satisfying soil test recommendations

I recently did a soil test on my small home orchard, results show I need 3 lbs of Phosphorus and 1 lb of Potassium per 1000 sq ft.  I would like to avoid commercial fertilizers/salts for the sake of the soil microbiota, but all the organics that I have looked at have low levels of these minerals and to amend the soil, even just around the trees, will require large amounts of material.  Whereas superphosphate and potash would supply the needed minerals with relatively small amounts and at much less cost.
AT this time I am considering using a bulb planting auger and adding superphosphate/potash in these holes placed at the drip line and spaced every 2 foot.  I assume this will have minimal effect on the general soil and hope I can supply the minerals needed by the trees/plants.  
I have mulched heavily and used as much compost as I can over the last couple of years, also used small amounts of biochar, cover crops and have been trying to establish companion plants.
any suggestions or comments?

My suggestion would be to use compost tea:

https://permies.com/t/117604/composting/Types-Compost-Teas-Exist-Favorite

I would use pelletized chicken litter. It stays in the topsoil and will give way more kick than the listed nutrient value. If you get your soil working some of the deficits showing on your soil test will lessen. Soil tests are not the holy grail for understanding what is really happening with your soil. Depending on the pH and the soil lab, the recommendations may be way off base. I found this to be the case with my high pH soil here in western MN. My recent soil tests said I needed a lot of phosphorus and potassium but when I did a plant tissue test with Midwest Labs on some tillering oats, my soil was in quite good balance. Showing adequate phosphorus and somewhat of a potassium excess. I did not believe the soil test result and recommendation I was getting because my eyes and the weeds present were saying otherwise. If you have lambs' quarter, redroot pigweed, cocklebur growing nicely you have working soil and no need for phosphorus. Healthy Crops is a trove of information on why modern agriculture has failed in soil building and growing healthy food. Many of the modern methods like fungicides actually promote the symptoms they are professing to cure. The plant sap is altered by the fungicide and the plant is made susceptible to plant disease. Pay special attention to the trace minerals as they have great importance in healthy soils. The Law Of The Minimum.

https://gaiafoundation.org/healthy-crops-a-new-agricultural-revolution/

Wood Ash has an NPK (Nitrogen/Phosphorus/Potassium) of 0-1-3 which may aid you and it is easily available for many folks. I really like the suggestion of utilizing composted or pelleted Chicken Manure as it may help as well but it also contains its share of nitrogen.

Before you amend anything, let me ask you... how are the plants doing in the orchard? Are the trees having any issues with growth or fruiting? I have seen people get tunnel visioned because a particular soil report says the sample was low in some factors but that doesn't mean the tree's roots don't have access to the nutrients somewhere else. I have had quite a bit of success reading my plants and adjusting if I see any odd symptoms developing. An annual cover of compost does a lot of work for me in my growing spaces with the occasional amendment if the plants seem to be having an issue.

This thread on Potash might interest you as well.

Have you been noticing issues with the plants and trees that caused you concern? Has this area been subject to chem-ag products before you started with it?

Depending on the soil test you had done it's possible it is only showing you the nutrients that are readily available or water soluble. Chem-ag products might help short term but set back soil life substantially.

As long as the trees are not showing signs of immediate deficits then I would keep focusing on growing the soil and soil life. It's this life that will break down nutrients that are likely already in your soil and added with every addition of mulch and compost and make them available to your plants. If you have a wooded area with good leaf litter you can look closely and be able to see some of the life and transport some of that where you need it. With mulch and roots it should thrive on it's own after that.

If you think the soil lacks enough life then I have done one time addition of a product like Great White. There are lots of these products to choose from. This is the one I have used for abused/dead soils in the past.

https://plantrevolution.com/products/great-white

For the most part things seem pretty healthy.  I have a few elderberries planted in three places, one group, the oldest, had leaves that weren't as green as normal and had decreased yield last year.   Tomato and vegetable harvest in general was poor.  A couple of younger apple trees and a pear tree did not grow as much last year as they had previously, but no obvious signs of deficiency.
Until three years ago I was the one that used chemical fertilizers, then I started learning about the soil life and have been trying to change.  Since then I have been mulching heavily, mostly using wood chips but also with leaf mold/ground leaves, pine straw and even lots of dead/partially rotted wood.  As originally stated I use limited, (all I can make), amounts of compost and biochar, but I have a little over an acre planted in trees/bushes and it only goes so far.    I have used limited amounts of compost tea.  
I actually ask my county extension agent if it would be beneficial to add gypsum to my clay soil, she waffled about it but wanted me to do the soil test.  The last one was 4 years ago, at that time I added the recommended amounts of potassium and phosphorus, triple super phosphate and potash.

I don't have access to sufficient quantities of chicken manure or wood ash.  I could make the ash but would rather turn the wood to biochar if possible.

Sounds like things are ok and you're on the right track. I would keep doing what you're doing while resisting the urge to use chemicals. Things will improve every year. Encourage as much variety of habitats as you can. Feed the soil not the plants!