Botanically, speaking, you may have more luck if you use an appropriate prairie grass mix for your field, whatever would be appropriate to the soil type and climate, and not just turf grass. Turf grass needs a lot of maintenance but native plants should take much better.
I know that if you claim an improvement, it must be part of the property at the time of sale to count as an adjustment. For example, if you bought the home in 2000, and replaced the furnace in 2001 and again in 2020, only the 2020 replacement counts, you lose the adjustment from the 2001 furnace that was taken out.
Using that logic, I would say that you can include your costs to establish proper ground cover, even if that takes several years. However, if you decided in 10 years to plow it all under and plant corn, you would not be able to count the earlier work as an improvement for the cost basis.
