Short-Term Effects of Pile Burn on N Dynamic and N Loss in Mediterranean Croatia

There is a lack of information in the rural Mediterranean area about agricultural pile burning impacts on soil nitrogen (N) dynamic and the N loss. Therefore, this research aims to study the impacts of moderate (MS), and high (HS) severity burn on N transformation and N losses, compared to an unburned (C) during the first year. The experimental plots (10 m2) were established in Croatia (43°58′ N 15°31′ E), in a slope ~18°, with a southwest exposition. Five days after the burn, C treatment had a significantly higher total N (TN) than MS and HS. Generally, the runoff was significantly different between burned and C treatments. Sediment yield, concentrations, and TN loss were significantly higher in MS than in C treatment. The concentrations of ammonium (NH4-N) and nitrate (NO3-N) in the runoff, and their losses were higher in burn treatments than in C treatment. These values were high in the first three months after burn, although the peaks in later periods correspond to extreme rainfall events. Principal component analysis showed that sediment yield was associated with sediment concentration, runoff, and TN loss (Factor 1). In addition, rainfall amount and intensity were inversely related to NH4-N concentration and losses (Factor 2). The NO3-N concentration was positively related to NO3-N losses. Overall, MS treatment had severe effects on N loss and, sediment yield can be used as an indicator of soil degradation after pile burns.