1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)

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    Allelopathy based bio-synthesized nanoparticles and bio-utilization for the management of water hyacinth (Eichhornia crassipes (Mart.) Solms)
    (Department of Agronomy, College of Agriculture , Vellayani, 2023-06-09) Harikrishnasagar , V; Susha ,V S
    The research work entitled “Allelopathy based bio-synthesized nanoparticles and bio-utilization for the management of water hyacinth (Eichhornia crassipes (Mart.) Solms)” was undertaken at College of Agriculture, Vellayani during 2020-2022 to evaluate the efficacy of allelopathic weed extract mediated biosynthesized nanoparticles on water hyacinth; bio-utilization of water hyacinth as nutritive manure and its physico-chemical characterization.The effect of plant extract mediated bio-synthesized nanoparticles on water hyacinth was studied at College of Agriculture, Vellayani during June 2022 in completely randomized design with ten treatments and three replications. The treatments included T1: Lantana camara aqueous leachate at 3%, T2: Lantana camara mediated silver nanoparticles at 0.1%, T3: Lantana camara mediated silver nanoparticles at 1%, T4: Parthenium hysterophorus aqueous leachate at 3%, T5: Parthenium hysterophorus mediated silver nanoparticles at 0.1%, T6: Parthenium hysterophorus mediated silver nanoparticles at 1%, T7: Coleus amboinicus aqueous leachate at 3%, T8: Coleus amboinicus mediated silver nanoparticles at 0.1%, T9: Coleus amboinicus mediated silver nanoparticles at 1%, T10: Distilled water (control). Allelopathy-based biosynthesized silver nanoparticles were synthesized in the lab following a biosynthesis protocol. Characterization studies of the three biosynthesized silver nanoparticles (AgNPs) revealed that the reduction of silver ions (Ag+) to silver nanoparticles (Ag0) occurred. It was initially indicated by colour change and was confirmed by UV-vis spectroscopy. The absorbance ranged between 287 nm and 450 nm. Zeta potential data showed higher stability for P. hysterophorus mediated silver nanoparticles (-32.7 mV) and Dynamic Light Scattering data showed a PDI (Polydispersity Index) of 0.52 and an average size of 213 nm. The SEM image of parthenium mediated silver nanoparticles showed almost spherical shape. X-ray diffraction profile of three plant mediated AgNPs suspension showed face centred cubic structure. The average size of allelopathy-based bio-synthesized nanoparticles was found to be 13.76 nm, 9.96 nm and 17.29 nm respectively for lantana mediated AgNPs, parthenium mediated AgNPs and coleus mediated AgNPs which were calculated using the Debye-Scherrer’s equation.While comparing the effect of allelopathy based aqueous leachates and biosynthesized AgNPs on morphological parameters of water hyacinth, it was found that all the treatment applications showed negative effect on morphological parameters when compared to control. The P. hysterophorus mediated AgNPs affected the plant morphology in a concentration dependent manner. P. hysterophorus mediated AgNPs recorded lowest number of leaves (3.0), bud diameter (3.16 cm), length (5.0 cm) and width (5.26 cm) of leaves and root length (17.46 cm) at 9 days after treatment (DAT). The same treatment showed 100 per cent reduction in biomass within 12 DAT. There was 100 per cent reduction of root and shoot fresh and dry weight and there was no regeneration of ramets till 15 DAT with 100
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    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.
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    Comparative biology and growth behaviour of Pennisetum polystachyon (L.) Shult and P. pedicellatum Trin
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2000) Karthik, A; George Thomas, C
    Pennisetum polystachyon (L.) Shult. and P. pedicellatum Trin. are two major grass weeds that are widespread in young plantation crops and non-arable areas of the tropics. The present investigation was undertaken to have an understanding on the biology, growth behaviour and fodder production potential of these two Pennisetum spp. at the Research Farm, College of Horticulture, Vellanikkara during 1998-2000. Germination tests were conducted at monthly intervals. P. polystachyon did not show any dormancy and started germination as soon as the seeds are collected (December). P. pedicellatum seeds remained dormant during December and January and it started germination by February only. Both species showed above 80 per cent germination by late March. Germination percentage started to decline in P. polystachyon after April. Phenological characters of both species were noted from a natural population during the year 1999. Seeds of Pennisetum spp. started germination soon after the receipt of monsoon showers by the end of April. Flowering started after the completion of the rainy period in September. Plants started senescence by mid December in P. polystachyon and mid November in P. pedicellatum. Both Pennisetum species studied showed remarkable regeneration ability from different cutting heights. The percentage of plants regenerated was similar in both species, Allelopathic reactions of roots, leaves and seeds were also studied. Boiled and unboiled extracts were prepared and germination test were conducted using cowpea, bhindi and cucumber as test crops. The cold and boiled leaf extracts of both species did not show any effect on germination of test crops. However, cold root extract of both Pennisetum spp. reduced the germination percentge of bhindi. Cold root extract of both species also showed some promotery effect on shoot length in cowpea. Seed extracts showed inhibitory effects only on cowpea germination. Growth was comparatively fast in P: pedicellatum than P. polystachyon during its early stages. P. polystachyon showed higher leaf : stem ratio than P. pedicellatum. Growth indices like LAR, LWR, RGR, AGR and NAR were similar in both Pennisetum spp. In terms of total green fodder production, P. pedicellatum was superior to P. polystachyon. Two cuttings, one at 70 days after sowing and the other just before flowering recorded maximum fresh weight of fodder. Though crude protein content was similar in both the species, P. pedicellatum showed a higher crude fibre content than P. polystachyon. The results indicate that as the fodder quality is good, utilizing these grasses as cattle feed can be one of the strategies for managing them. However, cultivation of these grasses for fodder purposes involves some risks because of their high reproductive capacity and persistence.
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    Autoallelopathy of selected multipurpose tree species and the effect of their leachates on Agricultural test crop
    (Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2017) Neenu, P; Jamaludheen, V