Liming impacts barley yield over a wide concentration range of soil exchangeable cations

Liming has widespread and significant impacts on soil processes and crop responses. The aim of this study was to describe the relationships between exchangeable cation concentrations in soil and the relative yield of spring barley. The hypothesis was that yield is restricted by the concentration of a single exchangeable cation in the soil. For simplicity, we focused on spring barley which was grown in nine years of a long-term experiment at two sites (Rothamsted and Woburn). Four liming rates were applied and in each year the relative yield (RY) and the concentrations of exchangeable cations were assessed. Liming had highly significant effects on the concentrations of most exchangeable cations, except for Cu and K. There were significant negative relationships (either linear or exponential) between the exchangeable concentrations of Mn, Cd, Cr, Al, Fe, Cu, Co, Zn and Ni in soil and soil pH. The relationships between RY and the concentrations of selected exchangeable cations (Mn, Ca and Al) were described well using log-logistic relationships. For these cations a significant site effect was probably due to fundamental differences in soil properties. At both sites the concentrations of exchangeable soil Al were excessive ([ 7.5 mg kg-1) and were most likely responsible for reduced barley yields (where RY B 0.5) with soil acidification. At Rothamsted barley yield was nonlimited (where RY C 1) at soil exchangeable Mn concentrations (up to 417 mg kg-1) greater than previously considered toxic, which requires further evaluation of critical Mn concentrations

Are current dynamic water quality models too complex? A comparison of a new parsimonious phosphorus model, SimplyP, and INCA-P

Catchment-scale water quality models are becoming increasingly popular tools for exploring the potential effects of land management, land use change and climate change on water quality. However, the dynamic, catchment-scale nutrient models in common usage are complex, with many uncertain parameters requiring calibration, limiting their usability and robustness. A key question is whether this complexity is justified. To explore this, we have developed a parsimonious P model, SimplyP, incorporating a coupled rainfall-runoff model and a biogeochemical model able to simulate streamflow, suspended sediment, particulate and dissolved P dynamics. The model’s complexity is compared in a small rural catchment in northeast Scotland. For three land use classes, less than six SimplyP model parameters must be determined through calibration alone, the rest may be based on measurements; INCA-P has around 40 unmeasurable parameters. Despite simpler process-representation, SimplyP produced a slightly better dissolved P simulation during both calibration and validation, and produced similar long-term projections in response to changes in land management. Results support the hypothesis that INCA-P is overly complex for the study catchment. We hope our findings will help prompt wider model comparison exercises, as well as debate amongst the water quality modelling community as to whether today's models are fit for purpose. Simpler models such as SimplyP have the potential to be useful management and research tools, building blocks for future model development (prototype code is freely available), or benchmarks against which more complex models could be evaluated

FERTILISATION STRATEGIES ACROSS EUROPE: CURRENT SITUATION, POTENTIAL AND LIMITS FOR A HARMONISED APPROACH

Peer reviewe

Soluble phosphorus dynamics in an agricultural watershed

Both particulate phosphorus (PP) and soluble phosphorus (SP) contribute to the eutrophication of water bodies. This research focuses on the mechanisms and factors controlling SP exports at the watershed scale in a case study located in Southern France. Variability in the P concentrations and fluxes was analysed over a period of 6 years in a 302-ha rural watershed. During most of the hydrological periods, reservoirs and pathways for PP and SP seemed to be different both in time and space; differences were greatest during storm flows of the early wet season. Their high SP fluxes and concentrations were due to the P released from agricultural soils as shown by a P mass balance downstream/upstream. During these flushing periods, soluble forms of P follow a hydrochemical behaviour quite similar to solutes and are transferred in relationship to subsurface flows, as shown by a detailed monitoring of the transition from dry to wet season on an agricultural sub-watershed

Analyse des exportations de phosphore d’origine diffuse d’un bassin versant rural

International audiencePhosphorus is an important pollutant leading to lake eutrophication. Diffuse pollution accounts for a substancial share of the total phosphorus load. To improve our knowledge of this pollution, we conducted a watershed study in a small, rural, 302-ha watershed (Lake Léman area). To study the spatial distribution and temporal dynamics of phosphorus in the watershed and the corresponding variation in phosphorus speciation, 40 stormflow events over a 4- year period were analysed. We began by defining the ’state’ of the watershed using a) periodic field surveys of signs of erosion, b) the length of the flowing ditches and streams (active hydrological network) and the waterpathways on the fields, c) the overall water budget, and d) grab samples of stream water from a network of subwatersheds. Four states that reflected contrasting watershed conditions were identified. Analysis of the data on phosphorus flux at the outlet of the watershed, in conjunction with the observations on the state of the watershed, allowed us to develop a conceptual model of phosphorus export from the watershed and several hypotheses about phosphorus transfer. (© Inra/Elsevier, Paris.)On cherche, à travers l’étude d’un bassin versant rural, à identifier les mécanismes de la pollution diffuse phosphorée, ses modalités d’émission et de transport et ses impacts potentiels sur les milieux récepteurs. Les exportations de phosphore ont été étudiées pendant 4 ans sur le Mercube, bassin versant rural de 302 ha sans pollution ponctuelle, situé sur la rive française du Léman. Le principe de l’étude consiste à comparer des « états de bassin » avec des flux et des spéciations mesurés à son exutoire. La définition de l’état de bassin repose sur des campagnes d’observation et de mesures des écoulements présents sur le bassin versant. Quatre états reflétant des situations hydriques contrastées ont été définis. Ils se distinguent par la diversité spatiale des différents stocks de phosphore mis en jeu. Leur succession saisonnière décrit un cycle étroitement lié aux cycles culturaux et météorologiques. Afin de comprendre l’influence de ces états sur les quantités de phosphore émises vers le lac et sur sa spéciation, une quarantaine de crues ont été échantillonnées à l’exutoire du bassin.Cette analyse des transferts diffus de phosphore nous amène à proposer un modèle typologique des exportations de phosphore. Elle aboutit aussi à renouveler les conceptions concernant les processus de transfert des formes solubles et particulaires de phosphore. (© Inra/Elsevier, Paris.

