Accumulation and remobilization of nitrogen in a vegetative winter wheat crop during or following nitrogen deficiency

International audienc

Integrated Control of Nitrate Uptake by Crop Growth Rate and Soil Nitrate Availability under Field Conditions

There is still disagreement about whether crop growth rate or soil nitrate concentration control nitrogen absorption by crops under ®eld conditions. The in¯uence of these factors on the control of N uptake rate was examined in the absence of water stress, using data on dry matter production, above-ground nitrogen accumulation and soil nitrate concentration from several N-fertilizer experiments on winter wheat, winter oilseed rape and maize. The results con®rmed that crops can accumulate nitrogen far in excess of the `critical dilution curve', which de®nes the minimum amount of nitrogen needed for maximal growth rate: the N concentration in plants could exceed the critical N concentration by 70 to 80 % for the three species studied. The nitrate uptake rate index (NUI) was calculated as the ratio of actual and critical N uptake rates, at intervals of 1 week. NUI varied with nitrate concentration in the 0±30 cm soil layer according to a Michaelis±Menten equation (with one or two components). This response was compared with the kinetics of saturation of the nitrate uptake systems: the high a�nity transport system (HATS) and the low a�nity transport system (LATS). As a result, it is proposed that there is a critical N dilution curve delimiting two domains of N use by plants. This is linked to the two nitrate transport systems, with HATS working at low nitrate concentrations, below the critical dilution curve, and LATS at high nitrate concentrations, above the curve. NUI provides another method for calculating the actual nitrate uptake rate, which depends on the maximal crop growt

Effect of take-all root infections on nitrate uptake in winter wheat

International audienc

Nitrate uptake rate by soybean and wheat plants determined by external nitrate concentration and shoot-mediated demand

2 tables 3 graph.International audienc

A simplified conceptual model of carbon/nitrogen functioning for QTL analysis of winter wheat adaptation to nitrogen deficiency

International audienc

Differential change in root protein patterns of two wheat varieties under high and low nitrogen nutrition levels

International audienc

Fonctionnement d'un peuplement de blé en conditions de nutrition azotée sub-optimale

National audienc

Les transferts dans STICS

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STICS : un modèle générique pour simuler les cultures et leurs bilans hydrique et azoté. I. Théorie et paramétrage appliqués au blé et au maïs

International audienceSTICS (Simulateur mulTIdiscplinaire pour les Cultures Standard) is a crop model constructed as a simulation tool capable of working under agricultural conditions. Outputs comprise the production (amount and quality) and the environment. Inputs take into account the climate, the soil and the cropping system. STICS is presented as a model exhibiting the following qualities: robustness, an easy access to inputs and an uncomplicated future evolution thanks to a modular (easy adaptation to various types of plant) nature and generic. However, STICS is not an entirely new model since most parts use classic formalisms or stem from existing models. The main simulated processes are the growth, the development of the crop and the water and nitrogenous balance of the soil-crop system. The seven modules of STICS - development, shoot growth, yield components, root growth, water balance, thermal environment and nitrogen balance - are presented in turn with a discussion about the theoretical choices in comparison to other models. These choices should render the model capable of exhibiting the announced qualities in classic environmental contexts. However, because some processes (e.g. ammoniac volatilization, drought resistance, etc.) are not taken into account, the use of STICS is presently limited to several cropping systems. (© Inra/Elsevier, Paris.)STICS est un modèle de culture conçu comme un outil de simulation opérationnel en conditions agricoles. Ses variables de sortie sont relatives à la production, à la fois en quantité et en qualité, et à l’environnement. Ses entrées sont relatives au climat, au sol et au système de culture. STICS est présenté comme un modèle montrant les qualités suivantes : robustesse, facilité d’accès aux données d’entrée, souplesse d’évolution par une présentation modulaire et généricité (facilité d’adaptation à divers types de plantes). Pourtant, il ne s’agit pas d’un modèle entièrement nouveau dans les formalismes utilisés. Ils sont, pour la plupart, issus de modèles existants. Les grands processus simulés sont la croissance et le développement de la culture ainsi que les bilans hydrique et azoté du système sol-culture. Les sept modules de STICS sont décrits successivement avec une discussion sur les choix théoriques comparés à ceux d’autres modèles : développement, croissance aérienne, composantes du rendement, croissance racinaire, bilan hydrique, environnement thermique de la culture, bilan azoté. Il ressort que ces choix confèrent à priori au modèle les qualités annoncées dans un contexte environnemental classique. Cependant, l’absence de prise en compte de certains processus (exemples : volatilisation de l’ammoniac, résistance à la sécheresse, ...) restreint pour l’instant son utilisation à certains systèmes de culture. (© Inra/Elsevier, Paris.