You do not need to use fertilizer on your oak seedlings when they are in the 32 cell propagation trays. The young seedling get nutrients from the seeds. Once you transplant the seedlings to 3 gallon pots mix in one teaspoon of Osmocote per pot once a year. Young trees are not heavy feeders and it is best if they are fed a slow release plant food. Make sure the soil drains well and water just enough to keep the soil slightly moist. Poke your finger into each pot and water when the top three inches of soil is dry. Trees are shrubs do not need as much water as flower and vegetable plants so feel the soil before you water. I see a huge forests of oak trees in your future. Keep growing, Marianne Binetti