The management of ground water recharge in south-eastern Australia relies on
the formulation of agricultural practices that utilise rainfall before it
moves below the root-zone. Annual cycles of soil water content were therefore
measured in a red-brown earth subjected to 5 fallow-free crop sequences, to 2
crop sequences that included fallow, and to 3 pastures. Changes in soil water
content induced by wheat, barley, lupin, pea, safflower, canola, and fallow
were compared with those of annual pasture and 2 monocultures of the
deep-rooted perennials phalaris and lucerne in 3 years of study.
Mean minimum soil water content (0–1.6 m) seen in December and May was
approximately 355 mm in lucerne and phalaris, 410 mm in annuals (crops and
pasture), and 475 mm in fallow. Corresponding soil water deficits appropriate
to lucerne, annuals, and fallow were 185, 135, and 65 mm, respectively.
Lucerne and annuals both removed approximately 85 mm water from the upper 0.6
m of the soil profile. Differences arose in the subsoil below 0.6 m, where
lucerne, annuals, and fallow produced soil water deficits of approximately
100, 50, and 25 mm, respectively. The difference in soil water deficit of
deep-rooted perennials and annuals was therefore caused by the extra 50 mm of
water extracted by lucerne and phalaris below 0.6 m in the period
September–December. The dry subsoil endured through summer to promote
the storage, by soil, of rainfall in winter.
The data suggest that the spatial utility of an agronomic recharge control
option in south-eastern Australia depends on the magnitude of the soil water
deficit associated with the vegetation. The soil water deficit, relative to
winter (May–August) rainfall, discriminates between areas where annuals
suffice for recharge control, where lucerne and phalaris are required for
recharge control, and where agronomic annuals and perennials are both
conducive to high rates of drainage.
Effects of water deficit on the growth and yield formation of maize (Zea mays L.)
