Browsing by Author "Savitha Antony"

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Management of salvinia (Salvinia molesta D. S. Mitch.) in rice ecosystem
(Department of Agronomy, College of Agriculture, Vellanikkara, 2023-03-06) Basil Chackochan; Savitha Antony
Salvinia molesta, the invasive aquatic fern common in wetlands of Kerala, has attained the status of a troublesome weed in cultivated rice fields in many parts of the State. Biological control using the weevil Cyrtobagous salviniae is feasible for stagnant water bodies as it takes a long time to manage the weed. Hence, a study was undertaken to check the efficacy of a few new generation rice herbicides and eco-friendly chemical measures to control salvinia infestation in paddy fields. The experiment was conducted from September 2021 to August 2022 at the College of Agriculture, Vellanikkara, Thrissur. A few selected treatments were tested for field efficacy at farmer’s rice field in Aikarnad panchayath in Ernakulam district, where the weed infestation was severe. Salvinia was cultured in trapezoidal wide mouthed cement tanks of 0.30 m2 area and 30 L capacity. There were 15 treatments, laid out in CRD design with three replications. The treatments were lime and gypsum @ 0.10 kg/m2, carfentrazone-ethyl @ 0.02 and 0.04 kg/ha, (cyhalofop-butyl + penoxsulam) and (florpyrauxifen-benzyl + cyhalofop-butyl) @ 0.15 kg/ha, (butachlor + penoxsulam) @ 0.82 kg/ha, 2,4-D amine @ 1 kg/ha, acetic acid, salicylic acid, NaCl and copper sulphate each @ 5% w/v, glufosinate ammonium @ 0.3 and 0.5 kg/ha, and an untreated check. The percentage of control, as well as phytotoxicity symptoms, were observed periodically and scoring was done. Regrowth of salvinia (if any) was recorded at 10, 20, 30, and 40 days after treatment and fresh biomass were weighed at 40 days. Water samples were collected from tanks 10 days after treatment application and pH, EC, carbonate, bicarbonate, calcium, sulphate, nitrate, chloride, total hardness, biological oxygen demand, chemical oxygen demand, dissolved oxygen, alkalinity and acidity were analysed. Sediment samples were collected and observations on pH, EC, organic carbon, available N, P, K, Ca, and S were estimated. The data were subjected to statistical analysis using the statistical software GRAPES. Almost 95 percent control of salvinia was observed when sprayed with herbicides glufosinate ammonium, (florpyrauxifen-benzyl + cyhalofop-butyl), (cyhalofop butyl + penoxsulam) and (butachlor + penoxsulam). The selective herbicide, carfentrazone-ethyl was slow in action and a lower dose of 0.02 kg/ha was enough to get satisfactory control by 40 days of spraying. Among the various chemicals tested, salicylic acid, copper sulphate and acetic acid were effective and statistically at par (90 percent control). However, a few new sprouts of salvinia were observed in tanks treated with salicylic acid, copper sulphate and acetic acid 40 days after spraying. 2,4 -D amine (17% control) and lime (32% control) were not effective against salvinia and some regrowth was also observed. NaCl and gypsum were ineffective and gypsum was even found to stimulate the growth of salvinia. Sodium chloride spray @ 5% did not affect salvinia though there was a conspicuous hike in EC of water to 2.48 dS m-1 compared to 0.29 dS m-1 in untreated check, indicating its tolerance to a slightly saline situation. The pH of the water in treated tanks ranged from 6.66 -9.16 and the highest value was recorded with the lime application. Bicarbonate, carbonate, and alkalinity showed the same trend, the highest value was observed in the treatment with lime. Changes in pH and EC of water were prominent with lime, gypsum and copper sulphate application. However, these changes did not produce any direct impact on the growth suppression of salvinia. As expected, significantly high calcium content was observed with gypsum (CaSO4.2H2O) application (112 mg L-1) which is above the acceptable limit. The sulphate content and total hardness were below the permissible limit for all treatments. Chloride content was within the safe limit (< 4 meq L-1) as per FAO standards for all other treatments except for NaCl. Chemical oxygen demand was above the desirable limit of 1 mg/L and in glufosinate ammonium, carfentrazone-ethyl, (cyhalofop-butyl + penoxsulam), NaCl, and gypsum application. The dissolved oxygen level was within the desirable limit for all other treatments except for lime and copper sulphate. Biological Oxygen Demand (BOD) was high in treatments where undecomposed salvinia