Evaluation of soil fertility, soil quality, nutritional status and fruit quality in a Citrus orchard in Southern Italy.

Summary

The aim of the work is to evaluate on a long term perspective the effect of application of different organic fertilizers on tree nutritional status, yield, fruits quality and soil fertility in a orange [Citrus sinensis (L.) Osbeck, cv. ‘Valencia late’], grafted on C. aurantium (L.) orchard cultivated on sandy loam soil, sized 1.8 hectars and located in Eastern Sicily.
In a randomized block experimental design with three replicates (60 trees each plot), four treatments are compared. Treatments 1 and 2 receive two different composts; treatment 3 is fertilized using dried poultry manure and the control treatment is treated by mineral/synthetic fertilizers. Every year, each plot receives the same amount of total N, matching the needs of the crop.
Nutritional status of trees and yield are evaluated determining the leaf content of macro and micro elements, chlorophyll content, xylem potential, trunk circumference, total yield, fruits weight and a number of fruit quality characters. The soil sampled in each plot was analyzed for total organic carbon, total nitrogen, C/N ratio, humified fraction, biomass carbon, potentially mineralisable N in anaerobic conditions, potentially mineralisable C, carbon mineralisation quotient and metabolic quotient. Moreover, the Community Level Physiological Profile (by Biolog technique) has been defined, also calculating derived biodiversity and versatility indexes.
According to the obtained results, the long term application of organic fertilizers has determined: i) high yields, similar to those obtained with the application of mineral/synthetic fertilizers; ii) better fruit quality characteristics; iii) increase of long term soil potential fertility.