infertile, in fertile

Infertile or infertile ( one word ) means unable to conceive or reproduce, or unable to support crops or other plants --
She is infertile; they are waiting to adopt a child.
The label says this birdseed is infertile, but it's sprouting and growing weeds.
This soil is infertile; everything we plant in it dies.

In fertile or in fertile ( two words ) means [ in ] capable of producing or sustaining crops or other plants, or capable of conceiving young ( fertile ) --
Make sure to sow the seeds in fertile soil, and they will sprout in a week or two.
Climbing roses planted in fertile ground will grow to the top of the trellis.

Now that you know that, you can say--
"This seed has been treated to render it infertile; it won't sprout even in fertile ground."