Gel has been used in watering home plants while people are on vacation or otherwise forgetful/negligent (more the later for me). Gel stores the water and breaks down over time providing water to the plant and some level of fertilization to the soil.

Gel also decreases the rate of evaporation of water. A percentage of gel can be added to the water being sprayed onto fields. This should reduce direct loss due to spraying into the air, but should also better retain the water that reaches the ground.

The percentage will be less than full jello level, but higher than nothing (experimentation required), and should based on the crop's tolerance to this method and existing watering systems. But that's the big upside; it can be implemented in existing systems.