Citrate Root Exudation under Zn and P Deficiency

Zinc and phosphorus are essential nutrients with low bioavailability in calcareous soils. Some plants exude organicacids to increase the solubility of these two nutrients. The objective of this study was to examine citrate exudation rates of different lupin (Feodora and Energy) and rapeseed (Dunkeld, Yickadee and Rainbow) cultivars under deficiencies of Zn and P. The plants were cultivated into three different nutrient solutions (complete, -Zn, and -P) with pH around 7. Under Zn deficiency, rapeseed cultivars lost about 80% of its shoot fresh weight, but the roots did not exude any organic acids such as citrate, malate or oxalate. Both lupin and rapeseed cultivars exuded citrate onlyunder phosphorus deficiency. The exudation rates of Feodora and Energy were 3.89 μmol g-1 RDW h-1 and 3.45 μmol g-1 RDW h-1, respectively, while that of Dunkeld was 15.1 μmol g-1 RDW h-1. The results indicated that lupin and rapeseed lost their production under Zn deficiency but they did not exude organic acid, while under P deficiency both plants exuded citrate.Keywords: Citrate; deficiency; exudation rate; lupin; phosphorus; rapeseed; Zn[How to Cite: Siane BAE. 2012. Citrate Root Exudation under Zn and P Deficiency. J Trop Soils, 17 (3) : 219-225. doi: 10.5400/jts.2012.17.3.219][Permalink/DOI: www.dx.doi.org/10.5400/jts.2012.17.3.219]

Spatial Distribution of Trace Elements in Rice Field at Prafi District Manokwari

Mapping spatial variability of trace elements in rice Ḁeld is necessary to obtain soil quality information to en-hance rice production. ἀis study was aimed to measure concentration and distribution of Zn, Cu, Fe, Pb, and Cd in two diᴀerent sites (SP1, SP2) of PraḀ rice Ḁeld in Manokwari West Papua. ἀe representative 26 soil samples were analysed for their available trace metal concentration (DTPA), soil pH, and C-organic and soil texture. ἀe result indicated that Fe toxicity and Zn deḀcient problems were encountered in both sites.  Rice Ḁeld in SP2 was more deḀcient in Zn than SP1. Site with the highest trace elements (Zn, Fe, Cu, and Cd) concentration had low soil pH and high C-organic. Acidic soil has higher solubility of metals; while high C-organic could improve the formation of dissolve organic carbon-metal binding, hence it improving the trace metals concentration in soil solution

Salinisation des terres agricoles dans les zones côtières ˸ analyse des sols et des eaux, de l’échelle du paysage à celle de l’agrégat de sol

