IMPACT OF SOME BIOSTIMULANT SUBSTANCES ON GROWTH PERFORMANCE OF WASHINGTON NAVEL ORANGE TREES

In a field experiment, Washington navel orange trees were treated with three biostimulants substances; potassium humate, active dry yeast and amino green (amino acids mixture) to study the effect of these substances on vegetative growth and leaf contents of Na and Cl. Potassium humate was applied at 10 and 20 g /tree as soil application. In addition, yeast extract at 0.2 and 0.4% and amino green II at 0.25 and 0.50% were applied as foliar application. The results showed that tree height, leaf area, leaf fresh and dry weights and volume index were positively affected by biostimulants treatments. Generally, the highest values of vegetative growth parameters were achieved with potassium humate, active dry yeast and amino green in descending order. The data also revealed that all biostimulants treatments significantly decreased leaf Na and Cl contents compared to untreated trees; it means that such substances (especially potassium humate) can be used to reduce the negative impact of salinity in soil or irrigation water. In general, biostimulants substances had a beneficial effect on growth performance and leaf contents of Na and Cl of Washington navel orange trees. In this concern, potassium humate at 20 g/tree was considered the favorable treatment.