Error in my sql server query

Question

  SELECT FARM.item,A.farmer_id,

A.farmer_season,A.farm_visitno

FROM dbo.tbl_farmer_farmdetails A

INNER JOIN dbo.tbl_farmerregistration B ON B.farmerctscode = A.farmer_id

CROSS APPLY [dbo].[StringSplits](A.farm_detailsdata,',') AS FARM

WHERE B.farmerseason = '2018'

 

 

When i run the above query shows error as follows

 

Operand data type varchar is invalid for subtract operator.

 

please let me know what is the mistake in my above sql query. i tried for several it shows the same error only. please help me.