Tree growth, mineral nutrition and nutrient leaching losses from soil of salinized citrus

Abstract

The effects of salinized irrigation water on tree canopy and root growth, water use, foliar nutrition and leaching losses below the rootzone were studied during a 2-year period using single tree lysimeters. Eighteen 6-year-old ‘Valencia’ orange trees on either Carrizo citrange (CC) rootstock or sour orange (SO) rootstock were each transplanted into 7.8 m 3 drainage lysimeters and irrigated with water having an electrical conductivity (EC) of 0.3, 1.6 or 2.5 dS m −1 using a 3:1 ratio of NaCl:CaCl 2. To test for effects of the lysimeter tanks, six additional trees (three on each rootstock) were transplanted directly into soil without tanks and were also irrigated with the lowest salinity water. All trees were fertilized at recommended rates in 50 split applications per year. A similar tank with no tree was also fertilized and irrigated with the lowest salinity water to determine nutrient recovery from soils without roots. During the second year, up to 70% of the applied N and up to 80% of the applied K was recovered in the drainage water from this blank tank with no tree. At the end of the study, trees outside the tanks were smaller but were nutritionally similar to the low salinity trees in lysimeters. Trees on CC were larger, tended to have greater root densities, higher evapotranspiration (ET) and were associated with less leaching of ions and nutrients into drainage water from the tanks than trees on SO. High salinity irrigation water reduced canopy growth and ET but increased total fibrous root dry weight. Trees on CC accumulated more Cl in leaves and in fruit juice than those on SO. Overall, leaching loss of total N varied from 2 to 8% of that annually applied. Salinized trees tended to lose more N and up to twice as much K to drainage water as non-salinized trees. Based on differences between N recovered from the blank tank and tanks with trees during the second year, N uptake efficiency was as high as 68% for non-salinized trees and 64% for salinized trees.