Soil Sampling Equipment Recommendation:

JMC Backsaver N-2 Handle with Sampling Tube ($200-$420)
Best method for plow-layer sampling. Very portable. Footpedal offers extra leverage in dry soils. Several tubes available.

JMC Conventional Handle with Sampling Tube($135-$405)
Works well in tilled soils only. No footstep. Uses same sampling tubes as option one.

JMC T-Handle, Mallet, and JMC Sampling Tube ($220-$425)
Inexpensive method for sampling hard soils. Uses same sampling tubes as option one.

JMC Low-Cost Sampler with Step ($67)
Works best in tilled soils. Sampling tube is part of the probe.

JMC Low-Cost Sampler ($37)
Cheapest alternative for obtaining occasional samples at lowest cost.

JMC Environmentalist's Sub-Soil Probe ($2250-5350)
Although the sampling tube is 36 inches long, you can use a 12 inch or 18 inch long liner in the tube by blocking off the rest of the tube with a spacer. This probe features a sliding drop-hammer and a foot-operated jack. Great system for all soils now and more capabilities later.