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Rice is one of the staple food crops of India, and Karnataka is one of the major rice-producing states. The primary method of rice establishment in Karnataka is transplanting, but farmers are opting to shift to direct-seeding of rice. Weed management is critical for realizing optimal yield of direct-seeded rice (DSR). The objective of this review was to synthesize the published literature on weeds and weed management in rice in Karnataka, identify improved weed-management technologies for delivery to farmers, and suggest research needs. Some 98 weed species are reported to be associated with rice in Karnataka. Weed control to date in Karnataka has mostly been based on herbicides. Hand-weeding was found to be effective in all methods of rice establishment. However, it is time-consuming, tedious, and costly because labor is becoming scarce and unavailable, and labor wages are higher. Several PRE and POST herbicides that were effective in other Asian countries were also found to be effective in managing weeds in rice established by different methods in Karnataka. Bensulfuron plus pretilachlor and pyrazosulfuron in aerobic rice and pendimethalin, thiobencarb, bispyribac-sodium, cyhalofop, fenoxaprop plus chlorimuron plus metsulfuron, and fenoxaprop plus ethoxysulfuron in dry-DSR were found effective in managing weeds. In wet-DSR, butachlor plus safener and pretilachlor plus safener were effective. Thiobencarb, pendimethalin, pretilachlor, azimsulfuron plus metsulfuron, bispyribac-sodium, butachlor, cinosulfuron, oxadiazon, and quinclorac were found promising for weed management in transplanted rice. Integration of herbicides with hand-weeding or intercultivation was found to be effective in rice established by different methods. Options that were found economical in managing weeds varied across the different rice-establishment methods. The need for developing location-specific, sustainable, integrated weed management and extension of available technologies for the farming community in Karnataka is emphasized.
Pyrite phase of FeS2 has attracted substantial attention in the field of thin film solar technology because of its high optical absorption coefficient (~5 x 105 cm-1 at hν > 1.3eV) and the band gap of 0.95 eV. In this research, we have grown highly pure iron pyrite films using a low temperature atmospheric pressure chemical vapor deposition technique. The synthesis temperature is in the range of 375-400°C and Di-tert-butyl disulfide (TBDS) is used as the sulfur precursor. TBDS is a safe and low cost sulfur source unlike H2S, which is highly toxic and requires extreme care in handling. The films obtained were uniform and free from common impurity phases such as troilite and marcasite. The FeS2 films grown earlier with CVD synthesis and sulfurized using H2S had pinholes and contained secondary phases like marcasite and troilite. The FeS2 pyrite phase was confirmed using various characterization techniques that included SEM, EDS, XRD and XPS.
Recent trend in thin film solar cells is to use earth abundant materials such as zinc and iron. Zinc phosphide (Zn3P2) has been has been explored as a choice for solar cell absorber and is currently reviving attention. Zinc phosphide is synthesized from earth-abundant constituents. We have already optimized zinc phosphide phase both in nanocrystalline and bulk thin film form. The purpose of this study is to study growth conditions at different temperatures. In this study, Trioctylphosphine (TOP) is used as a source of phosphorous which reacts with zinc and results in the growth of Zn3P2. The synthesized zinc phosphide phase has been characterized using SEM, EDS, XRD and XPS. We report a simple and repeatable process for synthesis of Zn3P2 phase.