quality decreased continuously. S2 tea plantation used some organic fertilizer in combination with chemical fertilizer for a long time, the soil pH value gradually improved, soil acidification weakened, and tea yield and quality improved steadily. After long-term use of organic fertilizer in S3 tea plantation, soil acidification was significantly improved, which was conducive to the normal growth of tea trees and the yield and quality of tea reached the maximum. The results of interaction analysis showed that the long-term use of chemical fertilizer had a negative effect on the growth of tea trees, and the combination of organic fertilizer and chemical fertilizer improved the growth of tea trees to some extent, but the effect was poor, while the long-term use of organic fertilizer was the most beneficial to the growth of tea trees and most conducive to ensuring the yield and quality of tea. This study provides important practical significance for the remediation and fertilizer regulation of acidified tea plantation soils. In the process of field experiment, climate is a variable factor, and attention should be paid to the effect of climate change on fertilization efficiency in subsequent experiment.

Relationship of soil pH value and soil Pb bio-availability and Pb enrichment in tea leaves

BACKGROUND

Lead (Pb) is not an essential element for the growth of tea trees, but it is an important index for evaluating the quality and safety of tea. Lead is a sensitive metal to pH. Exploring the changing trend of soil Pb and enrichment coefficient of Pb in tea leaves affected by soil acidification is significant for tea planting and tea quality safety control.

RESULTS

A percent of 37.57% of the 364 tea plantations in Anxi county of China showed soil acidification that is a soil pH value < 4.5. However, the total Pb content in the soil and Pb content of tea leaves met the requirements stipulated in China. The soil available Pb content and Pb content in tea leaves were both significantly negatively correlated with soil pH value, and increased with the decrease of soil pH value. The soil available Pb content had a significant positive correlation with soil total Pb content. However, the soil total Pb content had no significant correlation with soil pH value. Moreover, the soil Pb bio-availability coefficient and the Pb enrichment coefficient of tea leaves decreased with the increase of soil pH value.

CONCLUSION

More than a third of tea plantations in Anxi county had been acidified. The decrease of pH value leads to an increase in the bio-availability coefficient of soil Pb content and the enrichment coefficient of Pb content in tea leaves. The lower soil pH value resulted in the increase of the absorption and accumulation of Pb by tea trees, thus an increase of Pb content in tea leaves. © 2021 Society of Chemical Industry.

Morbidity Profile and Cholinesterase Levels among Sprayers in Selected Tea Plantations in South India

BACKGROUND

The tea plantation industry is composed of a complex chain of workers whose functions often overlap. There has been an extensive use of pesticides in this sector, and in the long term, these can have detrimental effects on the chemical sprayers working in the tea plantations.

AIMS

To assess the morbidities related to pesticide toxicity and document the most recent plasma cholinesterase levels among the pesticide sprayers working in selected tea plantations in South India.

METHODS

A cross-sectional study was conducted among 290 chemical sprayers in selected tea plantations in South India after approval from the Institutional Ethics Committee and permission from the plantations. A structured interview schedule was administered by face-to-face interview with the selected sample. The blood cholinesterase detection done at the Estate Hospital was documented by the interviewer.

RESULTS

The mean age of the participants was 45.6 ± 8.5 years and all of them were males. About 35.2% of the participants had reported at least one symptom of organophosphorus toxicity. The most common symptom was headache (21.7%) followed by itching of the eyes (20%) and watering of the eyes (16.2%). The blood cholinesterase values were normal in most of the sprayers in the study and only four (1.4%) sprayers had values less than the reference range. There was a significant association between the duration of work, method of spraying, and the blood cholinesterase levels indicating that greater duration of exposure and more direct contact with the chemical raise the cholinesterase levels significantly.

CONCLUSION

The symptoms of pesticide toxicity were reported among the sprayers. The blood cholinesterase levels were normal for most of them.

