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Catch crops (CC) reduce nitrate leaching, and may resolve a major concern in nitrogen (N) intensive agriculture. CC efficiency depends on N uptake ability, which is related to root development, biomass partitioning, and competition with soil microbes. We investigated the effect of N addition on this with three CC species.Three CC species were grown in pots with three N concentrations. Shoot and root biomass, C:N content, and specific root length were determined, whereas residual N, dissolved organic N (DON) and C, and microbial biomass N and C were measured.Addition of N did not consistently effect plant biomass nor its partitioning, probably because of overall high N. However, CC did reduce residual N, and so did soil microorganisms, likely facilitated by C-release from roots. Moreover, plant presence reduced DON, likely through uptake by soil microorganisms, partly followed by plant uptake.CC not only take up residual N themselves, but also trigger considerable N uptake by soil microorganisms that thrive on C-release from roots. This plant-microbe-nitrogen interaction has to be considered when evaluating CC systems. It remains unclear to which extent soil microorganisms immobilise inorganic N and mineralise or take up DON.

The interaction between carbon and flows within the plant is at the center of most growth and developmental processes. Understanding how these fluxes influence each other, and how they respond to heterogeneous environmental conditions, is important to answer diverse questions in forest, agriculture and environmental sciences. However, due to the high complexity of the plant-environment system, specific tools are needed to perform such quantitative analyses.Here we present CPlantBox, full plant modelling framework based on the root system model CRootBox. CPlantbox is capable of simulating the growth and development of a variety of plant architectures (root and shoot). In addition, the flexibility of CPlantBox enables its coupling with external modeling tools. Here, we connected it to an existing mechanistic model of water and carbon flows in the plant, PiafMunch.The usefulness of the CPlantBox modelling framework is exemplified in four case studies. Firstly, we illustrate the range of plant structures that can be simulated using CPlantBox. In the second example, we simulated diurnal carbon and water flows, which corroborates published experimental data. In the third case study, we simulated impacts of heterogeneous environment on carbon and water flows. Finally, we showed that our modelling framework can be used to fit phloem pressure and flow speed to (published) experimental data.The CPlantBox modelling framework is open-source, highly accessible and flexible. Its aim is to provide a quantitative framework for the understanding of plant-environment interaction.

To enhance a root trait-based selection program for rain-fed wheat breeding in Afghanistan, we simulated an efficient pre-breeding drought system. Plants were grown in 1 m pipes as control or 2 m pipes to simulate drought conditions soaking ground water up by capillary action supplemented by two different life supporting irrigations from top of the pipes (T1 and T2 droughts). T1 was used for studying genetic diversity in 360 Kihara Afghan wheat landraces (KAWLR). Both drought treatments were used to evaluate root traits in 30 selected genotypes. KAWLR showed large root length variations under T1, categorized as long root (>200 cm; LR), medium root (100-150 cm; MR) and short root (20-100 cm; SR) systems. LR genotypes were more drought resistant in terms of greater plant survivability under T1 and T2 compared with other groups and were capable of adjusting their root biomass partitioning at deepest part of the soil profile. Majority of the LR genotypes originated from predominantly rain-fed provinces, and most of their agronomic traits were strongly correlated with root biomass deep in the soil in response to drought. Three LR genotypes, including the longest root genotype LR-871 (KU7604), are recommended for rain-fed wheat breeding in Afghanistan.

International audience; This study focuses on the chemotaxis, colonization and rice growth promoting ability of indole acetic acid (IAA) and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase-producing rhizobacteria Rhizobium leguminosarum bv. trifolii SN10, previously isolated from root nodules of Trifolium alexandrium L. We show here that R. leguminosarum bv. trifolii SN10 promote the growth of four different rice varieties grown in India in terms of biomass, root branching and N content. In addition, using scanning electron microscopy and viable cell counts, we provide evidence that the bacteria successfully colonize the root surface of the rice variety which showed maximum growth promotion upon inoculation. Not only this, R. leguminosarum bv. trifolii SN10 exhibit a strong chemotaxis response towards the rice seed and root exudates despite the presence of a bacteriostatic phenolic compound, 7-hydroxycoumarin (umbelliferone). Further, R. leguminosarum bv. trifolii SN10 secretion of phytohormones such as IAA and ACC deaminase suggest the potential of the plant growth promoting rhizobacteria to be used as biofertilizer to enhance rice crop production in the subcontinent.

