Gradual responses of grapevine yield components and carbon status to nitrogen supply

Aim: Nitrogen is a major element conditioning grapevine growth, yield and aromatic profiles of berries and wines. Different tools can be used in order to detect differences in N status of the plant, including direct measurements of soil, plant nitrogen status (eg. petiole; must), or indirect observations of plant nutritional status such as leaf transmittance or reflectance (eg. SPAD; NDVI). However, the relationships between these indicators of nitrogen status and the overall plant functioning over vintages remain poorly known. The present study aimed at quantifying key vegetative and reproductive responses to plant nitrogen status over two successive seasons under different nitrogen supply levels. Methods and results: Potted plants of Sauvignon Blanc grafted onto SO4 were grown outdoors in 2017 and 2018 with no water limitation. Four mineral nitrogen fertilization levels (equivalent to 0 kg of N ha-1 or 0U, 20U, 40U, 80U) and one organic nitrogen fertilization level (40U) were imposed in 2017. These treatments were doubled in 2018 to increase the degree of nitrogen supply and consequently, the range of observed effects on plant growth and yield. Plant nitrogen status (SPAD) was monitored weekly during both growing cycles. Yield components were determined over the two seasons. Lastly, plant carbon status was addressed through dynamic measurement of plant development and photosynthesis, and destructive measurement of dry matter accumulation and carbon storage in annual and perennial organs at flowering, veraison and harvest. The SPAD values progressively decreased under lower N supply (0N) during the first year (from 31 to 16) and they were more than halved between the maximum and the minimum N treatments straight after budburst in year two (40 for 160N and 19 for 0N). Then, the differences in SPAD values among treatments were maintained up to harvest (2018). The gradient of N status resulted in a gradient of berry numbers per inflorescence (from 180 to 34 berries/inflorescence for 80N and 0N, respectively in 2018) and of individual berry dry matter at harvest (from 0.13 to 0.41 g for 160N and 0N, respectively in 2018). Quantitative relationships between N status and the relative reductions (% of reduction per %SPAD decrease) in terms of C gain (leaf area, photosynthesis), C growth (shoot, berry, trunk and root dry matter) and C storage (trunk and root) were fitted at flowering, veraison and harvest. The reduction in C gain under lower N supply was mainly related to the decrease in total leaf area before flowering (-1.64%). Although the photosynthesis rate tended to decrease under N deficiency over the season, it only poorly contributed to the reduction in C gain. The whole plant C growth was inhibited when N status decreased (-1.13% at harvest), due to the inhibition of shoot dry matter before veraison (-1.81%) and to a lower extent, to the lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest. Part of the reduction in root dry matter was related to the lower starch reserves (-0.31%) at harvest. Interestingly, starch reserves tended to be higher under organic N supply than mineral N supply. Conclusion: The present results provided a general framework of carbon gain and use over time (within and between seasons) as impacted by N supply levels and form. Such a framework will be useful when building a model of the pluri-annual dynamics of carbon balance related to yield elaboration in grapevines

Effet de l'apport d'azote minéral avant le débourrement sur la qualité de la jeune pousse foliaire chez le scion de peuplier (Populus tremula x alba) : estimation des flux d'azote issus de la remobilisation et de l'absorption par un marquage 15N en conditions contrôlées

