The best fertilizer for squash is a balanced 10-10-10 fertilizer. The nitrogen helps the plant grow, while the potassium and sodium improve fruit production. The fertilizer may be either granular or water soluble.
Squash should be fertilized when planted and again as it begins to grow. Too much fertilizer can cause the plant to burn.
In addition to fertilizer, squash requires regular watering. To determine if squash needs watering, the soil should be checked for moisture at a depth of 4 inches. Dry soil at this depth indicates a need for water. Squash should be watered once a week in the summer if it doesn't rain.