Browsing by Author "Sindhu, P V"

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Agronomic management for enhancing yield and quality of stevia (Stevia rebaudiana Bertoni)
(Department of Agronomy, College of Agriculture, Vellanikkara, 2023-03-08) Junaidath, P; Sindhu, P V
Stevia rebaudiana is an alternative sugar crop that is becoming popular in various parts of the world. It belongs to the sunflower family, Asteraceae, and is native to Paraguay (South America); hence called Paraguay’s sweet herb. Being a natural sweetener it is also known as sweet leaf, honey yerba, honey leaf, meeti tulsi, sweet chrysanthemum, and candy leaf. The plant contains steviol glycosides (SVglys), which has importance in the human diet as a low-calorie and high-potency sweetener. In addition to sweetening properties, Stevia rebaudiana also has anti-hyperglycemic, anti-cancer, hepatoprotective, anti-hypertensive, anti-caries, antioxidant, and anti-bacterial properties. Since the fresh herbage is the main economic part of stevia, production of more leaf biomass with higher steviol glycosides is the main criterion for crop performance. The present study entitled “Agronomic management for enhancing yield and quality of stevia (Stevia rebaudiana Bertoni)” was conducted at the Department of Agronomy, College of Agriculture, Vellanikkara, Thrissur during September 2021 to May 2022. The objective of the study was to standardize proper spacing and pinching time for stevia. A field experiment was conducted in Factorial Randomized Block Design (FRBD) with three replications. The treatments consisted of three spacing levels viz., 15 cm × 10 cm, 20 cm × 10 cm, and 15 cm × 15 cm, and four pinching intervals viz., pinching at 20 days after planting (DAP), pinching at 30 DAP, pinching at flower bud initiation and no pinching (control). Both spacing and pinching significantly influenced growth parameters such as plant height, number of branches and leaves, fresh and dry leaf yield, per plant herbage yield, and total herbage yield. Taller plants were seen with closer spacing (15 cm × 15 cm) throughout the crop growth period. Though the growth parameters were higher at a spacing of 15 cm × 10 cm at early growth stages of stevia (20 DAP), in subsequent stages, these were higher in wider spacing of 15 cm × 15 cm. Closer spacing resulted in the highest total herbage yield at harvest (10925 kg ha-1). Pinching is an important agronomic technique that helps to enhance vegetative growth. In general, yield related characteristics like the number of branches and leaves were found to be higher in pinched plants than in nonpinched plants. Plant height was significantly lower in the pinched plants compared to the unpinched plants. Plant height reduced drastically when pinching was performed during their early vegetative growth. At the flower bud initiation stage, a minimum plant height was seen in the plants where pinching was carried out at 20 DAP compared to pinching done at 30 DAP. One month after planting, 20 DAP-pinched plants had more branches and leaves, while at the beginning of the flower bud, 30 DAP-pinched plants had more. At the time of harvest, plants pinched at the beginning of the floral bud initiation produced the highest overall herbage yield, followed by plants that had received pinching at 30 DAP, no pinching, and pinching at 20 DAP, respectively. The interaction between spacing and pinching was also significant with respect to total herbage yield. Planting stevia at a spacing of 15 cm × 10 cm with pinching at the initiation of floral buds proved to be the best treatment concerning total herbage yield at harvest. Total glycoside content was unaffected by different plant spacings and pinching. However, significant variation was observed for total glycoside yield (kg ha-1) concerning spacing and pinching. It was higher in the stevia planted at a closer spacing of 15 cm × 10 cm, and received pinching at flower bud initiation The study suggests growing stevia at a closer spacing (15 cm × 10 cm) and pinching at the flower bud initiation stage for higher herbage and glycoside yield under Kerala conditions.
