Organic fertilization and crop load in yield and quality of organic nectarines in Italy

Abstract Organic fertilization in orchards aims at increasing soil fertility, at impacting plant productivity and environmental sustainability. This study aimed at verifying the effects of organic fertilization and fruit load on two nectarine cultivars with high and low fruit loads. The experiment was carried out in an orchard under organic management in Fratta Terme, Po valley, in northeastern Italy. Nectarine cultivars Big Top and Carene, implemented in 2017 and grafted onto GF677, were used. Three levels of compost (0, 20 and 40 t dw ha-1) were combined with two fruit loads (low and high) to set up a factorial experimental design with two factors and four randomized replicates. Compost was incorporated at 20 cm depth. The following parameters were evaluated: nitrate- and ammonium- N concentrations in soil at 20 - 40 cm depth, macro and micronutrients in leaves, tree yield, number of fruits, fruit mass and diameter, soluble solids and pulp firmness. The supply of compost enhanced nitrate-N release in soil. In both cultivars, macro- and micronutrient concentrations in leaves were not affected by organic fertilization or fruit load, except for iron, which increased as a consequence of the compost supply. Low crop load induced higher fruit size in both varieties, a fact that was observed after pit hardening. However, the organic fertilization rate did not influence tree yield, fruit mass and soluble solids.

摘要：果园有机施肥旨在提升土壤肥力，改善植物生产力并保障环境可持续性。本研究旨在验证有机施肥与坐果量对两个油桃品种的影响，两个供试品种分别具有高、低坐果量特性。实验于意大利东北部波谷地区弗拉塔泰尔梅的一处有机管理果园中开展。供试材料为2017年定植、嫁接于GF677砧木的‘Big Top’与‘Carene’两个油桃品种。设置3个堆肥（compost）施用水平（0、20、40 t·dw·ha⁻¹，其中dw为干重dry weight），结合2个坐果量梯度（低、高），采用双因素完全随机实验设计，设置4次重复。堆肥施入20 cm土层深度。本研究测定的指标包括：20~40 cm土层的土壤硝态氮、铵态氮浓度，叶片大量元素与微量元素含量，单株产量、果实总数、单果质量与果实直径，可溶性固形物含量以及果肉硬度。研究结果显示，堆肥施用可促进土壤硝态氮的释放。两个品种的叶片大量、微量元素含量均不受有机施肥或坐果量的影响，但铁元素含量随堆肥施用显著升高。低坐果量处理下，两个品种的单果质量均更高，该现象在硬核期后即可观测到。不过有机施肥水平并未对单株产量、单果质量以及可溶性固形物含量产生显著影响。