Reconnecting crop and cattle farming to reduce nitrogen losses to river water of an intensive agricultural catchment (Seine basin, France): past, present and future

Abstract

International audienceNitrate and pesticide contamination of surface and groundwater has become a major problem in intensive farming regions in Europe, with nitrate concentrations reaching values above the standard defined in 2000 by the European Water Framework Directive. In the Seine basin, a major issue is the closure and abandonment of drinking-water wells, which force water managers and drinking-water producers to explore solutions for water resource protection. Organic farming has appeared as a credible alternative to conventional farming, and this study explores the potential of organic farming to reconcile agricultural production and water quality. On the basis of agricultural statistics, survey questionnaires and experimental data, the nitrogen soil surface balance (N-SSB) has been established at the scale of a small 104-km 2 catchment (The Orgeval sub-basin), representative of the intensive cash crop farming in the Seine basin. The N-surplus for arable land in specialized organic cash crop systems has been found to be half that of current conventional systems (15 kg N ha À1 yr À1 versus 30 kg N ha À1 yr À1 , respectively). The N-yield in organic systems is 21% lower than in conventional systems, but total fertilization (mostly symbiotic N fixation) is also 26% lower. Whereas 2–3 years of forage legume (e.g., alfalfa) as a starter crop of the typical 7-to 10-year diversified rotation builds up N soil fertility and helps prevent weeds without pesticides, the existence of an outlet for this fodder production is a limiting factor for the economic sustainability and the environmental benefits of these farming systems. Therefore, we explored the possibility of a reconnection of livestock and crop farming systems in the Orgeval catchment, a traditional dairy farming and Brie cheese production region. We calculated the N-SSB for this type of a reconnected livestock and cropping system and found a value very close to the specialized organic cash crop system with full utilization of fodder production, leading to profitable animal production, essentially as milk in this farm design. This reconnected system is compared with the estimated situation in 1955 before separation of plant and livestock production. Furthermore, the N-SSB values were converted into infiltrating sub-root concentrations and used as a boundary condition to a biogeochemical model. Organic cropping and organic reconnected livestock cropping systems result in a 50% reduction of surface water nitrate concentrations, a surface water quality 20% better than that reconstructed for 1955, with an overall higher protein production

Chemical weathering and CO2 consumption rate in a multilayered‐aquifer dominated watershed under intensive farming: The Orgeval Critical Zone Observatory, France

“…The highest concentrations of K + and NO 3 − recorded during the spring season (April and June 2014) are suggestive of a fertilizer‐type source. High concentrations of K + and NO 3 − are recorded between March and May when farmers spread fertilizers, mainly in the form of manure and N‐P‐K‐rich fertilizers (Garnier et al, ).…”

“…A classical tracer for such purpose is Cl − (Hagedorn & Whittier, ; Stallard & Edmond, ). However, at the Orgeval CZO, Cl − cannot be used as a proxy for seawater inputs to the rivers due to the fact that Cl − is contained within mineral fertilizers such as K‐Cl (Garnier et al, ). For example, this is shown by the excess in Cl − (compared with Na + ) shown by most Mélarchez River samples, particularly during the dry season, when the river is fed by the superficial aquifers from the loamy layer (Figure ).…”

“…The role of agricultural practices on organic carbon dynamics and erosion has been documented by previous work (Van Oost et al, ; Quinton, Govers, Van Oost, & Bardgett, ). The importance of N and P fertilization on biogeochemical cycles at the watershed scale in Europe has been addressed in a number of studies (Garnier et al, ) and at the Orgeval CZO specifically (i.e., Billen et al, ; Mulholland et al, ). Altogether, these studies have demonstrated how agricultural practices have strongly modified the global cycles of C, P, and N. About half, the applied N in fertilizers is incorporated into crops that are harvested from fields and used for human food and livestock feed.…”

Advances in NANI and NAPI accounting for the Baltic drainage basin: spatial and temporal trends and relationships to watershed TN and TP fluxes

“…Inefficient use of manure N and P can result from mismatches between the locations of intensive livestock production and areas of crop production, and associated losses in transport and handling of manure (Oenema et al 2007). Bringing livestock and crop production closer together, and applying manure and mineral fertilizer at levels closer to the apparent net crop demand should see improvements in both agricultural efficiency and environmental quality (Nesme et al 2015;Garnier et al 2016).…”

Effect of Nitrogen Fertilizer and Seeding Rate on Yield of Alfalfa and Weeds

“…Weed affects the stability of alfalfa stands because of competition with alfalfa for light, nutrients, and water resources, which result in decreased yields and quality [10][11]. Herbicide application is a widespread practice in many production systems for efficient weed control, but they have the potential to cause serious environmental pollution [12], particularly of ground and surface water [13][14]. In addition, some weeds become Pol.…”