mat sank to the bottom of the tank as a result of spraying of carfentrazone ethyl, (butachlor + penoxsulam), (cyhalofop butyl + penoxsulam), salicylic acid and acetic acid. Various treatments did not alter the pH of sediments and the values ranged from 5.8 to 6.7, which was close to the initial pH of 6.5. Electrical conductivity increased in all treatments compared to a value of 0.05 dS m-1 observed in untreated check. In general, organic carbon, available nitrogen, and potassium content of the sediment were higher in all the treatments that showed more than 85 per cent control of salvinia. The treatments which showed efficiency under tank study gave good control under field situation also, though the efficiency was lower. The herbicides (butachlor + penoxsulam), glufosinate ammonium, and (cyhalofop butyl + penoxsulam) registered 70, 60 and 50 percent control respectively. Acetic acid spray caused severe phytotoxicity to rice, though it could effectively control the weed and hence cannot be recommended in cropped situation. Under field condition, there was no significant change in sediment quality due to various treatments. From the present study, it can be concluded that the premix herbicides (butachlor + penoxsulam), (cyhalofop butyl + penoxsulam) and (florpyrauxifen – benzyl + cyhalofop – butyl) can be used for quick control of salvinia in a standing rice crop. Being a broad-spectrum nonselective herbicide, glufosinate ammonium can be recommended for preplant application only. From an ecological point of view detailed studies on long term effect of these herbicides/chemicals on the aquatic organism and water quality parameters have to be undertaken, before arriving at a conclusive recommendation.
Occurrence, germination ecology and management of dodder (Cuscuta campestris yuncker)
(Department of Agronomy, College of Agriculture, Vellanikkara, 2025-02-05) Ansheth, K P; Savitha Antony
Field dodder (Cuscuta campestris Yuncker) is an obligate stem-parasitic weed native to North America that has spread to various parts of Asia. Cuscuta infestations cause substantial reduction in both the quantity and quality of crop. Recently, cuscuta infestation is reported in many seasonal crops and the severity of these infestations has also intensified following the floods in 2018. If cuscuta infestation is not managed timely, it is too strenuous for mechanical removal; hence, pre-emergence management is the only option. Post-emergence applications of herbicides control cuscuta and also damage the host plant and hence not a viable option in most of the cropped situations. The present study entitled "Occurrence, germination ecology and management of dodder (Cuscuta campestris)" was conducted from July 2023 to October 2024 to investigate the occurrence of C. campestris in the central zone of Kerala, assess the effect of various ecological factors on its germination and to develop effective post-emergent chemical management strategies against this parasitic weed. Survey was conducted throughout Kerala to identify the distribution and host range of C. campestris, with focus on the districts of Thrissur, Ernakulam, Palakkad, Kozhikode, and Malappuram. The weed was common in converted rice fields, agricultural fields, rice fallows and roadside wastelands. The incidence was observed in 42 host species belonging to 22 families. Of these, 90% were dicots, and the rest (10%) were monocots. Some of the crops infested with cuscuta were tapioca, banana, bitter gourd, cowpea, chilli, brinjal, tomato, amaranthus and a few ornamental plants. The most preferred weed hosts are Mikania micrantha and Sphagneticola trilobata, which belong to the family Asteraceae. The experiments were conducted to study the germination response of seeds to various dormancy breaking treatments, pH, burial depth, and moisture levels. Due to the presence of hard seed coat, germination percentage was only 33%. Sandpaper scarification and concentrated H2SO4 treatments resulted in more than 80% germination. Soil moisture status also influenced seed germination and irrigation at alternate and two day interval favoured good germination (85%). The lowest germination (18%) observed in fully saturated soil. The highest germination (85%) was observed at neutral pH (7) with reduced germination at both higher and lower pH levels. Emergence was the highest from surface soil layer (92%) and reduced at depths beyond 2 cm. Germination was unaffected by light or dark conditions. A temperature range of 28-33 °C favoured germination, but significant reduction observed at 