Tow behind sprayer recommendation needed

Purchased a new home a year ago. 2 acres of yard to mow and make the envy of the area now.... Purchased a new Scag Freedom Z last fall. I would like to do my own weed spraying and lawn fertilizing. Would anyone have a recommendation of the size of a sprayer for this size of yard? I'm thinking 22-24 gallon should suffice, and there are several at local stores (Fleet Farm, Northern Tool, etc...) in this size, but I would rather buy the right size off the bat instead of regretting it later.

Thanks in advance for any suggestions

It may be different where you live depending upon what kind of grass you have, but I use 2,4-D and the mixing rate is 1 gallon to about 75 gallons of water. That covers three acres, so you'd have to scale it back. I put it on with a Fimco 25 gallon sprayer.

I have one of these and really like it. Also a fan of 24D (Tractor Supply Amine 400)

http://www.northerntool.com/shop/tools/product_200578565_200578565

They offer the same sprayer with a 26 gallon capacity.

Several of my customers have fitted a spray tank to their ROP rather than towing a sprayer behind them.
That way they can spray and mow at the same time ( if you have lap bars that you can hold in one hand. )