USE OF AGRO-INDUSTRIAL BY-PRODUCTS IN PEAR FERTILIZATION: PRELIMINARY RESULTS

Organic waste such as agro-food industry by-products are mainly destined to landfill or incineration, with high disposal costs and strong environmental impact. Their use in agriculture can be a way to recycle materials that still maintain a high fertilizing value. The aim of the experiment was to evaluate the value of soil applied apple juices by-products as fertilizer for pear trees. A 3-year experiment was carried out in a mature pear orchard (‘Abbé Fétel’ grafted onto quince MC) in the Po valley (Italy), where the following treatments were compared: 1) unfertilized control; 2) mineral N fertilization (60 kg N ha^-1 year^-1 split in two spring applications); 3) apple juice by-product (1.3 t ha^-1 year^-1, equal to 60 kg N ha^-1), fully supplied at petal drop; 4) apple juice by-product, at twice the rate of the previous treatment 3. Soil nitrate-N and microbial carbon were measured 4 times per year. Moreover, soil organic matter, total N and pH were determined yearly, as well as tree growth, yield, fruit quality, leaf and fruit nutrient concentrations. Soil nitrate-N concentration was increased by the mineral N fertilizer. The application of apple juice by-product increased microbial carbon. Tree growth, yield and fruit quality were not affected by treatments, while mineral N fertilization raised leaf and fruit N concentration.