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Subject: Agronomy × Author: Nishan, M A × Start date: 2012 × Type: Thesis ×
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    ThesisItemOpen Access
    Management of water cabbage (Limnochairs flava (L.) buchenau) in wetland rice ecosystem
    (College of Agriculture, Vellayani, 2012) Nishan, M A; KAU; Sansamma, George
    An investigaton entitled ‘Management of water cabbage (Limnocharis flava (L.) Buchenau) in wetland rice ecosystem’ was carried out in the wetland of the Instructional farm attached to the College of Agriculture, Vellayani from February 2011 to January 2012. The major objectives of the experiment were, to study the biology of water cabbage (Limnocharis flava (L.) Buchenau), to evaluate certain new generation herbicides for managing it and to assess the potential of the weed biomass as an organic source. For the study of weed biology (Part I), a part of the weed infested field was selected for the experiment and prepared thoroughly as in the case of rice cultivation and the sample plants were observed from their emergence onwards. The ontogeny of the weed, its vegetative, and reproductive characters and also their allelopathic influence on germination and early growth of rice were studied. The field experiment on weed management (Part II) was laid out in Randomised Block design with eight treatments replicated thrice. The treatments included azimsulfuron @20 and 30 g a.i. ha-1, bispyribac sodium @20 and 30 g a.i. ha-1), (metsulfuron methyl+ chlorimuron ethyl) @ 4 and 6 g a.i. ha-1 and 2, 4-D @ 1 kg a.i. ha-1 along with a weedy check as control. The potential for utilization of the weed biomass through vermicomposting (Part III) was also assessed during the investigation. The data on weed biology indicated that water cabbage had very efficient reproductive mechanism which explains the invasive nature of the weed. A single plant was found capable of producing more than one lakh seeds and about 90 per cent of them germinated under favourable conditions. The plants exhibited pseudovivipary, through production of ramets which gave an additional advantage for the plant to spread. Germination studies revealed that maximum weed seed germination occurred under direct sunlight in crowded condition in the wetland soil condition. Direct sunlight was found necessary for the seed germination. Allelopathic studies showed that the fresh leachate of water cabbage was found to exert a positive effect on the vigour index of rice seedlings while substantial reductions in seedling growth were observed when treated with decayed plant leachate. The results of the field study on weed control efficiency of the different herbicides indicated that 2, 4-D @1 kg a.i. ha-1 was most effective for controlling water cabbage. Among the new generation herbicides (metsulfuron methyl + chlorimuron ethyl) @ 6 g a.i. ha-1 and bispyribac sodium @ 30 g a.i. ha-1 were equally effective for controlling water cabbage. The results of soil microbial studies indicated that the soil treated with the herbicides had much higher microbial population than the untreated plots except in the case of bispyribac sodium. The cost of managing the weed by using new generation herbicide was found considerably lower than that by manual weeding. The chemical analysis of the vermicompost prepared from the weed biomass recorded favourable nutrient composition. The micronutrients and heavy metals were within the safe limits except for the copper content. More over, the luxuriantly growing weed biomass was promising for bioremediation, to remove pollutants from aquatic ecosystems.
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    ThesisItemOpen Access
    Nutrient management for organic rice based cropping system
    (College of Agriculture, Vellayani, 2016) Nishan, M A; KAU; Girijadevi, L
    The experiment entitled “Nutrient management for organic rice based cropping system” was conducted at the “Organic Farm” attached to Department of Agronomy, College of Agriculture, Vellayani, Thiruvananthapuram, Kerala, during the first (virippu), second (mundakan) and third crop season of 2013-2014 and 2014-2015 respectively. The main objectives of the experiment were to develop a nutrient schedule for organic rice - rice- amaranthus cropping system, to assess the residual effect of organic nutrition, to evaluate the impact on soil health and to compute the energetics and economic feasibility of organic rice based cropping system. The virippu rice was laid out in randomised block design (RBD) with five treatments and four replications. The variety used was Uma. The treatments were T1: Ad hoc KAU Organic POP recommendation (Option-3): 30 kg N by FYM, 30 kg N by vermicompost, 30 kg N by neem cake, Azospirillum (2 kg ha-1) and P solubilising bacteria (2 kg ha-1), T2: 100 % POP recommendation as organic (FYM @ 5 t ha-1, 45 kg N by FYM, 22.5 kg N by vermicompost, 22.5 kg N by neem cake), T3: 75 % POP