Allelopathy for weed management in field crops
(Department of Agronomy, College of Agriculture , Vellanikkara, 2022) Shakkira, K K; Sindhu, P V
Weeds have been a persistent menace for farmers since the advent of agriculture. Among several methods adopted for controlling weeds, chemical control is the widely used and most effective. However, the extensive use of herbicides has led to the generation of a wide range of problems including development of herbicide resistant weeds. As a result, extensive research is being done to exploit non chemical methods of weed management. The mechanism of allelopathy has been suggested as a potential biorational method towards this goal. Hence the present study entitled “Allelopathy for weed management in field crops” was conducted during February-October 2021 in the Department of Agronomy, College of Agriculture, Vellanikkara, Kerala Agricultural University, Thrissur. The study consisted of two parts viz., screening Andrographis paniculata, Plectranthus ambonicus and Tagetes minuta for their allelopathic potential, and evaluating alleloapathic effect of these plant extracts on weeds and the test crops rice, cowpea and green gram. Cold water, hot water and methanol extracts of these plants were prepared at six concentrations viz., 5 %, 10 %, 15 %, 20 %, 25 % and 30 % in a completely randomized design (CRD) in factorial arrangement with three replications. In the first experiment plants were screened for their allelopathic potential against upland weeds in 165 plastic trays (25 cm x 20 cm x 5 cm) that were filled to three-quarters with uniform quantity of soil (1.5 kg) collected from an open area. Best 10 treatment combinations from this experiment and a control with distilled water were carried over to the second experiment. The second experiment consisted of two parts; in petri plates to test the phytotoxic activity on test crops (cowpea, green gram and rice) and in pot culture study with test crops and weeds. Both studies were carried out in completely randomized design (CRD) in factorial arrangement with two factors and three replications. Factor A consisted of time of application (on the day of sowing and 6th day after sowing). Factor B consisted of the best 10 allelopathic treatments from experiment 1. Experiment on screening allelopathic plants for their potential to control upland weeds revealed the significant influence of the plants, the method of extraction and the concentration of extract on weed growth parameters such as weed density and weed dry weight. Broad leaved weeds were more sensitive to allelopathic extracts than grass weeds. Reduction in weed germination count and dry weight after one month of application was noticed with methanol extract of Tagetes minuta at 30 per cent concentration and was 6.67 nos./m2 and 21. 33 g/m2 respectively as compared to control (68.33 nos./m2 and 54. 25 g/m2 ). Pre mergence application of Andrographis paniculata methanol extract at 30 per cent concentration was the next best treatment. Allelopathic effect of plants was significant only for a short period of time i.e. up to one week after application, indicating absence of residual action. Germination indices and seedling growth parameters of test crops were adversely affected by the application of allelopathic extracts. Among test crops, cowpea and green gram were more sensitive to allelopathic extracts than rice. A notable delay in germination of test crops, in shoot and root length, and in fresh and dry weights were observed by the application of allelopathic treatments. Phytotoxicity symptoms were observed on test crops both under laboratory condition and in pot culture. Root decay and reduction in number of rootlets were observed by the pre emergence application of 30 and 25 per cent methanol extract of Tagetes minuta. When Tagetes minuta methanol extract was applied at 30 or 25 per cent as pre mergence treatment, germination of cowpea and green gram started on the 4th and 5th day after sowing as compared to the 2nd day in control. Root length reduction was more pronounced than shoot length reduction. The reduction was 43.29 and 41.46 per cent in cowpea, and 41.56 and 37.05 per cent in green gram, due to pre emergence application of 30 and 25 per cent methanol extract of Tagetes minuta in petri plates. In pot culture study, root reduction of 70.85 and 71.01 per cent in cowpea and green gram by the pre emergence application of 30 per cent methanol extract of Tagetes minuta as was observed. A notable delay in weed germination and weed dry weight reduction were observed by 30 and 25 per cent Tagetes minuta methanol extract applied as pre emergence treatment and their residual inhibitory effect in the soil persisted up to one week. Based on the results of the study, pre emergence application (on the day of sowing) of methanol and cold water extracts of Tagetes minuta and Andrographis paniculata at 30 per cent concentration can be recommended for control of broad leaved weeds in uplands.
Crop weather relations on yield, quality and weed dynamics of kiriyath(andrographis paniculata(burm.f.) wall.ex nees.)