Salinization of water and soil is a major process of degradation of arable land. At the same time, salt and salt areas, such as estuaries, are hot spots for biodiversity. These areas should therefore be considered as complex systems that need to be studied in order to preserve their ability to perform different ecosystem functions and services.The work of thesis is positioned in the global framework of the understanding of the evolution of agricultural lands of coastal margins, subjected to the processes of salinization. The main objective was to contribute to the production of knowledge on the functioning of these systems, with a view to proposing sustainable remediation strategies. For this we have adopted a multi-step approach, based on observation and analysis of the system at different levels of organization: from the production perimeter to the soil aggregate. Specifically, we conducted our study on the town of Sérignan (Hérault - France) downstream of the Orb river basin.Landscape-level observations required easy-to-access characterization methods that allowed for high throughput analysis. We have therefore opted for methods based on the measurement of the electrical conductivity of soils and water. The analysis of the spatial distribution of the variable "electrical conductivity" allowed us to quantify salt pressure, identify salt sources and specify the nature of the processes responsible for increasing salt concentrations in the root area. Then, in order to gather our observations and hypotheses in a formalism that represents the salinization process, we have constructed a conceptual model of the water flows between the different compartments that make up this complex system.The observation at the landscape level, also allowed us to identify six reference plots, suitable to translate different hydro-pedological operations. On these plots, the detailed morpho-structural and geochemical analysis of the soil profiles as well as the monitoring of the piezometric levels allowed us to test the robustness of the structural stability as an indicator of the capacity of the soils to perform their functions. This overall assessment at the soil profile level seemed relevant to us i) to judge the overall salt leaching capacity, and ii) to integrate the entire root volume surveyed by the vine. The correlative analysis shows that A horizon horizons (MWD) appear to be more dependent on land cover, organic matter content and clay fraction whereas for B horizons, stability values are more correlated with the salt content strongly related to the presence of the underlying saturated zone. Moreover, the detailed analysis of the Na+ and Cl- contents suggests that the salts are precipitated in the pore volume, rather than adsorbed (Na+ case) on the CEC. There is therefore a potential for "desalination", without the need for desorption, based on the solution, leaching and export of solutes via the drainage network.Finally, for these 6 plots, we compared the physico-chemical characteristics and the microbiological activity of the A horizons. Here, our interest was in the global evaluation of the mineralization potential function of organic matter from respiration measurements, using MicroRespTM devices. We have shown that for A horizons, structural stabilities were significantly higher in wasteland conditions than in vineyard conditions. However, these wasteland conditions had the highest values for the electrical conductivity of soils. One possible explanation is that stability is more important in relation to the higher organic matter content at the surface of the fallow soils, as well as higher levels of labile carbon. This explanation is consistent with the observation of plant cover dominated by species inducing rhizodepositions. In addition, some studies suggest that the labile fraction of organic carbon and total nitrogen increase the potential for macro-aggregation, especially for fallow soils.La salinisation des eaux et des sols constitue un processus majeur de dégradation des terres arables. Dans le même temps, les zones sodiques et salines telles que les estuaires, constituent des hot-spot de biodiversité. Ces zones doivent donc être considérés comme des systèmes complexes qu’il est nécessaire d’étudier afin de préserver leur capacité à assurer différentes fonctions et services écosystémiques.Le travail de thèse se positionne dans le cadre global de la compréhension de l’évolution des terres agricoles de marges côtières, soumises aux processus de salinisation. L’objectif principal était de contribuer à la production de connaissances sur le fonctionnement des ces systèmes, en vue de proposer des stratégies de remédiation durables. Une démarche d'adaptation en plusieurs étapes, fondée sur l’observation et l’analyse du système à différents niveaux d’organisation : du périmètre de production à l’agrégat de sol. Nous avons mené notre étude sur la commune de Sérignan (Hérault - France) en aval du bassin du fleuve Orb.L’observation au niveau du paysage nécessitait adopter des méthodes de caractérisations faciles d’accès et autorisant un haut débit d’analyse. Des méthodes fondées sur la mesure de la conductivité électrique des sols et des eaux. L’analyse de la distribution spatiale de la variable « conductivité électrique », nous a permis de quantifier la pression saline, d’identifier les sources de sel et de préciser la nature des processus responsables de l’augmentation des concentrations en sel dans la zone racinaire. Nous avons construit un modèle conceptuel des flux d’eau entre les différents compartiments constitutifs de ce système complexe que représenter le processus de salinisation.L’observation au niveau du paysage, nous a aussi permis d’identifier six parcelles de référence, propres à traduire différents fonctionnements hydro-pédologiques. Sur ces parcelles, l’analyse morpho-structurale et géochimique fine des profils de sol ainsi que le suivi des niveaux piézométriques nous a permis de tester la robustesse de la stabilité structurale comme indicateur de la capacité des sols à assurer leurs fonctions. Cette évaluation globale à l’échelon du profil de sol nous semblait pertinente i) pour juger de la capacité globale de lixiviation des sels, et ii) pour intégrer l’ensemble du volume racinaire prospecté par la vigne. L’analyse corrélative montre que les stabilités (MWD) des horizons. A semblent plus dépendantes de l’occupation des sols, de la teneur en matière organique et de la fraction argileuse alors que pour les horizons B, les valeurs de stabilité sont plus corrélées à la teneur en sels fortement liée à la présence de la zone saturée sous-jacente. Par ailleurs, l’analyse détaillée des teneurs en Na+ et Cl- suggère que les sels sont précipités dans le volume poral, plutôt qu’adsorbés (cas de Na+) sur la CEC. Il existe donc un potentiel de « désalinisation », sans nécessité de désorption, fondé sur la mise en solution, lixiviation et exportation des solutés via le réseau de drainage.Enfin, pour ces 6 parcelles, nous avons confronté, les caractéristiques physico-chimiques et l’activité microbiologique des horizons A. Là, notre intérêt s’est porté sur l’évaluation globale de la fonction de potentiel de minéralisation des matières organiques à partir de mesures de respiration, à l’aide des dispositifs de type MicroRespTM. Nous avons montré que pour les horizons A, les stabilités structurales étaient significativement plus élevées en conditions de friches qu’en condition de vignoble. Pourtant, ces conditions de friches présentaient les valeurs les plus élevées pour la conductivité électrique des sols. Une explication possible est que la stabilité soit plus importante en relation à la teneur en matière organique plus élevée en surface des sols en friches, ainsi qu’à des teneurs plus élevées en carbone labile

