The field studies were conducted at the research farm, Bidhan Chandra Krishi Viswavidyalaya, Nadia, West Bengal, India during rabi seasons of 2017–18 and 2018–19. The objective of the research was to establish a relationship between disease severity of Alternaria blight with epidemiological factors in Indian mustard under Integrated Nutrient Management. Severity of disease in the specified time intervals was measured under 10 different nutrient management treatments combinations. Results showed that the highest intensity of Alternaria blight was observed with a mean maximum temperature of 19.3 to 24.4°C, mean minimum temperature of 7.6 to 14.1°C, average temperature of 13.5 to 19.3°C and an average relative humidity of more than 70%. The nutrient management in different combinations resulted different disease severity on leaves and pods and with increase in the age of the plant, significant increase in disease severity was observed. Maximum increase in disease severity was observed on 95 days after sowing (DAS) (44.77%) followed by 80 DAS (38.99%) and 65 DAS (32.99%) irrespective of their different treatments. Minimum disease severity was observed (13.83%) when the plots were treated with Azotobacter @ 250 g kg-1 seed, Phosphobacteria @ 250 g kg-1 seed along with FYM @ 7.5 t ha-1. Empirical relationship was established between different weather factors and Alternaria blight under different nutrient management practices which will be useful to forecast the first appearance of the disease accurately.
Photolysis of oxyfluorfen, an herbicide of the nitrodiphenyl ether class, was studied in aqueous methanol under UV and sunlight. UV irradiation was carried out in a borosilicate glass photoreactor (containing 250 ppm oxyfluorfen in 50% aqueous methanol) equipped with a quartz filter and 125 watt mercury lamp (maximum output 254 nm) at 25 ± 1°C. Sunlight irradiation was conducted at 28 ± 1°C in borosilicate Erlenmeyer flasks containing 250 ppm oxyfluorfen in 50% aqueous methanol. The samples from both the irradiated conditions were withdrawn at a definite time interval and extracted to measure oxyfluorfen content by gas chromatography-flame ionization detector for rate study. The half-life values were 20 hours and 2.7 days under UV and sunlight exposure, respectively. Photolysis of oxyfluorfen yielded 13 photoproducts of which three were characterized by infrared spectrophotometer and (1)H NMR and (13)C NMR spectroscopy. The rest of the photoproducts were identified by gas chromatography-mass spectrometry (GC-MS) and thin layer chromatography (TLC). An ionization potential 70 eV was used for electron impact-mass spectrometry (EI-MS) and methane was used as reagent gas for chemical ionization-mass spectrometry (CI-MS). Two of the photoproducts were also synthesized for comparison. The main phototransformation pathways of oxyfluorfen involved nitro reduction, dechlorination, and hydrolysis as well as nucleophiles displacement reaction.
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