recommendation as organic (FYM @ 5 t ha-1, 33.75 kg N by FYM, 16.88 kg N by vermicompost, 16.88 kg N by neem cake), T4: Integrated Nutrient Management (INM) (KAU POP recommendation : FYM @ 5 t ha-1+ 90:45:45 kg NPK ha-1) and T5: Control (No application). For mundakan rice, the experiment was laid out in split plot design with 17 treatments in 4 replications. These 17 treatments comprised of T1, T2, T3 and T4 of virippu rice, each tested at 4 different levels of nutrition (L1-100%, L2-75%, L3-50% and L4- 0%) and one control. During third crop season, the performance of 16 treatment combinations of mundakan was tested each at 4 different levels of nutrient recommendation of amaranthus (N1-100%, N2-75%, N3-50% and N4-0%). The experiment was laid out in split split plot design with 64 treatment combinations and 4 replications. The variety used was Arun. The same experiments were repeated during second year. The results of the study revealed the superiority of 100% INM with respect to yield and economics in rice-rice-amaranthus system. Among the organic treatments, Ad hoc organic POP recommendation of KAU was less economic when compared to 100% POP as organic.Perusal of the data on organic treatments revealed that application of 100% POP as organic recorded the highest grain yield (5570 kg ha-1 and 5178 kg ha-1) in virippu rice and was on par with 75% POP as organic during both the years. Application of 75% POP as organic to virippu rice fb 100% POP as organic for mundakan rice recorded the highest grain yield (4474 and 4976kg ha-1) and was on par with 75% for mundakan rice during both the years. 100% POP as organic in virippu rice fb 100, 75, or 50% POP as organic to mundakan rice also recorded on par yield with above treatments during both the years. Perusal of data on rice rice system yield also confirmed the results. The analysis of yield data on ricerice-amaranthus system revealed that application of 100% POP as organic to virippu rice fb 100% POP as organic to mundakan rice fb 100% RDN as organic for amaranthus recorded the highest system yield (21.90 and 21.82 t ha-1) and was on par with 75 and 50 % RDN as organic during both the years. Application of 100% POP as organic to virippu rice recorded the highest net income (60911 ` ha-1 and 44599 ` ha-1) and was on par with 75% POP as organic during both the years. Application of 100% POP as organic to virippu rice fb 50% POP as organic for mundakan rice recorded the highest net income for mundakan rice (38568 and 39474 ` ha-1). The analysis of the data on rice-rice-amaranthus system revealed that application of 100% POP as organic to virippu rice fb 100% POP as organic to mundakan rice and 50% RDN as organic to third crop amaranthus recorded the highest net income (157129 and 191790 ` ha-1) during both the years. Studies on energetics revealed the superiority of organic treatments over INM. The analysis of data on rice-rice-amaranthus system revealed that application of 100% POP as organic to virippu rice fb 100% POP as organic to mundakan rice fb 50% RDN as organic for amaranthus recorded the highest energy efficiency (26.91 and 23.77) during both the years. Soil physical properties were improved in organics compared to INM. Soil health studies revealed that dehydrogenase activity was more in organic treatments compared to INM. Build up of soil organic carbon was more in organics compared to INM. In both organic and INM treatments soil organic carbon decreased with decrease in nutrient levels but the rate of depletion was less in organics compared to INM. In general not much variation was observed in soil available nitrogen among different levels of organic nutrition while in INM treatments there was remarkable decrease with decrease in nutrient levels. A build up of soil phosphorus was observed both in INM as well as in organic treatments. Depletion in soil available potassium was observed in all treatments but the rate of depletion was less in organics compared to INM. From the study it can be concluded that, application of 75% POP as organic (5 t FYM, 33.75 kg N by FYM, 16.88 kg N by vermicompost and16.88 kg N by neem cake) was the most productive, profitable, energy efficient nutrient schedule for virippu rice. Application of 100% POP as organic (5 t FYM, 45 kg N by FYM, 22.5 kg N by vermicompost and 22.5 kg N by neem cake) in virippu rice followed by 50% POP as organic (5 t FYM, 22.5 kg N by FYM, 11.25 kg N by vermicompost and 11.25 kg N by neem cake) in mundakan was the most productive, profitable, energy efficient nutrient schedule for rice-rice system. Application of 100% POP as organic (5 t FYM, 45 kg N by FYM, 22.5 kg N by vermicompost and 22.5 kg N by neem cake) to virippu and mundakan rice fb 50% N as organic in amaranthus (50 t FYM, 30 kg N by cowdung vermicompost, 15 kg N poultry manure and 5 kg N by groundnut cake) was the most productive, profitable, energy efficient and sustainable nutrient schedule for organic rice-riceamaranthus system.