Fertilization and water stress interactions in young Eucalyptus grandis plants

Abstract

We determined whether fertilization with N and P affects water relations, and thereby water-stress tolerance, in young Eucalyptus grandis plants. To assess whether fertilization enhances osmotic adjustment under drought, 3-month-old E. grandis were planted in pots and fertilized with either N (1 g of urea) or P (12 g of calcium super phos phate). The soil was watered to attain one of two conditions: field capacity and –0.8 MPa. P fertilization when plants were well watered conditions increased solute accumulation, which might confer better performance under water stress. However, under water-stress conditions, nonfertilized and N-fertilized plants showed osmotic adjustment, while P-fertilized plants did not. P fertilization increased dry-mass allocation to leaves and decreased allocation to roots even under water-stress conditions. N-fertilized plants increased allocation to roots and maintained allocation to leaves under water-stress conditions in comparison with control plants, so they were not affected by water stress as much as P-fertilized plants were. This may explain why P fertilization increased growth when water was not limiting but had no effect under drought conditions. In the long term, changes in dry-mass allocation caused by P fertilization might increase susceptibility to water deficit.