il s'agit d'un type de produit dont les métadonnées ne correspondent pas aux métadonnées attendues dans les autres types de produit : DISSERTATIONMasterLa variation de la disponibilité en azote dans les sols au débourrement pourrait, dans le cas de l’arbre, avoir un impact plus important que prévu sur sa manière de gérer ses propres réserves carbonées et azotées et à terme, sur sa survie. L’objectif de cette expérimentation est de quantifier l’effet d’un apport précoce d’azote dans la solution nutritive avant le débourrement sur la qualité de la jeune pousse foliaire en lien avec les flux d’azote issus de l’absorption et de la remobilisation. Le protocole a consisté à cultiver des plants de peuplier en conditions contrôlées ayant reçu ou non de K15NO3 avant le débourrement dans une solution recyclée depuis la sortie de l’hiver jusqu’à l’étalement des limbes. Il ressort que l’apport d’azote précoce avant le débourrement n’a aucun effet sur le profil de débourrement et sur la croissance de l’arbre au cours de l’expérimentation. En revanche, l’apport d’azote augmente de façon importante la surface et la teneur en azote foliaires des jeunes pousses. De plus, l’utilisation du marqueur montre (i) que la moitié de l’azote absorbé avant le débourrement se retrouve dans la jeune pousse, (ii) l’écorce et les racines participent principalement au remplissage en azote de la jeune pousse

Biotic and abiotic factors impacting establishment and growth of relay intercropped forage legumes

In organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services vary considerably depending on the forage legume biomass. The aim of this study was to identify factors that affect forage legume establishment and growth to help farmers adjust the management of the cover crop.Sixteen field experiments were conducted over a period of five years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L. After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Climatic conditions, and the accumulation of legume and weed biomass were monitored from when the legume was sown to destruction of the cover crop.Our results showed that a minimum threshold of about 500 kg ha−1 biomass in the aboveground parts of the cover crop was needed at the end of intercropping to obtain the minimum biomass of 2000 kg ha−1 in September necessary to guarantee ecological services. To obtain sufficient legume biomass at the end of intercropping period, a thermal time greater than 1900 °Cd and more rainfall than 300 mm are required for legume growth. Moreover, a legume density of at least of 300 plants per square meter at the wheat flowering stage was a good indicator of legume biomass at the end of the intercropping period. Rainfall was a limiting factor of legume growth between the end of the intercropping period and September.Legume density at wheat flowering and climatic conditions during the intercropping period thus appear to be good indicators to predict to capacity of cover crop to produce sufficient biomass in September. These indicators can be used by farmers as a management tool for the cover crop

Using low-cost NIRS method for helping smallholder to detect nutritional deficiencies and imbalances