(Department of Agronomy College of Horticulture, Vellanikkara, 2018) Sreethu, M J; Sindhu, P V
Crop-weather relations on yield and quality of Iruveli [Plectranthus vettiveroides (K.C.Jacob) N.P. Singh and B.D. Sharma]
(Department of Agronomy, College of Horticulture, Vellanikkara, 2019) Sabika, K P; Sindhu, P V
Ecofriendly management of weeds in rice
(Department of Agronomy, College of Horticulture, Vellanikkara, 2008) Sindhu, P V; George Thomas, C
Competition from weeds and consequent yield reduction is a major problem in rice cultivation, which warrants proper weed management strategies. The present study was undertaken to develop and refine stale seed bed techniques and subsequent cultural practices for semi-dry and wet-seeded rice and to find out the optimum plant spacing, which can give maximum weed control efficiency coupled with better grain yield. Survey and documentation of prevailing weed control practices followed by rice farmers was another objective of the study. Surveys conducted in Palakkad, Kole, Kuttanad and Pokkali regions revealed the popularity of physical and chemical methods of weed control among farmers. Among various herbicides available for use in rice, Fernoxone (2,4-D) is the major chemical used by the majority of farmers of Palakkad, Kole and Kuttanad regions. The experiment on stale seed bed techniques for semi-dry rice was conducted during first crop seasons of 2006 and 2007 at Agricultural Research Station, Mannuthy and stale seed bed for wet-seeded rice was conducted in Alappad kole, Thrissur district during second crop seasons of 2005-06 and 2006-07. Seed bed preparation significantly influenced the germination and establishment of weeds both under semi-dry and wet-seeded conditions. Population and dry weight of weeds were the lowest in stale seed bed for 14 days. Stale seed bed technique adopted for forcing the germination of weed seeds showed differential response by different groups of weeds. Grass weeds gave the highest germination percentage immediately after seed bed preparation followed by broad leaf weeds. However, seed bed preparation was not effective on sedges. Stale seed bed technique provided a partially weed free environment during the early crop growth stages and allowed the crop to yield better than normal seed bed. The yield difference between normal seed bed and stale seed bed decreased with reduction in the stale seed bed period mainly because of the short time available to achieve the optimum environment essential for the germination of buried seeds. Among the sub plot treatments, pre emergence spraying of herbicides and concurrent growing of green manure crops gave significant reduction in the population and dry weight of weeds and thus better grain yield. Stale seed bed for 14 days gave the highest benefit ratio both under semi-dry and wet-seeded situation during both years of the experiment. Experiment to assess the influence of plant stand on crop-weed competition was conducted in farmer’s field at Alappad Kole, Thrissur district during the second crop season of 2005-06 and 2006-07. Canopy modification by altering plant spacing significantly helped the crop to maintain a dominant position over weeds as indicated by the decreased weed problems in closer plant spacing. Higher grain yields of 8858 kg ha-1 and 7825 kg ha-1 during first and second years of study were observed in closer spacing of 10 cm X 10 cm spacing under the recommended package of practices of Kerala Agricultural University followed by 20 cm x 10 cm. Among the weeded plots, the lowest grain yield was in SRI plots with cono weeding. Plants at wider spacing (30 cm X 30 cm) produced more number of tillers per hill. However, on unit area basis a reverse trend was observed. Increase in plant density under closer spacing significantly reduced the dry matter production of weeds. The weed problem was very high in SRI management, even after four cono weedings. The reduction in grain yield in unweeded plots under closer plant spacing was negligible when compared to weeded plots. This indicates the possibility of maintaining the field without much economic loss from weeds by transplanting 20-day old seedlings, with two seedlings per hill at a closer spacing of 10 cm X 10 cm. This is both economical and ecofriendly as the need for hand weeding or herbicides is eliminated. The present experiment indicates that SRI system does not hold much promise in regions where farmers follow recommended package of practices.
Effect of nutrient inter-relations on productivity of rice in lateritic soils
(Department of Agronomy, College of Horticulture, Vellanikkara, 2002) Sindhu, P V; Meera Menon, V
Efficacy of mulches for weed management in okra (Abelmoschus esculentus (L.) Moench.)