38°C. Field experiments were conducted at various cuscuta infested locations where the host plants were singapore daisy, tapioca, bitter gourd, and ornamental plants, to evaluate the effects of different chemical sprays on cuscuta and to assess the level of phytotoxicity on both the parasite and the host. Initial results on singapore daisy showed 100% cuscuta control with 5% solutions of urea, ammonium phosphate sulphate (Factamfos), diammonium phosphate (DAP), copper sulphate, ammonium sulphate, and ammonium chloride. A lower concentration of 3% solutions of urea and ammonium phosphate sulphate solution resulted in 86% and 93% control, respectively, by 10 days after treatment (DAT). Solutions of 19-19-19 (5%) and nano urea (4 ml/L) were not effective and resulted in only 13% and 20% control with no injury to host. While herbicides like glyphosate, glufosinate ammonium, and 2,4-D effectively controlled cuscuta and caused significant host damage. Urea and ammonium phosphate sulphate (at 3% and 5%) were the most effective, selectively controlling cuscuta with minimal host phytotoxicity on crops like tapioca and shrubby ornamentals. The survey on C. campestris revealed its extensive distribution in converted rice fields and wastelands, mainly infesting dicots, and affecting crops such as tapioca, banana, bitter gourd, cowpea as well as various weeds and ornamental plants. Seed dormancy due to hard seed coat and scarification enhances its germination, while neutral pH gave higher germination. However, saturated soil and deep seed burial inhibit its emergence. The study indicates the possibility of using foliar sprays of urea or ammonium phosphate sulphate at 3 and 5% concentrations, along with an adjuvant for managing cuscuta in crops like tapioca, bitter gourd, ornamental plants. However, regrowth was observed within a week post-spray, indicating repeated treatments for sustained management.
Performance of hybrid napier cultivars under rainfed conditions
(Department of Agronomy, College of Horticulture, Vellanikkara, 2012) Savitha Antony; George Thomas, C
Hybrid napier, an inter-specific cross between bajra (Pennisetum glaucum (L.) R. Br.) and napier (Pennisetum purpureum Schum.) is a popular fodder grass with high nutritive value and herbage yield. Hybrid napier cultivars perform well under irrigated condition but their performance under rainfed condition is not evaluated. A field experiment was conducted at the College of Horticulture, Vellanikkara to evaluate the performance of 11 popular cultivars under rainfed conditions—CO-2, CO-3, CO-4, KKM-1, Suguna, Supriya, IGFRI-3, IGFRI-7, DHN-6, PTH and PBN-16. Slips were planted at a spacing of 60 cm X 60 cm in June, and growth, fodder yield and nutrient uptake were studied at 45 days interval. The first harvest was taken at 75 days after planting and subsequent harvests at 45 days interval. The cultivars differed significantly in various parameters such as plant height, tillers/plant, leaves/plant, leaf width, leaf length, leaf area index, net assimilation rate, relative growth rate, leaf area ratio, leaf: stem ratio and shoot: root ratio. Four harvests were made, the last being in January. Green and dry fodder yield were maximum during the first harvest, thereafter, yield decreased. In summer, no harvesting was done due to stunting and drying of plants. Among the eleven cultivars evaluated, CO-3 recorded the highest green fodder yield followed by DHN-6. Nutritive values and oxalate content showed significant differences among the cultivars. Crude protein content was maximum in CO-3 and IGFRI-3. In general, CO-3 showed supremacy over other cultivars in terms of overall nutritional quality. Oxalate content, an antinutritive factor, was found to be the highest in Suguna. Nutrient uptake was higher in the first harvest, and CO-3 had the highest nutrient removal. In summer, maximum RLWC was noticed in Supriya and CO-3, and the lowest in IGFRI-3. All the clumps of CO-3, CO-4 and PTH survived the dry periods and maximum mortality was noticed in PBN-16 followed by IGFRI-3, DHN-6, CO-2 and KKM-1. The study revealed that CO-3 is superior to all other cultivars with respect to yield, nutritive value and the ability to withstand drought, and hence, CO-3 is highly suited for rainfed cultivation. Since there was no mortality of clumps for CO-4 and PTH, these cultivars can also be considered. Although DHN-6 showed 25 percent mortality of clumps during summer, as it outyielded other cultivars during rainy period, it may be suitable for areas with well distributed rainfall.
