Tree growing on salt-affected soils in Pakistan, Thailand and Australia

• Nuclear Institute for Agriculture and Biology, Pakistan
• Department of Land Development, Thailand
• Atomic Energy Agricultural Research Centre, Pakistan
• University of Karachi, Pakistan
• University of Karachi, Pakistan
• Department of Conservation and Natural Resources, Australia

Soil salinity (high soluble salt concentrations), sodicity (high sodium concentrations) and waterlogging (low oxygen availability) have made enormous areas of previously productive agricultural land around the world marginal or unsuitable for farming. Severe examples of both irrigated and dryland salinity are found in Pakistan, Thailand and Australia. All three countries have also experienced depletion of forests and in Pakistan and Thailand there is a particular shortage of fuelwood for domestic energy needs.

Several promising Australian, other exotic and local species have been identified for planting on moderate and highly salt-affected sites in Pakistan and Thailand. The results showed evidence of considerable intra-specific variation in survival and growth for several of the Australian species. In this project the scientists will determine the extent of this variation so that recommendations can be made for large-scale plantings from improved seed sources.

The aim of this project, is to develop appropriate establishment and management techniques for Australian species of Acacia, Eucalyptus, Casuarina, Melaleuca and Sesbania in salt-affected areas of Pakistan, Thailand and Australia.

The specific objectives of the project are to:

improve the productivity of key species for salt-affected land;

determine the water use of key species on salt-affected land; and

develop a tree and shrub performance database to provide predictions of growth for salt-affected sites under a range of climatic conditions.

In Pakistan, scientists will conduct progeny trials using Eucalyptus camaldulensis and Acacia ampliceps and in Pakistan and Thailand existing species trials will continue. At some trial sites biomass assessments on harvested plants and water-use measurements on individual trees of selected species will be taken. Leaves from at least three sections of the canopy will be collected and symptoms noted. Ground leaf samples will be analysed at CSIRO and an elemental analysis will be made of soil samples, so researchers can statistically relate the soil and foliar results. If this analysis indicates bicarbonate toxicity, researchers at NIAB will conduct a pot study to evaluate the effect of soil bicarbonate levels on growth. The impact of inoculation with improved rhizobial strains on the growth of acacias; and the effect of the size and age of seedlings to salt application will also be studied.

Scientists will determine the water use of trees and plantations on land of varying salinity. In Australia this will form part of the effort to estimate water use by irrigated tree plantations in the Murray-Darling Basin. Seasonal and spatial changes in root-zone accumulation of salt as a function of the rate and quality of irrigation water will also be studied.