Life cycle assessment of Swiss organic farming systems

The impacts of organic and integrated farming systems in Switzerland on the environment have been assessed in a comprehensive study by the life cycle assessment method. This paper reports a comparison of the treatments of the DOC experiment. Organic farming showed clear ecological advantages particularly for eco- and human toxicity, resource use and biodiversity. These ecological advantages only partly apply to nutrient losses and are not always found for single products. Per kg of organic product, higher impacts were often found for global warming potential, ozone formation, eutrophication and acidification compared to integrated production. In the same crop rotation with the same amount of organic fertilisers there were no systematic differences in soil quality of organic compared with integrated production. Further improvement of the environmental performance of organic farming should focus on achieving higher yields of good quality – especially in potatoes and cereals - by using inputs more efficiently and minimising nitrogen losses

Multifunctionality of Sown Grassland Is Enhanced by Combining Four Complementary Species

We investigated species diversity effects and multifunctionality in an intensively managed grassland. A diversity experiment was set up with monocultures and mixtures comprising Lolium perenne, Dactylis glomerata, Trifolium pratense, and Trifolium repens, and was maintained for three years at 150 kg∙N∙ha-1∙ year-1. Ten functions were measured that represented i) forage production (aboveground biomass yield (μ), standard deviation of yield (σ), temporal stability (μ/σ), weed biomass), ii) N cycling (symbiotic-N2-fixation, N efficiency, NO3 in soil solution), and forage quality (crude protein content (CP), organic matter digestibility (OMD), metabolizable energy (ME)). We applied multivariate linear mixed-effects regression to estimate simultaneously species identity and diversity effects on the ten functions, and used the mean log response ratio (MLRR) across all functions to evaluate the diversity-multifunctionality relationship. Across the three years, all functions regarding production and N cycling revealed significant beneficial effects in the four-species equi-proportional mixture (used as a reference) compared to averaged monocultures. The reference mixture had 61% more biomass yield, 8% less variation, 68% higher stability, 81% less weed biomass, 96% and 46% higher symbiotic-N2-fixation and N-efficiency, respectively, and 87% less NO3 (each P ≤ 0.05, except variation). The reference mixture and averaged monocultures did not significantly differ in CP, OMD (g∙kg-1∙yield), and ME (MJ∙kg-1∙yield). This, however, resulted in significant beneficial effects between 52% and 72% in all three forage quality functions on a hectare basis (kg or MJ∙ha-1∙year-1). On average across functions, the four-species reference mixture had 1.8 times the performance of averaged monocultures, indicating enhanced multifunctionality in mixtures. The multivariate framework in combination with the MLRR as a measure of overall multifunctionality proved to be an effective tool for the evaluation of the diversity-multifunctionality relationship. We conclude that sown grass-legume mixtures at moderate N fertilization promote high multifunctionality and are a ‘ready-to-use’ option for sustainable intensification of agriculture

The effects of water regime on phosphorus responses of rainfed lowland rice cultivars

Background and Aims Soil phosphorus (P) solubility declines sharply when a flooded soil drains, and an important component of rice (Oryza sativa) adaptation to rainfed lowland environments is the ability to absorb and utilize P under such conditions. The aim of this study was to test the hypothesis that rice cultivars differ in their P responses between water regimes because P uptake mechanisms differ. Methods Six lowland rice cultivars (three considered tolerant of low P soils, three sensitive) were grown in a factorial experiment with three water regimes (flooded, moist and flooded-then-moist) and four soil P levels, and growth and P uptake were measured. Small volumes of soil were used to maximize inter-root competition and uptake per unit root surface. The results were compared with the predictions of a model allowing for the effects of water regime on P solubility and diffusion. Key Results The plants were P stressed but not water stressed in all the water regimes at all P levels except the higher P additions in the flooded soil. The cultivar rankings scarcely differed between the water regimes and P additions. In all the treatments, the soil P concentrations required to explain the measured uptake were several times the concentration of freely available P in the soil. Conclusions The cultivar rankings were driven more by differences in growth habit than specific P uptake mechanisms, so the hypothesis cannot be corroborated with these data. Evidently all the plants could tap sparingly soluble forms of P by releasing a solubilizing agent or producing a greater root length than measured, or both. However, any cultivar differences in this were not apparent in greater net P uptake, possibly because the restricted rooting volume meant that additional P uptake could not be converted into new root growth to explore new soil volume

Positive Mischungseffekte auf Ertrag und Stickstoffversorgung in Klee-Gras-Mischungen

High plant species richness has been shown to positively influence grassland biomass production. In mixtures containing two forage grass and two forage legume species we quantified the diversity-productivity effect and the nitrogen economy of the swards across a broad range of species proportions. Positive diversity-productivity effects resulted in higher yield (up to +35%) of the four-species grass-clover-mixtures than the highest yielding monoculture (transgressive overyielding). The diversity-productivity effect depended on the species proportion in the mixture and was maximal in well balanced mixtures with a clover proportion of 40 – 60%. Transgressive overyielding was significant over a fairly wide range of clover proportions. Well balanced grassclover- mixtures allowed obtaining up to 320 kg N ha-1 yr-1 deriving from symbiotic N2 fixation and allowed an optimal transformation of fixed N into dry matter yield. These mixtures allowed benefiting from maximal fixation activity of the legumes without reducing the uptake of N from soil and fertiliser by the grasses in the sward

Filling the gap in functional trait databases: Use of ecological hypotheses to replace missing data

