Abstract:
The effect of salinity and shallow water tables (1.4 m depth) used in combination with Regulated Deficit Irrigation (RDI) on peach trees (Prunus persica, L. Batsch) was studied over 2 years. Under RDI management a non-saline water table contributed up to 30% of water use. A lack of control of vegetative growth in the first season indicated that a shallow water table may interfere with RDI management. A decline in tree health and growth under RDI and a non-saline water table in the following season may have resulted from salinity and/or waterlogging effects. Saline irrigation under RDI management caused an additional decline in tree growth compared with RDI under non-saline conditions, and resulted in a reduction in productivity (yield and fruit size) and increased uptake of sodium (Na) and chloride (Cl) ions in various plant tissues. Similarly, a saline water table caused a decline in tree growth and fruit size in the first season and increased uptake of Na and C1 ions. For all treatments, accumulation of C1 in the leaves, Na and C1 in the fruit, Na in the bark and storage of Na in the butt wood and structural roots was demonstrated. Differences in mechanisms of transport of Na and C1 and the importance of older wood as a storage organ for ions are proposed. The potential for butt wood as a precise indicator of past salinity treatment is suggested. A combination of a shallow water table and moderate salinity environment was shown to present a potential health hazard for peach trees. The need for refinement of RDI management to incorporate leaching in the presence of saline irrigation and/or water tables is proposed. The management of drainage is also essential.