(Department of Agronomy, College of Horticulture, Vellanikkara, 2015) Faras Bin Muhammed, U P; Sindhu, P V
Environmental influence on yield and quality of stevia (Stevia rebaudiana Bertoni)
(Department of Agronomy, College of Agriculture ,Vellanikkara, 2022-05-05) Somanatham , Suhas; Sindhu, P V
Stevia (Stevia rebaudiana Bertoni) is natural sweetener of the Asteraceae family, commonly known as candy leaf, honey leaf, sweet leaf, or sugar leaf. The plant contains steviol glycosides (SVglys), which are of high interest in the human diet as a low calorie and high potency sweetener. As the leaf is the main economic part of stevia, production of more leaf biomass with higher steviol glycosides is the main criteria for crop performance. Since both biomass production and quality are equally important in medicinal plant cultivation, it is necessary to determine optimal growth factors that can ensure high yield and quality. The present study entitled “Environmental influence on yield and quality of stevia (Stevia rebaudiana Bertoni)” was conducted at the Department of Agronomy, College of Agriculture, Vellanikkara during the year 2020. The objective of the study was to determine the influence of growing conditions and planting dates on the biomass production and quality of stevia. The study consisted of a field experiment designed in split plot design with three replications and a pot culture. The aim of field experiment was to find out the effect of growing condition and planting dates on yield and quality of stevia. The main plot treatments consisted of two growing conditions viz., open and 50 per cent shade and the sub plot treatments consisted of four dates of planting viz., May 15th, June 15th, July 15th and August 15th. The pot culture study was designed in completely randomized design (CRD) to evaluate the phytochemical constituents of stevia leaves at different growth stages. Growth parameters such as plant height, number of branches, fresh leaf weight, dry leaf weight, herbage yield, and total biomass yield were significantly influenced by growing conditions and planting dates. Open condition (8406 kg/ha) and May planting (10162 kg/ha) resulted in the highest leaf yields of stevia. The interaction between growing condition and planting dates was also significant. May planting under open condition proved to be the best treatment with respect to leaf yield. Growing conditions and planting dates had a profound influence on physiological and biochemical parameters. May planting under open conditions resulted in higher CGR and RGR values. Planting in May under open condition resulted in the highest steviol glycoside content of 9.05 per cent. A positive correlation was observed between maximum temperature and plant height, number of leaves, fresh leaf weight, total biomass yield and total glycoside content. Whereas, negative correlation was found with respect to afternoon R.H and rainfall Pot culture study conducted to assess the variations in phytochemical constituents of stevia leaves at different growth stages and growing conditions revealed variations in parameters such as total carbohydrates, fat, protein, soluble sugars, reducing sugars, non reducing sugars and steviol glycoside contents. Total carbohydrates and moisture content was observed to be higher under shaded growing condition, whereas open condition resulted in higher contents of total fat, crude fibre, protein, total minerals, total soluble sugars, reducing and non reducing sugars, total energy and total steviol glycosides. Total carbohydrates, total fat, moisture, total soluble sugars, reducing and non reducing sugars and total steviol glycoside contents were higher at flower bud initiation stage. A slight reduction in carbohydrate content was observed towards maturity. The highest content of total protein was observed at full bloom stage. Total energy value increased from 45 DAP, reached a peak at flower bud initiation stage and decreased thereafter. It can be concluded that open growing condition, planting in the month of May and harvesting at flower bud initiation stage can be suggested for better leaf yield and quality of stevia under Kerala conditions.
Geospatial technologies and its application in agriculture
(Department of Agronomy, College of Horticulture, Kerala Agricultural University, 2020) Somanatham, Suhas; Sindhu, P V
Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)
(Department of Agronomy, College of Agriculture, Vellanikkara, 2021) Dayana Samson; Sindhu, P V
