The impact of irrigation water quality on water uptake by orange trees

Abstract

A greenhouse lysimeter study was carried out in Tottori (Japan) during August 2000 to explore the 
impacts of saline irrigation on water uptake by orange trees. Two lysimeters filled with sandy soil were 
used. Each lysimeter was planted with a tree. During the first half of August, both lysimeters (L1 and L2) 
were irrigated with non- saline water. In the second half of the month, L1 was irrigated with non-saline 
water (1.0 dS/m) and L2 with saline water (8.6 dS/m). At each irrigation event, 60 and 32 mm water was 
applied in the first and second half of August, respectively, when average water content of the soil 
profile was depleted to 70% of field capacity. Osmotic potential in L2 became more negative after 
application of the saline water. Evapotranspiration from L1 was consistently higher than that from L2. 
Average transpiration rate (T) reached 5.5 mm/day under non-saline irrigation, while T was only 3.8 
mm/day under saline treatment. Up to 99.5% of roots were in the top 60 cm of soil and 73% of the total 
water uptake was extracted from the same layer. Maximum water withdrawal by the tree was observed 
at layer of 30 - 60 cm in accordance with root-weight distribution.