1."Growers should also be aware that a lack of potassium can result in sparse amounts of flowers. Thus, you should increase potassium during mid- and late-flowering. Avoid nutrients deficiencies and use
Marijuana Booster." -The Weed Blog
2."In order to keep your plants growing strong during the flowering process, deciphering the proper amount of Potassium (K) your garden needs is vital. Potassium is a prime facilitator for carbohydrate metabolism. So, if your plants aren’t receiving the right amount, the plant’s sugar production slows dramatically which makes it difficult for your plants to store necessary energy they need to develop buds.
When a Potassium deficiency occurs, plant growth not only stalls, but it also affects the quality of buds, which will decline without proper nourishment. Using Potassium supplements during this stage of your garden’s lifecycle will aid in keeping the quality of your plant’s buds at optimal levels." -http://the420times.com/2015/03/exploiting-the-power-of-potassium-for-your-cannabis-plants/
3."At this stage, using a PK formula will ensure your plants get adequate phosphorus and potassium - the nutrients needed most at this stage. Many gardeners use different techniques to develop hardness and ripeness, some include: adding molasses to your feeding schedule and using Bombastic by Atami. Often, gardeners will deliberately stress the plant mildly right at the end of the flower stage.
Many of the desirable characteristics about Cannabis are largely a result of the biological defense mechanisms employed by the Cannabis plant. By creating somewhat stressful environment, you "trick" the plant into focusing its last energy at protecting itself from the stress and recovering which can lead to increased resin and potency of cannabinoids as well as an increase in essential oils.
Light shocking (finishing the plants out with 24 to 48 hours of straight darkness) and PK spiking (adding very high levels of Phosphorus and Potassium) are two methods that when used in moderation on healthy thriving plants, consistently delivers a small but noticeable boost in quality that can often serve as the "cherry" on top of your sundae." -http://
www.thenorthwestleaf.com/pages/articles/post/why-a-plants-final-3-4-weeks-of-grow-are-so-important