Les plantes terrestres prelevent les ions mineraux necessaires a leur nutrition essentiellement dans le sol, grâce a leurs racines. Cependant, la disponibilite de ces ions dans le sol varie de maniere tres importante, a la fois dans le temps et dans l’espace. Pour faire face a ces conditions fluctuantes, les plantes disposent de systemes d’adaptation tres elabores []. En particulier, et contrairement aux animaux, elles sont capables de modifier profondement leur developpement post-embryonnaire en fonction des conditions de ressources minerales dans le sol. Un phenomene tres interessant et particulierement etudie est le fait que les plantes stimulent la croissance de leurs racines specifiquement la ou les nutriments sont les plus abondants, et au contraire la freinent la ou ces nutriments font defaut (Figure 1) . Ceci est vrai pour un grand nombre d’ions essentiels comme le phosphate (PO4 2− ), le sulfate (SO4 2− ), l’ammonium (NH4 + ), ou le nitrate (NO3 − ), et permet ainsi aux vegetaux d’optimiser leur nutrition en exploitant preferentiellement les zones du sol riches en mineraux [].

O uso eficiente de fertilizantes requer o conhecimento de seus efeitos tanto na biomassa aérea quanto na radicular, permitindo que se identifique uma adubação adequada do ponto de vista de uma melhor partição entre ambas. A massa de raízes secas por volume de solo vem sendo utilizada, principalmente em espécies perenes, como subsídio para estimativas de biomassa radicular. Com esse objetivo, foram estudados os efeitos da adubação NPK na densidade radicular de três progênies de pupunheira (Bactris gasipaes Kunth), cultivadas em um Aluvial álico (corrigido por meio de calagem) em Ubatuba, SP (clima "Cfa"), durante o ano de 1993. O delineamento foi um fatorial fracionado, composto por quatro doses crescentes de nitrogênio (0 a 400 kg/ha/ano de N), fósforo (0 a 200 kg/ha/ano de P2O5 ) e potássio (0 a 200 kg/ha/ano de K2O), em experimento integrado (progênies e adubação). As amostras foram coletadas por ocasião da primeira colheita de palmito (outubro de 1993), quando as plantas (cultivadas no espaçamento de 2 x 1 m) tinham cerca de dois anos de campo. Utilizou-se o método do trado, coletando-se, por parcela experimental, duas amostras na linha e duas na entrelinha. Houve diferenças entre genótipos (GE), com as progênies 2 e 3 apresentando, em média, maior densidade radicular que a progênie 1 (5,15 e 6,20 contra 2,61 g/dm³, respectivamente). A interação GE x PO (posição da amostra) foi significativa, sendo que para as progênies 1 e 2 a maior densidade radicular foi obtida na linha (3,30 e 6,60 g/dm³ na linha, contra 1,92 e 4,70 g/dm³ na entrelinha, respectivamente), enquanto para a 3 a ordem foi inversa (5,57 g/dm³ na linha e 6,84 g/dm³ na entrelinha). Doses crescentes de potássio (K) apresentaram efeitos lineares positivos e significativos (R² =0,93 a 0,97) na densidade radicular das três progênies, com acréscimos entre dose mínima e máxima variando de 18 a 28%. Não houve efeito significativo isolado de P, enquanto doses crescentes de N proporcionaram um efeito linear positivo e significativo, mais evidente na progênie 1 (médias de 2,26, 2,39, 2,62 e 3,16 g/dm³ para as doses 0, 100, 200 e 400 kg/ha/ano de N, respectivamente). Não houve interação estatisticamente significativa entre GE e fertilizantes aplicados (NPK), exceto para GE x N x P. Embora com respostas diferenciais de acordo com a progênie, constatou-se que a maior densidade radicular foi sempre obtida nas doses mais elevadas de N.The efficient use of fertilizers requires a knowledge of their effects, not only on