Integration of biochar with nitrogen in acidic soil: A strategy to sequester carbon and improve the yield of stevia via altering soil properties and nutrient recycling.

The health of agroecosystems is subsiding unremittingly, and the over-use of chemical fertilizers is one of the key reasons. It is hypothesized that integrating biochar, a carbon (C)-rich product, would be an effective approach to reducing the uses of synthetic fertilizers and securing crop productivity through improving soil properties and nutrient cycling. The bamboo biochar at different quantities (4-12 Mg ha-1) and combinations with chemical fertilizers were tested in stevia (Stevia rebaudiana) farming in silty clay acidic soil. The integration of biochar at 8 Mg ha-1 with 100% nitrogen (N), phosphorus (P), and potassium (K) produced statistically (p ≤ 0.05) higher leaf area index, dry leaf yield, and steviol glycosides yield by about 18.0-33.0, 25.8-44.9, and 20.5-59.4%, respectively, compared with the 100% NPK via improving soil physicochemical properties. Soil bulk density was reduced by 5-8% with biochar at ≥ 8 Mg ha-1, indicating the soil porosity was increased by altering the soil macrostructure. The soil pH was significantly (p ≤ 0.05) augmented with the addition of biochar alone or in the combination of N because of the alkaline nature of the used biochar (pH = 9.65). Furthermore, integrating biochar at 8 Mg ha-1 with 100% NPK increased 22.7% soil organic C compared with the sole 100% NPK. The priming effect of applied N activates soil microorganisms to mineralize the stable C. Our results satisfy the hypothesis that adding bamboo biochar would be a novel strategy for sustaining productivity by altering soil physicochemical properties.

Achievement of higher biomass, yield and quality of essential oil of Tagetes minuta L. through optimizing the sowing method and seeding rate.

Tagetes minuta L. is known as an industrial crop in the world as it possesses an essential oil that is extensively used in the perfumery and flavor industries. The crop performance is influenced by the planting/sowing method (SM) and seeding rate (SR); however, the effects of these variables on biomass yield and quality of the essential oil of T. minuta remain unclear. As a comparatively new crop, the responses of T. minuta to different SMs and SRs have not been studied in the mild temperate eco-region. Thus, the biomass and essential oil yield response of T. minuta (variety 'Himgold') to SM (line sowing and broadcasting) and SR (at 2, 3, 4, 5, and 6 kg ha-1) were investigated. The overall fresh biomass of T. minuta ranged from 16.86 to 28.13 Mg ha-1, while the essential oil concentration in fresh biomass varied from 0.23% to 0.33%. Irrespective of the SR, the broadcasting method produced significantly (p ≤ 0.05) higher fresh biomass yield by approximately 15.8% and 7.6% compared with line sowing during 2016 and 2017, respectively. An increase in biomass yield was noted as the SR increased up to 4 kg ha-1. The SR at 4 kg ha-1 registered approximately 41.9%-56.1% and 3.3%-10.3% higher biomass yield than the SR at 2 and 6 kg ha-1, respectively. No significant (p ≥ 0.05) differences in essential oil concentration in fresh biomass were observed due to the different SMs and SRs. Thus, T. minuta may be sown by the broadcasting method in the mild temperate eco-region with an SR of 4 kg ha-1.

Ground-Level Pruning at Right Time Improves Flower Yield of Old Plantation of Rosa damascena Without Compromising the Quality of Essential Oil.

The essential oil of Rosa damascena is extensively used as a key natural ingredient in the perfume and cosmetic industries. However, the productivity and quality of rose oil are a big concern from the old plantation. It is hypothesized that rejuvenation of old rose plantations through ground-level pruning at right time could improve the yield of flowers and the quality of essential oil. Consequently, a field trial was led-out with 10 treatment conditions encompassing two pruning systems (ground-level pruning and ground-level pruning followed by top pruning at the end of December) and five different months of ground-level pruning (June-October) to understand the best pruning practices. In this experiment, the flower yield ranged from 18.32 to 62.40 q ha-1, and oil content varied from 0.035 to 0.049% under different pruning systems and months of pruning. Ground-level pruned plants, irrespective of the month, registered statistically (p ≤ 0.05) more flower yield (618.62 and 473.29 g bush-1) compared with ground-level pruning followed by top pruned plants in both seasons. The average across the pruning system, ground-level pruning in October registered statistically (p ≤ 0.05) greater yield of flowers (709.10 and 605.13 g bush-1) compared with the ground-level pruning from June to August. Despite significant variations in flower yield among the treatments, the percentage share of the major compounds particularly ß-citronellol+nerol and geraniol in the essential oil were not affected (p ≥ 0.05) by the pruning month and pruning system. Thus, the finding suggests that the production from the old plantation of R. damascena can be improved by ground-level pruning during October under mild-temperate conditions.

