Modelling nitrate transport under row intercropping system: Vines and grass cover

SummaryIn the context of reduction of agricultural non-point source pollution, an associated crop system often presents several advantages. The difficulty resides in the characterisation of each species’ contribution (dominant and dominated). This paper deals with the particular case of voluntary grass cover management between rows in a vine plot. We evaluate the spatial and temporal changes in the development of both crops: vine/grass cover system, in their ecological functioning and in the influences on water and nitrogen balances. We modify the SWMS_3D model to incorporate separate distribution of water and nitrogen demands for the two coexisting plant species. The parameterized model is then assessed using the measured data (water content, matrix potential and nitrogen content of the soil solution at depths of 30, 60, 90 and 120 cm) acquired from two monitored vine plots (vine “Tockay-Pinot Gris” plot grass covered every second row compared to a control plot that was chemically weeded vine “Riesling” plot, France, Alsace, Rouffach) between October 1998 and September 2000. The main results are the following. The vine’s mean total transpiration over the two growing seasons of 1998/1999 and 1999/2000 is simulated of 355 ± 9 mm per season. The matrix potential is reproduced accurately especially improving with depth and under the interrow. Despite a high variability due to soil heterogeneity, the nitrogen mass variations between measurements and simulations with the adapted model are coherent. Nevertheless we note that the model slightly underestimates the nitrogen mass for both types of observed cropping patterns, however the ratio between the two itineraries remains similar, yielding a reduction in nitrogen loss by at least 4-fold in favour of grass cover every second row plot during the period observed from 10/01/1998 to 09/30/2000.

Comparison of nitrate leaching (daily and cumulative in N–NO3 kg ha−1) from the WP plot and GCP plot from 10/01/1998 to 09/30/2000.Figure optionsDownload as PowerPoint slideHighlights
► Intercropping system (vines / grass cover) is simulated to characterize nitrate leaching.
► The model SWMS_3D is adapted to incorporate water and nitrate uptake for both species.
► Grass cover every second row simulation showed nitrate leaching reduction by at factor 4 fold.