Long-term evaluation of organic management of durum wheat in Central Italy

Italy is the most important European producer of organic (ORG) durum wheat [Triticum turgidum spp. durum (Desf.) Husn.]. Growth and yield of durum wheat are affected by weather conditions and by management systems (MS). The objective of this research was to determine the long-term impact of two different MS (ORG and conventional [CON]) and their interactions with weather conditions on durum wheat yields. The study was part of a long-term experiment in Pisa, Italy, comparing crop performance in a 5-year rainfed rotation (i.e., sugar beet [Beta vulgaris L. var. saccharifera] or maize [Zea mays L.] followed by common wheat [T. aestivum L. subsp. aestivum emend. Thell.], sunflower [Helianthus annuus L.], faba bean [Vicia faba L. var. minor], and durum wheat) over 15 years under ORG and CON MS. Durum wheat yields were 37% lower under ORG compared to CON on average, though similar yields were produced across the two systems during one of the 5-year cycles. There was a significant interaction between MS and climatic conditions for yield and yield components. A lower number of spikes per m² was observed in ORG wheat compared to CON, thus spotlighting on likely different soil N availability in the two MS at the double ridge stage. ORG management resulted in weed biomass increases over time, with 400% higher weed biomass under ORG by the end of the research period. The high interannual variability across both MS confirms that multi-year studies are needed to demonstrate the relative productivity of ORG versus CON MS.