1. KAUTIR (Kerala Agricultural University Theses Information and Retrieval)
Permanent URI for this communityhttp://localhost:4000/handle/123456789/1
Browse
3 results
Search Results
Item Relationship between weed density and yield loss in semi- dry rice(Department of Agricultural Statistics, College of Horticulture,Vellanikkara, 2001) Shiji, C P; Krishnan, SSacciolepis interrupta and Isachne miliacea are two major problem weeds of rice in Kerala. An investigation on the quantum of crop loss incurred due to different densities of these weeds was undertaken to study the extent of damage inflicted on the crop which would necessitate early control of these weeds. The observations recorded on the various crop and weed characteristics were analysed as a 52 factorial experiment. It was found that crop characteristics like total bio- mass of paddy at harvest, number of tillers of paddy at harvest, number of productive tillers at harvest, grain yield and strain yield. And weed characteristics like number of tillers of S. interrupta at 60 DAS, height of S. interrupta at 60 DAS, number of tillers of S. interrupta at harvest of rice, dry matter production of S. interrupta and drymatter production of 1. miliacea were found to be affected by the weeds. The intra and interspecific competition was also brought to light based on the analysis. Single weed species models like that of Cousens (1985), Hakansson (1983), the first model of Watkinson (1981), Marra and Carlson (1983), Wilson and Cussans (1983), Wilcockson (1977) and Carlson et al. (1981) fitted well to the yield loss - S. interrupta/ 1. miliacea density relationship whereas those models proposed by Ngouajio et al. (1999), Kropff and Spitters (1991), Dew (1972), Zakharenko (1968) and Chisaka (1977) fitted well only to the yield loss- S. interrupta density relationship. The extended version of the Cousens (1985) model by Swinton et al . . (1994a) to a multi-species model was also fitted to the data and the same explained the yield loss - S. interrupta + 1. miliacea densities relationship to a considerable extent. The reduced form of the multispecies model to an equivalent single species model as worked out by Swinton et al. (1994b) also had a good fit. The numerical assessment of yield loss _. S. interrupta + 1. miliacea density relationship as illustrated by Berti and Zanin (1994) revealed the extent of damage on the crop by the weeds. The new curvilinear models tried also explained the yield loss - weed density relationship with the exception that the role of 1. miliacea deterring the yield of crop could not be highlighted due to its peculiar way of growth. The threshold weed densities worked out on a economic loss basis revealed that even the presence of two S. interrupta plants in a square meter area was hazardous for the crop whereas even the presence of 321. miliacea plants in the same stipulated area was not as detrimental as S. interrupta.Item Effect of time of sowing and weed management on the performance of dry sown rainfed rice(Department of Agronomy, College of Agriculture, Vellayani, 1993) Jacob John; Thomas Alexander, VAn experiment was conducted at the College of Agriculture, Vellayani during the first crop season of 1992 to study the effect of time of sowing and weed management on the performance of dry sown rainfed rice using Onam variety. Split plot experiment in randomised block design with time of sowing as major treatments and weed management as minor treatments was adopted and the treatments replicated thrice. May 16, May 23 and May 30 were the first, second the third dates of sowing respectively. The weed management treatments included combination of butachlor with 2, 4-D, butachlor with hand weeding, hand weeding twice 20 and 40 DAS, complete weed free and un weeded control. Sowing on May 23 resulted in greater plant height, panicle weight, grain and straw yield, nutrient uptake, grain protein and lesser uptake of phosphorus and potash by weeds when compared to May 16 and May 30. The second best sowing date was May 16. When compared to un weeded control, hand weeding twice, combination of butachlor with hand weeding and butchlor with 2, 4-D gave higher plant height, tiller number, productive tiller number, panicle weight, thousand grain weight, grain yield, straw yield, nutrient uptake and grain protein out of which hand weeding was the best. Hand weeding also resulted in the lowest weed population, weed dry weight, nutrient uptake by weeds, weed index and the highest weed control efficiency. Initially, butachlor alone was ineffective in reducing weed population and its dry weight. However, the combination of butachlor with 2,4-D and butachlor with hand weeding was effective in later stages. The combination of butachlor with hand weeding resulted in higher weed control efficiency than butachlor with 2,4-D. The rice grains contained no applied weedicide