Potential of tea plants in carbon sequestration in North-East India.

The potential of carbon (C) sequestration through photosynthesis depends on the nature of different plant species. Tea (Camellia sinensis L.) is an evergreen perennial plant and cultivated over a wide region in the world, and its potential to sequestrate atmospheric carbon dioxide (CO2) in plant biomass is already evaluated. However, proportions of assimilated CO2 which tea plant can sequestrate in their biomass and in soil are not evaluated before. In this experiment, ten (10) 6-month old tea plants of four different cultivars (TV1, TV20, S3A/3, and TV23) were transplanted in the field and CO2 assimilation flux of tea plants was periodically measured under in situ condition using close-chamber method at 15 days interval throughout the year. The cumulative CO2 assimilation flux of young tea plants varied within 31.82-249.22 g CO2 plant-1 year-1; however, it was estimated that tea bushes also emitted 5.2-70.8 g CO2 plant-1 year-1 due to aerobic respiration. After 1 year, tea plants were uprooted and the changes in their biomass were compared as the measure of their C-sequestration within the study duration. The weight gain in the whole plant biomass was proportional to the CO2 assimilation potential of tea cultivars. Overall, tea plants sequestrated 50.8% of the assimilated atmospheric CO2 in their biomass. The study revealed that tea bushes release organic C through the root exudates, the amount of which was equivalent to 5.9-8.6% of the assimilated CO2. Those secreted root exudates have potential to increase organic C up to 44-48 kg ha-1 year-1 in tea-growing soil.

Enhanced microbial respiration due to carbon sequestration in pruning litter incorporated soil reduced the net carbon dioxide flux from atmosphere to tea ecosystem.

BACKGROUND: Tea (Camellia sinensis L.) bushes are periodically (at 3-4 year intervals) pruned (cut from top) to maintain vegetative growth stage and constant height. Plant residues (prunings litter) generated after pruning are generally left in the field as a potential source of organic matter in soil. Organic carbon (C) sequestration due to pruning litter incorporation is expected to increase microbial activity in soil. Being an evergreen plant, tea bushes assimilate atmospheric carbon dioxide (CO2 ) throughout the year; however, the relation between decomposition of pruning litters and net CO2 flux for tea plantation have not been studied before. The objective of this experiment was to evaluate the relation between organic C accumulation and microbial respiration in pruning litters incorporated soil and its subsequent effect on the net CO2 flux from the atmosphere to tea plantation. RESULTS: Tea bushes assimilated 1878.2-2371.2 kg CO2 ha-1 from the atmosphere within December to November; however, pruned bushes assimilated 1451.7-1840.8 kg CO2 ha-1 within the same period. Decomposition of pruning litters added organic matter in soil, which was mostly accumulated in larger soil aggregates having 2.0-0.25 mm size. Such organic matter accumulation significantly increased microbial respiration in those aggregates, which in turn increased the overall rate of CO2 emission from soil to the atmosphere. CONCLUSION: Decomposition of pruning litters leads to emission of 426.5-530.4 kg CO2 ha-1 from soil. Hence, pruned areas recorded relatively lower (16.0-27.4%) net CO2 flux from the atmosphere to tea ecosystem as compared to unpruned tea bushes. © 2019 Society of Chemical Industry.

Assimilating atmospheric carbon dioxide in tea gardens of northeast India.

Carbon dioxide (CO2) is the most important greenhouse gas in the atmosphere and phyto-assimilation is the most effective technique to mitigate global warming effect of CO2 gas in the atmosphere. Tea is an evergreen perennial plant and cultivated worldwide under subtropical humid climatic condition for harvesting its tender shoots. Tea bushes of different cultivars and ages are grown in combination to minimize possible adverse effect of biotic and abiotic stresses; hence distribution of tea plantation in a tea garden is complex in nature. Large shade trees are also an integral part of tea garden. Those plantations in tea garden have huge potential to capture atmospheric CO2; however, ability of tea bushes to mitigate global warming while producing tea shoots is not quantified before. The objective of this study was to quantify the potential of tea plantation to mitigate greenhouse effect (global warming mitigation potential, GWMP) due to assimilation of atmospheric CO2 gas. High yielding TV23 cultivar assimilated significantly higher amount of CO2 as compared to quality tea producing cultivars (S3A/3) and mature 25-30 years old tea bushes absorb more CO2 from the atmosphere as compared to younger tea bushes. Considering the mixed population of cultivars in tea gardens, overall, tea bushes sequestrated 5134.4 ± 831.6 kg CO2 ha-1 yr-1 in their biomass and had GWMP 3.47 ± 0.64 kg CO2 KMTH-1 yr-1. Shade trees sequestrated 4037.4 ± 589.9 kg CO2 ha yr-1 from the atmosphere. Hence, the GWMP of whole plantation ((both tea bushes and shade trees) was 6.19 ± 1.7 kg CO2 KMTH-1 yr-1. In this study, tea bushes sequestrated 52.7-61.3% of the total CO2 sequestrated by the plantations in tea garden. This study enabled to understand that tea bushes play significant role in mitigating global warming by assimilating and sequestrating atmospheric CO2 and the estimated value of global warming mitigation potential may be used for direct estimation of C sequestration by plantations in tea garden using its productivity value.

