Business & farm

I cannot get my head around why a non deductible expense, box 18 code C on K-1 decreases adjusted basis.  For example, on a 1065 for bare land, is keeping the fire danger down by keeping the weeds cleaned up (hiring someone) .  I don't plan to take the expenses off anywhere...just a cost of maintaining the bare land in a state with lots of fires.  Why would the decrease my basis in the bare land which increase my profit when I sell it?  whoops..hmmmm. ..have I just said the answer?  Thanks for letting me reach out TT helpers!