Littérature scientifique sur le sujet « Nitrogen Nutrition Index (NNI) »

In order to investigate the feasibility of using rice leaf critical nitrogen concentration as a nitrogen nutrition diagnosis index, a three-year positioning experiment with large-spike rice cultivar (Wuyoudao4) and multiple-spike rice cultivar (Songjing9) under five nitrogen levels (0, 60, 120, 180, and 240 kg·ha−1) was conducted. A critical nitrogen dilution curve and a nitrogen nutrition index (NNI) of rice leaf dry matter were constructed for Wuyoudao4 (Nc = 1.96LDM−0.56, R2 = 0.87, NNI was between 0.6–1.26, and Normalized Root Mean Square Error (n-RMSE) = 13.07%) and Songjing9 (Nc = 1.99LDM−0.44, R2 = 0.94, NNI was between 0.64–1.29, and n-RMSE = 15.89%). The relationship between dry matter and nitrogen concentration of rice leaves was a negative power function, and the model had good stability over the three years. The developed critical nitrogen concentration dilution curve, based on leaf dry matter, was able to diagnose nitrogen nutrition in rice efficiently. The model established in this study could be used to directly regulate and control the nitrogen nutrition of rice leaves.

Vegetation indices (VIs) can be useful tools to evaluate crop nitrogen (N) status. To be effective, VIs measurements must be related to crop N status. The nitrogen nutrition index (NNI) is a widely accepted parameter of crop N status. The present work evaluates the performance of several VIs to estimate NNI in sweet pepper (Capsicum annuum). The performance of VIs to estimate NNI was evaluated using parameters of linear regression analysis conducted for calibration and validation. Three different sweet pepper crops were grown with combined irrigation and fertigation, in Almería, Spain. In each crop, five different N concentrations in the nutrient solution were frequently applied by drip irrigation. Proximal crop reflectance was measured with Crop Circle ACS470 and GreenSeeker handheld sensors, approximately every ten days, throughout the crops. The relative performance of VIs differed between phenological stages. Relationships of VIs with NNI were strongest in the early fruit growth and flowering stages, and less strong in the vegetative and harvest stages. The green band-based VIs, GNDVI, and GVI, provided the best results for estimating crop NNI in sweet pepper, for individual phenological stages. GNDVI had the best performance in the vegetative, flowering, and harvest stages, and GVI had the best performance in the early fruit growth stage. Some of the VIs evaluated are promising tools to estimate crop N status in sweet pepper and have the potential to contribute to improving crop N management of sweet pepper crops.

SUMMARYCrop nitrogen (N) status is an important indicator of crop health and predictor of subsequent crop yield. The present study was conducted to analyse the relationships between nitrogen nutrition index (NNI), nitrogen biomass difference (ΔNB) and spectral indices in wheat, and then attempt to improve field N management. Spectral indices and concurrent sample N and biomass parameters were obtained from the Shihezi University experimental site in Xinjiang, China during 2009 and 2010. The results showed that all spectral indices were significantly correlated with NNI. Regression functions with the highest determination coefficient (R2) and the lowest root mean square error (RMSE) were used to improve prediction of NNI, and then the selected spectral index was used to estimate NNI and ΔNB. The strongest relationships were observed for the products of modified normalized difference 705 × biomass dry weight (BND705) and the enhanced vegetation index 2 (EVI2) for estimating NNI. There were also strong relationships between the NNI and the normalized NNI (ΔNNI) as well as between ΔNNI and ΔNB, with a linear relationship between ΔNB and the spectral index BND705 and a linear relationship between ΔNB and the spectral index EVI2. These results indicated that BND705 and EVI2 can be used to improve the accuracy of NNI estimation, and the correlations of ΔNB and NNI with BND705 and EVI2 can be used to further improve field N management in wheat.

