PhD Thesis

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End date: 1999Subject: search.filters.subject.Agronomy

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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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    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.
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    Agronomic evaluation of chemical and bio-agents on phosphorus dynamics in red loam soils of southern Kerala
    (Department of Agronomy, College of Agriculture, Vellayani, 1995) Viswambharan, K; Sasidhar, V K
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    Effect of different inputs on productivity and quality relations in njavara (Oryza sativa)
    (Department of Agronomy, College of Horticulture, Vellanikkara, 1996) Meera Menon, V; Potty, N N
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    Ecophysiology and management of Isachne in rice fields of Onattukara
    (Department of Agronomy, College of Horticulture, Vellanikkara, 1996) Abraham Varughese; Tajuddin, E
    Isachne miliacea Roth is the most dominant weed in the 28,000 ha of low land rice fields of the coastal sandy Onattukara region, situated in Kollam and Alapuzha districts of Kerala. A serious of investigations were undertaken at Rice Research Station, Kayamkulam, during 1991 to 1994 with the objective to identify the major weeds in the rice ecosystem and to bring out the ecophysiology of 1. Miliacea and to find out a suitable weed management strategy for the rice based cropping system of Onattukara. Isachne miliacea was found to be the dominant weed in rice during Kharif and Rabi seasons. The weed seeds germinate in April – May, attains its peak vegetative growth in July and flowers in October. The seeds mature in November and the plants dry off in January with the onset of summer. The weed is propagated by seeds and stem cuttings. Germination of seeds can be prevented by submerging the seeds in the area in water even to a depth of one centimetre. The forcing of the stem cuttings of 1. Miliacea to a depth of five centimetre below the soil surface or maintaining a submergence for more than five centimetre can effectively check the vegetative multiplication of the weed. Seeds attained physiological maturity in November and remained dormant upto March. Seeds of the season that remain on the surface germinate fully in April – May with the pre – monsoon showers while the buried seeds remain dormant. Burying the seeds to more than five centimetre depth and water stagnation in July to November induced secondary dormancy. Viability of the seeds was lost faster at shallow depth of burial. Crop weed competition studies were conducted in Kharif and Rabi for two years with different densities of 1. Miliacea. Weed competition was severe in dry dibbled Kharif compared to wet transplanted Rabi. Even a small density of five 1. Miliacea plants per square metre produced appreciable biomass and reduced the DMP of rice substantially. Integrated weed management study was conducted in Kharif and Rabi for two years in a split – plot design in three randomised blocks. Kharif season treatments formed the main plots for Rabi trial. In Kharif five pre – emergence herbicides were compared with local practice. Local practice of hoeing on 15 DAS and HW twice on 25 and 40 DAS gave maximum grain yield. Application of oxyfluorfen 0.1 kg ha-1 followed by HW on 30 DAS was on par with local practice and ranked second. The performance of other herbicides anilofos 0.40 kg, butachlor 1.25 kg and thiobencarb 1.25 kg per hectare were also satisfactory when followed by one HW on 30 DAS. Pretilachlor 0.50 kg ha-1 was phytotoxic to rice. The tested herbicides effectively controlled 1. miliacea upto harvest of rice compared to local practice. During Rabi the effect of pre-plant spray of glyphosate and hand weedings were compared. Among the treatments a pre – plant spray of glyphosate after harvest of Kharif controlled 1. miliacea best and gave maximum rice yield in Rabi season. Kharif treatments did not show any significant influence on yield of rice during Rabi. From the study it could be concluded that pre – emergence spray of oxyfluorfen 0.1 kg ha-1 followed by one HW on DAS in Kharif and pre – plant application of glyphosate 0.75 kg ha-1 on residual weeds immediately after the harvest of the Kharif crop gave efficient weed control and economic yield of rice in the rice based cropping system involving rice – rice – fallow of Onattukara region.
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    Seed production in stylosanthes gracilis under varying levels of population density, nutrition, moisturiser regimes and cuttings
    (Department of Agronomy, College of Agriculture, Vellayani, 1989) Balachandran Nair, G K; Sreedharan, C
    An investigation was carried out during the period from July 1980 to March 1982 in the Instructional Farm, College of Agriculture, Vellayani to study the agronomic techniques required for maximum seed production in Brazilian lucerne (Stylosanthes gracilis). The following three separate field experiments were conducted and data collected and analysed. The first experiment entitled ‘influence of cultivars and plant population on seed production’ was laid out as a22 Factorial Experiment in R. B. D and replicated five times with the objective to find out the best cultivar of Stylosanthes gracilis for seed production along with the seed rate. The treatments consisted of combinations of two cultivars of Stylosanthes gracilis viz. Schofield and Cook, and two seed rates viz. 2.5 and 5 kg/ha. The second experiment entitled ‘nutritional requirements of Stylosanthes for seed production’ was laid out as a32 Factorial Experiment in R. B. D and replicated thrice with the treatment combinations of three levels of phosphorus viz.80, 120 and 160 kg P2 O5/ha and three levels of lime viz. no lime, 375 and 750 kg lime/ha. The objective was to assess the phosphorus and lime requirement of the crop for maximum seed yield. The third experiment entitled ‘Effect of moisture regimes and cuttings on seed production’ was conducted as a 32 Factorial Experiment in R.B. D and replicated thrice with treatment combinations of three irrigation schedules (IW/CPE ratios) viz. 0.50, 0.75 and 1.00 and three cutting schedules viz. no cutting, one cutting and two cutting. The objective was to investigate the efficiency of irrigation schedules and cuttings on seed yield. The results from the investigation revealed that the variety cook produced significantly higher seed yield of about 64 kg/ha as against 35 kg/ha obtained from the variety schofield. The seed rate of 5 kg/ha gave the higher seed yield of about 56 kg/ha as against the seed yield of about 43 kg/ha under the seed rate of 2.5 kg/ha. The seed yield attributing characters like setting percentage of seeds and number of seeds per plant were maximum for the variety cook. All the growth characters contributed to about 66 per cent of the variation in seed yield. The highest net return per hectare was obtained when the variety schofield was grown under a seed rate of 2.5 kg/ha. Application of phosphorus at 120 kg and lime at 375 kg per hectare gave maximum seed yield of about 80 kg/ha. It was also found that higher levels of phosphorus like 120 or 160 kg/ha helped to increase the setting percentage of seeds. The biometric characters such as spread of plants, number of branches and LAI were significantly influenced by the application of 120 kg phosphorus and 375 kg lime per hectare. The nutrients uptake was also enhanced by the application of phosphorus and lime at the above levels. The growth characters influenced the seed yield by 53 per cent. The economic optimum doses of phosphorus and lime for maximum seed yield were found to be 149 kg and 593 kg per hectare respectively. The highest gross and net returns were obtained from plots treated with phosphorus and lime at 120 kg and 375 kg per hectare respectively. Irrigating the crop at IW/CPE ratio 1.00 gave the maximum seed yield of 89 kg/ha. When the crop was left without cut it produced the highest seed yield of 92 kg/ha. The maximum setting percentage of seeds and leaf production were observed when the crop was irrigated at ratio 1.00 and without cut. The no cutting treatment gave maximum number of seeds per plant. The biometric charaters like height, spread, number of branches and length of branches were all found maximum in treatments where no cutting was given. Maximum water use efficiency for seed production was recorded by the lowest irrigation ratio of 0.50 and also when the crop was left without cut. About 46 per cent of the variation in seed yield was explained by the growth characters. Maximum net return per hectare was obtained when the crop was irrigated at IW/CPE ratio 1.00 and without cut.