Chemical Diversity of Essential Oil of Valeriana jatamansi from Different Altitudes of Himalaya and Distillation Methods.

Valeriana jatamansi is an important temperate herb that is used in the pharmaceutical and essential oil industries. In India, this species is now on the verge of extinction due to the over-exploitation of its rhizomes from its natural habitat. It is hypothesized that the variations in bioactive compounds in its essential oil are very high among the wild populations as well as cultivated sources. Thus, this study was conducted to evaluate the chemical profiling of essential oil of four wild populations (Rupena, Kugti, Garola, and Khani) and two cultivated sources (CSIR-IHBT, Salooni), which were distilled at three consecutive days. The variation in oil concentration in roots/rhizomes was found significant (p ≤ 0.05), and the maximum value (0.35%) was registered with the population collected from Kugti and Khani. In essential oil, irrespective of population and distillation day, patchouli alcohol was the major compound, which ranged from 19 to 63.1%. The maximum value (63.1%) was recorded with the essential oil obtained from Garola's population and distilled on the first day. The percentage of seychellene was abruptly increased with subsequent days of extraction in all the populations. The multivariate analysis revealed that the essential oil profiles of Rupena, Kugti, Garola, and CSIR-IHBT populations were found to be similar during the first day of distillation. However, during the second day, Rupena, Kugti, Khani, and CSIR-IHBT came under the same ellipse of 0.95% coefficient. The results suggest that the population of Kugti is superior in terms of oil concentration (0.35%), with a higher proportion of patchouli alcohol (63% on the first day). Thus, repeated distillation is recommended for higher recovery of essential oil. Moreover, repeated distillation can be used to attain V. jatamansi essential oil with differential and perhaps targeted definite chemical profile.

Moisture stress and nitrogen availability modulate the secondary metabolite profiles, enzymatic activity, and physiological and agronomic traits of Stevia rebaudiana.

Performances of crops are mainly influenced by frost, heat and availability of soil-water and nitrogen (N). However, little is known about the interaction between soil-water and N on Stevia rebaudiana. Thus, a field experiment was conducted with fifteen treatment combinations comprising three levels of soil-moisture (irrigation at 20, 50 and 75 kPa soil-water-potential) and five N levels (0-140 kg ha-1) to understand how soil-moisture and N influence growth, physiological and biochemical activities of stevia. Plants irrigated at 50 kPa registered 6.3-18.9% and 20.7-21.2% higher dry leaf yield compared with 20 and 75 kPa, respectively. No significant (P ≥ 0.05) differences in concentrations of total steviol glycosides (TSGs) in leaf were found due to moisture regimes. Total soluble sugars (TSS), proline, total phenols were decreased significantly (P ≤ 0.05) with plants irrigated at 20 kPa whereas SOD, CAT, and POX were decreased at both excessive and deficit water conditions. Photosynthetic rate (PN) and stomatal conductance (gs) decreased with plant irrigated at 75 kPa. Anatomical changes in leaf were also observed due to different moisture regimes. Among the N levels, 105 kg ha-1 registered approximately 50-53% higher dry leaf yield compared with control (0 kg N ha-1), irrespective of irrigation level. Excess (140 kg ha-1) and shortage of N significantly decreased the PN, gs, and enzyme activities. Concentrations of TSS and TSGs were higher with N at 105 and 70 kg ha-1, respectively. Our results emphasize that irrigation at 50 kPa and application of N 105 kg ha-1 is the suitable combination for sustainable cultivation of stevia.

Introduction, adaptation and characterization of monk fruit (Siraitia grosvenorii): a non-caloric new natural sweetener.

