Farmers using phase farming may find they have greater flexibility in light of findings that lucerne pasture can deplete the subsurface water profile, and fix worthwhile nitrogen, in only two years.
A study at Wagga by CSIRO Plant Industry scientists looked at soil water balance during the transition from lucerne pasture to crop. The lucerne had dried the profile to at least 2 m within two years, suggesting that a short pasture phase might be adequate to reduce recharge.
During the third and final year of the lucerne phase in the Wagga rotation soil, water extraction was limited to
the top metre of the soil. The researchers could not detect any additional uptake of soil water below that depth. The control on recharge to groundwater effected by lucerne through subsoil drying in the previous two years did not change in the final year.
The researchers report the three-year occupation of the red clay soil by lucerne did not appear to affect water flow or crop response.
Contact: Mr Frank Dunin 08 9333 6683