Irrigation management of Anna apple trees in relation to growth, yield, fruit quality, leaf constituents and plant water relations.

摘要

Anna apple trees grown on loamy sand soil during 1998 and 1999 in Egypt were irrigated when the soil moisture tension reached to 20, 30, 40, 50 and 70-cb (centibars) in the top 30 cm soil layer. The data in both seasons generally indicated that vegetative growth, fruit set and yield attained their maximum values at 40-cb soil moisture tension. Moreover, the soil moisture tensions at 50 or 70-cb caused a significant reduction in these characters. With regard to fruit quality, TSS and sugar content reached their maximum values with soil moisture tension of 40-cb; lower values were associated with high water stress (50 and 70-cb). Juice acidity and fruit firmness increased with increasing soil moisture tension. Leaf sugars and free proline contents substantially increased with increasing soil moisture tensions, while contents of leaf starch, total carbohydrates, total chlorophyll and leaf water contents exhibited the opposite trend. The studied contents of leaf minerals significantly decreased withsoil moisture tensions of 50 or 70-cb compared with the other treatments. Water use significantly decreased with increasing soil moisture tension. Soil moisture extraction decreased with increasing soil moisture tension at the top soil layer (0-30 cm), and it increased at the deeper layers (30-60 and 60-90 cm). The best water-use efficiency was observed at a soil moisture tension of 40-cb. The present results indicated that irrigation at 40-cb-soil moisture stress was best for apple trees to promote fruit yield and water-use efficiency.