Agricultural practices regulate the seasonality of groundwater-river nitrogen exchanges

Soil System Budgets (SSB) of nutrients are generally performed annually over arable land to infer their use efficiency and water pollution risk in highly exploited agricultural watersheds. They seldom partitioned into seasonal budgets matched with nutrient transport adjacent river reaches. We calculated soil nitrogen (N) a Mincio River sub-basin (Italy), we analyzed the dissolved inorganic N net export reach draining such sub-basin. Our results show differences SSB excess winter even more spring, equilibrium among sources sinks during autumn deficit summer. Seasonal loads transported by were not correlated as they peaked late summer at minimum early spring. Fertilization uncoupled significant uptake supports whereas crop inputs deficit. Nitrification cannot explain nitrate accumulation reach, suggesting alternative dynamics driving local hydrology. Flood irrigation large solubilization, upward migration groundwater piezometric head spring periods. is likely replaced nitrate-rich when recharge exceeds certain threshold coinciding Irrigation then interrupted head, together exchange, decreases. This work suggests that deep understanding watersheds flooding on permeable soils needs reconstruction vertical pathways river-groundwater interactions. Moreover, partitioning annual combination practices allows identification hot moments cycling. Agricultural minimizing excess, its mobility surface suggested for this area.