Kerala is considered a treasure house of medicinal and aromatic plants, however, due to indiscriminate harvesting; the existence of most of these plants is under threat. Cultivation is the only option to ensure the continual supply of high quality raw materials without diminishing natural resources. Due to small holding size and a greater focus on cash crops, the scope for commercial production of medicinal plants as a pure crop in Kerala is restricted. So, the practical alternative is to bring them under intercropping with priority crops such as food and commercial crops. Cassava (Manihot esculenta Crantz) is the most important starchy root crop grown in the tropics. The wide spacing, together with slow initial growth and development, makes cassava compatible to intercropping with short duration annual crops. The present study entitled “Medicinal plants as intercrops in cassava (Manihot esculenta Crantz)” was carried out at the Agronomy farm, Department of Agronomy, College of Agriculture, Vellanikara from September 2020 to April 2021 to assess the feasibility of intercropping cassava with the medicinal plants Indigofera tinctoria, Plectranthus vettiveroides and Sida alnifolia. The experiment was laid out in Randomized Block Design (RBD) with 10 treatments replicated thrice. The treatments included sole crops of cassava and medicinal plants, cassava + single row of medicinal plants, and cassava + double rows of medicinal plants. The observations on growth, yield and yield attributes of main and intercrops, and quality parameters of medicinal plants were recorded. Competitive indices and economics of cultivation were also computed. Intercropping significantly influenced the growth and yield attributes of both main and intercrops. With respect to plant height of cassava, significant variation was observed only at later stages of crop growth. Shorter cassava plants were observed when intercropped with Sida alnifolia (162.84 cm). In general, medicinal plants grown under intercropping system recorded taller plants, except for Indigofera, where sole cropping resulted in taller plants.The sole crop of cassava produced higher per plant tuber yield of 3.24 kg (32417 kg/ha) and was at par with cassava with single row of Plectranthus (3.12 kg/plant). The lowest tuber yield was recorded when cassava was intercropped with double row of Sida (1.77 kg/plant). Similar trend was observed in itop yield and dry matter production per plant. The yield of medicinal plants was the highest in sole crops, followed by single row intercropping and double row intercropping. Same trend was observed for quality parameters of medicinal plants. The quality of Indigofera tinctoria, expressed by indican content, was higher in sole crop (1.40 per cent) and was on par with single row inter crop (1.39 per cent). Sole crop of Plectranthus vettiveroides registered the highest essential oil content of 0.60 per cent, followed by cassava + single row of Plectranthus (0.40 per cent). Sole crop of Sida alnifolia produced highest total alkaloid (3.07 per cent) and was at par with single row intercrop (2.94 per cent). Cassavas intercropped with double rows of medicinal plants were more efficient in controlling weeds than sole crop of cassava or cassava + single row of medicinal plants. Sole crop of cassava recorded the highest total weed density and dry matter production at 30 DAP, 60 DAP and 90 DAP. Sida alnifolia controlled the weeds more effectively than other medicinal plants, both as sole crop or as intercrop with cassava. Competition indices like land equivalent ratio (LER), relative crowding coefficient (K or RCC), competitive ratio (CR), cassava equivalent yield (CEY) and aggressivity were assessed for evaluating intercropping efficiency. All intercropping systems recorded LER of values greater than one, indicating the yield advantage over sole cropping. The highest LER (1.41) was recorded when cassava was intercropped with double row double row of Plectranthus vettiveroides and LER was lower when Sida alnifolia was intercropped either as single row or as double rows (1.01 and 1.05 respectively). Higher RCC and CR values and positive aggressivity values for cassava indicated dominance of cassava over medicinal plants. K (RCC) of all treatments was greater than one, indicating yield advantage of the system. The highest CEY was recorded for cassava + Indigofera as double row, with cassava equivalent yield of 43895 kg/ha, and the lowest CEY was for sole crop of Sida alnifolia (3000 kg/ha). Among the medicinal plants evaluated, Indigofera tinctoria, either as double row or as single row, could be recommended as the best medicinal intercrop for cassava. Intercropping cassava with single row Plectranthus vettiveroides was the next best alternative.
