Alfalfa regrowth after a cut may be encouraged by subsurface irrigation without allowing shallow-rooted weeds to emerge. A large variety of drip tubes are available on the market. The polyethylene tubes have built-in emitters set at certain intervals along the tube. Water drips out of the emitter opening at the end of a turbulent pathway, where the pressure is dissipated and water just dribbles out. The spacing and the flow rate of the emitters on subsurface drip tubes are variable according to the product.
Products are available at variable wall thickness.
The higher the MIL number, the thicker the wall, which extends the life of the tube. The cost also goes up with the increase in wall thickness. The polyethylene tubes fitted with pressure-compensating emitters make them suitable to distribute water uniformly in sloping fields. Pressure differential due to ground slope is avoided. Naturally, these tubes cost more.