shoot biomass, but also on below-ground biomass, to identify an adequate fertilization level from the point of view of a better partition between both. Dried root mass per soil volume has been used, especially in perennial crops, as a substitute for estimates of root biomass. With this objective, the root density of three progenies of the pejibaye palm (Bactris gasipaes Kunth) was studied under a combination of four nitrogen (0 to 400 kg/ha/year of N), phosphorus (0 to 200 kg/ha/year of P2O5) and potassium (0 to 200 kg/ha/year of K2O) doses, in a field experiment. The area was located at Ubatuba, SP, Brazil, in an allic alluvial soil, corrected by liming. The samples were collected during the first heart of palm harvest (October, 1993), when the plants (cultivated in a 2 x 1 m spacing) were two years old. Samples were collected, between and within planting rows, using a root-soil auger sampler, 50 cm from the main stem and at a 0-20 cm soil depth. There were differences among genotypes (GE), with progenies 2 and 3 showing, on average, higher root densities than progeny 1 (5.15 and 6.20, against 2.61 g/dm³, respectively). The interaction GE x PO (sample position) was significant: progenies 1 and 2 showed the highest root densities within planting rows (3.30 and 6.60 g/dm³ within row, against 1.92 and 4.70 g/dm³ between rows, respectively), while progeny 3 showed an inverse order (5.57 g/dm³ in the within row, and 6.84 g/dm³ between rows). There was a positive linear response to applied potassium (R² =0.93 to 0.97), with increments between minimum and maximum doses varying from 18 to 28%. There was no isolated significant effect of P, while increasing doses of N provided a positive and significant linear effect, more evident in progeny 1 (averages of 2.26, 2.39, 2.62 and 3.16 g/dm³ for the doses 0, 100, 200 and 400 kg/ha/year of N, respectively). There was no significant interaction between GE and fertilizers (NPK), except for GE x N x P. Although the responses varied with progeny, higher root density was always found at high nitrogen doses.

Potato (Solanum tuberosum L.) requires abundant nitrogen (N) to perform well and has low nitrogen use efficiency (NUE). We assessed phenotypic variation among 189 potato cultivars for NUE and the association between NUE and ecophysiological variables describing canopy development (CDv), under high and low N input. In 2009 and 2010, 189 cultivars were grown with N supply (soil N + fertiliser N) of 75 or 180 kg N/ha at Bant, the Netherlands. CDv was assessed weekly as the percentage of soil covered by green potato leaves (%SC). Data were analysed using a model that described CDv as a function of thermal time, based on the Beta function and estimates of cardinal temperatures. Nitrogen significantly affected model-derived, biologically relevant, curve-fit parameters for each cultivar. The t 1 (i.e., thermal time required to reach maximum soil cover (Vx)) was higher at low than at high N. Other parameters were higher at high than at low N, especially Vx and the period over which it was maintained. Nitrogen also affected tuber dry matter yield, tuber size and weight distributions, N content and N uptake but not tuber dry matter percentage. The total area under the %SC curve was highly correlated with yield in both years. Cultivars performing well under high N also performed well under low N. There was large variation in NUE component traits among cultivars; maturity type partially explained this variation. Variables of the CDv model captured this variation, N effects on light interception and its correlation with yield.

