Pre-sowing Treatment Methods and Technical Points for Walnut Seeds
Seeds kept in dry storage must be treated with appropriate measures before sowing to promote germination and shorten the sprouting period. Seeds after sand storage can be sown directly, but sowing after sprouting gives better results.
(1) Cold water soaking Before spring sowing, soak the dry-stored seeds in cold water for 7-10 days, changing the water once a day so they absorb water fully, then sun-dry the soaked seeds so the suture lines of the walnuts split open, and they are ready to sow. Where there is a river, the walnuts can be placed in running water for a better effect. Those that do not split open can be picked out and repeatedly soaked and sun-dried until they split open before sowing. Seeds that still do not open after 2-3 rounds of treatment have a low germination rate after sowing, emerge late and grow weakly.
Pictured: walnut
(2) Lime water soaking According to the experience of Nanpiancheng, Fenyang City, Shanxi Province, slake 1.5 kg of quicklime in 10 kg of water, pour in 10 kg of walnuts, press the walnuts down with stones, then add cold water and soak for 7-8 days without changing the water, then scoop them out and bury them in moist sand covered with plastic film to keep warm and force sprouting; after a few days the suture lines split open and they are ready to sow.
(3) Warm water soaking Place the seeds in warm water at 80°C ("four parts boiling, one part cold"), stir with a wooden stick until the water temperature drops to room temperature, then continue soaking for 7-10 days, changing the water once a day; once the seeds split open they are ready to sow.
(4) Hot water soaking For seeds that urgently need to be sown, boiling water equal to 1.5-2 times the weight of the seeds can be used to soak them for 2-3 minutes, without stirring, and they can be sown right after soaking. This is an emergency measure and is generally not recommended.
Based on the characteristics of walnut seeds, dry-stored seeds have a very high germination rate after pre-sowing treatment, and dry storage is low-cost and simple to handle. In production it is best to use low-temperature dry storage, then soak the seeds in spring and sun-dry them until they split open before sowing, which saves time and labour and also prevents the seeds from going mouldy during sand storage.
A commonly used method of forcing sprouting is: mix walnut seeds with 4 times their volume of moist sand (60% moisture content), stir evenly, spread on a sunny surface in a 20 cm thick layer, cover with plastic sheeting, let the sun shine on them during the day, cover with straw mats at night to keep warm, and turn the pile once in the morning and once in the afternoon each day; once the sprouts have slightly emerged they are ready to sow.