Response of pear trees to different fertilization treatment

During 2015 and 2016 we investigated the influence of different organic (cattle manure, Humus Vita Stallatico (HVS)), organo-mineral (Multi Comp Base (MCB)) and mineral fertilizers (calcium ammonium nitrate (CAN), compound (NPK) and natural zeolite (Agrozel) as a soil conditioner on the yield and fruit physico-chemical properties of pear cv. 'Williams' grafted on quince BA.29 rootstock. Results showed that fertilizers, years and their interaction significantly changed the evaluated properties. Yield per tree and hectare was the highest with compound NPK application and the lowest in the control variant. Fruit weight (FW) was higher when NPK was used in comparison with the Agrozel application and the control variant. Manure, CAN, NPK and HVS induced similar and higher fruit length (L) than control, whereas NPK induced higher fruit diameter (D) than manure, Agrozel, CAN applications and control with no significant differences between them. Agrozel and NPK induced similar and higher fruit shape index (sphericity) values in comparison with manure and CAN application. Soil application of NPK induced higher surface area than Agrozel and control. Fertilizers did not affect flesh firmness (FF). Soil application of manure, MCB, NPK and HVS increased soluble solids content (SSC) in comparison with other treatments, whereas the highest acidity was observed in the control variant. Agrozel induced the highest pH juice, invert sugars (IS) and sweetness index (SI). The best ripening index (RI) was found with NPK fertilization. Total sugars (TS) and sucrose (SC) contents were the highest in the MCB variant. Generally, fruit physical and chemical properties were better in the first year of the investigations. However, the significant interaction fertilizer x year indicates that some fertilizers did not show a consistent effect in certain years.