APEX simulation of best irrigation and N management strategies for off-site N pollution control in three Mediterranean irrigated watersheds

Abstract

Simulated annual values were in general more accurate than simulated monthly values. 13 APEX predicted that improving irrigation management (change of irrigation system 14 and/or scheduling) will decrease N loads in IRF over current values by 45% (Akarsu), 15 40% (La Violada), and 8% (Sidi Rached). However, improved N fertilization only will 16 reduce N loads in IRF by 17% (Akarsu) or below 5% (La Violada and Sidi Rached). 17Improving irrigation management will increase IRF NO 3 -N concentrations by 19% in La 18 Violada and will decrease or will remain the same in the other two watersheds. APEX 19 simulations identified the main soils (shallow and low water holding capacity soils) and 20 crops (heavily fertilized or shallow-root crops) N polluters within the studied watersheds. 21Overall, APEX simulated that the improvement of irrigation performance was the best 22 management strategy to decrease off-site N pollution while maintaining or increasing crop 23 yields in the three studied Mediterranean watersheds. 24

Modeling Agricultural Land Management to Improve Understanding of Nitrogen Leaching in an Irrigated Mediterranean Area in Southern Turkey

“…Recently, best management techniques such as drip irrigation [26] and rain water harvesting techniques [27] have been tried to put into practice in order to save both irrigation water and fertilizers. In the Mediterranean climate, irrigation is inevitable for maximizing the crop yield [28]. To increase crop yield and quality and at the same time to decrease the leaching below the rooting zone, managing nutrient concentrations in irrigation water is necessary, according to crop requirements [29].…”

Grey water footprint reduction in irrigated crop production: effect of nitrogen application rate, nitrogen form, tillage practice and irrigation strategy

“…The current study, using the APEX model, simulates a net irrigation supply of 638 mm and a maize yield of 11.1 t ha −1 , while in an earlier study, employing the AquaCrop model (Steduto et al, 2011), we simulate an irrigation supply of 630 mm and a maize yield of 11.9 t ha −1 (Chukalla et al, 2015). APEX is reported to adequately simulate evapotranspiration for different management practices with the Penman-Monteith equation for semi-arid conditions in the Mediterranean, including Spain (Cavero et al, 2012). The study by Milly and Dunne (2016), however, reported that Penman-Monteith overestimates evapotranspiration for non-water stress conditions, which suggests that ground-truthing with field experiments is necessary.…”

Assessment of Groundwater Vulnerability to Nitrate Based on the Optimised DRASTIC Models in the GIS Environment (Case of Sidi Rached Basin, Algeria)

“…Located in Mitidja's western plain, the study has focused on Sidi Rached aquifer where high concentrations of nitrates have been recorded mainly caused by intensive and unsustainable agricultural practice [1,2]. Indeed, a number of studies has established that nitrate concentrations in groundwater were ranging from 20 mg/L to more than 200 mg/L and that the source of this pollution emanates from the leeching of chemical fertilizers (ammonium nitrate, ammonium phosphate and potassium sulphate) [3][4][5]. Nitrogen, in particular in the form of nitrates, being very soluble, generally reaches groundwater dissolved in percolating water and it is the most common aquifer contaminant [6].…”

“…The APEX (Agricultural Policy Environmental EXtender model) was used to assess the best management practices for reducing off-site N loads in the IRF (Irrigation Return Flow) of three Mediterranean irrigated watersheds (Akarsu in Turkey, La Violada in Spain and Sidi Rached in Algeria) [4]. Overall, APEX simulated that the improvement of irrigation performance was the best management strategy to decrease off-site N pollution.…”