# harv\_idx

This variable will force the ratio of yield to total above-ground biomass to the specified value. If biomass is cut and removed (e.g., in hay cuttings), *harv\_idx* must be used to specify the amount of biomass cut. For grain harvest, the harvest index in the plant growth database ([**plants.plt**](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/databases/plants.plt)) is used instead of *harv\_idx*, which assumes that only the seed is being harvested.