Potassium is gernaelly act as osmoregulatory substance if you apply at subsequent stage in crop. it make the plant harden also and consisting is due to potassium affect lodging problem.
There are a series of morphological and physiological reasons that potassium can increase stem strength. When potassium is optimized morphologically the number and sizes of vascular bundles improve. When potassium is optimized translocations of nutrients are facilitated. The potassium deficiency stimulates a leakage of nutrients and this is something that stimulate necrotropic stalk rot pathogens and facilitates the development of stem boring insects. Potassium is seem important for Nitrogen nutrition and some have suggested it is important for silicon issues. The increase of silicon can improve the defense reaction and the structure of stalks especially in high silicon plants such as rice. Silicon has been shown to improve both the defensive metabolism but also the drought reaction and structural aspects. In rice Silicon optimized can mitigate diseases to the extent of some of the most effective fungicides. This is noted in the soils which are low in silicon and plants which have high requirements.
Looking at the Mulden nutrient interactions the optimization of potassium is synergistic to Manganese and Iron. Manganese plays a key biochemical role in lignification which is a hardening reaction related to recovery from injury. It would make sense that as Potassium is synergistic with Mangananese and Manganese with lignification that this might be related to the ability to achieve the greater stiffening of tissues and the disease reactions related to necrotropic pathogen. As a macro nutrient interaction balanced KPN is about to enhance root health stalk and a prolonging of juevenility. The juevenile stage is less vulnerable to damage and an its enlongation called stay green can have diverse positive cropping influences. While P is very much plant responsive in the early rooting and establishment stages nitrogen in vegetative establishment potassium has been seen as macronutrient associated with translaction of photosynthetate to seed or tubers in plants that generate large amounts of starch and sugar.
When looking for optimized potassium it is important to have a complete soil and plant analyses and look at the relative ratios of nutrients. The applications of potassium can impart a low Magnesium conditions unfavorable to both plants but perhaps more debilitating to animals. Potassium is particularly deficient in older red acid soils such as oxisols and ultisols. The plant Mexican sunflower is notable for having a high potassium content which can favor its use as cover crop or organic amendment source. I am attaching a draft of a mini review which you might find interesting.
Dear Vaibhav Amrasinh Rajemhadik Some soils are rich in potassium which would be over 200 in the soil analysis. A staple crop like potatoes have very high requirement for potassium. Most acid oid tropical soils are not very rich in potassium. The potassium in those cases are depleted. The use of soil and tissue tests can confirm the needs and trials can determine the critical economics.
Looking that this map you can see that in the United States where I am most familiar while potassium might be at good levels in the areas which are colored red to purple in the yellow green and bluish areas mostly in central Midwest and western zones. On the other hand, the potassium can be quite limiting particularly in our southeast quadrant. This limited potassium state is concentrated in ultisols red forested soils which are old and leached and concentrated in the Southeast quadrant of our country. I am presently living in this area and am well familiar with the multiple deficiencies and toxicities of this soil type. The ability to use soil and plant analysis allows us to tailor our nutrient programs according to actual needs and avoid un necessary amendment and getting the right amounts of needs in the right areas.
If soil content high potassium, but plant can not able to uptake it due to compition with Ca /Mg it will be respond only when we apply potassic fertilizers which content readily available form of K