using acacia as a fertilizer

jakfruit etiquette says...
Nitrogen in leaves on top of the soil might take a while to become available to the plants. Acacia sawdust from sawmills can be benefit to garden beds.
Lucerne mulch also has Nitrogen, it becomes available as worms and micros break it down into the soil. Soybean powder (protein/Nitrogen)is used as an N source in Vegan gardening.
You might consider drying the Acacia leaves and grinding as fine as possible to make it more available/faster.
Not sure if the tannins in the leaves could be any problem ?
Composting the Acacia leaves might also be an option.