Idk about ag exemptions but assuming youre not going to be over weight I would apply for the 30 day overwith permit and you're good to go for loads up to 13' wide. Keep in mind if it applies to you that the legal height in Texas is 14' with front overhang at 3' and rear overhang being 4'. Depending on where you are going there may be cerfews for moving OW loads in and around different cities and the cities may have a designated route(s) they want you to detour to but the back 2 pages of your permit will have that info.
Just my 2 cents
30/60/90-Day Permits | TxDMV.gov