Onion, a widely consumed vegetable across the country throughout the year, is mainly cultivated in three seasons i.e. during kharif, late kharif, and rabi. The crop being harvested during the rabi accounts for 60% of onion production, hits the markets from March to June. The same crop continues to meet the consumer demand till October-November every year before the kharif crop is harvested and brought to the market. Therefore, it becomes pivotal to successfully store rabi onion so as to maintain its supply in the markets. The Onion is a semi-perishable crop and 30-40% of the crop gets lost during the storage. During natural calamities, the losses go beyond 40% that leads to heavy stress both on demand and supply. The supply volatility creates market distress causing a steep rise in the price of onion that eventually affects the end consumers. A adequate storage facility will help in checking the supply volatility and steep rise in onion prices.
Storage facility available in India-
Naturally ventilated structures: In India, the onions are mostly stored in the ventilated storage structures without any control of temperature and relative humidity. The farmers construct the different types of ventilated storage structures based on the capacity required.
Low cost thatched roof bamboo storage structure: This type of storage structure is usually constructed with bamboo framework having the roof made up with sugarcane leaves. This type of storage structure is low cost and easy to construct, but leads up to 42% losses of onion during four months of storage.
Bottom and side ventilated storage structure: This type of structure has a provision of ventilation from bottom and sides. But, still results in increasing the losses up to 46% in four months storage.
Cold storage structure: In such types of storage facilities, the onions are stored at 0-5°C and 60-65% RH that leads to much lesser losses as comparative to ventilated storage structure. The cost of construction and running cost are very high as energy required to maintain the storage facility in the temperature range of 0-5°C is high. The other problems are condensation and require lot of energy and time. The bulbs start sprouting immediately after they are removed from the cold storage.
Design of New Cold Storage-
There is an urgent requirement to develop a well-engineered onion storage structure that can help to maintain the controlled conditions (temperature and relative humidity) that are required to reduce storage losses of onion with low cost of construction and running.
The present invention developed by ICAR-Directorate on Onion and Garlic Research, Pune aims at storing onion bulbs in controlled conditions having proper ventilation that enhances their storage life significantly by utilizing low energy while minimizing sprouting, rotting, and physiological weight loss. The design and development of the cold storage was done under Public Private Partnership mode.
The storage structure was designed for maintaining the temperature of 27 ± 2 °C and RH of 60 to 65% with air circulation system. The losses in the ventilated storage structure were also recorded during the same storage period. The storage structure designed has maintained conditions that are necessary for significantly reducing physiological weight loss, unwanted sprouting and rotting in stored onion bulbs. The concept of DOGR-cold storage has been filed for patent at Patent Office, Mumbai with the application number 201821049581 titled “A storage structure for storing onion bulbs and a method thereof”.
Advantages of DOGR- cold Storage (27 ± 2 °C)-
The 4 months of storage in DOGR-Cold storage depicted a total loss of 7.14% and 5% in cold storage. The ventilated structure without any control of temperature and relative humidity depicted the losses of 54%.
About 27% post storage sprouting was registered within 15 days after it is taken out from cold storage. Whereas, in newly developed DOGR-cold storage, the sprouting was not observed even after one month after it is taken out from the storage. Running cost and construction cost of DOGR-cold storage are expected to be less in comparison to cold storage.
It is possible to construct DOGR-cold storage for low capacity as low as 2 tonnes and can be scaled up to 2000 tonnes, whereas, same is not feasible in cold storage.
It can also be utilized for curing of onion during kharif and rabi season.
This structure will be useful to store kharif onion with negligible sprouting, which is a major constraint for storage of kharif onion.
The same structure can be utilized for other purposes also, like banana ripening and other applications with little modification or addition of required facility.
DOGR-onion cold storage can be constructed by farmers also at their field with low capacity for avoiding distress selling during main season (May-June) especially in the States of Madhya Pradesh, Rajasthan, Uttar Pradesh, Delhi and Bihar, where temperature reaches up to 46°C and storage of onion is extremely difficult.
Source:ICAR-Directorate on Onion and Garlic Research, Pune
