Water integration by plants root under non-uniform soil salinity

Soil salinity over root zone usually demonstrates temporal and spatial variations. By changing irrigation management practices it is possible to change both the frequency of salinity fluctuations and its distribution over the root zone. The objective of this study was to experimentally investigate how plants integrate soil salinity over its rooting depth when irrigated with saline water. Consequently, detailed experiments with alfalfa were conducted in some lysimeters containing packed loamy sand soil. The target soil salinities were created by changing quantity and quality of applied saline water. Results indicated that the uptake rate preliminary reacts to soil salinity. But at given water content and salinity, the "evaporative demand" and "root activity" become more important to control the uptake pattern. The obtained results also indicate that root activity is inconstant during the stress period. By increasing salinity, the activity of that part of the root system is also increased. Thus, most water is taken from the less saline part and the uptake at other parts with higher salinities never stops. Consequently, the reduced uptake in one compartment resulting from high salinity is not only compensated from other parts with less salinities, but also from the same increment by increasing root activity.