Nitrate leaching from organic and conventional arable crop farms in the Seine Basin (France)

Abstract

In the Seine Basin, characterised by intensive arable crops, most of the surface and groundwater is contaminated by nitrate (NO 3 -). The goal of this study is to investigate nitrogen leaching on commercial arable crop farms in five organic and three conventional systems. In 2012-2013, a total of 37 fields are studied on eight arable crop rotations, for three different soil and climate conditions. Our results show a gradient of soil solution concentrations in function of crops, lower for alfalfa (mean 2.8 mg NO 3 -N l . For a full rotation, the estimated mean concentrations is lower for organic farming, 12 ± 5 mg NO 3 -N l -1 than for conventional farming 24 ± 11 mg NO 3 -N l -1 , with however a large range of variability. Overall, organic farming shows lower leaching rates (14-50 kg NO 3 -N ha ). Overall, we show that organic farming systems have lower impact than conventional farming on N leaching, although there is still room for progress in both systems in commercial farms.

Nitrogen soil surface balance of organic vs conventional cash crop farming in the Seine watershed

“…4). These results were in accordance with those of Benoit et al (2014) who showed with a network of ceramic cups in OF and CF farms in the Seine watershed that for a full rotation, the estimated mean concentrations were lower for OF, 12 ± 5 mgNO 3 -N.l −1 than for CF 24 ± 11 mg NO 3 -N.l −1 , with, however, a wide range of variability depending on the crop, lower for alfalfa (mean, 2.8 mg NO 3 -N.l −1 ) and higher for crops fertilized after legumes (15 mg NO 3 -N.l −1 ). Remarkably, the surplus of arable land from most organic mixed crop livestock farms in our sample is lower than the lowest threshold value (Fig.…”

“…Benoit et al (2014) showed that for organic fertilizers such as poultry manure or vinasse, the soil solution concentrations were directly impacted by the total N amount applied, while the application of compost before vinasse decreased the soil solution concentrations from 22.8 to 10.4 mg NO 3 -N.l − 1 . In the present study, one-third of the organic farms studied were amended with compost, which could reduce the leachable fraction of N surplus.…”

“…Most studies, comparing leaching in OF and CF show that leaching rates per ha are lower (30-50%) on organic than on conventional fields (Benoit et al, 2014;Stopes et al, 2002;Haas et al, 2002;Honisch et al, 2002;Stolze et al, 2000;Hansen et al, 2000;Korsaeth and Eltun, 2000;Berg et al, 1999;Reitmayr, 1995), although some authors found around 20% more leaching in OF than it has been measured in CF (Sapkota et al, 2012;Kelm et al, 2008;Torstensson et al, 2006;Kristensen et al, 1994). When the leaching rate is expressed per unit of output, results are more mixed, slightly lower leaching rate in favor of OF (Benoit et al, 2014), non-significant differences (Mondelaers et al, 2009;Kirchmann and Bergström, 2001), or disfavor OF (Korsaeth, 2008). (ii) Soil fertility (Stockdale et al, 2002) and long-term sustainability related to the dependence of organic systems to nutrients coming from the conventional agro-industry, through imported feedstuffs, beeding, manure, meat-and-bone meals, beetpulp residues … (Nowak et al, 2013;Goulding et al, 2009).…”

Virginia mallow (Sida hermaphrodita (L.) Rusby) as perennial multipurpose crop: biomass yields, energetic valorization, utilization potentials, and management perspectives

“…Challenging and competitive market conditions in the European bio-economy lead to increasingly intensified agricultural cultivation practices that typically involve monoculture management. However, these practices entail ecologically adverse effects as exemplified by nitrate leaching, excessive soil erosion, as well as the die-back of insects and birds in agriculturally dominated areas (Montgomery, 2007;Beketov et al, 2013;Goulson, 2013;Benoit et al, 2014;Thomas, 2016;Hallmann et al, 2017;Heldbjerk et al, 2017). To countersteer these developments and to improve the resilience of agricultural systems, the diversification of crops and the (re-) creation of habitat heterogeneity seem indispensable (Benton et al, 2003;Lin, 2011).…”

A critical review of the impacts of cover crops on nitrogen leaching, net greenhouse gas balance and crop productivity

“…Garnier, Anglade, & Billen, 2014) cover crops can all reduce N leaching, but with different efficiencies. In the United States,Kaspar, Jaynes, Parkin, Moorman, and Singer (2012) reported that the use of non-legume cover crops (e.g.…”