Weeds cause crop loss indirectly by reducing the quantity of resources available for growth. Quantifying the effects of weed interference on nitrogen (N) supply, crop growth, and N nutrition may assist in making both N and weed management decisions. Experiments were conducted to quantify the effect of N addition and weed interference on soil nitrate-N (NO3-N) over time and the dependence of corn growth on NO3-N availability, determine the corn N nutrition index (NNI) at anthesis, and evaluate if relative chlorophyll content can be utilized as a reliable predictor of NNI. Urea was applied at 0, 60, and 120 kg N/ha to establish N treatments. Season-long weedy, weed-free, and five weed interference treatments were established by delaying weed control from time of crop planting to the V3, V6, V9, V15, or R1 stages of corn development. Soil NO3-N ranged from 20 kg N/ha without N addition to 98 kg N/ha with 120 kg N/ha added early in the season, but crop and weed growth reduced soil NO3-N to 10 kg N/ha by corn anthesis. Weed presence reduced soil NO3-N by up to 50%. Average available NO3-N explained 29 to 40% of the variation in corn shoot mass at maturity. Weed interference reduced corn biomass and NNI by 24 to 69%. Lack of N also reduced corn NNI by 13 to 46%, but reduced corn biomass by only 11 to 23%. Nondestructive measures of relative chlorophyll content predicted corn NNI with 65 to 85% accuracy. Although weed competition for factors other than N may be the major contributor to corn biomass reduction, the chlorophyll meter was a useful diagnostic tool for assessing the overall negative effects of weeds on corn productivity. Further research could develop management practices to guide supplemental N applications in response to weed competition.

Non-destructive acquisition and accurate real-time assessment of nitrogen (N) nutritional status are crucial for nitrogen management and yield prediction in maize production. The objective of this study was to develop a method for estimating the nitrogen nutrient index (NNI) of maize using in situ leaf spectroscopy. Field trials with six nitrogen fertilizer levels (0, 75, 150, 225, 300, and 375 kg N ha−1) were performed using eight summer maize cultivars. The leaf reflectance spectrum was acquired at different growth stages, with simultaneous measurements of leaf nitrogen content (LNC) and leaf dry matter (LDW). The competitive adaptive reweighted sampling (CARS) algorithm was used to screen the raw spectrum’s effective bands related to the NNI during the maize critical growth period (from the 12th fully expanded leaf stage to the milk ripening stage). Three machine learning methods—partial least squares (PLS), artificial neural networks (ANN), and support vector machines (SVM)—were used to validate the NNI estimation model. These methods indicated that the NNI first increased and then decreased (from the 12th fully expanded leaf stage to the milk ripening stage) and was positively correlated with nitrogen application. The results showed that combining effective bands and PLS (CARS-PLS) achieved the best model for NNI estimation, which yielded the highest coefficient of determination (R2val), 0.925, and the lowest root mean square error (RMSEval), 0.068, followed by the CARS-SVM model (R2val, 0.895; RMSEval, 0.081), and the CARS-ANN model (R2val, 0.814; RMSEval, 0.108), which performed the worst. The CARS-PLS model was used to successfully predict the variation in the NNI among cultivars and different growth stages. The estimated R2 of eight cultivars by the NNI was between 0.86 and 0.97; the estimated R2 of the NNI at different growth stages was between 0.92 and 0.94. The overall results indicated that the CARS-PLS allows for rapid, accurate, and non-destructive estimation of the NNI during maize growth, providing an efficient tool for accurately monitoring nitrogen nutrition.

Nitrogen nutrition index (NNI), harvest index (HI), dry matter accumulated by different organs were estimated several times during the vegetation period of potato plants grown in the both field and pot experiments at the Experimental Station in Jadwisin, Poland. Nitrogen fertilizer as NH₄NO₃ was applied at three doses (40, 120, and 200 kg·ha=<sup>-1<sup> N) in the field experiment and 2,7 g N in 1996 and 4g N in 1997 and 1998 per each plant in the pot experiment. Results showed that the values of NNI both in field and pot experiments increased from emergence till the about closing rows and then they gradually decreased. The NNI values were dependent on N rates. The higher were N doses, the higher were values of NNI. These differences were especially present during the first half of vegetation periods. The excess of N in potato plants (NNI values above 1,O) was recorded in the greater part of vegetation periods in plants grown at the dose 200 kg·ha^-1 N and for short length of time at the rate 120 kg·ha^-1 N. The excess of nitrogen was associated with the highest values of total biomass accumulation and with decreasing ofthe harvest index; (average NNI=0,53). Unsuffieient level of nitrogen nutrition (NNI values below 1,0) was found for the whole vegetation periods in all plants grown in pots and in the field at the dose 40 kg·ha^-1 N. These plants produced less total biomass but more of it was distributed to the tubers with average values of HI: 0,68 in field and 0,78 in pot experiments. Plants grown in the field under warmer weather conditions had better nitrogen nutrition status than those grown under cooler and wetter ones.

