NOTE: I want to say that this question originally asked to raise the pH, therefore, that is what the answer refers to.

Dolomitic or calcitic lime is the best option. It is not super fast, but should be applied before planting instead of after if you want to raise the pH. Both of these take some time to dissolve, but are very effective at lowering the pH. If ample irrigation or rainfall is present, results should be achieved within 3 months or so. Rule of thumb is one ton of lime per acre to go from a pH of 5.5 to a pH 6. So, 1.5 to 2 tons should get you to a “perfect” pH of 6.3. Bear in mind that pH is logarithmic and you have to increase the liming material 10 fold for every point you want to achieve. If it requires two tons to go from a 5 to a six, it will take 20 to go from a 6 to a 7 and 200 to go from 7 to 8. All soils are different. Sand requires less lime, but a soil with a lot of organic matter will require more. Most general liming recommendations are based on a clay soil which is half way between sand and high organic matter soils.

To make this easier: 1 ton of lime to the acre to pounds per square feet: (1*2000)/43,560=0.05 pounds of lime per square foot. A 50 pound bag of lime at Home Depot will last you a good while.

P.S. Do not use baking soda as it is sodium bicarbonate. Sodium is not good for plants at all. It can cause salt injury due to osmotic irregularity.