Microsite management for enhancing root yield and quality of ashwagandha (Withania somnifera (L) Dunal)
(Department of Agronomy, College of Agriculture, Vellanikkara, 2024-12-12) Giridharan, R; Sindhu, P V
The winter cherry (Withania somnifera (L.) Dunal), often known as Indian Ginseng, is an annual herbaceous medicinal plant belonging to the Solanaceae family. The Sanskrit name ashwagandha was given to this plant due to the smell of the roots resembling a sweating horse. Though all the plant parts are rich in secondary metabolites, roots constitute a significant part of the trade. Ashwagandha roots are rich in bioactive compounds like steroidal lactones, alkaloids and flavonoids. Recognizing its market potential, the National Medicinal Plants Board, India, has endorsed its commercial cultivation. Ashwagandha cultivation has good potential in Kerala due to high market demand. As it is a new crop in Kerala, before recommending it for commercial cultivation, it is necessary to standardize the nutrient management practices to ensure high yield and quality. The present study was undertaken from August 2023 to January 2024 in the Department of Agronomy, College of Agriculture, Vellanikkara, to assess the effect of organic manures and biostimulants on the growth, yield and quality of Ashwagandha (Withania somnifera (L.) Dunal). The experiment was laid out in Factorial Randomized Block Design (FRBD) and replicated thrice. The treatments consisted of four levels of organic manures viz., FYM @ 5 t/ha, FYM @ 10 t/ha, vermicompost @ 2.5 t/ha, vermicompost @ 5 t/ha and four levels of biostimulants viz., water spray, seaweed extract @ 0.4%, humic and fulvic acid @ 0.4%, and chitosan @ 0.1%. The total quantity of organic manures was given as basal, and biostimulants were sprayed at one and three months after planting (MAPs). Organic manures and biostimulants significantly influenced the plant height, number of branches/plant, fresh biomass and dry biomass/plant. A higher number of roots were observed in plants with vermicompost @ 5 t/ha (4.62) and seaweed extract (4.91). The dry weight of roots per plant was recorded maximum in plants with vermicompost @ 5 t/ha (3.22 g) and seaweed extract (3.59 g). Interaction between organic manures and biostimulants was also significant concerning dry root weight per plant. The treatment combination of vermicompost @ 5 t/ha and seaweed extract gave a higher dry root yield of 4.79 g/plant. Organic manuring and biostimulant application significantly influenced physiological and biochemical parameters. However, total chlorophyll content was unaffected throughout the growth stages. Higher total alkaloid content was observed when vermicompost was applied @ 5 t/ha (2.07 %) and the lowest was noticed in FYM @ 5 t/ha (1.62 %). Plants sprayed with seaweed extract recorded the highest total alkaloid content of 2.17 % among different biostimulants. Crop growth rate (CGR) and relative growth rate (RGR) were higher in plants that received vermicompost @ 5 t/ha and seaweed extract. At all the stages of observations, organic manures do not significantly influence the relative leaf water content of ashwagandha plants. However, biostimulants considerably increased the relative leaf water content at 60 and 120 DAP. Enhanced N, P and K uptake was observed in plants fertilized with vermicompost @ 5 t/ha. The soil organic carbon content increased in FYM @ 10 t/ha (1.36 %) applied plots compared to pre-experimental status (1.11 %). Significantly higher soil microbial biomass carbon was found in plots fertilized with FYM @ 10 t/ha (258.56 mg kg-1). Soil available N, P and K were higher in the soil that received the same treatment. A higher B:C ratio of 2.25 was realised from the treatment combination of FYM @ 10 t/ha along with foliar application of seaweed extract, followed by FYM @ 5 t/ha with humic and fulvic acid (2.15). The lowest B:C ratio of 0.39 was noticed in the treatment combination vermicompost @ 5 t/ha with humic and fulvic acid. The study revealed that the growth and yield of ashwagandha can be improved through organic nutrient management. Applying basal application of vermicompost @ 5 t/ha boosted growth and yield. Supplementing this with seaweed extract as a foliar spray at 0.4% enhanced the quality. While combining vermicompost and seaweed extract optimized crop growth, yield and quality, the most profitable combination comprised FYM @ 5 t/ha with seaweed extract spray.
Microsite variations of okra [Abelmoschus esculentus (L.) Moench.] under different weed management practices
(Department of Agronomy, College of Horticulture, Vellanikkara, 2017) Shamla, K; Sindhu, P V
Organic farming: Can it meet today's needs?