In order to investigate the feasibility of using rice critical nitrogen concentration as a nitrogen nutrition diagnosis index, a two-year positioning field gradient experiment using four rice varieties and four nitrogen levels (0, 75, 150, 225 kg·ha–1 for early rice; 0, 90, 180, 270 kg·ha–1 for late rice) was conducted for early and late rice. The critical dilution curves (Nc%) of the double-cropped rice based on leaf dry matter (LDM) were constructed and verified using the field data. Two critical nitrogen dilution curves and nitrogen nutrition indexes (NNI) of rice LDM were constructed for early rice [Nc% = 2.66LDM−0.79, R2 = 0.88, NNI ranged between 0.29–1.74, and the average normalized root mean square error (n-RMSE = 19.35%)] and late rice [Nc% = 7.46LDM−1.42, R2 = 0.91, NNI was between 0.55–1.53, and the average (n-RMSE = 15.14%)]. The relationship between NNI and relative yield was a quadratic polynomial equation and suggested that the optimum nitrogen application rate for early rice was sightly smaller than 150 kg·ha–1, and that for late rice was about 180 kg·ha-1. The developed critical nitrogen concentration dilution curves, based on leaf dry matter, were able to diagnose nitrogen nutrition in the double-cropped rice region.

The objective of this study was to determine how much improvement red edge-based vegetation indices (VIs) obtained with the RapidSCAN sensor would achieve for estimating rice nitrogen (N) nutrition index (NNI) at stem elongation stage (SE) as compared with commonly used normalized difference vegetation index (NDVI) and ratio vegetation index (RVI) in Northeast China. Sixteen plot experiments and seven on-farm experiments were conducted from 2014 to 2016 in Sanjiang Plain, Northeast China. The results indicated that the performance of red edge-based VIs for estimation of rice NNI was better than NDVI and RVI. N sufficiency index calculated with RapidSCAN VIs (NSI_VIs) (R2=0.43–0.59) were more stable and more strongly related to NNI than the corresponding VIs (R2=0.12–0.38).

Grasslands are rarely irrigated, thus water deficits often induce a reduction of the nitrogen nutrition index (NNI) during summer. This is measured using the ratio between the actual N concentration and the minimum N concentration required to achieve the maximum growth rate. NNI is derived from the standing biomass by a simple relationship. This paper details the results of a field experiment, combining 2 levels of irrigation with 2 levels of nitrogen fertilisation during the summer, on 2 commonly cultivated grass species in pure swards (tall fescue, Festuca arundinacea L., and Italian ryegrass, Lolium multiflorum). Plant water status, NNI, root length density (RLD), soil volumetric water content (θv), and mineral nitrogen concentration [N] were followed under water deficit and recovery. In both species, RLD was high (>6 cm/cm3) in the 0–0.25 m soil layer. Whereas the NNI of tall fescue responded strongly to its water status, Italian ryegrass was most often above optimal nitrogen nutrition because of its slow growth in that particular season and its higher superficial RLD. However, its NNI generally followed the θv closely, whereas tall fescue exhibited a delay in response of NNI upon rewatering, suggesting lasting effects of water deficits on the absorption capacity of roots in that species.

With the objective to evaluate the effects of nitrogen levels (0, 40, 80, 120 and 160 kg of N ha-1) on green dry matter (GDM) yield and morphogenetic and structural characteristics and nitrogen nutrition index (NNI) of Brachiaria brizantha cv. Piatã, was installed an experiment under field conditions in Roraima´s savannas. Nitrogen fertilization increased significantly (P<0.05) GDM yields, number of tillers, number of leaves tiller-1, average leaf size, leaf area index, leaf senescence rate, leaf appearance and elongation rates. Maximum GDM yields, leaf elongation rates, leaf length and number of leaves tiller-1 were obtain with the application of 145.9; 118.2; 108.9 and 133.6 kg of N ha-1, respectively. Nitrogen nutrition index alone with 120 or 160 kg N application was higher than the grass N internal critical level. The NNI, efficiency of utilization and apparent N recovery were inversely proportional to the increased N levels.

