From spacing to seeds
In the Seed tab, each crop starts from a common Seed rate that you change. Or set Row spacing, Spacing in the row and Seeds per hill: the app counts the plants, then divides by the Germination of your seed lot to give the seeds to sow.
From seeds to bags
Add the 1000-grain weight, printed on the seed bag or weighed yourself, and the app gives the Seed for the field by weight, then the bags with the Seed bag size and their price.

