Significantly different pollination rates on Apples?
Got several varieties of apples. Pollination rates vary from near 100% (Sweet 16) to near zero (Lodi). Other are in between but towards the lower end. Cortland is 35% with lots of dead flowers. I also have one variety unknown that makes small apples for cider that gets near 100% pollination. This tree in particular blooms early.
Trees are 3-5 years old, semi-D, mulched, with about 150' of each other, mostly gently sloping sandy soil, same fertilizer. There are three mature crabapples in the same area.
Only difference I can see is Sweet 16's are on a more steeply sloped area.
Possible reasons for difference? I assume since some get well pollinated that its not a bee issue??
thx in advance for help.