residues. Hand weeding, combination of butachlor with hand weeding and butachlor with 2,4-D resulted in greater profit and benefit – cost ratio than un weeded control. However, the highest profit was obtained with hand weeding twice.Item Management of rock bulrush (schoenoplectus juncoides (roxb.) palla) in wet seeded rice(Department of Agronomy, College of Agriculture, Vellayani, 2018) Fathima Umkhulzum, S; Ameena, MAn investigation entitled "Management of rock bulrush (Schoenoplectus juncoides (Roxb.)Palla) in wet seeded rice" was conducted at College of Agriculture, Vellayani during 2016 to 2018. The major objective were to study the biology of the weed rock bulrush (Schoenoplectus juncoides (Roxb.) Palla) and to develop an effecetive and economic method for its management in wet seeded rice. Field experiment was undertaken in farmer's field at Nemom block, Thiruvannathapuram during rabi season (November 2017 to march 2018). Weed biology was studied by observing sample plants in weedy check plots starting from the emergence of the weed. The experiment was laid out in Randomized Block Design with 8 treatments replicated thrice. The experiment was laid out in Randomized Block Design with 8 treatment replicated thrice. The weed management practices tested were:T1-bensulfuron methyl+ pretilachlor @ 60+600 g ha-1 at 4-7 days after sowing (DAS) followed by (fb) hand weeding (HW) at 35-40 DAS; T2-penoxsulam @ 22.5 g ha-1 at 15 DAS fb HW at 35-40 DAS;T3 - ethoxysulfuron @ 15 g ha-1 at 15 DAS fb HW at 35-40DAS;T4-carfentrazone-ethyl @20 g ha-1 at 15 DAS fb HW at 35-40 DAS;T5-metsulfuron methyl +cholimuron ethyl @ 4 g ha-1 at 20 DAS fb HW at 35-40 DAS;T7- HWtwice at 20 and 40 DAS and T8-weedy check. Pre-germinated seeds of var. Sreyas (M) 22) were broadcasted in the puddled soil following all cultural practices as per KAU PoP (KAU, 2011) except weed management. Study on weed biology revealed that the weed behaved as annual/perennial depending on field situation, with an average duration of 106 days in continuously cultivated fields. Phenology of rock bulrush revealed that the weed took 5 days for seed germination, 22 days for flowering, 33 days for spike maturity and 68 days for seed maturity after wet seedign of rice. The weed echibited a lodging behaviour after spike maturity . Seeds were observed to be the main propagule however, vegetative buds and rhizomes also helped in propagation. Lodging after spike maturity and spiny apex of seeds were found to facilitate seed dispersal. The weed was observed to be a prolific seed producer (862 seeds plant-1) with a biomass production of 0.96 t ha-1 as worked out from weedy check plots. The nutrient content of the weed was analyzed to be 0.90,0.33 and 1.14 per cent NPK respectively. Among th weed management practices tested, ethoxysullfuron @ 15 g ha-1 at 15 DAS fb HW at 35-40 DAS (T3) wa significabtly superior to all other treatments with respect to number of productive tillers m-2 (382), number of grains panicle-1 (134.27), filled grains panicle-1 (115.85), grain yield (5750 kg ha-1 and straw yield (9955 kg ha-1). Grain yield recorded in penoxsulam @ 22.5 hg ha-1 at 15 DAS fb HW at 35-40 DAS (5500.76 kg ha-1) was on par with T3. These treatments also recorded higher B: C ratios of 2.26 and 2.11 respectively. At 45 and 60 DAS, lower weed density (2.09 and 3.15 respectively) and weed dry weight (0.13 and 1.83 g m-2 ewspectively) were recorded for enthoxysulfuron @ 15 g ha-1 at DAS fb HW at 35-40 DAS. Higher weed control efficienceis of 99.82 and 98.07 per cent were obtained in plots treated wih ethoxysulfuron @ 15 g ha-1 at 15 DAS fb HW at 35-40 DAS during critical stages of crop weed competition (45 and 60 DAS). Penoxsulam @ 22.5 g ha-1 at 15 DAS fb HW at 35-40 DAS was on par with T3 at 45 and 60 DAS recording weed control efficeincies of 99.07 and97.90 per cent respectively. Uncontrolled weed growth in wet seeded broadcasted rice could cause a yield reduction of 52.18 percent. Higher crop uptake (kg ha-1 ) of N (219.01), P (39.32) ane K (228.55) were recorded in T3 and it was statistically on par with T2, T6 and T7. The weed removal of N, P and K (8.61, 3.13 and 10.95 kg ha -1 respeectively) were aslo lower with ethoxysulfuron @ 15 g ha-1 15 DAS fb HW at 35-40 DAS. Schoenoplectus juncoides was observed to be an emerging sedge weed in the cultivated wet lands with round upright culms having annual or perennial nature, reproducing by seeds or rhizhomes with a biomass production of 0.96 t ha -1, if uncontrolled. The weed could be effectively controlled by ethoxysulfuron @ 15g ha-1 or penoxsulam @ 22.5 g ha-1 both at 15 DAS fb HW at 35-40 DAS. Considering the economics, ethoxysulfuron @ 15 g ha -1 at 15 DAS followed by hand weeding at 35-40 DAS could be adjudged as the most effective strategy for the management of Schoenoplectus juincoides (Roxb.) Palla in wet seeded rice.