(College of Horticulture, Kerala Agriculture University, 2004) Sindhu, P V; George Thomas,C
Phytosphere variations of sida hemp [Sida alnifolia L.] under varying agronomic management
(Department of Agronomy, College of Horticulture, Vellanikkara, 2019) Vidhu Priyadarsini, P T; Sindhu, P V
Production technology for enhancing yield and quality of stevia (Stevia rebaudiana Bertoni)
(Department of Agronomy, College of Agriculture, Vellanikkara, 2025-08-27) Pittala Manoj Kumar.; Sindhu, P V
Stevia rebaudiana is a natural source of steviol glycosides, offering a healthier sugar alternative. Globally, stevia is widely cultivated, and several Indian states have successfully grown it. However, in Kerala, commercial cultivation is limited due to lack of suitable varieties and scientific production technology. To address this, a study entitled “Production technology for enhancing yield and quality of stevia (Stevia rebaudiana Bertoni)” was conducted at the Department of Agronomy, College of Agriculture, Vellanikkara, from 2021 to 2024. The objectives of the study were to collect and characterize stevia accessions based on morphological, biochemical, physiological, and yield parameters, and to standardize nutrient management for growth, yield, and quality. As part of the first experiment, titled ‘Characterization of Stevia rebaudiana accessions’ twenty-six accessions were collected from different states of the country and were evaluated in a completely randomized design with three replications during October 2021 to January 2022. Significant variability across qualitative, quantitative, and biochemical traits were observed. The plant height ranged from 47.8 to 72.7 cm, and fresh leaf weight ranged from 6.40 to 18.37 g/plant. Accessions exhibited diverse morphological characteristics, particularly in leaf shape and colour as well as stem and inflorescence colouration, which formed the basis for cluster categorization. Gower’s distance method with Ward’s clustering analysis based on leaf traits grouped the accessions into four clusters with 78 per cent dissimilarity, distinguishing oblanceolate leaves with acute tips in Clusters I and II (crenate and incised margins, respectively), and obovate leaves in Clusters III and IV (with obtuse and acute tips, respectively). Based on 14 quantitative characters, accessions were further grouped into three distinct clusters with 66 per cent dissimilarity. Cluster I (12 accessions) exhibited higher trait values, Cluster II (6 accessions) had lower values, and Cluster III (8 accessions) displayed intermediate values. The principal component analysis (PCA) of 14 quantitative characters revealed that the first four principal components accounted for 85% of the total genetic variability, with PC1 explaining 44% and being influenced by traits like plant height, leaf width, and days to first flowering. Heritability analysis showed 13 out of 14 traits had high heritability, with specific leaf weight and fresh leaf weight exhibiting very high heritability. Fresh leaf weight was strongly correlated with branch and leaf count, and path analysis showed total leaf count had a significant direct effect on fresh leaf weight. Accessions Acc. 8 (Mala, Thrissur), Acc. 5 (Parappanangadi, Malappuram) and Acc. 13 (IIHR, Bangalore) were superior for leaf yield. Significant biochemical variability was observed among accessions for stevioside, rebaudioside A, and total steviol glycosides (TSGs). Euclidean cluster analysis grouped accessions into four clusters based on biochemical traits, and PCA showed that the first three components explained 83% of the total variability. Acc. 22 (Krishnapuram, Allapuzha), Acc. 9 (Pattikkad, Thrissur), and Acc. 10 (Tammanam, Ernakulam) were identified as superior for TSG content. Combined scoring for leaf yield and TSG content identified Acc. 5 (Parappanangadi, Malappuram), Acc. 8 (Mala, Thrissur), and Acc.7 (Puthenvelikara, Ernakulam) as the most promising accessions with high leaf yield and total steviol glycoside content. For the standardization of nutrient management for better growth, yield, and quality of stevia, two separate field experiments were conducted, one under an organic management system and the other with an integrated nutrient management system. The experiment on ‘Effect of organic manures on growth, yield, and quality of Stevia rebaudiana was conducted in Randomized Block Design (RBD) with seven treatments and three replications from April to August in 2022 and 2023. The treatments included three levels of farmyard manure (FYM) at 5, 10, and 15 t ha-1 and three levels of vermicompost at 2.5, 5.0, and 7.5 t ha-1, compared with an absolute control. The application of organic manure significantly influenced the growth and yield parameters of stevia. Taller plants with more branches and leaves were observed under FYM @15t ha-1, followed by vermicompost @ 7.5t ha-1 and FYM @10t ha-1. The highest fresh herbage yield was recorded under FYM @15t ha-1 (6157 kg ha-1), followed by vermicompost @7.5t ha-1 (5616 kg ha-1). Crop growth and relative growth rates were also superior under FYM @15t ha-1 throughout all the growth stages. The application of vermicompost @2.5t ha-1 resulted in the highest stevioside (5.18 per cent) and total glycoside contents (6.19 per cent), although rebaudioside A (Reb-A) remained unaffected by organic manure treatments. However, concerning total glycoside yield (kg ha-1), the best treatment was vermicompost @2.5t ha-1. The application of FYM @15t ha-1 led to higher soil organic carbon and soil available potassium. On the other hand, soil available nitrogen and phosphorus were highest under vermicompost @7.5t ha-1, followed by FYM @15t ha-1. The experiment on integrated nutrient management for stevia was laid out in factorial RBD with three replications during April to August in 2022 and 2023. The treatments included levels of manures as factor A (No manure, vermicompost @2.5t ha-1 and FYM @5 t ha-1) and levels of NPK as factor B (20:10:10, 40:20:20 and 60:30:30 kg NPK ha-1). The combined application of FYM @5t ha-¹ and NPK @ 60:30:30 kg ha-¹ resulted in the highest growth and fresh herbage yield (5736 kg ha-1). Vermicompost @ 2.5t ha-¹ + NPK @ 40:20:20 kg ha-¹ recorded the highest stevioside (6.04 per cent) and total glycoside (6.45 per cent) contents, while the highest rebaudioside A content was found under FYM @5 t ha-¹ + NPK @20:10:10 kg ha-¹. Combined application of vermicompost @ 2.5t ha-¹ + NPK @ 40:20:20 kg ha-¹ resulted in the highest total glycoside yield (kg ha-1).
