What type of filters are recommended for farmers?

I think you mean water filters here. If so, it can be tricky to find out a good dirty water filter and filtration system, which suits your requirements. In my opinion, we have to first find out how much the water is exactly dirty. Does it have hard solids or soft solids? Is there any quantity of living organisms?

Following are the filter to purify water with a low concentration of solids:

Y-Strainers, Cartridge filters, Sand and other media filters.

Filters for Low Medium Concentration of Solids:

Y-Strainers, Cartridge filters, Rotor flush Self-Cleaning filters, Sand and other Media Filters, Self Cleaning Screen Filters and Hydrocyclones.

Filters for Low Medium to Heavy Concentration of Solids:

Run Down/Parabolic Screens, Rotorflush Filters, and Filter Pumps, Hydro cyclones (for heavy solids).

Water with A Heavy Concentration of Solids:

Slurry separators, Centrifuges, Filter Presses.