Fact 1: Decomposition increases amount of organic matter in soil.

Fact 2: Organic mulch improves the soil.

Given the two facts above, answer the question "What improves the soil?" with the following options: 
- decomposition
 - erosion
 - green manures
 - evaporation
 - fire
 - nutrients
 - dehydration
 - water conservation


 

 decomposition        