PG Thesis

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    Compatibility of herbicides and insecticides for tank mix application in wet seeded rice
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2017) Anjana Devaraj, G; Prameela, K P
    Weeds and insect pests are the major biotic constraints in rice production. Chemical methods of control of insects as well as weeds is very common in rice production. Separate application of the chemicals is expensive and labour intensive with the result that many farmers of Kerala adopt tank mix application of different chemicals without due consideration to efficacy and compatibility. The present study entitled “compatibility of herbicides and insecticides for tank mix application in wet seeded rice” was conducted in a farmer’s field at Alappad Kole lands of Thrissur district, from August 2016 to January 2017. The experiment aimed at studying the compatibility of two commonly used herbicides (bispyribac sodium and cyhalofop-butyl) with two new generation insecticides (flubendiamide and imidacloprid) for tank mix application in wet seeded rice. Another objective of the study was to assess the pest control efficiency of herbicides and insecticides. Out of 14 treatments, four treatments in the trial included sequential and mixed application of bispyribac sodium with two insecticides separately. The next four included cyhalofop-butyl substituted for bispyribac sodium. The remaining treatments were application of herbicides alone, hand weeding with and without application of insecticides and unweeded control. Weed spectrum of the experimental field included barnyard grass (Echinochloa crus-galli), hippo grass (Echinochloa stagnina) and red sprangletop (Leptochloa chinensis) among grasses. Major broad leaf weed was water primrose (Ludwigia parviflora). Yellow nut sedge (Cyperus iria) was the only sedge species which was the major weed of the experimental plot. Treatments were studied for their phytotoxic effects on rice and no toxicity symptoms were observed in tank mix or sequential application. Weed counts, weed dry matter production and weed control efficiency were estimated at different stages of crop growth. Comparing sequential application and tank mix application of bispyribac sodium and flubendiamide, the mixed application resulted in high weed dry weight and low weed control efficiency. Yield parameters and yield were recorded low in this treatment. For sequential and combined applications of bispyribac sodium and imidacloprid, weed control efficiency, weed dry weight, yield and yield attributes were on par. Weed dry weight was low and weed control efficiency was high for mixed application of cyhalofop-butyl and flubendiamide. Yield and yield attributes were also high for this treatment. Weed dry weight, weed control efficiency, yield attributes and yield were comparable for sequential and mixed applications of cyhalofop-butyl and imidacloprid. Insect pest infestation was very low in the experimental field. Rice leaf folder (Cnaphalocrocis medinalis), white backed plant hopper (Sogatella furcifera), red spotted earhead bug (Menida versicolor) and yellow stem borer (Scirpophaga incertulas) were the insect pests noted. Observation on insect count showed that there was no significant difference among treatments with respect to insect pest counts at 5, 7 and 11 days after spraying which was comparable to unweeded control. Hence efficacy of insecticides when tank mixed with herbicides could not be interpreted. Hand weeding was the best treatment in terms of weed control efficiency, yield and yield attributes. However, the highest B: C ratios were registered by the treatments cyhalofop-butyl + flubendiamide and bispyribac sodium + imidacloprid. Highest net return was recorded in bispyribac sodium + imidacloprid. Unweeded control recorded lowest values for yield and B: C ratio. With respect to efficacy of herbicides used, the study indicated that the two insecticides tried were compatible with cyhalofop-butyl. In the case of bispyribac sodium, the insecticide imidacloprid appeared to be compatible, but mixing of flubendiamide cannot be recommended since weed control efficiency was very low.
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    Transition to organic agriculture in Kasaragod district: A multi dimensional analysis
    (Department of Agricultural Extension, College of Horticulture, Vellanikkara, 2016) Seenu Joseph; Jiju P Alex
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    Water and weed management for aerobic rice
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2017) Akhil T Thomas; Deepa Thomas
    Aerobic rice culture is a technology to improve the water productivity in rice culture. Water and weed management are two important aspects of this promising technology. It is well established that yield reduction in rice happen if the soil moisture level falls below the field capacity. Unlike in flooded conditions,weeds pose greater problem in aerobic rice production.A field study was undertaken at Agronomic Research Station (ARS), Chalakudy from September 2016 to January 2017 for developing appropriate water and weed management strategies for aerobic rice. The treatments comprised of three levels of irrigation in the main plot (irrigation at 10 mm cumulative pan evaporation (CPE), 20 mm CPE and 30 mm CPE) and five weed management treatments in the subplot (pre emergent herbicide oxadiargyl followed by hand weeding, oxadiargyl followed by 2,4- D sodium salt, oxadiargyl followed by bispyribac sodium at 20 days after sowing (DAS), hand weeding at 20 and 40 DAS and an unweeded control). Depth of irrigation was 3 cmand the total water applied including effective rainfall amounted to 933 mm, 574 mm, 403 mm in I1, I2 and I3 respectively. Irrigation at 10 mm CPE recorded higher values for growth parameters like plant height and number of tillers per meter as well as yield and yield attributes.Higher root volume also was recorded in these plots .Relative leaf water content and chlorophyll content were higher under frequently irrigated plots (10 mm CPE) than less irrigated plots. Moisture stress lead to inhibition of leaf production and decline in leaf area in aerobic rice. Higher availability of moisture, reduced stress, better growth and yield attributes contributed to higher yield under irrigation at 10 mm CPE. Moisture stress caused reduction of 44 percent grain yield under irrigation at 30 mm CPE over irrigation at 10 mm CPE. Hand weeding at 20 and 40 DAS resulted in better growth, yield and yield attributing factors of aerobic rice. Oxadiargyl followed by bispyribac sodium at 20 DAS and oxadiargyl followed by hand weeding at 20 DAS were the next bettertreatments which were on par.Weed competition resulted in 64 percent reduction in grain yield. Oxadiargyl when applied pre-emergent waseffective in controlling the first flush of weeds in the field. All the treatment combinations with oxadiargyl recorded the lower weed dry matter production and weed density. As the crop advanced to flowering, hand weeding at 20 and 40 DAS resulted in lower weed dry matter production and weed density. Better growth and yield in this treatment suggested a long critical period of weed competition in aerobic rice. Irrigation at 30 mm CPE registered the highest water productivity of 0.96 kg m-3, but with severe yield loss. Among weed management treatments hand weeding at 20 and 40 DAS recorded the highest water productivity (1.13 kg m-3) and the lowest was from unweeded control (0.37 kg m-3). Irrigation at 10 mm CPE in combination with hand weeding at 20 and 40 DAS registered the highest growth and grain yield (2791 kg ha-1) and recorded water productivity of 0.88 kg m-3. However irrigation at 10 mm CPE in combination with oxadiargyl followed by bispyribac sodium at 20 DAS resulted in the highest net return (Rs 51477 per hectare) and B:C ratio (2.3).
