Response of wheat crop during transition to organic system under Mediterranean conditions

Organic agriculture is an ecological production management system aimed at sustainable production of safe food, environmental protection and maintenance of soil health. The objective of this study was to evaluate, in a period of organic transition, the effects of different organic fertilizers on wheat yield, grain quality and soil characteristics. The research was performed in an experimental farm of Southern Italy (Foggia), over a three year period. An organic commercial fertilizer and compost, obtained from municipal wastes, with and without a commercial bioactivator, were compared in a randomized block design. Grain yield and quality and soil total organic carbon content (TOC) were measured. The Henin-Dupuis model was also tested to simulate soil organic C dynamics after organic fertilizer application. Among the years, significant differences were observed in grain yield and quality, indicating that wheat crop response was influenced by the weather conditions. The grain and straw yield was not significantly affected by the organic fertilizer used, though the compost resulted in significantly lower grain quality compared with the organic commercial fertilizer. In any case, at the end of the experimentation, the compost resulted in significantly higher TOC (+4%) compared to the organic commercial fertilizer. The results showed that the compost may be used as an alternative to sustain wheat productivity, feasible also from an economic point of view and to conserve soil fertility. Finally, under the local Mediterranean conditions, the soil organic C dynamics could be defined by the Henin-Dupuis model, also considering the C supply of annual root residues.