G. Wessolek et al., INFLUENCE OF SLOPE AND EXPOSITION ON WATER-BALANCE OF LOESS SOILS, Zeitschrift fur Pflanzenernahrung und Bodenkunde, 157(3), 1994, pp. 165-173
Laboratory and field measurements as well as deterministic simulation
models were used to determine the water components of loess derived so
ils with different expositions and slopes in the hilly region South of
Hannover, Germany. Studies were investigated from 1987-1990 on three
positions of a loess slope with 8 % inclination, 200 m length and nort
hern exposition. Crop rotation was sugar beet, winter wheat, sugar bee
t. Results show that the soil water budget is strongly related to slop
e position, relief and plant available water in the rootzone. It was f
ound that drainage at the bottom of a slope is often higher than on to
p of the slope. On slopes with northern exposition groundwater recharg
e increases with inclination whereas actual evapotranspiration decreas
es. For slopes with southern exposition the opposite reaction can be e
xpected. The thickness of loess deposits and the root depth determine
the plant available water; a sensitivity study demonstrates how ground
water recharge decreases with the amount of plant available water. Thi
s reaction is independent of the exposition of the slope. Field and si
mulation studies show that runoff occurs under sugar beet whenever soi
l is bare or sparsely covered, rainfall intensity is high and topsoil
is sealed. Moreover, in loess derived soils interflow may occur on sit
es with stagnic horizons. Sensitivity analyses show that this process
probably takes place whenever saturated hydraulic conductivity of this
horizon is less than 10 cm/d.