Functional trait databases are powerful tools in ecology, though most of them contain large amounts of missing values. The goal of this study was to test the effect of imputation methods on the evaluation of trait values at species level and on the subsequent calculation of functional diversity indices at community level using functional trait databases. Two simple imputation methods (average and median), two methods based on ecological hypotheses, and one multiple imputation method were tested using a large plant trait database, together with the influence of the percentage of missing data and differences between functional traits. At community level, the complete-case approach and three functional diversity indices calculated from grassland plant communities were included. At the species level, one of the methods based on ecological hypothesis was for all traits more accurate than imputation with average or median values, but the multiple imputation method was superior for most of the traits. The method based on functional proximity between species was the best method for traits with an unbalanced distribution, while the method based on the existence of relationships between traits was the best for traits with a balanced distribution. The ranking of the grassland communities for their functional diversity indices was not robust with the complete-case approach, even for low percentages of missing data. With the imputation methods based on ecological hypotheses, functional diversity indices could be computed with a maximum of 30% of missing data, without affecting the ranking between grassland communities. The multiple imputation method performed well, but not better than single imputation based on ecological hypothesis and adapted to the distribution of the trait values for the functional identity and range of the communities. Ecological studies using functional trait databases have to deal with missing data using imputation methods corresponding to their specific needs and making the most out of the information available in the databases. Within this framework, this study indicates the possibilities and limits of single imputation methods based on ecological hypothesis and concludes that they could be useful when studying the ranking of communities for their functional diversity indices. (Résumé d'auteur

Seasonal dynamics and turnover of microbial phosphorusin a permanent grassland

Microbial activity is known to be high under permanent grassland, but consequences for soil phosphorus (P) dynamics and availability are not well understood. Our main objective was to assess the microbial P turnover derived from the seasonal fluctuations in microbial P (measured as hexanol-labile P (Phex) at 13 sampling times during 9months) in a permanent grassland in Switzerland as affected by different P fertilization treatments (P inputs of 0 (NK) or 17kgPha−1year−1 in the form of superphosphate (NPK) or dairy slurry (DS)). Plant P uptake, available inorganic P measured as resin-extractable P (Pres), potential organic P mineralization indicated by acid phosphomonoesterase activity and climatic conditions were also recorded. Despite significant differences in plant P uptake and Pres (NPK > DS > NK), the turnover rate of Phex was similar in all treatments (approximately once per growing season). Thus, the seasonal P flux through Phex was similar to the stock of Phex, which was about 18, 25 and 37kgPha−1 in NK, NPK and DS, respectively, and larger than the corresponding seasonal plant P uptake of 6, 17 and 12kgPha−1. The estimate of Phex turnover based on seasonal dynamics did not confirm previous tracer-based findings of a much faster Phex turnover under low availability of inorganic P, and the magnitude of Phex turnover depended on the number of sampling points taken into account. Fluctuations in Pres and Phex were related to soil moisture and indicated competition between plants and microorganisms for available P

Modelling biological N fixation and grass-legume dynamics with process-based biogeochemical models of varying complexity

This work was conducted by the Models4Pastures consortium project under the auspices of FACCE-JPI. Funding was provided by: the New Zealand Government to support the objectives of the Livestock Research Group of the Global Research Alliance on Agricultural Greenhouse Gases; AgResearch’s Strategic Science Investment Fund as a contribution to the Forages for Reduced Nitrate Leaching (FRNL) research programme; the input of UK partners was funded by DEFRA and also contributes to the RCUK-funded projects: N-Circle (BB/N013484/1), UGRASS (NE/M016900/1) and GREENHOUSE (NE/K002589/1). R.M. Rees and C.F.E. Topp also received funding from the Scottish Government Strategic Research Programme. Lutz Merbold and Kathrin Fuchs acknowledge funding received for the Swiss contribution to Models4Pastures (FACCE-JPI project, SNSF funded contract: 40FA40_154245/1) and for the Doc.Mobility fellowship (SNSF funded project: P1EZP2_172121). Lorenzo Brilli, Camilla Dibari and Marco Bindi acknowledge funding received from the Italian Ministry of Agricultural Food and Forestry Policies (MiPAAF).Peer reviewedPublisher PD

Assessment of spatial variability of multiple ecosystem services in grasslands of different intensities

Grasslands provide multiple Ecosystem Services (ES) such as forage provision, carbon sequestration or habitat provision. Knowledge about the trade-offs between these ES is of great importance for grassland management. Yet, the outcome of different management strategies on ES provision is highly uncertain due to spatial variability. We aim to characterize the provision (level and spatial variability) of grassland ES under various management strategies. To do so, we combine empirical data for multiple ES with spatially explicit census data on land use intensities. We analyzed the variations of five ES (forage provision, climate regulation, pollination, biodiversity conservation and outdoor recreation) using data from biodiversity fieldwork, experimental plots for carbon as well as social network data from Flickr. These data were used to calculate the distribution of modelled individual and multiple ES values from different grassland management types in a Swiss case study region using spatial explicit information for 17,383 grassland parcels. Our results show that (1) management regime and intensity levels play an important role in ES provision but their impact depends on the ES. In general, extensive management, especially in pastures, favors all ES but forage provision, whereas intensive management favors only forage provision and outdoor recreation; (2) ES potential provision varies between parcels under the same management due to the influence of environmental drivers, related to topography and landscape structure; (3) there is a trade-offs between forage provision and other ES at the cantonal level but a synergy between forage provision and biodiversity conservation within the grassland categories, due to the negative impact of elevation on both ES. Information about multiple ES provision is key to support effective agri-environmental measures and information about the spatial variability can prevent uncertain outputs of decision-making processes