International audience; In France, agronomists have studied the effects of cropping systems on soil structure using a field method based on a morphological description of soil structure. In this method, called "profil cultural" or soil profile in English, the soil structure of the tilled layer is observed on a vertical face of a pit. Subsoil and more especially the transition layer between topsoil and subsoil have not always been given specific consideration. However, these layers undergo the effect of cropping systems through soil compaction or smoothing/smearing. A more accurate quantification of earthworm macropores and cracks in the transition layer would enable a more precise evaluation of the agronomical potential of the soil, manifest in root development or water retention. Thus, the aim of this paper is to present the profil cultural method in detail, along with the improvements we have made to quantify the ability of roots to penetrate compacted zones in the transition layer. We propose two indicators: (i) number of earthworm burrows per m(2) counted on a horizontal surface at the bottom of the transition layer in the soil pit (ii) cracking quantified by taking a 50-mm x 50-mm x 100-mm sample of soil from the transition layer and examining the number of cracks. Results from experiments on different tillage treatments are used to demonstrate why it is worthwhile to take into account cracks and earthworm activity. Soil profiles were examined in mouldboard ploughed and no tillage fields, and described using the profil cultural method and the new indicators. Root maps were also traced to observe the effect of soil structure on root growth. Preliminary results show that the classification of cracking and the quantification of the number of earthworm burrows per m(2) can explain observed root development in subsoil. This first approach towards a better observation of subsoil structure and the effect it has on roots needs to be confirmed through further research, and especially via quantification and scoring of soil structure impact on roots. (c) 2012 Elsevier B.V. All rights reserved.

International audience; Modelling nutrient uptake by crops implies considering and integrating the processes controlling the soil nutrient supply, the uptake by the root system and relationships between the crop growth response and the amount of nutrient absorbed. We developed a model that integrates both dynamics of maize growth and phosphorus (P) uptake. The crop part of the model was derived from Monteith's model. A complete regulation of P-uptake by the roots according to crop P-demand and soil P-supply was assumed. The soil P-supply to the roots was calculated using a diffusion equation and assuming that roots behave as zero-sinks. The actual P-uptake and crop growth were calculated at each time step by comparing phosphate and carbohydrate supply-demand ratios. Model calculations for P-uptake and crop growth were compared to field measurements on a long term P-fertilization trial. Three P-fertilization regimes (no P-fertilization, 42.8 kg P ha(-1) year(-1) and 94.3 kg P ha(-1) year(-1)) have led to a range of P-supply. Our model correctly simulated both the crop development and growth for all P-treatments. P-uptake was correctly predicted for the two non-limiting P-treatments. Nevertheless, for the limiting P-treatment, P-uptake was correctly predicted during the early period of growth but it was underestimated at the last sampling date (61 day after sowing). Several arguments for under-prediction were considered. However, most of them cannot explain the observed magnitude in discrepancy. The most likely reason might be the fact that biomass allocation between shoot and root must be modelled more precisely. Despite this mismatch, the model appears to provide realistic simulations of the soil-plant dynamic of P in field conditions

Interactions between structural architecture and resource allocation affect the ability of plants to utilise environmental resources. Architecture defines the structural layout and relationships of organs and other structural units at different hierarchical levels in plants. Resource allocation determines how competing structural units are awarded resources at different levels of hierarchy. Functional-structural plant models combine architecture and resource allocation as interacting components of plant growth and functioning. Existing functional-structural plant models concentrate on growth of unitary trees and therefore, lack sufficient structural definition to simulate growth of clonal plants. On the other hand, simulation models designed to consider clonal growth rarely attempt to simulate clonal architecture at a more detailed level than individual ramets. This paper introduces a functional-structural type model, TILLERTREE, which integrates the architectural growth of bunchgrasses with resource capture and allocation of nitrogen and carbohydrate. Resource allocation is implemented using a procedural algorithm based on object hierarchy and priority, and not mechanistically. The model is used to illustrate that growth of bunchgrass clones is regulated by patterns of resource allocation between competing units at low levels of hierarchy, by considering the effect of resource rules controlling secondary tiller recruitment on clonal growth. Simulations are conducted using a chosen model C4 bunchgrass species Themeda triandra.

