If you are planting legumes the optimum pH of the soil should be 6.5-7.0, P should be between 30-50 ppm with optimum being closer to 50, and K should be 100-200 ppm with the higher level being most optimal.
If these basic fertility requirements are not present, then your yields will be decreased.
If the soil pH is too low, then more N fertilization is required to make up for lack of bacterial nitrogen fixation.
Lime additions are cheaper than fertilizer and bringing up the soil pH will help you maximize the natural ability to legumes to produce their own nitrogen.
A typical application of 2 tons of lime for 3 to 4 years would cost about $10-20.00/year compared with 250 lbs of nitrogen every year to the tune of $60-100/year.
If you are planting grasses they are a little more acidic tolerant. The optimum pH for grasses is 6.0-6.5 with the P and K being in the same range as above.