## 2 Materials and Methods  
### Experimental Details  
The experimental site is located at the Lusignan INRA (National Institute for Agricultural Research) experimental farm, France (46\({}^{\circ}\)25\({}^{\prime}\)12.91\({}^{\prime\prime}\) N; 0\({}^{\circ}\)07\({}^{\prime}\)29.35\({}^{\prime\prime}\) E), which covers \(\sim\)22 ha (Figure 1). INRA and CNRS (National Centre for Scientific Research) jointly designed the long-term observational study to gain a better understanding of the environmental impacts resulting from different grassland management practices and grassland/cropping rotations. The study site was established on temporary grasslands that were sown in spring 2005 (March-April). Before 2005, part of the observational site was grassland, and the other part was alternated between grass and crop rotations for 17 years. The total surface area of the experimental site was plugughed to establish a base line for the system before sowing grass in 2005. The upper soil horizons are characterized by a loamy texture, classified as Cambisol, whereas lower soil horizons have a clayey texture rich in kaolinite and iron oxides, classified as a Paleo-Ferralsol [58; 59]. The sown grasslands consisted of a mix of three grass species (_Lolium preenne, Festuca arundinacea_, and _Dactylis glomera L_). For the original experiment, the 22 ha of the study area were divided into four blocks of five 0.4 ha plots and four larger plots of 3 ha to test seven different treatments (shown in different colors in Figure 1) [60]. The treatments relevant for the present work are two of the 3 ha plots with pasture being either moved or grazed. The towers footprints are crucial in experimental set up of eddy covariance and a detailed footprint study was performed [26]. The wind rose, which is identical for the two paddocks, is reported in Figure 1. Footprint analysis indicated that ~70% of the median percentage of the footprint was in the field, which is a similar fraction than that found in other similar studies [26]. For the present study, two temporary sworn grasslands paddocks, each of a size of ~3 ha and of rectangular shape, were equipped with two eddy covariance measurement systems and a meteorological station (Figure 1). One of the paddocks was regularly moved (P2), with harvested hay exported off-site to feed animals during periods of insufficient vegetation growth (mainly drought periods and during winter). Dairy cows regularly grazed the other paddock (P4), with all animal exceta directly returned to the paddock, except for the fraction that was deposited off site during milking and during the daily transit times from the milking shed to the field. Both paddocks received regular applications of nitrogen fertilizer, with higher rates applied to the moved than the grazed paddock (Appendix A). For the two contrasting grassland systems studied here, the dates of mowing and grazing, the length of each grazing event, the animal stocking densities, and timing and amounts of N fertilizer applications varied in the different years. Details are given in Appendix A. Over the 5-year study period (2006-2010) the mowed paddock received 1290 kg N ha\({}^{-1}\) split into 17 fertilizer applications and was moved 17 times with 3 cuts per year, except for the wetter than normal summer half-year 2007 (5 cuts). Over the same period, the grazed paddock received 590 kg N ha\({}^{-1}\) (not including N returned in dung and urine during grazing) over 14 applications and was grazed 37 times with grazing events spread, on average, over 5 consecutive days. Figure 1: **(a)** Field site layout of the Agroecosystem Biogeochemical Cycles and Biodiversity (ACBB) experimental farm (22 ha). Different colors are used to distinguish different treatments. The treatments relevant for the present work are shown by stars indicating the location of the eddy covariance masts on the two studied paddocks (P2: mowed paddock; P4: grazed paddock). **(b)** The wind rose shows the frequency and intensity of winds blowing from different directions.