Salinisation des terres agricoles dans les zones côtières ˸ analyse des sols et des eaux, de l’échelle du paysage à celle de l’agrégat de sol

Salinization of water and soil is a major process of degradation of arable land. At the same time, salt and salt areas, such as estuaries, are hot spots for biodiversity. These areas should therefore be considered as complex systems that need to be studied in order to preserve their ability to perform different ecosystem functions and services.The work of thesis is positioned in the global framework of the understanding of the evolution of agricultural lands of coastal margins, subjected to the processes of salinization. The main objective was to contribute to the production of knowledge on the functioning of these systems, with a view to proposing sustainable remediation strategies. For this we have adopted a multi-step approach, based on observation and analysis of the system at different levels of organization: from the production perimeter to the soil aggregate. Specifically, we conducted our study on the town of Sérignan (Hérault - France) downstream of the Orb river basin.Landscape-level observations required easy-to-access characterization methods that allowed for high throughput analysis. We have therefore opted for methods based on the measurement of the electrical conductivity of soils and water. The analysis of the spatial distribution of the variable "electrical conductivity" allowed us to quantify salt pressure, identify salt sources and specify the nature of the processes responsible for increasing salt concentrations in the root area. Then, in order to gather our observations and hypotheses in a formalism that represents the salinization process, we have constructed a conceptual model of the water flows between the different compartments that make up this complex system.The observation at the landscape level, also allowed us to identify six reference plots, suitable to translate different hydro-pedological operations. On these plots, the detailed morpho-structural and geochemical analysis of the soil profiles as well as the monitoring of the piezometric levels allowed us to test the robustness of the structural stability as an indicator of the capacity of the soils to perform their functions. This overall assessment at the soil profile level seemed relevant to us i) to judge the overall salt leaching capacity, and ii) to integrate the entire root volume surveyed by the vine. The correlative analysis shows that A horizon horizons (MWD) appear to be more dependent on land cover, organic matter content and clay fraction whereas for B horizons, stability values are more correlated with the salt content strongly related to the presence of the underlying saturated zone. Moreover, the detailed analysis of the Na+ and Cl- contents suggests that the salts are precipitated in the pore volume, rather than adsorbed (Na+ case) on the CEC. There is therefore a potential for "desalination", without the need for desorption, based on the solution, leaching and export of solutes via the drainage network.Finally, for these 6 plots, we compared the physico-chemical characteristics and the microbiological activity of the A horizons. Here, our interest was in the global evaluation of the mineralization potential function of organic matter from respiration measurements, using MicroRespTM devices. We have shown that for A horizons, structural stabilities were significantly higher in wasteland conditions than in vineyard conditions. However, these wasteland conditions had the highest values for the electrical conductivity of soils. One possible explanation is that stability is more important in relation to the higher organic matter content at the surface of the fallow soils, as well as higher levels of labile carbon. This explanation is consistent with the observation of plant cover dominated by species inducing rhizodepositions. In addition, some studies suggest that the labile fraction of