EUTROPHICATION

IMPROPER POST HARVEST STORAGE CAUSES LOSSES IN ONION FARMING

Onion is considered as a staple vegetable in the diet among Nepalese family. There is sustainable demand of onion throughout the year in Nepal. Although the farmers are honestly working but due to lack of technical knowledge in field of Postharvest management they are not getting optimum price and it leads to disappointment among the farmer day by day.
Unscientific Post harvest is being troublesome due to fluctuation of price in onion market. Although, the demand of the onion remains same throughout the year except in Sep to Nov. As in our country most of our national festival fall in this period like Dashain, Tihar etc but in this period supply of onion to market is low because of off season for onion production so demand gets highly increased. Domestic production of country fails to fulfil demand of onion even in on season of onion production. More than 50% of onion is imported from India and other country according to data published by Kalimati of 2068 B.S.
Nepal has not been able to produce onion according to desired amount and so Nepal has imported 20 million kg of onion worth Rs3.26 billion in the fiscal year 2015/016.Scientific Post harvest storage of onion can also play role in increasing national GDP and ort.
Onion generally comes in three color they are white, yellow & red (appears purple). The edible portion in onion is modified stem known as bulb.
Nearly 60% onion is produced in month of April and May and remaining 20% and 20% as off season farming in Oct to Nov & Jan to Feb. From June to November only stored onion is used in the country. So if Post harvest storage is not done properly then sometime there is surplus supply to market and sometime scarcity.
There are various types of losses due to improper handling and unscientific storage like weight loss, rotting, sprouting of bulb etc.

Measures for checking losses

selection of suitable variety of onion. Light red onion variety like N241 have very good shelf life. Generally dark red, yellow and white onion variety have poor storage life.

Season for planting also affect postharvest losses like rabi (spring season) onion harvested in April/May is best suited for long term storage. Kharif or late kharif (rainy season) harvested on Oct -Nov & Jan-Feb respectively exhibit early sprouting and other losses.

Balanced fertilizer applied at appropriate time enhances the life span of onion 

excessive irrigation closes maturity reduces storage quality as this result in bull-necked bulb which is responsible for rotting. Drip irrigation is best irrigation as it improves bulb quality and storage.

During the time of Harvest the top should be cut leaving 2-3 cm with bulb so neck dries completely and suitable for storage. after cutting bulb are graded according to size and then single and double bulb are separated.

size of bulb also determine storage. Onion bulb of 55 to 75 mm diameter are better size for storage than large and small sized bulb.

after grading onion bulbs are dried in heaps for 10-15 days which facilitates the drying of outer skin of onion bulb and helps in keeping them for longer period in storage.

storage structure should be constructed in elevated region and should be free from moisture, roof can be made asbestos sheet or Bangalore tiles and bottom of wood or bamboo. Roof should exceed 3 feet to check rain.

Onion in cold storage; storage loss very low but most loss due to sprouting so before treating in cold storage. It should be treated with gamma rays so sprouting can be checked.

Onion shelf life can be increased at home by storing whole onion at dark and dry place having plenty of air circulation and plastic bags or closed container should be avoided.
                                       Gaurav Thakur
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