S13 - Session P1 - Meta-analysis on the effects of living mulches in organic and conventional vegetable production: Influence on soil nitrogen uptake and weed suppression

Authors: Sophie Stein *, Malena Mehring, Jens Hartung, Kurt Möller, Sabine Zikeli

Living mulches (LM) are increasingly used in agricultural production systems due to their benefits in providing ecosystem services. Legumes as LM can supply nitrogen (N) via biological N 2 fixation, while all LM are used to suppress weeds, increase water infiltration, reduce nitrate leaching and soil erosion. However, by competing for limited resources such as light, water, and nutrients, LM may negatively affect cash crop yields. Therefore, a meta-analysis was conducted to further investigate LM systems in organic and conventional vegetable production regarding their influence on N uptake and weed suppression. Due to wide row spacing and sufficient water supply due to irrigation, vegetable production is well suited for LM systems. However, the results of this analysis showed mainly disadvantages of the LM systems. Cash crop yields in the LM systems were reduced with 13.5 Mg ha -1 compared to 17.4 Mg ha -1 in the control without LM. N uptake in the cash crops was 58.8 kg N ha -1 and 34.5 kg N ha -1 in the control and LM systems, respectively. The LM systems also did not adequately reduced weed density and biomass. However, LM treatments without herbicide use showed a significantly decreased weed density compared to a control without LM. This result suggests a particular suitability of LM systems for weed suppression in organic vegetable production. Moreover, an additional descriptive analysis on the N dynamics in LM systems showed lower nitrate leaching. However, LM growth control measures differed greatly among studies, and research has shown that changes in seeding date, tillage, herbicide and fertilizer treatments have significant impacts on LM systems' performance, making comparison difficult. Therefore, it is recommendable to investigate suitable cultivation approaches of the LM systems in the form of field trials.