DO MICROPLASTICS IN VINEYARD SOIL AFFECT THE BIOAVAILABILITY OF VINE NUTRITION?

Abstract

Microplastics can alter physicochemical and biogeochemical processes in the soil, but whether these changes have further effects on soil fertility, and if so, whether these effects vary depending on the type of soil in the vineyard and the type of plastic used in the vineyard. Knowing what types of plastics are currently used in vineyards in Slovenian viticultural regions as strings to tie vines to the stake, the aim of our study was to assess the effects of microplastic particles from polypropylene (PP) and polyvinyl chloride (PVC) on the availability of macro (potassium (K), Potassium (K), calcium (Ca), magnesium (Mg) and phosphate (P)) and micronutrients (iron (Fe), copper (Cu), manganese (Mn) and zinc (Zn)) in two vineyard soils contrasting in pH and mineralogy. For this purpose, a short-term soil incubation experiment (120 days) was carried out in which the soil samples were enriched with micro-PP and micro-PVC particles. After the incubation period, macro- and micronutrient availability were measured. The results show that micro-PP particles have a stronger influence on the availability of macronutrients in the soil. Phosphate availability decreased by up to 30%, potassium availability by 20% and magnesium by 10%. However, the macronutrient most affected was nitrate, as the availability of this element decreased by more than 90% with the presence of micro-PVC particles in the soil. These results were observed in both soil types (calcareous and acidic soils). On the other hand, the presence of micro-PP particles in the soil had a greater effect on the availability of micronutrients, but not to the same extent as micro-PVC – the availability of iron was reduced by 10% and that of Cu by 10%. If we assume PVC and PP contamination of vineyard soils, we can assume that nutrients should be supplied by spraying vines with soluble fretilizers in higher concentrations, as this is the most common method to specifically minimise micronu- trient deficiencies in vineyards. On the other hand, Cu, which is present in fungicidal sprays and may be present in toxic concentrations in vineyard soils, was the least affected micronutrient and could also be active in the presence of microplastic particles. Although research on the effects of microplastics on nutrient cycling in soils is still in its infancy, microplastics directly affect some soil properties that may also have indirect effects on soil nutrient cycling, e.g. cycling of C, N, P and other elements.