4Ganicanswered grow question 6 years ago I use lemon juice and Baking soda in a pinch, using litmus papers will help A LOT if your pen breaks, i always keep some in stock just in case. But in a super pinch you can take soil samples from your plants and add vinegar to one sample and Baking soda to the other (after adding a bit of RO/distilled water to the sample) If the sample with vinegar in it fizzes your soil is to Alkaline, if your sample with Bicarb fizzes your soil is to acidic. If nothing happens that means the pH is close to the pH of the Vinegar or Bicarb. This wont tell you exactly what the pH is, but it will give you an idea of how acidic or alkaline it is. Hope this helped