Inorganic nitrogen losses from irrigated maize fields with narrow buffer strips

Abstract

Vegetated buffer strips (BS) can help prevent nitrogen (N) losses from fields by subsurface lateral flow, thus protecting water resources. The purpose of this study was to determine if narrow BS would effectively remove dissolved inorganic N from subsurface lateral flow. Nitrate-N (NO3-N) and ammonia-N (NH3-N) concentrations in subsurface lateral flow were measured at 1 m depth in a BS system consisting of five treatments: G: strip of grass (Fescue arundinacea); GS: strip of grass and line of native shrubs (Fuchsia magellanica); GST1: strip of grass, line of shrubs and line of native trees 1 (Luma chequen); GST2: strip of grass, line of shrubs and line of native trees 2 (Drimys winteri); and C: bare soil as control. Water samples for the NO3-N and NH3-N measurements were collected between June 2012 and August 2014 in observation wells located at the inlet (input) and outlet (output) of each treatment. The analyses showed that vegetated BS had NO3-N removal efficiency ranging from 33 to 67 % (mean 52 %), with the G treatment showing the best performance in reducing NO3-N concentrations in subsurface lateral flow. The BS treatments were not effective in reducing NH3-N concentrations. The results suggested that N uptake by grass is the main process associated with the NO3-N retention capacity of vegetated BS.