L’optimisation des apports azotés représente un enjeu majeur pour réduire les pollutions tout en maintenant un rendement élevé et une qualité satisfaisante de la récolte. Les apports d’azote (N) sont aujourd’hui mal valorisés par les cultures et une meilleure prise en compte de la variabilité spatiale et temporelle des besoins des plantes permettrait d’ajuster ces apports et améliorer leur valorisation. Pour cela, la connaissance du statut azoté du couvert végétal en cours de croissance est primordiale. La présente thèse porte sur le suivi non-destructif de l’indice de nutrition azoté (INN) du blé tendre d’hiver (Triticum aestivum L.). Afin de mettre en place la méthode de suivi de l’INN, des essais présentant un gradient de fertilisation ont été étudiés durant trois années. Durant cette période, le statut azoté a été évalué au moyen de mesures destructives, par l’utilisation d’un capteur optique foliaire (Dualex, Force A, Orsay), mais aussi au moyen de caméras multispectrales montées sur drone. Les mesures obtenues avec le Dualex ont présenté une corrélation élevée et stable avec l’INN, particulièrement au stade deux nœuds (r² = 0.78). La première année, des indices de végétation (IV) communément utilisés, calculés à partir de mesures de réflectance dans quatre longueurs d’ondes obtenues à l’aide d’une caméra Sequoia (Parrot, Paris, France), ont été évalués. Les corrélations obtenues entre les IV et l’INN étant moyennes et les IV étant peu discriminés entre eux, cela a conduit à l’étude d’une gamme plus large de longueurs d’ondes via l’utilisation d’une caméra multispectrale modulable Kernel (Mapir, San Diego, USA) mesurant la réflectance dans 15 longueurs d’ondes, de 405 à 940 nm. De nouvelles combinaisons ont ainsi été testées sur base des formulations de 8 IV. Au total 248 combinaisons ont été évaluées, mettant en évidence l’intérêt des combinaisons associant le vert et le proche infrarouge (PIR) en début d’élongation et les associations du PIR avec la portion orange-début du rouge du spectre en fin d’élongation et au stade gonflement. Quatre modèles de prédiction non paramétriques ont été construits et évalués sur base des informations collectées. Malgré l’absence d’améliorations des performances par rapport à de combinaisons simples d’IV, ces modèles devraient permettre d’être plus stables grâce à la prise compte d’un nombre plus important de longueurs d’ondes que les IV seuls. Le modèle de régression par les moindres carrés partiels (PLS), qui a présenté le plus d’intérêt, a été ensuite combiné avec des mesures prises par proxidétection afin d’améliorer la capacité de prédiction du statut azoté de façon notable. Un modèle combinant mesures prises par proxi- et télédétection a donc été construit et mériterait d’être testé en parcelle agriculteur. Cette étude a été complétée par un suivi des composantes de rendement, mettant en évidence le nombre d’épis par m² comme la composante de rendement la plus influencée par la fertilisation, mais aussi la plus déterminante pour le rendement. Enfin, la dernière partie du travail a porté sur le suivi des performances agronomiques et environnementales de quatre outils d’aide à la décision (OAD) proposés actuellement aux agriculteurs pour piloter la fertilisation. Les OAD ont majoritairement conseillé un dépassement de la dose bilan calculée en début de saison. En pratique, cela ne s’est pas traduit par une amélioration significative des performances à la récolte. Toutefois, la mauvaise valorisation des apports a conduit à augmenter la teneur en N minéral du sol à la récolte, particulièrement en année sèche, présentant un risque potentiel de lessivage. En perspective à ce travail, une méthode de fertilisation dynamique, basée sur un diagnostic précoce du statut azoté ou de la disponibilité en N minéral, serait pertinente et pourrait être proposée sous forme d’un modèle de suivi de l’INN combinant des mesures prises par proxi- et télédétection
Increase the Nitrogen (N) use efficiency (NUE) to minimize the N pollution while maintaining high crop yield and satisfactory quality at harvest is essential for the development of sustainable agriculture. A better consideration of the spatial and temporal variability of N requirements would allow to adapt N fertilizer rate in space and time to match crops’ demand to increase N recovery. Knowledge of the crop's N status during growth should therefore make it possible to improve fertilisation practices. In this context, the main purpose of this thesis project was to make non-destructive monitoring of the winter wheat (Triticum aestivum L.) N nutrition index (NNI) during crops’ growth with the aim of subsequently integrating this knowledge into a dynamic management approach to N fertilisation. For this purpose, three experimental fields showing various patterns of NNI dynamics were monitored in the North of France, both on field with destructive measurements and with a leaf-clip sensor (Dualex, Force A, Orsay, France), but also with multispectral cameras embedded on unmanned aerial vehicles (UAV). During the three growing seasons (2019-2021), Dualex leaf-clip presents a stable and relevant application to predict NNI at stage two nodes (R²=0.78). For the first year, commonly used vegetation indices (VI) were calculated from pictures taken by Sequoia camera (Parrot, Paris, France) and evaluated to monitor NNI. The correlation between these VI remains average. According to these results, it was difficult to select a discriminant VI among commonly used VI which confirms the interest in studying new wavelengths to increase VI sensitivity to change in N status. Since 2020, to enhance the investigation of the relationship between VI and NNI, a six-lens multispectral modular camera (Kernel camera, Mapir, San Diego, CA, USA) was used and allow to take picture in 15 wavelengths, from 405nm to 940nm. Measurements taken at 15 wavelengths made it possible to calculate eight VI, with a total of 248 different wavelength combinations. Among these combinations, the combination of green and near-infrared measurements at the beginning of elongation and the associations of the near-infrared with the orange-early red portion of the spectrum at the end of elongation were of interest. Four non-parametric prediction models were then construct and evaluated to consider more explanatory variables than simple VI which combine only few wavelengths’ measurements. The partial least squares (PLS) regression model, which was of most interest in this study, was then combined with proximal sensing measurements to significantly improve the ability to predict N status. A prediction model of NNI combining remote and proximal sensing measurements was therefore built and should be tested in a farmer's plot. This study was completed by monitoring yield components, highlighting the number of spikes.m-² as the yield component most influenced by fertilisation but also the most determinant for yield. Finally, a second part of this work aims to compare the agronomic and environmental performances of 4 decision support tools (DSTs) used by farmers, with the classical balance sheet method (BSM), at the crop succession scale. The fertilizer N dose advised by DSTs was mostly higher than those calculated with the BSM without any significant increases neither in crop yield nor in grain quality. The excess of fertilizer N was weakly recovered by crop and led to over-fertilization, more pronounced in dry condition. In this context, a dynamic fertilisation method based on a diagnosis of nitrogen status or mineral N availability earlier in the season is relevant and could be based on a NNI monitoring model combining proximal and remote sensing measurements

