Who the pilgrims learn about fertilizer

It was a Native American called Tisquantum, also known as Squanto.

Squanto was a native American who could speak English. He had been captured a slave as a young boy and taken to Spain. From Spain he was sent to England and from where he managed to move back to his home region in modern-day Massachusetts.

On arriving back, he found out that his tribe has been effectively wiped off.

His English skills came in handy and he become close to the Pilgrims in the area. He taught them how to use the local soil to grow crops and essential food.

Historians believe that if it wasn't for Squanto, the Pilgrims would have perished within a few months.