Contrasting effects of EDTA applications on the fluxes of methane and nitrous oxide emissions from straw-treated rice paddy soils.

BACKGROUND: Submerged rice paddy soils are the major anthropogenic source of methane (CH4 ) emission to the atmosphere. Straw incorporation for sustaining soil organic C pool increases CH4 emission flux from rice paddy soils. Though the rate of nitrous oxide (N2 O) emission is much less than CH4 , the former has 298 times higher global warming potential (GWP) than equivalent quantity of carbon dioxide. The effect of chelating agents, such as EDTA, on N2 O emission and on GWP due to CH4 and N2 O emissions has not been evaluated before. RESULTS: The emission of CH4 gas from submerged soil may be mitigated by EDTA application; however, it also increases concentration of nitrate-N in soil, the precursor of N2 O gas formation under anaerobic condition. In this experiment, irrespective of straw application, EDTA-treated soils emitted less CH4 to the atmosphere than the corresponding control. Though N2 O emission was increased from soil due to EDTA applications, total GWP was at least 15% reduced in EDTA treated soils during rice cultivation. The plant growth and rice grain yield was not affected by EDTA application. CONCLUSION: EDTA application at 5.0 ppm might be used to reduce total global warming potential during rice cultivation. © 2016 Society of Chemical Industry.

Cattle Manure Enhances Methanogens Diversity and Methane Emissions Compared to Swine Manure under Rice Paddy.

Livestock manures are broadly used in agriculture to improve soil quality. However, manure application can increase the availability of organic carbon, thereby facilitating methane (CH4) production. Cattle and swine manures are expected to have different CH4 emission characteristics in rice paddy soil due to the inherent differences in composition as a result of contrasting diets and digestive physiology between the two livestock types. To compare the effect of ruminant and non-ruminant animal manure applications on CH4 emissions and methanogenic archaeal diversity during rice cultivation (June to September, 2009), fresh cattle and swine manures were applied into experimental pots at 0, 20 and 40 Mg fresh weight (FW) ha-1 in a greenhouse. Applications of manures significantly enhanced total CH4 emissions as compared to chemical fertilization, with cattle manure leading to higher emissions than swine manure. Total organic C contents in cattle (466 g kg-1) and swine (460 g kg-1) manures were of comparable results. Soil organic C (SOC) contents were also similar between the two manure treatments, but dissolved organic C (DOC) was significantly higher in cattle than swine manure. The mcrA gene copy numbers were significantly higher in cattle than swine manure. Diverse groups of methanogens which belong to Methanomicrobiaceae were detected only in cattle-manured but not in swine-manured soil. Methanogens were transferred from cattle manure to rice paddy soils through fresh excrement. In conclusion, cattle manure application can significantly increase CH4 emissions in rice paddy soil during cultivation, and its pretreatment to suppress methanogenic activity without decreasing rice productivity should be considered.

C and N accumulations in soil aggregates determine nitrous oxide emissions from cover crop treated rice paddy soils during fallow season.

Combination of leguminous and non-leguminous plant residues are preferably applied in rice paddy soils to increase the rate of organic matter mineralization and to improve plant growth. However, organic matter addition facilitates methane (CH4) emission from rice paddy soil. Mineralization of organic nitrogen (N) increases NO3-N concentrations in soil, which are precursors for the formation of nitrous oxide (N2O). However, N2O is a minor greenhouse gas emitted from submerged rice field and hence is not often considered during calculation of total global warming potential (GWP) during rice cultivation. The hypothesis of this study was that fluxes of N2O emissions might be changed after removal of flooded water from rice field and the effect of cover crops on N2O emissions in the fallow season might be interesting. However, the effects of N-rich plant residues on N2O emission rates in the fallow season and its effect on annual GWP were not studied before. In this experiment, combination of barley (non-leguminous) and hairy vetch (leguminous) biomasses were applied at 9 Mg ha(-1) and 27 Mg ha(-1) rates in rice paddy soil. Cover crop application significantly increased CH4 emission flux while decreased N2O emissions during rice cultivation. The lowest N2O emission was observed in 27 Mg ha(-1) cover crop treated plots. Cover crop applications increased N contents in soil aggregates especially in smaller aggregates (<250 µm), and that proportionately increased the N2O emission potentials of these soil aggregates. Fluxes of N2O emissions in the fallow season were influenced by the N2O emission potentials of soil aggregates and followed opposite trends as those observed during rice cultivation. Therefore, it could be concluded that the doses of cover crop applications for rice cultivation should not be optimized considering only CH4, but N2O should also be considered especially for fallow season to calculate total GWP.