Soil nitrogen (N) is a major factor limiting forest growth. While inorganic N forms such as ammonium (NH4) and nitrate (N03-) have been the focus of plant N nutrition studies, a growing body of research has shown direct uptake of organic N forms (including amino acids) is common across the plant kingdom. However, there are few examinations of the contribution amino acid N makes to plant nutrition in temperate forest regions. The main goals of this thesis were to determine i) potential contributions amino acid-N and inorganic-N could make to N-nutrition of some temperate forest plants, ii) N-form adaptations among species that could lead to N-niche partitioning among them, and iii) the influence of m ycorrhizae on plant growth and N-form uptake. I determined the relative availabilities of amino acid N and inorganic N in three sites near Jordan River, British Columbia, biomass production of four species of forest plants. some associated with m ycorrhizae, when given inorganic (NH4-, N03-) or organic (glycine, glutamic acid) N, and short-term uptake (24 hours) of labelled N H4+, N03-, glycine, and glutamic acid using Sitka spruce (Picea sitchensis ), Douglas-fir (Pseudotsuga menziesii ), blueberry (Vaccinium ovalifolium) and salmonberry (Rubus spectabilis). All species performed well when supplied with N prim arily as NH4+, and NH4+ tended to be the most available N -source in all soils tested. Soils dominated b y salmonberry tended to have greater N03- production and lower amino acid-N: inorganic-N ratios compared to soils dominated by blueberry. This corresponded to the good growth and short-term 15NO3-uptake of salmonberry when grown with N supplied primarily as N03-, compared to other N-form treatments. Blueberry grew significantly more when given NH4- and N03-compared to amino acids. Thus, while blueberry has the ability to take up and use N03-for growth, sites on which it was dominant had low N03- availability. Mycorrhization did not improve biomass production, and in some cases actually decreased biomass. However, 15N uptake tended to be improved in mycorrhizal plants compared to non¬mycorrhizal plants. The comparable rates of short-term 15N uptake from amino acids and inorganic-N by all plants. in addition to the coin parable amino acid-N and inorganic-N availability in soils, suggested that am ino acids may be significant contributors to the N - nutrition of these tern perate species. However, biomass production was often reduced in amino acid treatments, which this was not always reflected by short-term '5N uptake.

