>>2728498Test your soil acidity. Acidic soil can make tomatoes taste more sour. Make an indicator as in pic related and gather up a bunch of representative soil samples from a few different depths. Cover the samples with the indicator and let it sit for a while. The longer the better. Strain each sample or wick up the indicator with a paper towel and compare the color to the chart. You want your soil pH to be between 6 and 7.