PhD Thesis

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End date: 2019Subject: search.filters.subject.Agronomy

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    Nutrient and moisture optimization in banana (Musa AAA. Grand Nain)
    (Department of Agronomy, College of Agriculture, Vellayani, 2016) Bindhu, J S; Girija Devi, L
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    Production potential of two fodder grasses under different management practices
    (Department of Agronomy, College of Agriculture, Vellayani, 1986) Raghavan Pillai, G; Madhavan Nair, K P
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    Effect of NPK on seed progeny and air layers in cashew ( Anacardium occidentale L. )
    (Department of agronomy, College of Agriculture Vellayani , Trivandrum, 1985) Harishu Kumar, P; Sreedharan, C
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    Agronomic interventions for a sustainable rice based cropping system in paddy fields
    (Department of Agronomy, College of Agriculture, Vellayani, 2016) Vipitha, V P; Babu Mathew, P
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    Nutritional resource use efficiency in rice production
    (Department of Agronomy, College of Horticulture, Vellanikkara, 2004) Vallal Kannan, S; John, P S
    The chemical constraints for higher yields in laterite soils are identified as low cation exchange capacity and organic matter content, high acidity, iron and aluminium toxicity, high phosphorous fixation and poor nutrient status. Investigations carried out to identify the limiting factors and their mode of action in laterite soil revealed direct effect of excess iron absorption, their metabolic interference, unfavourable Ca + Mg / K ratio, and deficiency of certain elements manifested as negative effects of some others. Management of organic manuring modified by amelioration with suitable amendments was reported to be an ideal remedial measure for reducing the above chemical constraints. An experiment was conducted at Agricultural Research Station, Mannuthy during 2001-2002, to characterize and quantify the effect of organic sources on nutrient supply, amelioration and inactivation of the deleterious factors in rice , culture and to study the supplementary requirements of inputs and complementary effects on yield improvement. It was also intended to develop a technology by integrating various inputs and their levels to ensure high resource use efficiency and consequently higher productivity. The plant height and tiller production was highest in the treatment green manure + lime + ash at active t.illering, panicle initiation and 50 per cent flowering. The total dry matter production was highest in the green manuring + lime and green manuring + lime + ash treatment. All the growth parameters such as plant height, tiller count and total dry matter production showed a stepwise improvement with doubling of K, doubling of K along with addition of lime and ash and doubling of K with addition of lime, ash and sulphur over the treatment where K was given at normal rate and without any ameliorants. The highest chlorophyll content both 'a' and ob' was found as resulted in the fallow - green leaf manure treatment, however, this was not reflected in the process of yield formation since the highest yield was observed for the treatment, green manure + lime + ash. The favourable cell sap pH around 6.21 was observed in the treatment green manure + lime + ash which resulted in the highest grain and straw yield. The highest grain and straw yield of 6.64 and 6.75 t ha-I, respectively was observed in the treatment combination green manure + lime + ash x N as NH4S04 + half P + lime + ash + double dose of K which indicate the importance of addition of lime, ash and sulphur as ammonium sulphate in the fertilizer package of rice in laterite soil. The following conclusionsare drawn from the results of the experiment. In the mundakan - summer - virippu rice cropping system in laterite soil leaving the land fallow' during summer may considerably reduce the yield during virippu if not supplemented with adequate organic manure and ameliorants like lime and ash. If the summer season is kept fallow, green leaf manu ring could be a better substitute for addition of organic matter to the laterite soil. Paddy straw incorporation at 15 days before the virippu cropping in laterite soil was found to reduce the yield of virippu rice probably due to high rate of immobilization ofN. The increase in acidity and consequent higher solubilization and uptake of Fe in virippu crop was evidently due to summer fallow which favour natural oxidation of Fe and Mn. Ameliorants like lime and ash added both during summer green manuring and virippu rice crop enhanced the rice growth and yield through modification of pH, supplementation of potash and calcium. Enhancement ofN:K ratio to 1: 1 was found to enhance rice productivity in laterite soil. Addition of K application did not increase the K content in the plant but reduced Fe uptake. Changing the N source to ammomum sulphate and thereby sulphur I fertilization was found to increase growth and yield of rice. Ammonium sulphate treatment helped mainly to increase plant height but not tiller production. Among yield attributes spikelet production was very much influenced by sulphur fertilization. The physiological and uptake efficiency of the N derived from green manuring was higher compared to other organic sources and consequently resulted in better agronomic efficiency. This indicates the need for a green manure - rice system in laterite soil to enhance soil and crop productivity. The green manured rice with ameliorants such as lime and ash, and ammonium sulphate as N and S source resulted in the highest net return and B:C ratio of2.25.
