Throughout history people have been using fertilizers. When people put manure on their fields, they grow better. Bird guano from the Galapagos was an incredibly popular fertilizer, having built up on rocks in the sea. The islands of guano were being cut up and sold, but that started to grow thin.
Bird guano island, atlass obscura, unkown
Then, in 1798, Chilean Nitrate was discovered by a native woodcutter named Negreiros. He started a campfire, and saw that the ground had begun to melt, and run like a stream. He reported the activity to his Curé at Camiña, who declared it to be hellfire, and asked to see the area. The Curé took a sample of that earth, and discovered it was nitre. Throwing the remainder into his garden, he later found it grew better.
Chilean Nitrate, IndiaMART, unkown