Need:

Onion and garlic are required every day in the kitchen; however, they are harvested once or twice in a year. To maintain steady supply for domestic as well as export market they need to be stored. Onion is harvested during Kharif (Oct-Nov. 20%), Late Kharif (Feb-March 20%) and Rabi (April-May 60%) seasons. However garlic is harvested in rabi only. Kharif and Late Kharif onion harvest is consumed within one or two months as there is heavy demand during those months and therefore does not require storage. Rabi harvest is in high quantity and available across country. These bulbs need storage to ensure availability till next Oct-Nov and also gain more profit over a period of storage. In case of garlic, it is harvested during March - April and the same material is used for daily consumption for almost a year.

Harvesting:

Onion should be harvested after 50% neck fall and garlic after 50% drying of leaves. Plants should be pulled out along with bulbs. The bundles of onion plants should be kept in windrows in such a way that bulbs of first row will be covered by tops of second row. This is called field curing or windrow curing. Field curing along with tops done for three - four days facilitates reverse transaction of abscisic acid from leaves to bulb which improves storage capacity and covering of bulbs by tops improves colour of the bulbs. Tops are cut leaving 2 cm neck on the bulbs after field curing. Bulbs are graded such as split, bolted, diseased etc and sorted out, and remaining bulb are heaped under the shed and dried for 15 days, which is known as called shed curing. Bulbs are stored in storage structures after shed curing. Immediately after harvest garlic plants are graded and 20-25 plants tied in bundles along with tops. The tops should be divided in three segments and they are interwoven tightly. Such bundles are kept in upright position in shed for curing for 15 days. Then the bundles are stored in storage structures.

Storage losses:

Storage losses of rabi harvest of onion range from 30% to 60% due various factors. Physiological loss of weight (25-30%) is a major followed by sprouting of bulbs is to the tune of 10-15% and microbial decay or rotting due to fungal diseases (10-15%). In case of garlic storage losses are to the tune of 15-20% only in which major losses are again due to physiological loss of weight i.e. water loss and fungal rots. Both the crops are affected by storage diseases such as black mould, blue mould, gray mould, basal rots, smudge, soft rot, bacterial rot etc. To avoid these losses, crop rotation, use of IPM module, cleaning and disinfection of storage structure must be followed appropriately.

Storage structures:

DOGR has carried out extensive R&D on storage structures and found that ‘Bottom and side ventilated two rows structure’ is suitable for 25 to 50 tons capacity and ‘Bottom and side ventilated single row low cost storage structure’ is suitable for 5 to 10 tons capacity. The schematic diagrams (not to size) are as follows:

Onion graders :

In India grading of onion is usually performed manually either before storage or before marketing. The drudgery of human labour involved for grading of onion has been reduced by hand operated as well as motorized onion grader. The onion is graded in three grades i.e. ‘A’ (60-80mm), ‘B’ (50-60mm) and ‘C’ (35-50mm) grades according to the equatorial size of the bulbs. It is recommended that Only A and B grade bulbs should be selected for storage. The accuracy of grading is 90% as compared to 70% in manual grading when these graders were used. The cost of grading with machine is around Rs. 90/tones as compared to Rs. 180/tones in manual grading. The capacity of motorized grader is 1.5 to 2.0 tons per hour, which is 20 times higher than manual grading. The grading charges would be around Rs. 50/ tones as compared to Rs. 180/ tones in manual grading.