Siraitia grosvenorii, an herbaceous perennial plant, native to the southern parts of China, is commonly used as a low-calorie natural sweetener. It contains cucurbitane-type triterpene glycosides known as mogrosides. The extract from monk fruit is about 300 times sweeter than sucrose. In spite of its immense importance and International demand, Siraitia grosvenorii (Swingle) is not commercially cultivated outside China since scientific information for cultivation of this species is lacking. Planting material of monk fruit plant was not available in India. Thus, the seeds of monk fruit were introduced in India from China after following International norms. Then the experiments were conducted on different aspects such as seed germination, morphological and anatomical characterization, phenology, flowering and pollination behaviors, and dynamic of mogroside-V accumulation in fruit. The hydropriming at 40 °C for 24 h was found effective to reduce the germination time and to increase the germination rate (77.33%). The multicellular uniseriate trichomes were observed in both the leaf surfaces, however, higher trichomes density was observed in the ventral surface of males compared to females. The microscopic view revealed that the ovary was trilocular (ovary consists three chambers) having two ovules in each chamber or locule. Most of the fruits were globose or oblong type with 5-7 cm in length and 4-7 cm diameter. Mogroside-V content in fruit at 80 days after pollination was 0.69% on dry weight basis. The rate of increase of mogroside-V accumulation from 50 to 70 days was very slow, whereas a sharp increase was observed from 70 to 80 days. The higher receptivity of stigma was observed with fully open flowers. The floral diagram and formula have also been developed for both male and female flowers. Our results highlighted that monk fruit can be grown in Indian conditions.

Crop-ecology and nutritional variability influence growth and secondary metabolites of Stevia rebaudiana Bertoni.

BACKGROUND: Plant nutrition and climatic conditions play important roles on the growth and secondary metabolites of stevia (Stevia rebaudiana Bertoni); however, the nutritional dose is strongly governed by the soil properties and climatic conditions of the growing region. In northern India, the interactive effects of crop ecology and plant nutrition on yield and secondary metabolites of stevia are not yet properly understood. Thus, a field experiment comprising three levels of nitrogen, two levels of phosphorus and three levels of potassium was conducted at three locations to ascertain whether the spatial and nutritional variability would dominate the leaf yield and secondary metabolites profile of stevia. RESULTS: Principal component analysis (PCA) indicates that the applications of 90 kg N, 40 kg P2O5 and 40 kg K2O ha-1 are the best nutritional conditions in terms of dry leaf yield for CSIR-IHBT (Council of Scientific and Industrial Research- Institute Himalayan Bioresource Technology) and RHRS (Regional Horticultural Research Station) conditions. The spatial variability also exerted considerable effect on the leaf yield and stevioside content in leaves. Among the three locations, CSIR-IHBT was found most suitable in case of dry leaf yield and secondary metabolites accumulation in leaves. CONCLUSIONS: The results suggest that dry leaf yield and accumulation of stevioside are controlled by the environmental factors and agronomic management; however, the accumulation of rebaudioside-A (Reb-A) is not much influenced by these two factors. Thus, leaf yield and secondary metabolite profiles of stevia can be improved through the selection of appropriate growing locations and proper nutrient management.

Effect of decapitation and nutrient applications on shoot branching, yield, and accumulation of secondary metabolites in leaves of Stevia rebaudiana Bertoni.

The axillary buds of stevia (Stevia rebaudiana Bertoni) often remain dormant for a long time and sometimes remain dormant permanently until the plants enter into the reproductive stage. The present study was conducted to ascertain whether decapitation and foliar fertilization enhance the productivity and quality of stevia through breaking the apical dominance and increasing physiological activities. Ten treatment combinations comprising two cultural operations (non-decapitation and decapitation) and five foliar spray treatments (water spray control, KNO3 @ 5.0gL(-1), Ca(NO3)2 @ 4.06gL(-1), CuSO4·5H2O 2.0gL(-1) and (NH4)6Mo7O24 @ 1.0gL(-1)) were applied. The decapitation of apical buds of stevia increased the branches and increased dry leaf yield by 13 and 17% compared with non-decapitation during 2010 and 2011, respectively, without affecting quality. Foliar application of nutrient solutions also exerted a considerable effect on growth parameters, yield attributes and chlorophyll content, and significantly (P=0.05) higher dry leaf yield ranging from 8 to 26% over the control. Among the foliar spray treatments, KNO3 @ 5.0gL(-1) and Ca (NO3)2 4.06gL(-1) were found most effective in dry leaf yield. Thus, the decapitation of apical buds and foliar application of KNO3 and Ca (NO3)2 could enhance the productivity of stevia through improving the growth of axillary buds and physiological activities.