The Aztecs and the Spanish were both practicing agriculture, but it was in a different manner and with a different purpose. The Aztecs were reliant on agriculture for their food, so basically they were using it only to produce sufficient amount of food so that they can survive throughout the year. Practically it was a self-sustaining agriculture. The Spanish on the other hand, using the agriculture for production of food, but also used it for making profit from farming cash crops. This was something unseen in Mezoamerica, as the Spanish were using the fertile soil not to produce for themselves, but to produce for others, sell the products and the make wealth out of it.