International audienceLack of control over fertilization is one of the major factors in the yield gap between smallholders and large oil palm plantations (Monzon et al., 2023). The diagnostic tool known as leaf analysis method is used by a large number of plantations to manage their fertilization and relies on annual leaf analysis and specific long-term experiments (Dubos et al., 2022). However, this method is not accessible to smallholders, mainly due to the cost of annual leaf analysis. As a consequence, major imbalances in fertilization are generally observed. The most important nutrients to monitor in this crop are N, P, K and Mg (Woittiez et al., 2017). However, current methods to measure leaf nutrient status are long, costly and require hazardous chemical reagents. Recent developments in near-infrared spectrometry (NIRS) have made it possible to create increasingly low-cost measurement equipment, without the need to transform the leaflets (Prananto et al., 2020).We tested the possibility to use a small portable infrared spectrometer (Nirone S2.2 Evaluation Kit from Spectral Engines) in order to make fertilization management more accessible for smallholders. This spectrometer has a reduced spectral range of 1750-2150nm which has been selected in a prior study testing the correlation between leaflet contents with various spectral ranges. A total of 92 leaflets composite samples were taken from several plots of smallholders and large plantations in West Africa. The plots were located in marginal hydric conditions of Benin and in more favorable conditions of Nigeria, in plantations with different nutritional status, age and plant materials, allowing a large range of variability. Spectral Measurements were taken directly on fresh leaflets on the frond 17, using in classical leaf analysis. Laboratory measurements were got according to the standard methodology of Leaf Analysis. PLS regressions after preprocessing the spectra were used to set up predictive models for the concentration of N, P, K and Mg in the leaves. Goodness of predictions was evaluated by crossvalidation with 10 folds.In our conditions, the measured values (in % of DM) ranged from 1.5 to 3.0 (N), from 0.10 to 0.17 (P), from 0.23 to 1.03 (K) and 0.12 to 0.69 (Mg) which corresponds to leave nutrients content generally observed in oil palms plantations. A satisfying accuracy between measured and predicted nutrients contents was generally observed but depended on the considered nutrient. For instance, N was the better predicted nutrient (RMSECV=0.19). In contrast, Mg was quite poorly predicted (RMSECV = 0.092). In terms of error, the proportion of samples predicted with an error > 20% was lower for N and P (2% and 1%, respectively), compared to K (30%) and Mg (60%).Our results showed that using a portable and cheap infrared spectrometer could be used to easily and quickly predict nutrients contents in a wide-range of nutritional conditions. However, compared to the standard leaf analysis methodology, prediction accuracy is lower especially regarding Mg and K. In a context of advices to smallholders, the trade-off between time, cost and precision is in favor to lower cost even if it means being less precise. This technology appears interesting to (i) detect situations with severe deficiencies and/or imbalances and (ii) educate smallholders to best management practices.References:Dubos, B., Bonneau, X., Flori, A., 2022. Oil Palm Fertilization Guide. éditions Quæ, Versailles.Monzon, J.P., Lim, Y.L., Tenorio, F.A., Farrasati, R., Pradiko, I., Sugianto, H., Donough, C.R., Rattalino Edreira, J.I., Rahutomo, S., Agus, F., Slingerland, M.A., Zijlstra, M., Saleh, S., Nashr, F., Nurdwiansyah, D., Ulfaria, N., Winarni, N.L., Zulhakim, N., Grassini, P., 2023. Agronomy explains large yield gaps in smallholder oil palm fields. Agricultural Systems 210, 103689.Prananto, J.A., Minasny, B., Weaver, T., 2020. Chapter One - Near infrared (NIR) spectroscopy as a rapid and cost-effective method for nutrient analysis of plant leaf tissues. In: Sparks, D.L. (Ed.), Advances in Agronomy. Academic Press, pp. 1-49.Woittiez, L.S., van Wijk, M.T., Slingerland, M., van Noordwijk, M., Giller, K.E., 2017. Yield gaps in oil palm: A quantitative review of contributing factors. European Journal of Agronomy 83, 57-77

Early assessment of ecological services provided by forage legumes in relay intercropping

In organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services can vary considerably depending on the growing conditions. The aim of this study was to identify early indicators to assess these two ecological services, thereby giving farmers time to adjust the management of both the cover crop and of the following crop. Nine field experiments were conducted over a period of three years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L Two levels of fertilization were also tested (0 and 100 kg N ha(-1)). After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Legume and weed biomass, nitrogen content and accumulation were monitored from legume sowing to cover destruction. Our results showed that a minimum threshold of about 2 t ha(-1) biomass in the aboveground parts of the cover crop was needed to decrease weed infestation by 90% in early September and to ensure weed control up to December. The increase in nitrogen in the following maize crop was also correlated with the legume biomass in early September. The gain in nitrogen in maize (the following crop) was correlated with legume biomass in early September, with a minimum gain of 60 kg N ha(-1) as soon as legume biomass reached more than 2 t ha(-1). Legume biomass in early September thus appears to be a good indicator to predict weed control in December as well as the nitrogen released to the following crop. The indicator can be used by farmers as a management tool for both the cover crop and following cash crop. Early estimation of available nitrogen after the destruction of the forage legume can be used to adjust the supply of nitrogen fertilizer to the following crop

Intercropping strategies of white clover with organic wheat to improve the trade-off between wheat yield, protein content and the provision of ecological services by white clover

