GPS on its own especially with systems like WAAS is quite accurate these days, generally within a few meters. If you need more (which planting most crops does) there's also RTK [1], which permits centimeter-level accuracy from relatively inexpensive / simple setups. Here's an example of a local RTK base station with radio link in the industry [2], and additionally it's possible to get these corrections off cell network data connections [3]. Radio offers you more hyperlocal corrections which could improve accuracy a touch, but comes with all the downsides you'd expect of a local radio system so both are viable options.
[1] https://en.wikipedia.org/wiki/Real-time_kinematic_positionin... [2] https://www.deere.com/en/technology-products/precision-ag-te... [3] https://www.deere.com/en/technology-products/precision-ag-te...