Fortnightly soil water content measurements to
a depth of 2.1 m under 4 cocksfoot cultivars, 2 phalaris cultivars, 2 lucerne
cultivars and 1 Lotus corniculatus cultivar were used to
compare soil profile drying and to define seasonal patterns of plant water use
of the species over a 3-year period, on a duplex soil. Cultivars were also
selected, within species groups, for varying seasonal growth patterns to
assess this influence on soil water dynamics and growth. Over the 3-year
period, treatments with the highest and lowest measures of profile soil water
content were used to derive and compare values of maximum plant extractable
water. Plots were maintained for a further 3 years, after which soil water
content measurements in autumn were used to assess long-term effects of the
treatments. The effect of seasonal growth patterns within a species was
negligible; however, there were significant differences between species.
Twenty-one months after pasture establishment, lucerne alone had a drying
effect at 2.0 m depth and subsequently it consistently showed profiles with
the lowest soil water content. Maximum plant extractable water was greatest
for lucerne (230 mm), followed by phalaris (210 mm),
Lotus corniculatus (200 mm) and cocksfoot (170 mm).
Profiles with the lowest soil water content were associated with greater
herbage growth and greater depths of water extraction. The soil water deficits
developed by the treatments in autumn of the fourth year were similar to those
measured in autumn of the seventh year, implying that a species-dependant
equilibrium had been reached. Long-term rainfall data is used to calculate the
probabilities of recharge occurring when rainfall exceeds maximum potential
deficits for the different pasture species.
Long-Term Effects of Big Sagebrush Control on Vegetation and Soil Water