organic carbon and total nitrogen increase the potential for macro-aggregation, especially for fallow soils.La salinisation des eaux et des sols constitue un processus majeur de dégradation des terres arables. Dans le même temps, les zones sodiques et salines telles que les estuaires, constituent des hot-spot de biodiversité. Ces zones doivent donc être considérés comme des systèmes complexes qu’il est nécessaire d’étudier afin de préserver leur capacité à assurer différentes fonctions et services écosystémiques.Le travail de thèse se positionne dans le cadre global de la compréhension de l’évolution des terres agricoles de marges côtières, soumises aux processus de salinisation. L’objectif principal était de contribuer à la production de connaissances sur le fonctionnement des ces systèmes, en vue de proposer des stratégies de remédiation durables. Une démarche d'adaptation en plusieurs étapes, fondée sur l’observation et l’analyse du système à différents niveaux d’organisation : du périmètre de production à l’agrégat de sol. Nous avons mené notre étude sur la commune de Sérignan (Hérault - France) en aval du bassin du fleuve Orb.L’observation au niveau du paysage nécessitait adopter des méthodes de caractérisations faciles d’accès et autorisant un haut débit d’analyse. Des méthodes fondées sur la mesure de la conductivité électrique des sols et des eaux. L’analyse de la distribution spatiale de la variable « conductivité électrique », nous a permis de quantifier la pression saline, d’identifier les sources de sel et de préciser la nature des processus responsables de l’augmentation des concentrations en sel dans la zone racinaire. Nous avons construit un modèle conceptuel des flux d’eau entre les différents compartiments constitutifs de ce système complexe que représenter le processus de salinisation.L’observation au niveau du paysage, nous a aussi permis d’identifier six parcelles de référence, propres à traduire différents fonctionnements hydro-pédologiques. Sur ces parcelles, l’analyse morpho-structurale et géochimique fine des profils de sol ainsi que le suivi des niveaux piézométriques nous a permis de tester la robustesse de la stabilité structurale comme indicateur de la capacité des sols à assurer leurs fonctions. Cette évaluation globale à l’échelon du profil de sol nous semblait pertinente i) pour juger de la capacité globale de lixiviation des sels, et ii) pour intégrer l’ensemble du volume racinaire prospecté par la vigne. L’analyse corrélative montre que les stabilités (MWD) des horizons. A semblent plus dépendantes de l’occupation des sols, de la teneur en matière organique et de la fraction argileuse alors que pour les horizons B, les valeurs de stabilité sont plus corrélées à la teneur en sels fortement liée à la présence de la zone saturée sous-jacente. Par ailleurs, l’analyse détaillée des teneurs en Na+ et Cl- suggère que les sels sont précipités dans le volume poral, plutôt qu’adsorbés (cas de Na+) sur la CEC. Il existe donc un potentiel de « désalinisation », sans nécessité de désorption, fondé sur la mise en solution, lixiviation et exportation des solutés via le réseau de drainage.Enfin, pour ces 6 parcelles, nous avons confronté, les caractéristiques physico-chimiques et l’activité microbiologique des horizons A. Là, notre intérêt s’est porté sur l’évaluation globale de la fonction de potentiel de minéralisation des matières organiques à partir de mesures de respiration, à l’aide des dispositifs de type MicroRespTM. Nous avons montré que pour les horizons A, les stabilités structurales étaient significativement plus élevées en conditions de friches qu’en condition de vignoble. Pourtant, ces conditions de friches présentaient les valeurs les plus élevées pour la conductivité électrique des sols. Une explication possible est que la stabilité soit plus importante en relation à la teneur en matière organique plus élevée en surface des sols en friches, ainsi qu’à des teneurs plus élevées en carbone labile