Nitrogen (N) deficiency and weed infestation are the main factors limiting the yield and quality of organic soft winter wheat (Triticum aestivum L.). If forage legumes are associated with wheat, simultaneously or successively, they can help to reduce the impact of limiting factors through the ecological services they provide. The aim of this study was to evaluate two intercropping strategies to increase soft winter wheat yield and protein content and improve the provided ecological services (mainly N provisioning and weed control) by white clover (Trifolitum repens L.). White clover (Thfolium repens L. cv Aberdai) was intercropped with soft winter wheat (Triticum aestivum L. cv Renan) under organic conditions. Two strategies were compared, simultaneous intercropping versus relay intercropping using three field experiments. A control treatment with sole wheat crop was included in the three field experiments. Fertilization management on organic wheat was also tested (0 versus 100 kg N applied at spring time) to evaluate its incidence on cash and cover crop yields and protein content. White clover shoot dry matter (DM) was significantly higher in simultaneous intercropping compared to relay intercropping at wheat harvest (2.2 vs. 0.1 Mg DM ha(-1)) and at cover destruction (4.5 vs. 3.1 Mg DM ha(-1)). Wheat grain yield was not affected by the intercropping strategy while the protein content was significantly lower under simultaneous intercropping system (9.1% of the grain DM) compared to relay intercropping or in wheat as sole crop (10.0% of the grain DM). At cover destruction, both simultaneous and relay intercropped white clover significantly decreased weed shoot DM compared to sole wheat crop (-1.4 Mg DM ha(-1) for relay intercropping and -1.8 Mg DM ha(-1) for simultaneous intercropping). In comparison to relay intercropping strategy, N accumulation in white clover shoot DM was higher under simultaneous intercropping strategy at wheat harvest (52 vs. 2 kg N ha(-1)) and at cover destruction (123 vs. 83 kg N ha(-1)). In conclusion, our study has highlighted the positive effect of combining a simultaneous intercropping strategy with high N availability to guarantee a sufficient level of legume shoot DM as rapidly as possible to increase both N accumulation and weed control services, thus reducing the risk of impairing winter wheat yield and protein content

Modelling nitrogen and light sharing in pea-wheat intercrops to design decision rules for N fertilisation according to farmers’ expectations

International audienceCereal-legume intercropping has gained increased interest in Europe. Nevertheless, performance and especially the percentage of each species at harvest are often considered highly variable. Nitrogen (N) fertilisation can be a relevant driving factor affecting the percentage of each species at harvest. Soil N availability influences competition for light and nitrogen in cereal-legume intercrops. However, management of N fertilisation still remains unclear for intercrops. Few references on the effects of a range of strategies of N fertilisation are available to guide farmers with relevant decision rules considering their expectations. Here, a modelling approach was proposed to simulate interactions between light and N acquisition of a pea-wheat intercrop and to test different scenarios for the management of such intercrops. A model (Azodyn-IC) was built resulting from the combination of two existing individual-crop models (AZODYN and AFISOL) and by applying rules of light and soil inorganic nitrogen sharing between the intercropped pea and wheat. Evaluation of the model outputs with experimental data showed satisfactory predictions of the studied variables (N accumulation, LAI, and crop dry weight). The model validated both resource sharing and light-N interactions. Furthermore, the model was able to respond to increases in inorganic N availability based upon straightforward formalisms. Simulating unmeasured variables, such as root growth and light interception and use by each species, improved our understanding of the relative dominance of each species for acquiring resources. Eventually, the model was used to simulate different scenarios of N fertilisation over 26 years of climatic data to account for climatic variability. We demonstrated the interest of such a modelling approach to design decision rules of N fertilisation according to farmers’ expectations

Gradual responses of grapevine yield components and carbon status to nitrogen supply

