Squash and pH
pH refers to the acidity or alkalinity of soil. A pH of 7.0 indicates neutral soil, while anything lower is acidic and anything higher is alkaline. Like most garden vegetables, squash prefers slightly acidic soil. The ideal pH range for squash is between 5.5 and 6.8. Squash plants generally survive in a slightly wider range, but the crop yield is likely to be diminished.
 
Raising pH
If you have highly acidic soil in your garden, you can take measures to raise the pH and make the soil better suited to supporting squash. The most common strategy for raising pH is to incorporate lime into the soil, either in the form of ground agricultural limestone or pelletized lime. The amount you need to use depends on your soil type and the pH you are starting with. A soil test kit, available at most garden stores, can tell you the pH and nutrient content of your soil and make recommendations for possible amendments.
 
Lowering pH
It is also possible to lower the pH of soil, and some form of sulfur is typically used to accomplish this. Your options include iron sulfate, aluminum sulfate and pure elemental sulfur. Incorporating peat moss and other forms of compost can also help lower pH over time. The effect of lowering pH is often temporary, so it’s a good idea to retest your soil every few years and reapply as necessary.
 
Other Considerations
Squash grow best with full sun and loose, well-drained soil with plenty of organic content. Squash plants need lots of room to sprawl, so plant them about 3 feet apart. You can also plant seeds closer together, then thin out the weaker seedlings as they grow. Water your plants enough to keep the soil moist, but don’t allow the ground to become wet and waterlogged. If you have poorly drained soil, you can combat this by planting squash on small raised hills of soil.