Supplementary Applications of Phosphorus to Improve Yield and Fruit Quality of 'Le Conte' Pear Trees under Calcareous Soil Conditions

Phosphorus (P) deficiency is one of the major problems in agricultural soils for crop production around the world. Mono ammonium phosphate (MAP) as foliar application used an effective tool to enhance nutritional status of fruit trees not only overcome leaf p deficiency but also improve flowering, increase yield and enhance fruit quality. However, use of bio fertilizers such as phosphorus solubilizing bacteria (PSB) proved to friendly environmentally and economical way for increasing P availability and improving P use efficiency under P deficiency conditions. Consequently, the aim of the present trail was to study the effects of MAP at 1% foliar application and/or soil application of phosphorus solubilizing bacteria (PSB) solely or in combination as supplementary P doses (beside H3PO4 common P fertigated source) under calcareous soil conditions on full bloom time, flowering %, yield (kg/tree) and fruit quality not only fruit physical properties i.e. fruit weight, length (L) and circumference (C), shape index (L/C) and fruit firmness but also fruit chemical components via TSS%, acidity%, and TSS/acid ratio as well as nutrient status of macro & micro leaf contents (N,P,K, Fe, Zn and Mn) of "Le Conte" pear trees. The experiment was carried out during the two successive seasons on 12 years old 'Le Conte" pear trees budded on betulifolia rootstocks (Pyrus betulifolia) grown in calcareous soil under drip irrigation system from Nile river source in a private orchid at Km 80 Alex-Cairo desert Road, El-Nubaria district, El-Behaira, Egypt. All trees received the standard horticultural practices & the experiment was designed in a complete randomized block and the treatments were as follows: (T1) control; H3PO4 common P fertigated source. (T2) T1 + MAP at 1 % as foliar application. (T3) T1 + Bacillus megatherium P solubilizing bacteria (PSB) as soil application. (T4) T2 +T3. The result showed that foliar MAP spray (T2) and PSB soil application (T3) independently improved all aforementioned parameters. However, both T2&T3 gave more or less similar result values and no significant differences were detected between them. In this respect, T2&T3 when applied together (T4) maximized to a grate extend enhancement in most studied parameters and increased yield (kg/tree) by about (167%) than the control. Improvement in leaf P nutritional status after MAP foliar spray to an adequate level (>0.3%) in the range of P and N fertilized plants as well as availability of P, Fe, Zn and Mn following soil PSB application improved nutritional status and help in better management of P fertilization in pear trees grown under calcareous soil condition. Generally, T4 (MAP + PSb) is recommended treatment since, it promotes effectively the nutrient status that achieved the shortest time to FBD, highest flowering %, yield and fruit of "Le-Conte" pear trees under calcareous soil conditions.