Healthy plants need water and fertilizer to grow.
Pesticide prevents pests from infesting your fields.

However, too much of any of them is not healthy for the plants.
When the water percentage exceeds 63 %, the plants health will be reduced.
Fertilizer and pesticide already harm your plants at concentrations of 43 %.
If any of these three is zero, it will also harm the field.

If the health is below 20 %, the output of a field will shrink.
When the health is zero, all output will be lost.

Happy farming!