Nous avons étudié l'incidence du mode de couverture du sol (sol nu, apport d'écorces ou de composts, enherbe-ment) sur la fourniture en azote du sol de plusieurs vignobles expérimentaux en Champagne. La minéralisation nette d'azote parces sols au cours de l'automne et de l'hiver va de 9 à 45 kg N ha-1, sur une période de 118 à 182 jours. La vitesse de minérali-sation correspondante, exprimée en « jours normalisés » (correspondant à une température constante de 15 °C et une humiditéà la capacité au champ) est de 0.15 à 0.82 kg N ha-1j-1normalisé, tous traitements témoins confondus. La minéralisation n'estpas significativement affectée par les apports de produits organiques, sauf dans le cas des apports les plus anciens, les modifi-cations étant fonction de la nature et des doses de produits organiques apportés., We studied the effect of soil cover (bare soil, mulch of barks or composted organic materials, grass cover) on soil N dynamics in various experimental vineyards located in Champagne area (France). Soil cores were sampled periodically to measure water and mineral N in soil profile during autumn and winter. These measurements were used in a simple dynamic model (LIXIM) to calculate nitrate leaching and N mineralization. N mineralization potential of soils were also determined in laboratory incubations in controlled conditions. In most sites, soil inorganic N contents (0-75 cm) varied between 20 and 60 kg N ha-1, depending of the season. Soil inorganic N in plots receiving barks or composted barks or covered with grass did not differ significantly from control plots. Higher amounts of inorganic N were found in soils amended with refuse compost, peat or mixed compost (barks + farmyard manure) or composted farmyard manure. The model indicated that N leached varied from 8 to 77 kg N ha-1 and that the mean nitrate concentration in drained water was less than 50 mg NO3- L-1 except for plots receiving refuse compost or bark + farmyard manure compost. The calculated N mineralization varied from 9 to 45 kg N ha-1 over the autumn-winter period, i.e. 118 to 182 days. The N mineralization rate (Vp), expressed per 'normalised day' i.e. day at 15°C and field capacity, varied from 0.15 to 0.82 kg N ha-1 nd-1, including all sites and experimental treatments. Effect of organic matter addition on Vp was only observed for long-term experimental sites where large amounts of organic nitrogen had been added to soil using peat, refuse compost or compost mixtures with barks and farmyard manure. The Vp values measured in laboratory incubations showed the same trends and were in the same order of magnitude than those calculated with LIXIM model using in situ data. In average, the values measured in laboratory incubations underestimated the actual N mineralization in field conditions. The model was used to predict N mineralization and inorganic N in soil during the vegetative period using Vp values. It allowed to estimate the N uptake by vine: 10 ± 5 kg N ha-1 at flowering and 57 ± 5 kg N ha-1 over the whole growing period. These results show that soil N availability was sufficient to feed the vine during the whole growing period and that no inorganic N fertilisation was necessary, even in the grass covered soil. In this soil, water availability is probably the limiting factor when depressive effects are observed. On the long-term, it is necessary to manage the amount and quality of added organic matter since organic inputs may modify N availability and therefore vine behaviour, wine quality and environmental risks.