Spatial Distribution of Trace Elements in Rice Field at Prafi District Manokwari

Mapping spatial variability of trace elements in rice Ḁeld is necessary to obtain soil quality information to en-hance rice production. ἀis study was aimed to measure concentration and distribution of Zn, Cu, Fe, Pb, and Cd in two diᴀerent sites (SP1, SP2) of PraḀ rice Ḁeld in Manokwari West Papua. ἀe representative 26 soil samples were analysed for their available trace metal concentration (DTPA), soil pH, and C-organic and soil texture. ἀe result indicated that Fe toxicity and Zn deḀcient problems were encountered in both sites.  Rice Ḁeld in SP2 was more deḀcient in Zn than SP1. Site with the highest trace elements (Zn, Fe, Cu, and Cd) concentration had low soil pH and high C-organic. Acidic soil has higher solubility of metals; while high C-organic could improve the formation of dissolve organic carbon-metal binding, hence it improving the trace metals concentration in soil solution

Soil Aggregate Stability in Salt-Affected Vineyards: Depth-Wise Variability Analysis

International audienceSoil aggregate stability is an ideal integrative soil quality indicator, but little is known about the relevance of such an indicator with soil depth for salt-affected soils. The objective of this study was to determine soil aggregate stability and identify preponderant aggregation factors, both in topsoil and subsoil horizons in salt-affected conditions. We conducted field investigations by describing soil profiles in pedological pits and by collecting soil samples from different field units. Soils were sampled within different soil horizon types, from superficial tilled organo-mineral horizons to mineral horizons. For all soil samples, we determined the mean weight diameter (MWD) as an indicator of soil aggregate stability and also determined associated physical and chemical properties in some samples. The measured MWD value from 0.28 mm to 1.10 mm could be categorised as unstable, with MWD values and variability decreasing drastically from the topsoil to the deepest mineral horizons. Analysis of MWD in relation to physical and chemical properties suggested that the variability in the MWD value of A-horizons was influenced by both clay fraction abundance and soil organic carbon (SOC) content and the nature of the agricultural practices, while at deeper B-horizons, the decrease in SOC content and the variability in other soil properties with soil depth could be used to explain the overall low aggregate stability. In this study, investigations of soil pits coupled with measurements of soil aggregate stability indicated that it could be possible to restore soil structure quality by limiting deep soil profile compaction in order to improve salt leaching and exportation

Landscape evolution and agricultural land salinization in coastal area: A conceptual model

International audienceSoil salinization is a major threat to agricultural lands. Among salt-affected lands, coastal areas could be considered as highly complex systems, where salinization degradation due to anthropogenic pressure and climate-induced changes could significantly alter system functioning. For such complex systems, conceptual models can be used as evaluation tools in a preliminary step to identify the main evolutionary processes responsible for soil and water salinization. This study aimed to propose a conceptual model for water fluxes in a coastal area affected by salinity, which can help to identify the relationships between agricultural landscape evolution and actual salinity. First, we conducted field investigations from 2012 to 2016, mainly based on both soil (EC1/5) and water (ECw) electrical conductivity survey. This allowed us to characterize spatial structures for EC1/5 and ECw and to identify the river as a preponderant factor in land salinization. Subsequently, we proposed and used a conceptual model for water fluxes and conducted a time analysis (1962-2012) for three of its main constitutive elements, namely climate, river, and land systems. When integrated within the conceptual model framework, it appeared that the evolution of all constitutive elements since 1962 was responsible for the disruption of system equilibrium, favoring overall salt accumulation in the soil root zone