We at GeoPard have released the Soil Sampling Module. 

Among features - Grid & Zones, Core & Composite sampling support; Configuration of points distribution logic; Optimum Route calculation (zone-by-zone for composite sampling or optimal path length); Printing of labels (also supporting the custom logic of points name, can be good for your lab); Mobile app with the gps tracking.

Please check the Soil Sampling Module demo/tutorial (1 min dynamic video is there).

It's included in the subscription price or just $0.05 per ac per plan for pay-as-you go users.

There is also 1 month 250ac free trial.

Some examples of sampling plans created in GeoPard attached.

(geopard soil sampling plan 1 (full).png)

(geopard soil sampling plan 2 (full).png)

(geopard soil sampling plan 3 (full).png)

geopard soil sampling plan 1 (full).png (86KB - 5 downloads)

geopard soil sampling plan 2 (full).png (72KB - 4 downloads)

geopard soil sampling plan 3 (full).png (93KB - 4 downloads)