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    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
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    Influence of weed management practices on the soil quality attributes of ultisol
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2017) Shridhar, N; Durga Devi, K M
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    Effect of herbicides and chemical characteristics of soil on microbial biomass carbon and enzyme activity
    (Department of Soil Science and Agricultural Chemistry, College of Horticulture, Vellanikkara, 2017) Amritha, K; Durga Devi, K M
    Weed competition is one of the major factors limiting rice production in the tropics. Due to the scarcity and high cost of labour, weed management with herbicides is widely practiced. The problem associated with herbicides is the persistence of their residues in soil which interact with microorganisms thereby altering the microbial diversity and soil enzyme activity. Hence, the present investigation entitled “Effect of herbicides and chemical characteristics of soil on microbial biomass carbon and enzyme activity” was undertaken at College of Horticulture, Vellanikkara during 2016-2017. The objectives were: (i) to determine the impact of pre and post emergence herbicides on microbial biomass carbon and the soil enzymes namely dehydrogenase, urease, and phosphatase and (ii) to study the influence of chemical characteristics of the soil on microbial biomass carbon and enzyme activity. Representative soil samples were collected during March-April, 2016 from four sites viz., rice field of Agricultural Research Station, Mannuthy (medium organic matter soil with a history of herbicide application: S1 Control), non- cropped area of Agricultural Research Station, Mannuthy (medium organic matter soil without a history of herbicide application: S1 Absolute control), rice field of Kole land, Alappad (high organic matter soil with a history of herbicide application: S2 Control), and non- cropped area of Kole land, Alappad (high organic matter soil without history of herbicide application: S2 Absolute control). Physical, chemical, and biological characterization of the soil samples were done before starting the experiment. Pot culture experiment with rice variety Jyothi was conducted in the kharif season of 2016 with twelve treatments and six replications in factorial CRD (four herbicides under each soil type + four controls). The herbicides included pendimethalin, oxyfluorfen, bispyribac-sodium, and cyhalofop-butyl. Pre emergence herbicides (pendimethalin and oxyfluorfen) were applied at six days after sowing (DAS) and post emergence herbicides (bispyribac-sodium and cyhalofop-butyl) at 16 DAS. Soil samples were analysed at six intervals viz., on the day of herbicide application, but two hour before, then at 7, 15, 30, and 60 days after herbicide application (DAHA) and at harvest so as to evaluate the changes in the chemical and biological properties. Data on analysis of soil samples before the period of experimentation revealed that soils from rice field of Kole land recorded physical, chemical, and biological characteristics which are more favourable for the growth of microflora. The chemical characteristics like pH, electrical conductivity, and organic carbon followed a decreasing trend towards the harvest in all the treatments. Decline in microbial biomass carbon (MBC) was observed upto harvest except on 60 DAHA. Pendimethalin treatment in S1 soil (medium organic matter) registered the highest per cent reduction in MBC with respect to control at different intervals. Percentage reduction in MBC due to herbicide application was comparatively lower in S2 (high organic matter) throughout the period of study. Activity of dehydrogenase, urease, acid phosphatase and alkaline phosphatase was higher in S2 compared to S1. In all cases, the enzyme activity increased upto 60 DAHA with slight variations and declined thereafter registering a peak at 60 DAHA. Among the four enzymes studied, urease recorded maximum increase at 60 DAHA followed by acid phosphatase, dehydrogenase and alkaline phosphatase. All the vegetative and yield parameters of rice were high in S2 (high organic matter soil) irrespective of the treatment combinations. Adverse effects of herbicides on the plant characters were minimal. Whole plant analysis for major nutrients also exhibited appreciably higher values in S2 compared to S1. Out of the five biological parameters analysed, microbial biomass carbon showed the highest variation from control at all the sampling intervals. The adverse effects of herbicides on MBC and enzyme activity followed the order: pendimethalin > bispyribac-sodium > oxyfluorfen > cyhalofop-butyl. Organic carbon had highly significant and positive correlation with all the biotic components viz., MBC, dehydrogenase, urease, acid and alkaline phosphatase activity at different sampling intervals consequent to herbicide application. Further study should be focused on identification of microbial diversity, effect of rhizosphere on biological activity and analysis of biological parameters with respect to crop growth stages consequent to herbicide application.
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    Diversity of echinochloa spp. and their response to select herbicides
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2017) Aparna, K K; Meera V Menon
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    Weed management in elephant foot yam[amorphophallus paeoniifolius (dennst.)nicholson]
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2017) Lekshmi Sekhar; George Thomas, C