Fact 1: The looseness of soil has a positive impact on a plant 's roots' growth in that soil.

Fact 2: Deep burrowing earthworms improve soil porosity, water movement and plant root growth.

Given the two facts above, answer the question "Deep burrowing earthworms do what to the looseness of soil for root growth?" with the following options: 
- compact
 - improve
 - nutrients
 - destroy
 - erosion
 - support
 - decrease
 - Movement


 

  improve       