Gypsum is a good source of calcium and sulfur but is pH neutral. Will not sweeten soil.

The below link may help you on which grades of limestone may be best for you and why.

http://corn.agronomy.wisc.edu/Management/pdfs/a3671.pdf

Bryce

According to Bryce's link - there doesn't seem to be much difference between high mag versus high calcium . Just my worthless 2 cents.

Get a soil test from a quality lab such as Watters or Ward. Many university labs give the bare minimum results. Depending on your soils composition, you may need Ca or Mg or both. Look at the % base saturation from the test, you'll want Ca + Mg to be as close to 80% as possible and K to be 5-7%. Also remember, as you increase/decrease something it will drive out or tie up another element. Lower CEC soils (sand or loam) will not hold as many nutrients but will react faster. Higher CEC soils have more sites to bond and "hold" nutrients. Ca is larger and will increase permeability which is why some people add gypsum in tight soils. It's also beneficial in low CEC soils to have a higher % of Mg to slow down infiltration.

One advantage of pelletized over ag lime is pelletized is more effective . Less needed. Up to 10 times more. Same thread started last year .


How much pelletized lime equals ag lime?
A “1:10 ratio” rule of thumb has been promoted for comparing the short-term neutralizing effectiveness of pelletized lime to agricultural lime. (Example: if a soil test recommends the ENM equivalent of 2000 lbs of agricultural lime per acre apply 200 lbs of pelletized lime/acre).