Antropogenic input of nitrogen and riverine export from a Mediterranean catchment. The Celone, a temporary river case study

• Published in: Agricultural water management 2017-06, Vol.187, p.190-199
• Main Authors: De Girolamo, Anna Maria, Balestrini, Raffaella, D’Ambrosio, Ersilia, Pappagallo, Giuseppe, Soana, Elisa, Lo Porto, Antonio
• Format: Article
• Language: English
• Subjects: Mediterranean catchment; N balance; N export; Point and non point sources of N; Temporary river
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2017.03.025

[Display omitted] •We report N surplus in an agricultural watershed due to fertilizers and manure spreading.•The hydrological regime has a relevant role in controlling N transport in a temporary river.•A quantification of riverine N export at yearly or seasonal basis needs monitoring of floods.•Few flood events are responsible for nearly 60% of the total annual N load. In a catchmnent, nitrogen (N) export from terrestrial ecosystems to rivers is controlled by the hydrological processes and N balance. In the present paper, the soil system N budget and riverine export were quantified in a Mediterranean watershed, the Celone (South-East, Italy). The study area (72km2) consists of agricultural land (70%) and deciduous forests with three small residential areas. Major N inputs derived from fertilizers and animal manure, corresponding for the whole watershed area to 68 and 12kgNha−1yr−1, respectively. N input from point sources was 1% of total input and atmospheric depositions measured in a gauging station near the study area was quantified in ∼6kgNha−1yr−1. Crop N uptake was the main N output from agricultural land; it was estimated in ∼37kgNha−1yr−1 by using data on crop yields provided by local farmers. Total flux of N in surface water was quantified for a year at the outlet of the study area by using continuous measures of flow and discrete measures of N concentrations carried out with a different frequency during the normal and low flow and when floods occurred. The hydrological regime of the stream, which is a temporary river, plays an important role in N transport. Water quality was found to vary considerably through the year in terms of both nutrient concentrations and loads. Riverine N export was quantified in 41% of total N input, and it was mainly transported during flood events, ∼60% of the annual load was delivered during floods occurred in 38 days. Organic nitrogen and nitrate were the main N forms in surface water, and the contribution per hectare was about 24 and 14kgN, respectively. On a yearly basis, the difference between N inputs and outputs including riverine export was estimated in about 4kgNha−1yr−1 for the whole watershed area. This amount partly accumulates in soils in different N forms and the remaining part, mainly in form of nitrate, percolates through unsaturated soil towards groundwater. This study reports an important analysis of N pollution in a Mediterranean watershed with a temporary river system and limited data availability. D