> For the complete documentation index, see [llms.txt](https://swatplus.gitbook.io/io-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://swatplus.gitbook.io/io-docs/introduction-1/management-practices/harv.ops/harv_idx.md).

# 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**](/io-docs/introduction-1/databases/plants.plt.md)) is used instead of *harv\_idx*, which assumes that only the seed is being harvested.