What can i do instead of using synthetic fertilizer?

The following is a list of things you can use as an alternative

Composted Manure

Composted manure is a complete fertilizer, but its NPK ratio depends on the animal source. The rate tends to be higher in fresh manures, but these should not be applied to plant roots. Application rates also vary widely so check the label for the proper amounts

Fish Emulsions

Fish emulsion fertilizers are made up of partially decomposed and pulverized fish, and contain NPK ratios of 5-2-2.

Bone Meal

Bone meal is made from the ground bones of animals, and is a byproduct of the meat processing industry. It an excellent source of phosphorous and calcium, that is ideal for fertilizing bulbs and trees and shrubs in soils with a pH below 7.0.