Which of the following is not a benefit of green manure?

Green manure crops are cover crops that are grown and then tilled back into the soil to add organic matter and nutrients. 

The benefits of green manure include improving soil organic matter, increasing water infiltration, and building soil structure. 

Legume crops, which are commonly used as green manure, help to "build" soil structure over time by increasing aeration, water infiltration, and root growth and reducing the risk of soil erosion. 

Therefore, green manure destroys soil structure, which is incorrect as it is not a benefit of using green manure.