Call the TNLA and find out if your eligible to sit for the test. Also, ask about the pass rate and number of certified individuals. You will need 20 CEUs every 2 years so check for availability in your area. Check if irrigation CEUs will transfer.
I doubt any of my clients know what a TCLP is but all are familiar with Licensed Irrigators and Certified Arborist. I think getting your TDA applicators license would be a better return on investment.