O uso eficiente de fertilizantes requer o conhecimento de seus efeitos tanto na biomassa aérea quanto na radicular, permitindo que se identifique uma adubação adequada do ponto de vista de uma melhor partição entre ambas. A massa de raízes secas por volume de solo vem sendo utilizada, principalmente em espécies perenes, como subsídio para estimativas de biomassa radicular. Com esse objetivo, foram estudados os efeitos da adubação NPK na densidade radicular de três progênies de pupunheira (Bactris gasipaes Kunth), cultivadas em um Aluvial álico (corrigido por meio de calagem) em Ubatuba, SP (clima "Cfa"), durante o ano de 1993. O delineamento foi um fatorial fracionado, composto por quatro doses crescentes de nitrogênio (0 a 400 kg/ha/ano de N), fósforo (0 a 200 kg/ha/ano de P2O5 ) e potássio (0 a 200 kg/ha/ano de K2O), em experimento integrado (progênies e adubação). As amostras foram coletadas por ocasião da primeira colheita de palmito (outubro de 1993), quando as plantas (cultivadas no espaçamento de 2 x 1 m) tinham cerca de dois anos de campo. Utilizou-se o método do trado, coletando-se, por parcela experimental, duas amostras na linha e duas na entrelinha. Houve diferenças entre genótipos (GE), com as progênies 2 e 3 apresentando, em média, maior densidade radicular que a progênie 1 (5,15 e 6,20 contra 2,61 g/dm³, respectivamente). A interação GE x PO (posição da amostra) foi significativa, sendo que para as progênies 1 e 2 a maior densidade radicular foi obtida na linha (3,30 e 6,60 g/dm³ na linha, contra 1,92 e 4,70 g/dm³ na entrelinha, respectivamente), enquanto para a 3 a ordem foi inversa (5,57 g/dm³ na linha e 6,84 g/dm³ na entrelinha). Doses crescentes de potássio (K) apresentaram efeitos lineares positivos e significativos (R² =0,93 a 0,97) na densidade radicular das três progênies, com acréscimos entre dose mínima e máxima variando de 18 a 28%. Não houve efeito significativo isolado de P, enquanto doses crescentes de N proporcionaram um efeito linear positivo e significativo, mais evidente na progênie 1 (médias de 2,26, 2,39, 2,62 e 3,16 g/dm³ para as doses 0, 100, 200 e 400 kg/ha/ano de N, respectivamente). Não houve interação estatisticamente significativa entre GE e fertilizantes aplicados (NPK), exceto para GE x N x P. Embora com respostas diferenciais de acordo com a progênie, constatou-se que a maior densidade radicular foi sempre obtida nas doses mais elevadas de N. The efficient use of fertilizers requires a knowledge of their effects, not only on shoot biomass, but also on below-ground biomass, to identify an adequate fertilization level from the point of view of a better partition between both. Dried root mass per soil volume has been used, especially in perennial crops, as a substitute for estimates of root biomass. With this objective, the root density of three progenies of the pejibaye palm (Bactris gasipaes Kunth) was studied under a combination of four nitrogen (0 to 400 kg/ha/year of N), phosphorus (0 to 200 kg/ha/year of P2O5) and potassium (0 to 200 kg/ha/year of K2O) doses, in a field experiment. The area was located at Ubatuba, SP, Brazil, in an allic alluvial soil, corrected by liming. The samples were collected during the first heart of palm harvest (October, 1993), when the plants (cultivated in a 2 x 1 m spacing) were two years old. Samples were collected, between and within planting rows, using a root-soil auger sampler, 50 cm from the main stem and at a 0-20 cm soil depth. There were differences among genotypes (GE), with progenies 2 and 3 showing, on average, higher root densities than progeny 1 (5.15 and 6.20, against 2.61 g/dm³, respectively). The interaction GE x PO (sample position) was significant: progenies 1 and 2 showed the highest root densities within planting rows (3.30 and 6.60 g/dm³ within row, against 1.92 and 4.70 g/dm³ between rows, respectively), while progeny 3 showed an inverse order (5.57 g/dm³ in the within row, and 6.84 g/dm³ between rows). There was a positive linear response to applied potassium (R² =0.93 to 0.97), with increments between minimum and maximum doses varying from 18 to 28%. There was no isolated significant effect of P, while increasing doses of N provided a positive and significant linear effect, more evident in progeny 1 (averages of 2.26, 2.39, 2.62 and 3.16 g/dm³ for the doses 0, 100, 200 and 400 kg/ha/year of N, respectively). There was no significant interaction between GE and fertilizers (NPK), except for GE x N x P. Although the responses varied with progeny, higher root density was always found at high nitrogen doses.