Tillage, stubble retention and nitrogen fertilization are management practices that influence the productivity and sustainability of rainfed cropping systems. However, the application of these practices is limited by our understanding of the mechanisms that contribute to crop growth and yield, including water and nitrogen use efficiency. Canopy development and patterns of leaf senescence alter the partitioning of water and nitrogen (N) use, both before and after flowering, which impacts grain yield. The two central questions for this research were: (1) what are mechanisms of canopy development that contribute to yield in no-till and stubble retention systems?; and (2) under what circumstances do they increase yield, water and N use efficiency? The aims for this thesis were to evaluate crop response to no-till, stubble retention and N fertilization, in the contrasting systems of wheat (Triticum aestivum L.) and maize (Zea mays L.), to better understand mechanisms that regulate crop growth, patterns of senescence and yield, in addition to water and nitrogen use efficiency (NUE). A physiological approach that linked the traits regulating crop growth and yield was used to interpret crop responses to treatments. It is hypothesised that there are similarities in the mechanisms operating in no-till and stubble retention systems that could be improved to increase yield. Field experiments were conducted in the dryland wheat growing environments of southern Australia and in maize systems in a sub-humid tropical environment in Kenya. In Australia, experiments were conducted at Roseworthy and Karoonda using two tillage treatments (conventional tillage, CT and no-till, NT), four rates of stubble (zero, low, moderate and high) and three N timings, splitting the application of 100 kg N ha⁻¹ between sowing, tillering (GS22) and awn emergence (GS49) in the ratios of 100-0-0, 25-50-25, 0-50-50. At Roseworthy, historic Australian wheat varieties were evaluated under NT with the retention of moderate amounts of stubble and under CT without stubble. In Kenya, field experiments were conducted at Embu research station to evaluate the responses of maize to CT and NT, three amounts of stubble (0, 3 and 5 t ha⁻¹) and N rates of 0, 80 and 120 kg N ha⁻¹, as well as timing the of supply of 80 kg N ha⁻¹ at sowing, six leaf stage (V6) and 12-leaf stage (V12) in the fractions of 0-0-0, 80-0-0, 27-53-0, 27-27-27 and 0-40-40. Wheat grain yield ranged from 1.5-3.2 t ha⁻¹, and the effects of tillage were marginal. Grain yield increased from bare ground up to the application of moderate amounts of stubble but reduced at high amounts of stubble. Benefits of water capture and storage did not improve with the application of high amounts of stubble. Crop growth rate (CGR) between stem elongation and flowering was inversely correlated with tiller numbers, and explained most of the treatment differences. Sowing application of N produced large vegetative biomass which led to a decrease in CGR and radiation use efficiency between stem elongation and flowering, resulting in a decrease in grain yield compared with delayed N supply. Five decades of selection has not provided greater adaptation to NT and stubble retention in Australian wheat, despite grain yield increases of 21 kg ha⁻¹ year⁻¹ between 1958 and 2011. Substantial changes in canopy architecture were detected from older taller varieties with closed canopies to modern short-stature varieties with more open canopies. Modern varieties had greener leaves but showed faster rates of leaf senescence compared with the older counterparts. Maize grain yield ranged from 2.3-5.3 t ha⁻¹, with small effects from tillage and stubble supply. Rate and timing of N supply produced large effects and modified crop response to tillage and stubble. When stubble was removed, grain yield reduced by 10% while water storage at sowing decreased by 8% under NT compared with CT. Crop growth rate between six-leaf stage (V6) and flowering, and nitrogen nutrition index (NNI) partially explained treatment differences. Retention of stubble reduced CGR and NNI compared with bare ground. The value of stubble in water storage at sowing, and crop growth and yield was greater in a season that received < 300 mm rainfall compared with where rainfall was > 600 mm. Delaying N supply increased NNI, CGR and traits associated with NUE and grain yield compared with sowing applications of N. Patterns of senescence in maize, at both whole-plant and canopy-layer scales were marginally impacted by tillage and stubble retention. Leaf senescence was primarily driven by N supply and sink size. Time to loss of 50% of maximum leaf greenness was earlier in fertilized crops but delayed in the unfertilized controls. Rate of senescence was faster in fertilized crops compared with unfertilized controls at both whole-plant and canopy-layer scales. Grain yield, kernel number and nitrogen remobilization efficiency were associated with a faster rate of senescence in the top and mid layer leaves but with slower rates of senescence in the bottom layer. There were similarities in treatment effects and the mechanisms that regulated crop growth and yield between the two systems: (1) Grain yield was a function grain number, which in turn was proportional to CGR during the critical period of determination. Strategic supply of N at sowing and later stages increased CGR during the critical period for grain set, improved NNI and increased RUE, hence higher grain yield; (2) Grain yield was maximized at 2-3 t ha⁻¹ of stubble as demonstrated by the analysis of yield gaps, potentially due to water capture and storage and the regulation of soil temperature which impacted emergence and early growth; (3) N supply and sink size modified the patterns of senescence in both crops, whereby faster rates of senescence were associated with higher grain yield; and (4) N supply modified crop response to tillage and stubble. Treatment interactions were few, and varied with N supply and season. Effects of tillage system were marginal and independent of season. A mechanistic approach is discussed, which links treatment effects and the mechanisms regulating grain yield. In conclusion, the mechanisms of canopy development and yield limitation operating in NT and stubble retention were similar in both cropping systems. Higher fertilizer N rates and better timing of N supply are required for yield improvement in NT and stubble retention systems. While NT alone reduced yield, moderate amounts of stubble can improve water storage and grain yield, but this is subject to seasonal rainfall. Critical thresholds of 2-3 t ha⁻¹ of stubble indicate amounts over this limit could be allocated to alternative uses. Results show the importance of interpreting crop responses to NT and stubble retention on the basis of physiological principles.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Agriculture, Food and Wine, 2018