Weed management in cassava (Manihot esculenta Crantz)
(Department of Agronomy, College of Horticulture, Vellanikkara, 2016) Reshma, N; Sindhu, P V
Cassava, one of the most important tropical tuber crops, is known to sustain even under marginal soil conditions. Being a widely spaced crop with slow initial growth, a wide spectrum of weeds has been reported in cassava fields which may cause yield losses up to 90 per cent. Weeding is the main labour consuming activity of cassava fields as it is usually carried out by tillage practices and earthing up. Presently, chemical weed control is becoming popular among farmers as it is an efficient way of weed control with minimum labour cost. However, relying only on chemical weed control may not be feasible in the long term. Developing a complete weed management package by integrating chemical, physical and cultural methods may be the best option for cassava to achieve optimum yield. The present study entitled “Weed management in cassava (Manihot esculenta Crantz)” was carried out at the Agronomy farm attached to the Department of Agronomy, College of Horticulture, Vellanikkara from May to October 2015 to compare different weed management practices for cassava. The treatments included applications of three pre emergence herbicides viz., oxyfluorfen 0.2 kg/ha, pendimethalin 1.5 kg/ha and imazethapyr 80g/ha, directed application of glyphosate 0.8 kg/ha at 30 Days After Planting (DAP), all this four herbicides followed by one hoeing and earthing up at 60 DAP, hoeing and earthing up twice at 30 and 60 DAP, concurrent growing of fodder cowpea and in situ green manuring and earthing up at 60 DAP, and unweeded control plot. Weed management treatments significantly affected the growth and yield characters. Number of tubers per plant was high when cassava was intercropped with cowpea and when hoeing and earthing up was done twice. These two treatments also recorded longer cassava tubers. Higher tuber yields were recorded for the treatments hoeing and earthing up (31.20 t/ha), pendimethalin followed by earthing up (30.60 t/ha) and glyphosate followed byearthing up (28.40 t/ha). These treatments also showed higher top yield and greater dry matter production. The treatments significantly influenced the weed population and weed dry weight at all the four stages of plant growth. The herbicide oxyfluorfen could control 99 per cent of weeds at 30 DAP. Pendimethalin followed by earthing up was more effective in suppressing the weeds in later stages and it resulted in 94 per cent control of weeds during harvest. Weed control efficiency of all the treatments increased with a follow up earthing up. Pre emergence application of imazethapyr alone was less effective in controlling the weeds and it recorded a lower weed control efficiency compared to other plots. Weed index was lower in the treatments hoeing and earthing up, pendimethalin followed by earthing up and glyphosate followed by earthing up. Lower nutrient uptake by weeds was recorded in the treatment which received pre emergence application of oxyfluorfen during early stages of plant growth. At the time of harvest, the treatments pendimethalin followed by earthing up and glyphosate followed by earthing up recorded lower uptake of nutrients. The soil pH, organic carbon and phosphorus contents of the soil were statistically on par in all the plots after the experiment. However, the contents of available N and K showed significant differences among the treatments. Green manure cowpea intercropped plots recorded higher available nitrogen content after the experiment. The highest B:C ratio of 2.41 was obtained for the treatment pre emergence application of pendimethalin followed by earthing up. The treatment with application of pre emergence oxyfluorfen had a higher B:C ratio of 2.27. Even though hoeing and earthing up produced higher tuber yields, the B:C ratio was lower because of the additional labour requirement. The results of the present investigation suggest the possibility of reducing the number of earthings up in cassava by applying a pre emergence herbicide such as pendimethalin.