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    Phosphorus nutrioperiodism in rubber
    (Department of Agronomy, College of Agriculture, Vellayani, 2004) Jessy, M D; Meera Bai, M
    Mature rubber tree does not respond to application of phosphorus fertilizers consistently. In majority of the earlier fertilizer experiments on mature rubber, there was no response to application of phosphorus fertilizers, in terms of growth and yield. Trees continued to maintain leaf P status without application of P even when the soil P status was low. An experiment was initiated at the Rubber Research Institute of India, Kottayam in 1997 in an area planted in 1984 to study the response of mature rubber to phosphorus application. From planting to till the commencement of the experiment all trees were given uniform quantities of nutrients. Treatments were imposed from 1998 onwards. Detailed investigation was carried out in this experiment during 2002-2004 to explore the possibility of reducing the present dose of P fertilizer (30 kg P2O5 ha-1 year-1) for mature rubber. Phosphorus was applied at five levels (0,10,20,30 and 40 kg P2O5 ha–1 year¬1). Nitrogen and potassium were applied @ 30 kg ha-1 year¬1 at uniform rates. None of the growth characters studied, viz., girth, girth increment, length of tapping panel and bark thickness were influenced by the application of P. The yield and dry rubber content were also not influenced by levels of applied P. Trees which did not receive any P fertilizer continued to maintain leaf P status at comparable levels with that of the P applied treatments. Magnesium content of the leaves was generally higher in the P applied treatments after fertilizer application. Content of other nutrients (N, K, Ca, Fe, Mn, Zn and Cu) in the leaves was not affected by the different treatments. The accumulation of P and other nutrients in the dry matter was not influenced by application of P. The content of P and other nutrients (N, K, Ca, Mg, Fe, Mn, Zn and Cu) in the latex and their annual removal were not influenced by the levels of applied P. The quantity of litter added and the litter nutrient content were also not affected by the different treatments. Removal of P through latex was slightly less than addition through litter. Before defoliation the litter P content was comparatively less in the treatment which did not receive any P fertilizer indicating high P utilization efficiency of trees. Application of P did not influence the content of different P fractions (saloid P, Fe-P, Al-P, Ca-P, reductant P, occluded P and organic P) in soil. Organic P constituted more than 50 per cent of the total P in the soil. Total P content was significantly higher in the treatments which received higher levels of P. Soil available P status was higher in P applied treatments. In most cases, a decline in micronutrient content was observed in the treatments which received higher levels of P. More than 85 per cent of the roots were colonised by arbuscular mycorrhizal fungi (AMF), but no relation was observed between the levels of applied P and root colonization. Population of phosphorus solubilizing bacteria (PSB) in the rhizosphere was suppressed after application of P whereas the population of other microorganisms (total bacteria, phosphofungi, total fungi and actinomycetes) was not influenced. The trees which were not supplied with P improved their P acquisition by several processes. Secretion of acid phosphatase, an enzyme which hydrolyzes organic P, was found to be higher from the roots of trees which did not receive P fertilizers. Soil phosphatase activity was also higher in the rhizosphere of trees which did not receive any P fertilizer. Activities of phosphoenol pyruvate carboxylase (PEPC) and malate dehydrogenase (MDH), enzymes involved in the biosynthesis of organic acids were higher in the roots of trees which were not supplied with P fertilizers indicating the possibility of more exudation of organic anions and H+ from these trees. Rhizosphere pH was generally lower in the treatment which did not receive P fertilizers. Compared with non-rhizosphere soil pH, rhizosphere pH was comparatively higher in most cases. Roots of mature rubber trees explored a large area of soil (89.38 m2). More than 60 per cent of the fine roots explored the surface 10 cm layer indicating that the trees have a high P acquisition efficiency. A spatial difference in fine root production and distribution was observed between treatments. Trees which were not supplied with P produced more fine roots than trees supplied with P. Root hair production was also higher in the control trees. All these adaptations contributed to a high P acquisition efficiency of rubber trees which were supplied with P during active growing phase. The results of the present study indicate the self sustainability of phosphorus cycle in a well managed mature rubber plantation which was fertilized during the active growing phase of the plant suggesting the possibility of skipping P application in trees of that age group. This situation is likely to continue during the later phase also, however if a need is indicated through leaf P status, application of P can be resumed.
