One challenge when farming is keeping your crops hydrated. Based on the Rainfall in the area, the ground may have some latent moisture. However, this may not be enough especially for particularly water-intensive crops.
In order to see the hydration of any specific block, you must have a Hoe in hand.
Then simply look at any Farmland block, or any crop which requires hydration. You will see a tooltip which shows the current hydration as a percentage from 0% to 100%.
Hydration cannot be decreased except by moving to an area with less rainfall - however, it can be increased by the proximity to nearby water blocks, much like Vanilla farmland.