Approche expérimentale par crue artificielle de la participation du réseau hydrographique à l'exportation de phosphore par un petit bassin versant rural

International audienc

Analysis of the export of diffuse phosphorus from a small rural watershed

Phosphorus is an important pollutant leading to lake eutrophication. Diffuse pollution accounts for a substancial share of the total phosphorus load. To improve our knowledge of this pollution, we conducted a watershed study in a small, rural, 302-ha watershed (Lake Léman area). To study the spatial distribution and temporal dynamics of phosphorus in the watershed and the corresponding variation in phosphorus speciation, 40 stormflow events over a 4- year period were analysed. We began by defining the ’state’ of the watershed using a) periodic field surveys of signs of erosion, b) the length of the flowing ditches and streams (active hydrological network) and the waterpathways on the fields, c) the overall water budget, and d) grab samples of stream water from a network of subwatersheds. Four states that reflected contrasting watershed conditions were identified. Analysis of the data on phosphorus flux at the outlet of the watershed, in conjunction with the observations on the state of the watershed, allowed us to develop a conceptual model of phosphorus export from the watershed and several hypotheses about phosphorus transfer. (© Inra/Elsevier, Paris.)On cherche, à travers l’étude d’un bassin versant rural, à identifier les mécanismes de la pollution diffuse phosphorée, ses modalités d’émission et de transport et ses impacts potentiels sur les milieux récepteurs. Les exportations de phosphore ont été étudiées pendant 4 ans sur le Mercube, bassin versant rural de 302 ha sans pollution ponctuelle, situé sur la rive française du Léman. Le principe de l’étude consiste à comparer des « états de bassin » avec des flux et des spéciations mesurés à son exutoire. La définition de l’état de bassin repose sur des campagnes d’observation et de mesures des écoulements présents sur le bassin versant. Quatre états reflétant des situations hydriques contrastées ont été définis. Ils se distinguent par la diversité spatiale des différents stocks de phosphore mis en jeu. Leur succession saisonnière décrit un cycle étroitement lié aux cycles culturaux et météorologiques. Afin de comprendre l’influence de ces états sur les quantités de phosphore émises vers le lac et sur sa spéciation, une quarantaine de crues ont été échantillonnées à l’exutoire du bassin.Cette analyse des transferts diffus de phosphore nous amène à proposer un modèle typologique des exportations de phosphore. Elle aboutit aussi à renouveler les conceptions concernant les processus de transfert des formes solubles et particulaires de phosphore. (© Inra/Elsevier, Paris.

Comparison of Nitrogen Fertiliser recommendations in different West European countries

Nitrogen (N) budget at farm level is influenced by the fertilisation rates applied by farmers. At larger scales, it is closely linked to multiple environmental concerns relating to air, water and biodiversity. In this study, we analysed the way the N fertilisation recommendations are calculated in ten West European countries, in order to detect innovative algorithms, original calculations and references that could be shared among countries having equivalent crop practices. Our first result relates to published national official documents governing N fertilisation within each country. A detailed analysis of these documents reveals three categories of calculation methods: (i) ‘N mass balance’ (France, Italy, Spain), (ii) ‘Corrected standard’ (Germany, the Netherlands, Switzerland, Luxembourg), and (iii) ‘Pre-parameterised calculation’, relying on a soil N supply typology (United Kingdom, Ireland) or on a model parameterisation (Belgium). Sixteen parameters were identified throughout the 10 national methods. The more complex algorithms use 10 parameters (Italy, France), while the simplest only rely on 3 (Luxembourg). The most common parameters considered include the direct effect of N concentration in manure, the total N uptake by crop and the N released by crop residues. At the opposite end, very few countries explicitly take N leaching, the residual mineral N in soil at harvest and atmospheric losses into consideration. In addition to the previous theoretical approach, we have tested the extent to which the different methods converge or not when practically used. We therefore applied the ten national methods to two contrasting crop scenarios chosen in order to erase as much as possible the cultural and pedoclimatic specificities between the ten countries. The two case studies display large discrepancies in their recommendations, ranging from no fertilisation to 135 kg N/ha, and from 111 to 210 kg N/ha for a wheat crop fertilisation grown in a livestock and polyculture-farm scenario, respectively. The differences in the recommended rate are not accounted for by the complexity of the equations used. For the same conclusions, we identified differences in the consideration of manure’s N availability, N uptake by crop (even for the same yield) and in the leaching of N calculation. The degree of regulatory status of the calculation methods was a more interesting parameter. Two countries exhibit original tools that we consider worth highlighting: parallel to a simplified field N mass balance, Germany performs a second compulsory mass-balance at the farm scale considered to be a safeguard against risks of excess N budget. Another effective tool, implemented by Belgium, consists of controlling the residual soil mineral N at harvest in comparison to regional references