Control grass repartition with texture


So I want to make a grass field, nothing original really, and I want two particle systems on one plane in a way that makes them complete each other (in every place one of them isn’t, the other is).
Theoretically it should work assigning cloud texture to the first particle system, duplicate the system, invert the texture of the second one with the ramp and I should get a perfectly full and even grass field.

But it does not work : while the patterns do complete each other, one of the systems is significantly less denser than the other :

The two particle systems are the same, aside of the color-ramp of the texture, and the final goal is to make a grass field with patches of yellowish, smaller grass.
The idea comes from an old tutorial :

Any suggestion or advice is welcome.
With regards :slight_smile: