Effects of clipping on the nitrogen economy of four Triticum species grown in a Mediterranean environment

Dual-purpose utilization (herbage + grain) of ancient wheats and old durum wheat cultivars provides an interesting option for mixed farming systems in Mediterranean environments. Interest towards these species is partly due to their low nitrogen (N) requirements, but little information is available about their N economy, particularly under dual-purpose utilization. In this two-year field trial carried out in Sardinia (Italy), we assessed whether the morpho-physiological differences between emmer, einkorn, durum and Khorasan wheat translated into different N economies, and whether these economies were differentially impacted by dual-purpose utilization. At both clipping and anthesis, biomass accumulation played a key role in the genotypic variability in N uptake. At clipping, einkorn cultivars had produced the greatest amount of biomass and removed the greatest amount of N (74 kg ha−1) thanks to their late terminal spikelet; whereas Cappelli, Khorasan and Padre Pio showed the greatest biomass production and N uptake at anthesis (212 kg ha−1) owing to their tallness and morphology. The large genotypic variation observed in total N uptake at anthesis levelled off at maturity, mainly because of the N losses occurring at the canopy level after anthesis in cultivars Cappelli, Khorasan and Padre Pio. On average, clipped crops showed a lower (by about 46 kg ha−1) total N uptake at maturity compared with unclipped crops, but dual-purpose utilization did not negatively affect the N uptake if the N removed by clipping was taken into account. Clipping did not negatively affect N partitioning to the grain as the N harvest index increased after clipping as a consequence of the increased harvest index.