International audienceAim: Nitrogen is a major element conditioning grapevine growth, yield and aromatic profiles of berries and wines. Different tools can be used in order to detect differences in N status of the plant, including direct measurements of soil, plant nitrogen status (eg. petiole; must), or indirect observations of plant nutritional status such as leaf transmittance or reflectance (eg. SPAD; NDVI). However, the relationships between these indicators of nitrogen status and the overall plant functioning over vintages remain poorly known. The present study aimed at quantifying key vegetative and reproductive responses to plant nitrogen status over two successive seasons under different nitrogen supply levels. Methods and results: Potted plants of Sauvignon Blanc grafted onto SO4 were grown outdoors in 2017 and 2018 with no water limitation. Four mineral nitrogen fertilization levels (equivalent to 0 kg of N ha-1 or 0U, 20U, 40U, 80U) and one organic nitrogen fertilization level (40U) were imposed in 2017. These treatments were doubled in 2018 to increase the degree of nitrogen supply and consequently, the range of observed effects on plant growth and yield. Plant nitrogen status (SPAD) was monitored weekly during both growing cycles. Yield components were determined over the two seasons. Lastly, plant carbon status was addressed through dynamic measurement of plant development and photosynthesis, and destructive measurement of dry matter accumulation and carbon storage in annual and perennial organs at flowering, veraison and harvest. The SPAD values progressively decreased under lower N supply (0N) during the first year (from 31 to 16) and they were more than halved between the maximum and the minimum N treatments straight after budburst in year two (40 for 160N and 19 for 0N). Then, the differences in SPAD values among treatments were maintained up to harvest (2018). The gradient of N status resulted in a gradient of berry numbers per inflorescence (from 180 to 34 berries/inflorescence for 80N and 0N, respectively in 2018) and of individual berry dry matter at harvest (from 0.13 to 0.41 g for 160N and 0N, respectively in 2018). Quantitative relationships between N status and the relative reductions (% of reduction per %SPAD decrease) in terms of C gain (leaf area, photosynthesis), C growth (shoot, berry, trunk and root dry matter) and C storage (trunk and root) were fitted at flowering, veraison and harvest. The reduction in C gain under lower N supply was mainly related to the decrease in total leaf area before flowering (-1.64%). Although the photosynthesis rate tended to decrease under N deficiency over the season, it only poorly contributed to the reduction in C gain. The whole plant C growth was inhibited when N status decreased (-1.13% at harvest), due to the inhibition of shoot dry matter before veraison (-1.81%) and to a lower extent, to the lower dry matter in berries (-0.80%), trunks (-0.42%) and roots (-0.84%) at harvest. Part of the reduction in root dry matter was related to the lower starch reserves (-0.31%) at harvest. Interestingly, starch reserves tended to be higher under organic N supply than mineral N supply. Conclusion: The present results provided a general framework of carbon gain and use over time (within and between seasons) as impacted by N supply levels and form. Such a framework will be useful when building a model of the pluri-annual dynamics of carbon balance related to yield elaboration in grapevines

Combining pluriannual dynamics and Bayesian approach to analyze grapevine growth and storage as a function of nitrogen supply

International audienceThe effect of nitrogen (N) nutrition on grapevine carbon (C) production, allocation and storage has been well-studied at the annual scale, but poorly addressed at a pluriannual timestep. Also, the quantification of N supply on C functioning raises interesting questions from a statistics-based methodological point of view. The aim of this study was to quantify, in an integrated conceptual framework, the pluriannual effect of N nutrition on potted Sauvignon blanc grapevine growth and storage over two consecutive years. The consequences of using destructive measurements to address this issue was investigated using a hierarchical Bayesian model.The segmentation of leaf area dynamics with a period of growth followed by a plateau showed that leaf area growth rate and the duration of growth were both positively impacted by the chlorophyll content of the leaves measured by SPAD index. However, the initial carbohydrates had the opposite effect on leaf growth, raising a distortion in the estimation of initial reserves. The carbon production per unit of global radiation was mostly linked to the leaf area dynamics. The allocation of dry matter was highly reliant on the phenological stage, but it was poorly impacted by the total dry matter. The present study highlighted the importance of using appropriate statistical methods to overcome uncertainties due to destructive measurements. The genericity of the statistical approach presented may encourage their implementation in other agronomy studies. Based on our results, a simple ecophysiological conceptual framework of grapevine pluriannual growth under various nitrogen supplies was built. This latter provides a relevant basis for a future model of grapevine C and N balances and responses to N fertilization