Σκοπός της παρούσας διδακτορικής διατριβής ήταν η μελέτη της δυναμικής του αζώτου σε καλλιέργεια γλυκού σόργου. Χρησιμοποιήθηκαν φυτά γλυκού σόργου [Sorghum bicolor (L) Moench] ποικιλίας Keller και πραγματοποιήθηκαν αφ’ ενός πειράματα στο πεδίο αφ’ ετέρου πειράματα σε πλαστικά δοχεία. Τα πειράματα πεδίου πραγματοποιήθηκαν σε αγρόκτημα του Πανεπιστημίου Πατρών, τις καλλιεργητικές περιόδους του 2004 και 2005, και περιλάμβαναν δύο χειρισμούς (βιολογική και συμβατική διαχείριση της γονιμότητας του εδάφους), με τρεις επαναλήψεις ο καθένας σε πλήρη τυχαιοποιημένη διάταξη. Τα αποτελέσματα των πειραμάτων πεδίου, έδειξαν ότι η βιολογική διαχείριση της γονιμότητας του εδάφους ευνόησε τη διαθεσιμότητα του εδαφικού νιτρικού αζώτου. Το 2004, μέχρι και την ολοκλήρωση της άνθησης, τα φυτά του βιολογικού χειρισμού συσσώρευσαν περισσότερο άζωτο από ό,τι τα φυτά του συμβατικού χειρισμού, αν και οι διαφορές δεν ήταν στατιστικά σημαντικές, εκτός από τη δεύτερη δειγματοληψία, όπου τα φυτά του συμβατικού χειρισμού συσσώρευσαν 2,69 N gm-2, ενώ για τα φυτά του βιολογικού χειρισμού η αντίστοιχη τιμή ήταν 5,12 N gm-2. Το 2005, η συσσώρευση αζώτου ακολούθησε παρόμοια πορεία μέχρι τα μέσα της άνθησης και οι διαφορές δεν ήταν στατιστικά σημαντικές, εκτός από τη τρίτη δειγματοληψία, όπου τα φυτά του συμβατικού χειρισμού συσσώρευσαν 3,61 N gm-2, ενώ για τα φυτά του βιολογικού χειρισμού η αντίστοιχη τιμή ήταν 4,61 N gm-2. H επίδραση εμβολίων Azospirillum brasilense, σε παραμέτρους αύξησης φυτών γλυκού σόργου και στην πρόσληψη αζώτου από τα φυτά, υπό διαφορετικά επίπεδα αζωτούχου λίπανσης μελετήθηκε σε πειράματα σε πλαστικά δοχεία. Το κάθε πείραμα περιλάμβανε πέντε χειρισμούς με τριάντα επαναλήψεις, έκαστος. Τα φυτά που εμβολιάστηκαν με Azospirillum brasilense και έλαβαν τη μισή ποσότητα αζώτου, έδωσαν 7,69 g ξηρής βιομάζας φυτό-1 στο τέλος του πρώτου πειράματος και 4,89 g ξηρής βιομάζας φυτό-1 στο τέλος του δεύτερου πειράματος, ενώ τα φυτά που δέχθηκαν πλήρη λίπανση αζώτου χωρίς εμβόλιο έδωσαν 2,39 και 2,04 g ξηρής βιομάζας φυτό-1 στο τέλος του πρώτου και δεύτερου πειράματος αντιστοίχως. Οι διαφορές των χειρισμών ανά πείραμα ήταν στατιστικά σημαντικές. Το συνολικό προσλαμβανόμενο άζωτο από τα φυτά που εμβολιάστηκαν με Azospirillum brasilense και έλαβαν τη μισή ποσότητα αζώτου ήταν 153,23 και 99,96 mg φυτό-1 στο τέλος του πρώτου και του δεύτερου πειράματος αντιστοίχως. Οι τιμές ήταν υψηλότερες σε σχέση με τις τιμές του συνολικού προσλαμβανόμενου αζώτου των φυτών των λοιπών και οι διαφορές ήταν στατιστικά σημαντικές. Τα αποτελέσματα των πειραμάτων έδειξαν υψηλή αξιοποίηση του εφαρμοζόμενου αζώτου των φυτών που εμβολιάστηκαν με Azospirillum. Τα αποτελέσματα υποδεικνύουν την βιωσιμότητα ενός βιολογικού συστήματος καλλιέργειας, όσον αφορά την κάλυψη των αναγκών των φυτών σε άζωτο. Η υψηλή αξιοποίηση του αζώτου από τα φυτά γλυκού σόργου, οδηγεί στη μείωση εφαρμογής αζωτούχων λιπασμάτων και συμβάλλει στη μείωση του κόστους καλλιέργειας, στη μείωση εκπομπών αερίων του θερμοκηπίου και στην μείωση διήθησης νιτρικών στο υπόγειο υδροφόρο ορίζοντα.
