Comparison of carbon fluxes, growth and productivity of a winter wheat crop in three contrasting growing seasons

Three winter wheat growing seasons were compared in order to analyse crop development, CO2 fluxes and inter-annual variability in productivity. Crop development monitoring, leaf scale measurements and continuous eddy-covariance measurements were conducted in a production crop at the Lonzée experimental site in Belgium. The 3 years were characterised by similar soil proprieties (same site), similar management (sowing, harvesting, plant protection and nitrogen application, adhering to regional standards), and the use of recommended cultivars (the most productive ones for this region).The comparison of carbon fluxes, growth and productivity in the three growing seasons highlighted mechanisms affected by meteorological conditions and, in some cases, modulated by a cultivar effect. In particular, it was shown that (a) precociousness or lateness in stage development was triggered mainly by cumulated temperature during winter and early spring; (b) early development in one season could explain the larger ecosystem net carbon sequestration that year, but had no impact on grain yield; (c) low grain yield in one season was the result of a complex mechanism including drought in early spring, which hindered flag leaf development, and moist conditions in late spring, which restrained radiation and favoured the development of fungal diseases.In all cases, it was found that grain yield could not be related to gross primary productivity or net ecosystem exchange, suggesting that reallocation and translocation processes play a substantial role in grain filling.

► Differences observed in development stage were controlled by winter conditions.
► The observed inter-annual carbon flux differences were significant.
► Growth stage precociousness did not influence grain yield but had an impact on GPP.
► Yield was not correlated to either GPP or NEE.