[Evolution mechanism of ecosystem service value at the township-scale in Anxi County of Fujian Province, China]

To clarify the interaction between land-use change and ecosystem service, the traditional ecosystem service valuation model was modified using the adjustment coefficients of biomass factor and socio-economic factor to evaluate ecosystem service value (ESV) of 24 towns in Anxi County from 1999 to 2019, aiming to understand the ecological response to land-use change. The results showed that ESV of 24 towns in Anxi County decreased gradually during the study period, with a decrease of 0.004 to 0.295 million yuan. Forestland and cultivated land made the largest contribution to ESV, followed by grassland and water bodies, whereas the contribution of other land types were negative. ESV could be increased by converting other land types into forestland, but be decreased by converting other land types into orchard land area (mainly tea plantation). The chemical fertilizer-monoculture management pattern of ratooning tea plantation reduced ESV, while the ecological cultivation of tea plantation could effectively improve soil microbial diversity and soil fertility, and finally enhance ESV.

[Soil fertility characteristics and their influencing factors in tea plantations of Jiangxi Pro-vince, China]

To investigate soil fertility status and characteristics of typical tea plantations, we selec-ted 372 typical tea plantations of 21 areas across Jiangxi Province and analyzed the soil nutrient, spatial data, and their correlations with topography, soil type, elevation and plantation age. The results showed that soil pH, organic matter, alkaline nitrogen, available phosphorus, available potassium, total nitrogen, total phosphorus and total potassium of tea plantation in Jiangxi reached 53.9%, 60.1%, 56.1%, 22.9%, 38.5%, 43.7%, 11.1% and 95.5% of indices of high fertility, high efficiency and high yield tea plantation, respectively, with the available phosphorus showing a strong variation. Soil available copper, zinc, iron, manganese and boron reached 76.3%, 74.2%, 96.8%, 73.1% and 0.0% of the first-class standards for soil trace elements, respectively. Tea plantations with highest soil fertility located in central Jiangxi, followed by northeastern and northwestern Jiangxi, and lowest in southern Jiangxi. Soil pH was significantly positively correlated with organic matter, alkaline nitrogen, available phosphorus, available potassium, total nitrogen and total phosphorus but not for total potassium. For different topography, soil fertility was highest in the flat land, followed by the high mountains, and lowest in the mountains and hills. Across different soil types, soil fertility was higher in paddy soil, sandy soil and mountain yellow brown soil, followed by yellow soil, red-yellow soil and purple soil, and lowest in red soil. Soil pH, organic matter and total potassium increased while available phosphorus decreased with altitude. The organic matter, alkaline nitrogen, available phosphorus, total nitrogen and total phosphorus increased, but soil pH decreased with time. In summary, soil fertility of tea plantations in Jiangxi Province was generally good, with high organic matter, total potassium, available copper, zinc, iron and manganese. However, soil was acidic, available phosphorus and total phosphorus content was low, available boron was seriously limited. We suggest increase soil pH and potassium supply in central Jiangxi, increase potassium and nitrogen fertilizer supply in northeastern Jiangxi, increase organic matter and phosphorus fertilizer supply in northwestern Jiangxi, and increase nitrogen, phosphorus and potassium supply combined with organic fertilizers in southern Jiangxi. High mountain tea plantations should enhance available phosphorus and potassium supply. Mountain tea plantations should enhance nitrogen and phosphate supply. Tea plantations with red and yellow soil should increase pH and total potassium supply. Tea plantations with red soil should apply nitrogen, phosphorus and potassium fertilizers combined with organic fertilizers. Tea plantations with yellow soil and mountain yellow brown soil required additional phosphorus supply, and tea plantations with purple soil should increase soil organic matter supply. Tea plantations need to increase dolomite powder, physiological alkaline fertilizers and organic fertilizers to prevent soil acidification.

