Effectiveness of best management practices for non-point source agricultural water pollution control with changing climate - Lithuania's case

This study aimed at the evaluation of the change in the effectiveness of Best Management Practices (BMPs) for agricultural pollution control in terms of reduction of nutrient loads to surface water bodies in Lithuania in the context of climate change (CC). The SWAT model was used by applying two CC representative concentration pathways (RCP4.5 and RCP8.5), three time horizons (historical - 2000-2019, mid-century - 2040-2059, and end-century - 2080-2099), and five BMPs (arable land conversion to grasslands, reduced fertilization, no-till farming, catch-crops, and stubble fields throughout winter). The most effective (with the greatest nutrient reduction) BMPs include grasslands, stubble fields, and winter cover crops. No-plough farming and reduced fertilization BMPs appear to be the least effective ones. CC would increase the potential of reduced fertilization and conversion to grasslands BMPs up to 179% and 17%, respectively for total nitrogen (TN) reduction. Regarding total phosphorus (TP), the reduction potential would increase 226% for fertilization reduction, and remain approximate for grasslands (at median-4%). Due to winter reduction of loads, no-plough stubble fields, and winter cover crops would decrease by as much as 50%, 12% and 26%, respectively for TN, and 30%, 11%, and 17%, respectively for TP, compared to the historical period. The greatest change would be recorded for the most extreme CC scenario (RCP8.5) and the longest time horizon (end-century). The effectiveness of BMPs (except for no-plough) for TN load reduction would increase more, and on average would become greater in agriculture dominated areas (of central-northern Lithuania) than elsewhere, although the maximum reduction values would occur in western (and in some cases eastern) Lithuania (except for reduced fertilization). This suggests the importance of the application of the measures in both areas. BMPs (except for grasslands) are expected to have relatively little effect on the overall crop yield.