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    Response of cucumber (Cucumis melo L.) to drip irrigation under varying levels of nitrogen and potash
    (Department of Agronomy, College of Agriculture, Vellayani, 1997) Lakshmi, S; Sasidhar, V K
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    Soil test crop response studies in cassava in laterite soils of Kerala
    (Department of Agronomy, College of Agriculture, Vellayani, 1997) Kumari Swadija, O; Sreedharan, C
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    Phosphorus management in a rice based cropping system
    (Department of Agronomy, College of Agriculture, Vellayani, 1989) Annamma George; Sasidhar, V K
    In order to standardize an appropriate phosphorus management practice in a rice based cropping system involving rice-rice-cowpea/sesamum, field experiments were carried out in the rice fields of the Instructional Farm, College of Agriculture, Vellayani from June 1984 to September 1986. The experiment was laid out in a randomized block design with three replications. There were eight treatments. The treatments comprised of (1) continuous phosphorus application to all the three crops in the system (2) phosphorus application to the first and second crops of rice (3) phosphorus application to the first crop of rice and third crop of cowpea/sesamum (4) phosphorus application to the first crop of rice only (5) phosphorus application to the second crop of rice and third crop of cowpea/sesamum (6) phosphorus application to the second crop of rice only (7) phosphorus application to the third crop of cowpea/sesamum only (8) control plot with no addition of phosphorus to any of the crops in the system. The salient findings of the experiment are as follows: Phosphorus application had no significant influence on grain and straw yield of first crop of rice. But available nitrogen, available and total phosphorus and available potassium of the soil were increased with phosphorus application. Direct, residual and cumulative effects of phosphorus had no significant influence on grain and straw yield of second crop of rice. Phosphorus uptake could not show any variation due to the different treatments. Available and total phosphorus content of the soil were highest under cumulative phosphorus treatment. All the growth and yield attributes of third crop of cowpea and sesamum were increased by the direct and cumulative effects of phosphorus. Grain yield of cowpea was significantly increased by the direct application of phosphorus. Eventhough not significant the highest sesamum yield was accorded by the direct and cumulative application of phosphorus. Phosphorus uptake in all the growth stages of the crop was highest in direct phosphorus plots. Available and total phosphorus content of the soil was highest in continuous phosphorus applied plots. There was no significant influence on grain and straw yield of first crop of rice after cowpea and sesamum in the direct, residual and cumulative effects of phosphorus. Residual phosphorus was sufficient to maintain the available nitrogen status of the soil. Available phosphorus of the soil was increased by the direct, cumulative and continuous application of phosphorus and total phosphorus by continuous application of phosphorus. Balance sheet of available phosphorus revealed that the soil phosphorus level almost maintained, where phosphorus was applied only to the third crop of cowpea or sesamum. The highest net return and benefit-cost ratio for the rice-rice-cowpea and rice-rice-sesamum system was obtained when phosphorus was applied only to the third crop in the rice fallow and the residual effect being utilized by the succeeding rice crops.
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    Agronomic evaluation of rice cultivars for rainfed conditions of Kerala
    (Department of Agronomy, College of Agriculture, Vellayani, 1993) Sheela, K R; Thomas Alexander
    Two field experiments were conducted at the Cropping Systems Research Centre, Karamana and one pot culture trial at the College of Agriculture, Vellayani during 1991 and 1992, to select a suitable rice variety and nutrient level required for maximum rice production in the rainfed wetlands of Southern Kerala. The influence of seed hardening in inducing stress tolerance was also studied. In the study, experiment I included a pot culture trial with six varieties, viz., Jaya, Culture -4, M-102, Rasi, Ravi and Tulasi and six methods of seed hardening viz., water, triazole, NaH2PO4, KCI, cowdung extract treatments and a control in two moisture regimes. The significant results of the study were tested in the field. Experiment 2 included these six varieties and three nutrient levels, viz., 100, 75 and 50 per cent of recommended dose for medium duration varieties (90 : 45 : 45 kg N, P2o5 and K2o) and was conducted as a factorial experiment in RBD during the first crop season of 1991 and 1992. The results of the germination study revealed that KCI concentration of 2.50 per cent was ideal for seed hardening. Seed hardening improved germination of all the varieties and water treatment registered the highest vigour index values. In pot culture, Culture – 4 with water treatment registered the highest biomass production, grain and straw yields. The variety, Jaya had the highest root weight and root : shoot ratio. Among the seed treatments, water, KCI and triazole treatments favourably influenced the yield attributes, yield, root parameters and root : shoot ratio. Increasing the moisture regime from 50 to 100 per cent available water enhanced the growth characters, RWC, chlorophyll and decreased the proline content. The subsequent field trial with the highest grain yielding varieties and seed treatments confirmed the superiority of Rasi and Tulasi for increased grain yield, net income and benefit : cost ratio. The different seed treatments also had favourable influence on the above characters. The results of experiment 2 revealed that M – 102 recorded the highest plant height during both the years, while, Tulasi and Rasi had higher tiller number. The varieties, M-102 and Rasi registered higher straw yield than the others. Increased nutrient levels improved growth characters and straw yield. Pooled analysis of grain yield revealed that the varieties, Jaya, Rasi and Tulasi were good yielders and 75 per cent of the recommended nutrient level was sufficient to obtain high grain yield under rainfed conditions. Increased RWC values were observed in the drought tolerant varieties, Ravi, Tulasi and Rasi and at increased nutrient levels. Proline eontent was unaffected by varieties and nutrient levels. The variety, Jaya registered the highest uptake of major nutrients during 1991 while, Tulasi, Rasi and M-102 had higher uptake than the others during 1992. The highest nutrient level recorded the maximum uptake during both the years. Among the varieties, Jaya, Tulasi, Culture – 4 and Rasi recorded high net income and benefit : cost ratio. Among the nutrient levels, the variation between 100 and 75 per cent recommended nutrient dose was not significant with regard to net income and benefit : cost ratio. Under rainfed conditions, 75 per cent of the recommended nutrient dose was sufficient for the varieties, Jaya, Rasi and Tulasi to obtain commensurate yield, net income and benefit : cost ratio. Moreover, the yield and economic returns could be increased by resorting to seed hardening methods.