The long term trial, on a Templeton fine sandy
loam, is a factorial combination of 3 pasture
swards (pure WL320 lucerne,
lucerne-‘Grasslands Matua’ prairie grass and
lucerne-‘Grasslands Maru’ phalaris) and 2
grazing durations (long and short). The 0.04ha
plots were sown in November 1986 with lucerne
drilled across the grass rows. For the water use
study, in 1988-89, 8 m² mini plots of pure
lucerne, lucerne-phalaris, and lucerne-prairie in
deep or shallow soil were selected. Pure lucerne
plots produced annual dry matter (DM) yields
of 12700 kg/ha, lucerne-phalaris 11600 and
lucerne-prairie 10400. Deep soils had higher
production (12600 kg/ha) than did shallow soils
(10900 kg/ha). The lucerne-phalaris mixture
had about 75-95% lucerne, while lucerne in the
lucerne-prairie mixture ranged from 25% in
winter to 65% in summer. The lucerne-prairie
plots with deep soils had at least 60% lucerne
while shallow soils had as little as 25%. Mean
water use efficiency (WUE) was 25, 22 and 20
kg DM/ha/mm for pure lucerne, lucerne-phalaris
and lucetne-prairie, respectively.
Shallow soils had WUE of 21 kg DM/ha/mm
H₂O and deep soils 24 kg DM/ha/mm. Soil
water extraction ‘patterns differed little in
shallow soils, but in deep soils pure lucerne
extracted water to at least 100 cm while lucerne-phalaris
and lucerne-prairie extracted soil
moisture down to about 80 cm. Lucerne and
phalaris roots were both found down to 90 cm
and from O-20 cm most of the root mass was
lucerne. With the lucerne-prairie mixture from
O-20 cm, root mass was about 50% for each
species and lucerne root mass was significantly
reduced below 50 cm.[Show full abstract]
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