[N2 O Emissions from Tea Plantations with Sorghum Intercropping and Application of Big Urea Pills]

A large amount of fertilizers are applied to the tea plantations resulting in high nitrous oxide (N₂O) emissions. The area of Chinese tea plantations has been expanding in recent years, making them an important source of agricultural N₂O emissions. There is an urgent need for effective mitigation measures for N₂O emissions from tea plantations. In this study, the N₂O emission flux and related environmental factors are measured in Chinese mid-subtropical typical hilly tea plantation under three kinds of management measures, namely intercropping sorghum, applying big urea pills, and under conventional fertilization conditions. The aim of this experiment is to determine the main factors controlling N₂O emissions from the soils of the tea plantation and confirm the true effectiveness of the proposed N₂O emission mitigation measures. The results of a 2-year field experiment show that:① N₂O emissions were significantly correlated with soil chemical properties, temperature and rainfall, interaction between soil physical and chemical properties; soil chemical properties have the greatest impact on soil N₂O emissions. The concentration of soil NO₃^--N is the most important factor determining the size of N₂O flux in the tea plantation. The most important task of N₂O emission mitigation research in the tea plantation is to reduce the concentration of soil NO₃^--N; ② sorghum intercropping reduces N₂O emissions by 51.2% while not affecting the tea yield. From the perspective of mitigating global warming, sorghum intercropping is the best tea plantation management measure per the results of this study; ③ applying big urea pills effectively increases tea yield while simultaneously reducing the N₂O emissions by 34.7%. From the perspective of balancing economic benefits as well as mitigating global warming, application of big urea pills is undoubtedly the best tea plantation management measure as indicated by this study.

Carbon dynamics and environmental controls of a hilly tea plantation in Southeast China

Tea plantations are widely distributed and continuously expanding across subtropical China in recent years. However, carbon flux exchanges from tea plantation ecosystems are poorly understood at the ecosystem level. In this study, we use the eddy covariance technique to quantify the magnitude and temporal variations of the net ecosystem exchange (NEE) in tea plantation in Southeast China over four years (2014-2017). The result showed that the tea plantation was a net carbon sink, with an annual NEE that ranged from -182.40 to -301.51 g C/m2, which was a much lower carbon sequestration potential than other ecosystems in subtropical China. Photosynthetic photon flux density (PPFD) explained the highest proportion of the variation in NEE and gross primary productivity (GPP) (for NEE: F = 389.89, p < .01; for GPP: F = 1,018.04, p < .01), and air temperature (Ta) explained the highest proportion of the variation in ecosystem respiration (RE) (F = 13,141.81, p < .01). The strong pruning activity in April not only reduced the carbon absorption capacity but also provided many plant residues for respiration, which switched the tea plantation to a carbon source from April to June. Suppression of NEE at higher air temperatures was due to the decrease in GPP more than the decrease in RE, which indicated that future global warming may transform this subtropical tea plantation from a carbon sink to carbon source.

Prevalence, pattern, and factors associated with work-related musculoskeletal disorders among pluckers in a tea plantation in Tamil Nadu, India

Context:

Musculoskeletal pain is common among tea leaf pluckers and is attributed to the load they carry, long working hours, the terrain, and insufficient job rotations. As a result of this, their health and work capacity are affected.

Aims:

To assess the prevalence, patterns, and factors associated with work-related musculoskeletal disorders (WRMDs) among pluckers in a tea plantation in Annamalai, Tamil Nadu, India.

Settings and Design:

This cross-sectional study surveyed 195 pluckers selected by simple random sampling aged between 18 years and 60 years.

Materials and Methods:

The interview schedule had four parts––sociodemographic detail, Standard Nordic Scale, numeric and facial pain rating tool, and a tool to assess factors associated with WRMDs.

Statistical Analysis Used:

Statistical Package for the Social Sciences (SPSS) version 16.

Results:

Prevalence of musculoskeletal pain in the last 12 months and the last 7 days was 83.6% and 78.5%, respectively. The most common site for last 1 year was shoulder (59%) and for last 7 days was the lower back (52.8%). Independent t-test revealed that the mean age of those with pain was 6.59 year more and mean years of employment was 1.38 years more among the workers with pain compared to workers without pain. Increasing morbidities among workers was also significantly associated with an increase in WRMDs on Chi-square test.

Conclusions:

The prevalence of musculoskeletal pain was high among tea pluckers and the most common site during the last 12 months and the last 7 days was the shoulder and lower back respectively was mild in character. Increase in age and duration of employment was associated with WRMDs.