Effects on water and climate: area measure nutrient analysis

The evaluation study was published in 2020 as part of the 2014-2020 Rural Development Programme (RDP) for North Rhine-Westphalia (NRW).

The aim of this study is to estimate the effect of participation in area-based measures on the individual farm nitrogen balance by applying matching methods. Within the NRW RDP, area measures such as agri-environmental and climate measures (AECM) and organic farming are an important means of reducing nutrient inputs from agriculture into groundwater and water bodies in general. Despite the long-standing existence of these measures, there is limited empirical evidence on their impact, as farm data are scarce and analysis is hindered by potential selection bias.

The study employs a counterfactual approach, comparing farms participating in a measure (treatment group) with structurally similar but non-participating farms (control group). As the data are not randomised, a matching procedure is used to select comparable farms based on relevant variables, such as farm size, arable share and fertiliser use. These selection variables are based on the respective impact approach of the measure and are strongly correlated with the other variables, making further adjustments unnecessary. The comparison was always made within the same fertiliser year in order to minimise distortions.

Significant differences in the nitrogen (N) balances were found for organic farming, extensive grassland utilisation and, to a limited extent, contract farming and intercropping. The estimated differences in N balances tend to be of a magnitude that can also be found in the literature, primarily due to field trials. For extensive grassland utilisation, they are even higher than shown in the literature.