The best way to monitor and adjust pH levels outdoors is to use a soil testing kit. Soil testing kits are designed specifically for outdoor cultivation, allowing growers to accurately measure the pH of their soil and make adjustments as needed. The kits usually come with a pH probe that can be inserted into the soil and left for several minutes before taking a reading. Some kits also include a liquid solution that can be used to raise or lower the pH of the soil if necessary. This process should be done regularly throughout the growing season in order to ensure optimal plant growth and health.