Weird, but Wikipedia does say of the DR that almost 80% of the total land area [is] suitable for crop production and that the main exports are fruits such as avocado, papaya, bananas, cocoa, etc, which don't grow on arable land anyway. In 1998, arable land totaled 1,020,000 hectares; with land under permanent crops at 480,000 hectares.[0]

While on Haiti, it says that of the total arable land of 550,000 hectares, 125,000 hectares are suited for irrigation, and of those only 75,000 hectares actually have been improved with irrigation.[1]

So while I'm sure Haiti could do better than what they are doing now, it seems curious to say that it is more suited for farming than the Dominican Republic. I think the author might have misread numbers.

[0]https://en.wikipedia.org/wiki/Economy_of_the_Dominican_Repub...

[1]https://en.wikipedia.org/wiki/Economy_of_Haiti#Agriculture,_...