Agronomie 

About: Agronomie is an academic journal. The journal publishes majorly in the area(s): Hordeum vulgare & Population. It has an ISSN identifier of 0249-5627. Over the lifetime, 2045 publications have been published receiving 40562 citations.

Soil organic matter, biota and aggregation in temperate and tropical soils - Effects of no-tillage

Abstract: The long-term stabilization of soil organic matter (SOM) in tropical and temperate regions is mediated by soil biota (e.g. fungi, bacte- ria, roots and earthworms), soil structure (e.g. aggregation) and their interactions. On average, soil C turnover was twice as fast in tropical com- pared with temperate regions, but no major differences were observed in SOM quality between the two regions. Probably due to the soil mineralogy dominated by 1:1 clay minerals and oxides in tropical regions, we found a higher aggregate stability, but a lower correlation between C contents and aggregate stability in tropical soils. In addition, a smaller amount of C associated with clay and silt particles was observed in tro- pical versus temperate soils. In both tropical and temperate soils, a general increase in C levels (≈ 325 ± 113 kg C·ha -1 ·yr -1 ) was observed under no-tillage compared with conventional tillage. On average, in temperate soils under no-tillage, compared with conventional tillage, CH4 uptake (≈ 0.42 ± 0.10 kg C-CH4·ha -1 ·yr -1

STICS : a generic model for the simulation of crops and their water and nitrogen balances. I. Theory, and parameterization applied to wheat and corn

Abstract: STICS (Simulateur mulTJdiscplinaire pour les Cultures Standard) is a crop model constructed as a simula- tion tool capable of working under agricultural conditions. Outputs comprise the production (amount and quality) and the environment. Inputs take into account the climate, the soi1 and the cropping system. STICS is presented as a model exhibiting the following qualities: robustness, an easy access to inputs and an uncomplicated f~~ture 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 tum 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, clrought resistance, etc.) are not taken into account, the use of STICS is presently limited to several cropping systems. (O InraIElsevier, Paris.) crop modelling / wheat / corn / water balance / nitrogen balance

Rhizodeposition of organic C by plants: mechanisms and controls

Abstract: During their life, plant roots release organic compounds in their surrounding environment. This process, named rhizodeposition, is of ecological importance because (1) it is a loss of reduced C for the plant, (2) it is an input flux for the organic C pool of the soil and (3) it fuels the soil microflora, which is involved in the great majority of the biological activity of soils such as the nutrient and pollutant cycling or the dynamics of soil borne pathogens, for example. The present review first examines the mechanisms by which major rhizodeposits are released into the soil: production of root cap cells, secretion of mucilage, passive and controlled diffusion of root exudates. In a second part, results from tracer studies (43 articles) are analysed and values of C flux from the plant root into the soil are summarized. In average, 17% of the net C fixed by photosynthesis is lost by roots and recovered as rhizosphere respiration (12%) and soil residues (5%), which corresponds to 50% of the C exported by shoots to belowground. Finally, the paper reviews major factors that modify the partitioning of photoassimilates to the soil: microorganisms, nitrogen, soil texture and atmospheric CO2 concentration.

Investigation of a model inversion technique to estimate canopy biophysical variables from spectral and directional reflectance data

Abstract: L'objectif de cette etude etait d'evaluer l'interet des donnees de teledetection pour l'estimation des variables biophysiques des couverts vegetaux. Les donnees considerees etaient acquises au niveau du couvert dans plusieurs directions, pour differentes longueurs d'onde du domaine du visible et du proche infrarouge. Les variables estimees etaient l'indice foliaire, le contenu en chlorophylle des feuilles, la fraction de rayonnement photosynthetiquement actif absorbe par le couvert, et le pourcentage de couverture du sol. Une technique simple d'inversion de donnees basee sur des tables de correspondance a ete utilisee. Dans un premier temps, la taille de la table et le nombre d'elements selectionnes pour obtenir une distribution de la solution ont ete determines. Les performances d'estimation des variables en termes de distributions et de co-distributions des solutions ont ete evaluees dans le cas le plus simple en utilisant les reflectances rouge et proche infrarouge au nadir. L'echantillonnage spectral et directionnel optimal correspondant a la meilleure precision d'estimation de chaque variable consideree a egalement ete determine. Enfin, les effets de l'heterogeneite spatiale, des hypotheses du modele de transfert radiatif utilise pour generer la table de correspondance, ainsi que du bruit radiometrique, sur l'estimation des variables ont ete quantifies. Ces resultats sont discutes en vue de la definition des caracteristiques des capteurs a venir pour obtenir des estimations precises des caracteristiques des couverts vegetaux.

Effect of metal toxicity on plant growth and metabolism: I. Zinc

Abstract: Zinc toxicity and problems with regard to tolerance and ecological significance are briefly discussed. Differential tolerance of plant genotypes exposed to zinc toxicity is a promising approach to enrich our understanding of zinc tolerance in plants. Knowledge concerning the physiology and biochemistry with regard to phytotoxicity, uptake and transport of zinc and tolerance and its characterization are also discussed. The cytotoxic effects of zinc on plants are elucidated. The major change was seen in the nucleus of the root tip cells due to zinc toxicity. The chromatin material was highly condensed and some of the cortical cells showed disruption and dilation of nuclear membrane in presence of 7.5 mM zinc. The cytoplasm became structureless, disintegration of cell organelles and the development of vacuoles were also observed. The number of nucleoli also increased in response to zinc resulting in the synthesis of new protein involved in heavy metal tolerance. This review may help in interdisciplinary studies to assess the ecological significance of metal stress.