Shade tolerance, nitrogen nutrition,and harvest management in hybrid napier under rainfed condition
(Department of Agronomy, College of Horticulture,Vellanikkara, 2016) Savitha Antony; George Thomas, C
Hybrid napier, an inter-specific cross between bajra and napier, is a popular fodder grass because of its high yield potential and quality. Three field trials were conducted during 2013–2015 with the objectives of assessing shade tolerance of selected hybrid napier cultivars, finding out optimum nitrogen levels and harvesting frequency, and studying the influence of different cutting heights on regrowth and mortality of major cultivars under rainfed condition. The performance of six cultivars of hybrid napier(CO-3, CO-4, Suguna, IGFRI-3, DHN-6 and PTH) at three different shade levels (0 per cent, 25 per cent and 50 per cent) were studied under rainfed condition. Increasing shade levels had a facilitating effect on plant height, leaf length, leaf width, leaf area index, leaf area ratio, leaf weight ratio, leaf- stem ratio, chlorophyll content and PAR interception, whereas, number of tillers, number of leaves, specific leaf weight, and fodder yield were reduced under shade. ‘Suguna’ had the highest fodder yield followed by ‘CO-3’ and ‘CO-4’. Shade also affected the nutritive value and quality of leaves and stems. Oxalate content in plants increased with increasing shade and ‘IGFRI-3’ had the highest content. The effect of nitrogen levels (0, 100, 200, 300, and 400 kg/ha) and three cutting intervals (30, 45, and 60 days) were tested on hybrid napier cultivar ‘CO-3’. Cutting frequency and nitrogen affected plant growth, yield, and yield attributes. Delayed harvesting reduced fodder quality. Crude protein, crude fat, Ca, Mg, oxalate, and nitrate contents increased with increasing nitrogen levels while total ash, K and P contents remained unaffected. The nitrogen use efficiency (NUE) decreased with increasing cutting intervals and nitrogen doses. The highest NUE was recorded at 45 days cutting interval and with 200 kg/ha N. Soil organic carbon content increased after the experiment but available N, P, and K declined. The experiment to study the effect of different cutting heights (5, 10, 15, and 20 cm) on regrowth and mortality of major cultivars (CO-3. CO-4, Suguna, DHN-6 and PTH) revealed that cutting height management affected yield attributing factors such as tiller and leaf production and fodder yield. The fodder yield increased with increasing cutting height. Hybrid napier showed maximum regrowth rate when harvested at 20 cm height and showed a declining trend when harvested at lower cutting heights. The cultivars ‘CO-3’, ‘CO-4’ and ‘Suguna’ had comparable regrowth rate. The results from the present investigation have implications for Kerala where land and water are scarce resources for fodder production. As ‘Suguna’ and ‘CO-3’ performed better than other cultivars under shade, these two can be grown where the intercrops receive at least 50 per cent of the incoming solar radiation. Applying 200 kg/ha nitrogen and cutting at 20 cm height at 45-60 days interval seem to be satisfactory for hybrid napier under rainfed condition.