Nitrates are high-index salts that rapidly end up in the environment to bad effect and are entirely un-necessary in a properly managed system. I strongly suggest disregarding that last recommendation. Crop plants with high levels of nitrate resist insects and disease poorly and are unhealthy to eat, even though they may look lush and thriving. There are much better sources of K available. High use of nitrates in the form of synthesized salts is a major part of what is wrong with commercial ag. It is also what is wrong with most organic operations where the nitrates and phosphates are pumped in through animal manures while the rest of the nutrients are allowed to decline along with plant health.

yes to what Byron says, if the plants are blooming and setting fruit reasonably, you don't need to "force feed", especially that often - many of the foods we eat are good sources of P and K, so food waste compost provides everything any growing veggie needs - greensand is also high K - if you've limed recently, the calcium may be preventing K uptake, but if not, there isn't usually a problem in a decent garden soil w/ lack of K Bill

I found a horticultural abstract entitled, "Applications of Potassium silicate decrease black spot infection in rose Fuschia Meidiland". The conclusion: "The results indicate that using potassium silicate in irrigation water may be a useful component of a disease management system." Potassium silicate is a pH up, it makes the soil alkaline and imparts silicon to the leaves. Potassium silicate is sold as "Rhino Skin" for $7 at Planet-Natural .. I wonder how they extract that from Rhino Skin? http://www.planetnatural.com/product/rhino-skin-potassium-silicate/ I googled "Foods highest in silica" and found this info: "one of the best food sources for silica is oats. A breakfast muesli made with raw soaked oats eaten daily supplies lots of silica. (Guess why horses fed with oats are so strong and have such shiny coats?) Without silica there would be no lustre to our hair; we would have brittle nails, rough and itchy skin and no elasticity in our connective tissues." I got 42 oz, or 2 lb. of oats for $2 at the grocery store. I grounded that up in a coffee grinder, and fertilized Bolero, very pleased with the results ... cheaper than Rhino skin! Here is a link that might be useful: Horticultural abstract on potassium silicate This post was edited by Strawberryhill on Sun, Oct 6, 13 at 11:47

Have his doctor set him up with a nutritionist. I'm surprised his doctor didn't put him on cholesterol meds or recommend he see a nutritionist. This is a hard problem because a lot of things like certain fruits and veggies that will lower cholesterol are high in potassium and being celiac he can't eat things like oat bran to lower cholesterol. There is no magic food and the services of a nutritionist are needed to get this under control.