I have pulled out 2 acres of onions 3 days back and spread them along the length of a soil mound(2 feet high) beside a long trench. Ever since it started raining. The onion tops are still green and the roots are not dry. I would like to ask for forums’ expertise in this regard to educate me if this is matter of concern. If yes, how can I minimize the losses resulting out from rotting. The weather is still partly sunny and expect light rains for couple more days.
My farm is in Hiriyur taluk, Tumkur district.
When onion is harvested the leaves should have been dry or partially dry due to senescence on maturity . Where as you say your onion plants still looks green with roots fresh that is harvested and laid on 2 feet high ridges .
At this time you can not spray any chemical fungicide when onion is either harvested or close to harvest .
When you leave harvested onion with shoots and roots fresh on ridges it keeps it growth continuing though in slow rate …
Option is either you delay harvest for few days until rain is over or
You twist the the green leaves and fibrous roots and keep the onion in warm dry or safer place with good air circulation
If you feel the onion still looks green even after its original duration is over , better spray Maleic Hydroxide ( MH ) sort of Hormone that arrest cell division that is the reason for growth and green appearance and delayed the dormancy in onion
Anyhow you need to keep the onion from wet condition that favors the attack of fungus and bacteria on onion …responsible for causing rot disease …
Depending on the field situation you can choose any one of the above options…
But be very careful when doing harvesting in Onion and strictly follow necessary precautionary measures like harvest only when onion reaches the maturity that is indicated with dry and drooping shoots with leaf color turning grey white , bulb become hard and solid , no wet weather prevails around harvest time .Spraying of MH when plants looks green yet well after its duration , storage in warm dry weather with good air circulation…
It is only preventive measure than control measures that can let you have safer harvest as regards onion is concerned …
Thanks for the valuable advice Ramu sir.
What I understand from your explanation is that since the shoot is partly green, it would continue its slow growth. I presume that it may not result in immediate rotting even though they got drenched in rain. Now that the rains seem to have subsided, I have spread them in a thin layer so as to give them enough air and sun. I am planning to dry them on filed for couple more days until the moisture in the bulb is considerably reduced and then will move them under shade drying for one more week.
I still am left with 2 more acres due for harvest in a month (November). I will take note of MH in case if if I notice that the shoots are green even after the bulb maturity.
Generally any plant will set senescence ie retire from active physiological activity once it reaches maturity , exactly like what happens in human being when he is advancing through ages . The water content and nitrogen level will decrease , cell division and enlargement will be stopped and the plant will enter dormancy . By this time the shoot will start drying and changing color and bulb will go solid.
Suppose if you apply excess nitrogen late , the vegetative growth will continue keeping green shoot and delaying maturity. This may be one of the reason for green shoot at maturity.
Suppose if the market price is high for onion and crop is between 50% Maturity and Full maturity , the farmers will be forced to harvest the onion due to high market price …In this situation some experienced farmers might use MH to advance and speed up maturity and make early harvest …
As onion reaches maturity , the water content and nitrogen level will gradually decrease …When sudden wetness due to heavy rain at this time will increase the water content in bulb as well as shoot which in turn predispose the onion bulb to the disease by fungus as well as bacterial rot. So in this circumstance only remedy is to keep the onion away from excessive moisture . If suppose heavy rain occur when harvesting is done it is better to take the harvested onion to the shed and dry it either under fan or open space with matted floor and provide good air circulation …Only contingency arrangement like this will save onion crop .
It is the reason why the onion prices goes up alarmingly in the market when sudden flood caused by heavy South West monsoon during July to September damage vast onion field in Maharashtra and North karnataka and this even destabilize the Government making big political issue between ruling and opposite political parties …Because the pathogen is readily available in soil which very easily attack the onion either from soil or from base of the shoot which invite pathogen through flash of rain water …So no immediate cure is available for onion when it suddenly get wet in maturity.
Most of the time Onion harvest and South west monsoon coincide causing havoc to onion farmers as well as consumers…
It is also one of the reason that value addition is being planned in onion crop . When onion production is high it is harvested , cleaned , sliced , dehydrated and stored either as small pieces or powder …
If suppose you have got field picture , please post few of them for understanding