Impacts of controlled drainage during winter on the physiology and yield of winter wheat in Denmark

Abstract

Controlled Drainage (CD) is a measure designed to lower N-leaching from agricultural fields. However, raising the drainage depth in fields creating partially waterlogged conditions can have negative impacts on the yield and development of winter cereals. A combination of physical and chemical analyses was performed in an outdoor lysimetric setup under North European climatic and soil conditions to characterize the effect of CD on winter wheat yields of the cultivars Belgard (BG), Benchmark (BM) and Substance (SUB). CD treatments consisted of drainage depths of 10, 20 and 25 cm below the soil surface from January to April 2016. The control was a freely draining treatment with drains at 150 cm depth. Both chlorophyll fluorescence (Fv/Fm) and net photosynthetic rate (Pn) indicated that CD tended to not affect growth and dry matter (DM) yield at maturity, which were only influenced by cultivar. Fv/Fm tended to be lowest at 10 cm drainage depth, indicating increasing plant stress with shallower drainage depths. The BG cultivar generally had the lowest Pn rate of the three cultivars likely reflected in a 27% lower grain yield than the BM cultivar. The straw N-concentration was 21% higher in the BG compared to BM, but neither CD nor cultivar affected the grain N-concentration. N-uptake was controlled by the biomass production of the cultivars. CD affected the concentration of multiple nutrients such as Fe, Cu, and P, though no coherent pattern in nutrient changes was found. Overall, cultivar was the main factor controlling the concentrations and uptake of the nutrients. Hence, the only negative effect of CD on winter wheat yields was in relation to uptake of some nutrient, which is a rather unexplored topic. Finally, the consistently low Fv/Fm at the 10 cm drainage depth indicates that shallower drainage or prolonging the CD period could cause significant waterlogging stress.