3 The Use Limit of Soil Water Resources by red plum apricot
The state of vertical distribution of soil water in the root soil zone
space influence plant growth. Soil water stress influence root growth
and root water uptake. If
the
soil water content in the MID is equal to wilting point and soil water
content in the MID is equal to SWRULP, and there is not enough water
supply from precipitation, most red plum apricot changes the colour of
leaf from green to yellow or croci and
leaves
fall earlier than usual time in the growing season. Red plum apricot
tree almost ceased growing, and red plum apricot fruit does not
expanding, which influence the yield, quality and economic benefits of
red plum apricot fruit even if the roots extended to a depth of more
than MID and could absorb some water from
the soil layers more than 290 cm
deep, suggesting that the total amount water that red plum apricot roots
absorbed from soil per unit time does not satisfy the need of plant
transpiration and fruit development in the semiarid loess hilly region.
SWRULP is the limit of plants in using soil water resources. It can be
defined as the soil water storage in the MID when all of the soil layers
in the MID become DSLs. The soil depth, representative soil layer and
Wilting coefficient see table1, and , the SWRLP in red plum apricot is
212.7mm, which is different from 252.8 in caragana shrubland at the
middle and the top of the Heici mountain and 220.8 mm in alfafa grass,
showed that the SWRULP changed with site condition and vegetation type.