Evaluating changes in cellulolytic bacterial population to explain methane emissions from air-dried and composted manure treated rice paddy soils.

Compost application recorded ~20% reduction in methane (CH4) emission during rice cultivation as compared to air-dried manure treatment. The objective of this study was to evaluate the dependence of methanogens on cellulolytic bacteria (CB) to produce CH4 in organic-amended rice paddy soils. The presence of more decomposable organic C in manure was probably the key factor for higher CH4 emission from manure-treated soils as compared to compost application. Manure application facilitated anaerobic CB abundance in rice paddy soils, and that in turn increased concentrations of dissolved organic C compounds like carbohydrates in soil. Soluble organic C compounds are converted into acetate and/or carbon dioxide, which act as initial energy source for methanogens. Therefore, it could be concluded that CB positively influenced methanogen activity and methanogenesis and stabilized organic substrates like compost are more rational treatment to mitigate CH4 emission from rice paddy soil than cattle manure application.

Fractionation and characterization of humic acids from organic amended rice paddy soils.

Humic acids (HAs), mixture of several complex-structured aromatic and aliphatic compounds, are ubiquitous in the terrestrial environment. In this study, HAs were fractionated on the basis of their polarity (degree of humification). The fractions namely 200P, 300P and 400P were comparatively more humified than fractions like 800P and 800S. The application of organic amendments significantly increased concentrations of HA fractions especially the more humified fractions in rice paddy soils. Among the different fractions, 300P fraction was the most abundant in rice paddy soils and its concentration was significantly increased due to compost application. The compounds like methyl ketone and 3-phenylprop-2-enal contributed almost 90% of 300P fraction.

Hoeflea suaedae sp. nov., an endophytic bacterium isolated from the root of the halophyte Suaeda maritima.

A Gram-negative, aerobic, short rod-shaped bacterium, designated strain YC6898(T), was isolated from the surface-sterilized root of a halophyte (Suaeda maritima) inhabiting tidal flat of Namhae Island, Korea. Strain YC6898(T) grew optimally at 30-37 °C and pH 6.5-7.5. The strain inhibited mycelial growth of Pythium ultimum and Phytophthora capsici. Phylogenetic analyses based on 16S rRNA gene sequences indicated that strain YC6898(T) belongs to the genus Hoeflea in the family Phyllobacteriaceae. Its closest relatives were Hoeflea alexandrii AM1V30(T) (96.7% 16S rRNA gene sequence similarity), Hoeflea anabaenae WH2K(T) (95.7%), Hoeflea phototrophica DFL-43(T) (95.5%) and Hoeflea marina LMG 128(T) (94.8%). Strain YC6898(T) contained Q-10 as the major ubiquinone. The major fatty acids of strain YC6898(T) were C18:1ω7c (61.1%), C16:0 (11.9%), 11-methyl C18:1ω7c (9.6%) and C19:0 cyclo ω8c (8.0%). The polar lipids were phosphatidylcholine, phosphatidylethanolamine, phosphatidylmonomethylethanolamine, phosphatidylglycerol, unknown lipids and an unknown glycolipid. The total genomic DNA G+C content was 53.7 mol%. On the basis of phenotypic, chemotaxonomic and phylogenetic analysis, strain YC6898(T) represents a novel species of the genus Hoeflea, for which the name Hoeflea suaedae sp. nov. is proposed. The type strain is YC6898(T) (=KACC 14911(T)=NBRC 107700(T)).

Changes in fungal population of fly ash and vinasse mixture during vermicomposting by Eudrilus eugeniae and Eisenia fetida: documentation of cellulase isozymes in vermicompost.

Fly ash (FA) and vinasse (VN), two industrial wastes, are generated in huge amounts and cause serious hazards to the environment. In this experiment, different proportions of these two wastes were used as food for two epigeic earthworms (Eisenia fetida and Eudrilus eugeniae) to standardize the recycling technique of these two wastes and to study their effect on fungal especially cellulolytic fungal population, cellulase activity and their isozyme pattern, chitin content and microbial biomass of waste mixture during vermicomposting. Increasing VN proportion from 25% to 50% or even higher, counts of both fungi and cellulolytic fungi in waste mixtures were significantly (P ≤ 0.05) increased during vermicomposting. Higher cellulase activity in treatments having 50% or more vinasse might be attributed to the significantly (P ≤ 0.05) higher concentration of group I isozyme while concentrations of other isozymes (group II and III) of cellulase were statistically at par. Higher chitin content in vinasse-enriched treatments suggested that fungal biomass and fungi-to-microbial biomass ratio in these treatments were also increased due to vermicomposting. Results revealed that Eudrilus eugeniae and Eisenia fetida had comparable effect on FA and VN mixture during vermicomposting. Periodical analysis of above-mentioned biochemical and microbial properties and nutrient content of final vermicompost samples indicated that equal proportion (1:1, w/w) of FA and VN is probably the optimum composition to obtain best quality vermicompost.