A 30-years vineyard trial: Plant communities, soil microbial communities and litter decomposition respond more to soil treatment than to N fertilization

Abstract

Soil management strategies in viticulture should not only aim to optimize yield and quality of grapevines, but also sustain soil biodiversity and soil functioning. Here, we report on the combined effects of soil treatment and nitrogen fertilization on parameters related to soil fertility and litter decomposition, as well as plant, fungal, and bacterial communities in a long-term vineyard experiment, where these management practices have been applied since 1987. Plots in this vineyard (Hesse, Germany) were treated with different yearly amounts of nitrogen fertilizer (0, 30, 60, 90, 120, and 150 kg N ha−¹) with two types of inter-row soil treatment (tillage vs. permanent cover). We analyzed soil properties of the topsoil, decomposition parameters using the Tea Bag Index approach, the inter-row plant community, and microbial communities (bacteria and fungi) by next generation sequencing techniques.Long-term tillage decreased soil carbon and nitrogen levels as well as some plant available nutrients, whereas soil pH and plant available phosphorus increased. Elevated amounts of nitrogen fertilization slightly increased soil carbon and nitrogen levels. Relative mass loss of tea bag content due to decomposition was decreased, while stabilization of labile litter components was increased by tillage, compared to permanent cover treatments. Plant community patterns were changed by soil treatment with tillage inter-rows exhibiting annual, ruderal species and being more diverse compared to permanent cover inter-rows. Relative abundance of several bacterial phyla and fungal orders responded strongly to soil treatment. Changes in soil pH and levels of phosphorus could partly explain the underlying mechanisms involved in shifts of bacterial and fungal communities, respectively. In contrast, long-term nitrogen fertilization only slightly shifted plant and microbial community composition. This study shows that over the long-term, soil treatment strongly affects soil functioning and biodiversity, exceeding the effect of even high nitrogen fertilization levels.