Morphophysical pedotransfer functions for groundwater pollution by nitrate leaching in Central Chile

Abstract

Nitrate leaching (NL) is a major concern in agriculture due to its impact on human health and ecosystems. Solute movement through soil is governed by various hydraulic and physical properties that determine water flow. To study such relationships, a pedotransfer function of groundwater pollution was developed in two alluvial irrigated soils under long-term pig slurry applications. Two basins of central Chile, San Pedro (Typic Xerochrepts) and Pichidegua (Mollic Xerofluvents) were selected, where maize (Zea mays L.) was grown in spring-summer, while during autumn-winter period a ryegrass-barleyoat mixed crop was established in San Pedro and a fallow management applied in Pichidegua. Soils in cultivated and control sites were characterized in physical and hydraulic terms. Nitrogen and water budgets were determined measuring periodically (biweekly) N concentration (N-NO3 -and N-NH4 + ) and monitoring water contents in soil profiles, respectively. Dye tracer tests were performed with brilliant blue (BB) dye and the staining patterns analyzed. To contrast the effect of slurry additions over soil physical properties and over NL, t-Student tests were performed. Some accurate pollution groundwater NL pedotransfer functions were obtained calculated through least square fit models and artificial neural networks. Textural porosity, mean diameter variation, slow drainage porosity, air conductivity at 33 kPa water tension and N-NO3 -concentrations were directly related to NL. In terms of preferential flow analysis, stained path width > 200 mm was inversely associated to NL. Finally, dye tracer tests provided a better understanding of the characteristics and pattern of water/solute movement through soil to groundwater.

Evaluation of soil fertility and fertilisation practices for irrigated maize (Zea mays L.) under Mediterranean conditions in Central Chile

“…Recently, in Mediterranean zones of Chile there are further concerns because N and P over-fertilisation in irrigated maize fields can be associated with a high risk of diffuse pollution of water bodies (Casanova et al, 2013;Fuentes et al, 2014;Salazar et al, 2014). This is because in addition to applying high levels of N and P most of farmers utilise a furrow irrigation system with low application al., 2013).…”

Inorganic nitrogen losses from irrigated maize fields with narrow buffer strips

“…In Chile, some recent studies evaluated the impact of agricultural activities on the level of NO 3 -N in water bodies (Fuentes et al 2014(Fuentes et al , 2015Salazar et al 2014). They showed that measured NO 3 -N values in water bodies adjacent to agricultural areas in central Chile, where maize is the most common crop, usually exceed the Chilean water quality standard for drinking water (10 mg NO 3 -N L -1 ).…”

Net Nitrogen Mineralisation in Maize-Cover Crop Rotations in Mediterranean Central Chile

“…Particularly at the irrigated central Mediterranean of Chile, there are serious risks of diffuse pollution towards surface water bodies and groundwater due to excessive applications of N fertilisers for maize (Zea mays L.) cultivation, predominantly during autumn-winter when bare fallows are practised (Fuentes et al 2014;Salazar et al 2014;Corradini et al 2015;Nájera et al 2015). These concerns also extend to other Mediterranean climate regions of the world (Berenguer et al 2009;Gabriel and Quemada 2011;Salmerón et al 2011;Simeonova et al 2017).…”