Can the ground cause a fumble?

Answer 1

The Ground can cause a fumble in the NFL.

The ground cannot cause a fumble in the NFL during a play where the runner is being tackled. The ground can cause a fumble if a runner falls to the ground without the fall being the result of a tackle.

Instance where the ground can cause a fumble, per the The 2017 Official NFL Playing Rules, Rule 8, Section 7, Article 3, Item 1, which states:

"Recovery and Advance. Any player of either team may recover or catch a fumble and advance, either before or after the ball strikes the ground."

Instance where the ground cannot cause a fumble is covered under the Dead Ball Rule, Rule 7 Section 2 (a-q) The 2017 Official NFL Playing Rules, Rule 7 Dead Ball, Section 2, Article 1a states the ball shall be declared dead when:

"when a runner is contacted by an opponent and touches the ground with any part of his body other than his hands or feet. The ball is dead the instant the runner touches the ground."

Answer 2

If the ground causes a fumble the player is ruled down.