Evaluating nature-based agricultural practices and their influence on soil and water quality using a multi-parameter and long-term dataset

Current agricultural practices can have a strong impact on soil and water quality. Continuous manipulation of the soil deteriorates soil structure and promotes soil erosion. Application of pesticides, and leaching of excess nutrients through overfertilization decreases soil life and negatively affects surface water and groundwater quality, with consequences for ecosystems and drinking water provisioning. Therefore, it is necessary to find innovative farming approaches that mimic or restore the natural functioning of soils in agricultural systems, thereby enhancing soil health and soil hydrological functioning, and decreasing nutrient transport from agricultural fields to groundwater and surface water. So far, research into the effect of innovative and nature-based agricultural practices has largely focused on soil parameters, and only a few studies have assessed the combined effects of different agricultural practices based on soil and groundwater indicators. In this study, we present a unique combination of long-term data (i.e., the results of a 23-year long experiment), spatially highly resolved soil and groundwater concentrations of carbon, nitrogen, and phosphorus compounds, nitrate isotope data, and soil health parameters (e.g., soil biodiversity) to compare the effects of tillage (conventional tillage and non-inversion tillage) and organic matter amendments (artificial fertilizer, manure slurry, and compost addition) in both a conventional and organic farming system in the Netherlands. Our first results show that phosphorus and nitrogen dynamics on the agricultural fields are not coupled, and that organic sites behave differently to the other fields especially for nitrogen. For example, nitrate concentrations in groundwater below these fields are much lower and nitrate shows a strong denitrification signal. For phosphorus, application of animal manure appeared to be the main driver of high concentrations in both soil and groundwater. Moreover, soil biodiversity is generally higher in the organic farming system. Overall, the differences between conventional and organic farming systems are pronounced, while other agricultural practices seem to have a secondary role for soil health and water quality.