Evaluation of organic mulch use and nitrogen fluxes between mulch, soil and plants, in organic leek cultivation.

Mulching is an important agronomic practice, which found application especially in vegetable production. It could be performed through inorganic, organic or special materials, which have various characteristics and effects. Also, water saving irrigation systems are becoming more and more important and frequently applied in vegetable production to counteract climate change. This study evaluates the effects of the cultivation practices on leek growing. Specifically, no-mulch and mulch with a mixture of triticale and vetch were compared for the mulching main factor, whereas drip or sprinkler irrigation were compared for the irrigation system main factor. The aim of the trial was to evaluate (a) the effect of these two main factors on leek yield, quality and water productivity; (b) the influence of the irrigation type on mulch evolution and (c) the influence of both main factors on the N fluxes in mulch-soil-plant continuum. The trial was performed in central Germany, in the farm of the University of Kassel, following a complete randomized block design. Among the evaluated parameters, mulching increased total fresh biomass, dry biomass, marketable yield, shaft length and shaft diameter, while plant dry matter content was reduced. Irrigation system affected only shaft diameter, with drip showing higher values. As for water productivity and irrigation water productivity, they were increased by mulch compared to no-mulch treatment, while irrigation system reported no influence. Mulch evolution was not affected by irrigation system, but total dry matter, C content and C:N ratio decreased over time. Considering N fluxes, mulching increased N uptake, N leaching, while decreased soil Nmin in 0-60 cm soil layer and did not influence overall N budget. Irrigation didn’t show any influence on parameters related to nitrogen. Based on these results, mulch can be considered a valuable agronomic practice for leek cultivation, whereas drip and sprinkler irrigation appeared to be equally suitable. Further research is needed for better understanding of mulch evolution processes and N fluxes in mulch-soil-plant continuum.