Residue analysis and bulb sprouting in CIPC treated onion

Abstract

The effect of CIPC (isopropyl N-(3-chlorophenyl) carbamate), commonly known as chlorpropham was studied on different onion varieties as preharvest application in rabi and kharif seasons, as well as postharvest application on rabi produce. Three varieties, viz. Bhima Kiran, B. Shakti and N-2-4-1 were used in rabi season for pre- and post-harvest applications (hot fogging) in kharif season on B. Raj and B. Red. Sprouting of bulbs during storage was not affected when CIPC was applied as preharvest or postharvest treatment in rabi crop. However, the sprouting was significantly reduced when CIPC was sprayed as a preharvest application in kharif season. The spraying of 2% CIPC 75 days after planting was found to be the best treatment. The residues of CIPC in the rabi season (preharvest application) were as low as 0.08 mg/kg to a maximum of 1.84 mg/kg fresh weight. In the postharvest application, the CIPC residue ranged between 0.37 and 0.61 mg/kg fresh weight and residues were always below the permissible levels. The CIPC was found useful for forced ripening of kharif crop as phyto-toxicity symptoms were apparent in the studies conducted in kharif season when CIPC concentration was 1% or above.