If you fertilize you will increase yields on the off years but many trees only bear heavy crops every second or third year. It's just the genetics of the tree. The trees seem to overbear so much that they have to take a year off. If it was a fruit tree you could manually thin the crop. With nut trees your at the mercy of mother nature. To determine the exact bearing sequence you need to look up the information for each species. Some bear every other year, others have 1 on then two off. Fertilize, water if you can, trim off dead/dieing branches. You can sometimes shock a tree into bearing if you over trim. The tree puts its full resources into seed production. Unfortunately you'll set up for a poor bearing year the year after the good crop.

Dan O.