Irrigation Water Quality, Rooting Depth, and Nutrient Budgets in Citrus

摘要

The effects of salinized irrigation water on tree canopy and root growth, wateruse, foliar nutrition, and leaching losses below the root zone 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 cu m drainage lysimeters and irrigated with water having an electrical conductivity (EC) of 0.3, 1.6, or 2.5 dS m(sup -1) from a 3:1 ratio of NaCl:CaCl2. To test for effects of the lysimeter tanks, six additional trees (3 on each rootstock) were also transplanted directly into soil without tanks. These six trees, along with one additional blank tank without a tree, were fertigated with the lowest salinity water. 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 and to allow less ions and nutrients to leach into drainage water from the tanks than trees on SO. Thus, root density and irrigation water quality can influence leaching losses beyond the root zone.