Solutions for dormancy problems
Length of dormancy
In general the dormancy period has a duration of 2-4 months.The length depends a.o. on : Variety, maturity, growing conditions, storage conditions and injuries.
If the seed is still dormant at the time of planting, there are dormancy problems.
Avoid dormancy problems
The main measures that can be taken to avoid that seed is still dormant at the time of planting are:
- adjust the seed production season to the period that the seed is needed;
- use a storage method for the seed which is most appropriate for the seed: diffuse light
stores, naturally ventilated stores or refrigerated stores;
- use seed from another area, which is ready for planting in the preferable planting period;
- select varieties that fit best in the cropping systems;
- use dormancy breaking techniques.
Dormancy breaking techniques
These techniques are not very reliable and it is best to determine first if the solutions given above (1-4) can be used. The most frequently applied methods are: adjusted storage temperature, cutting of seed, use of chemicals.
Chemicals: dormancy breaking
The most used chemicals in dormancy breaking are carbon disulphide and gibberellic acid. The use of these chemicals is not widely spread and the results obtained cannot easily be predicted. Even if dormancy of the seed is broken, the crop will have a slow start compared to naturally sprouted seed.
Carbon disulphide
The tubers are placed in an airtight room for 72 hours. The room is for 70% filled with potatoes and the temperature is kept at 22 oC. The dosage of the CS2 is different for each variety and varies from 10-30 cm3 per m3. Carbon bisulphide is explosive!!!!!
Gibberellic acid
Gibberellic acid can successfully break dormancy if it penetrates the tuber. Since the skin does not allow the chemical to penetrate, it is only effective on cut pieces or on tubers with skin damage (e.g. freshly harvested tubers or slightly sprouted tubers).
There are a number of reasons why GA is only used in emergence cases. GA can have a number of negative side effects:
- GA is given as a dip treatment and thus there is a risk of spreading diseases,
- The chemical may delay tuber initiation, abundant haulm growth and formation of
misshaped tubers.
Storage of seed at high temperature
During the storage there is an influence of temperature on dormancy.
A period of low temperature ( 2 oC) as well as a period of high temperature (28 C0) shortens the dormancy period.
High temperature shortens dormancy, especially in case of long dormancy varieties.
Temperature and dormancy
At high temperature there is an increased risk for tuber attack by micro-organisms.
Some farmers store their seed in a heap (approx. 0.80 m high) under a cover which protects the tubers from rain. Such a heap is often situated in the sun and the potato temperature will be relatively high, while the CO 2 concentration as well as the air humidity is high. These conditions will shorten dormancy, but there is a risk of tuber rot. Important is that the seed lot entering the heap is healthy.
Cutting
Cutting sprouting of dormant seed is stimulates sprouting.
CUTTING OF SEED