The aim of the present thesis was to study the nitrogen dynamics in sweet sorghum crop. Sweet sorghum plants [Sorghum bicolor (L) Moench] variety Keller were used, and field and experiments were conducted. Field experiments were conducted during 2004 and 2005 growing seasons at the experimental station of the University of Patras, Greece and there were two treatments (biological and conventional soil fertility treatment), in a randomized complete block experimental design with three replications. The results showed that biological soil fertility treatment favour soil nitrate nitrogen concentration. In 2004, until completion of blooming, nitrogen uptake was higher in plants cultivated on biological fertility treated soil than in them cultivated on conventional but the differences were not statistically significant, except in second sampling, which nitrogen uptake was 2,69 N gm-2 in plants cultivated on conventional fertility treated soil and it was 5,12 N gm-2 in plants cultivated on conventional fertility treated soil. In 2005, until half of blooming, nitrogen uptake was similarly ranged for both treatments but the differences were not statistically significant, except in third sampling, which nitrogen uptake was 3,61 N gm-2 in plants cultivated on conventional fertility treated soil and it was 4,61 N gm-2 in plants cultivated on conventional fertility treated soil. Τhe effect of Azospirillum brasilense inoculation on growth parameters and nitrogen uptake in sweet sorghum plants fertilized with various nitrogen levels, was studied during pot experiments. Each experiment was including five treatments and thirty replications of each. Plants inoculated with Azospirillum brasilense and receiving half amount of nitrogen fertilizer produced 7,69 g dry biomass plant-1 at the end of the first experiment and they produced 4,89 at the end of the second one, while plants receiving full amount of nitrogen fertilizer and no inoculation produced 2,39 and 2,04 g dry biomass plant-1 at the end of the first and second experiment, respectively. Differences among treatments in each experiment, were statistically significant. Total nitrogen uptake in Plants inoculated with Azospirillum brasilense and receiving half amount of nitrogen fertilizer was 153,23 and it was 99,96 mg plant-1 at the end of first and second experiment, respectively. Those plants showed higher nitrogen uptake than plants from each other treatment and the differences were statistically significant. Results showed that treatments which inoculated with Azospirillum brasilense were the most efficient in terms of nitrogen uptake. These results indicate that biological management provides an adequate nitrogen nutrition to sweet sorghum crop. High nitrogen efficiency in sweet sorghum plants leads in reduced applying nitrogen fertilization and contribute in reduced crop cost, in reduced emission of the greenhouse gas and in reduced leaching of NO3-N to ground water.

Quatre-vingt-quinze squelettes humains issus des fouilles archéologiques du cimetière protestant Saint-Matthew (ville de Québec, 1771-1860) ont été étudiés en associant deux aspects de la paléonutrition : la paléochimie et la paléopathologie. Le but de cette recherche est d’explorer la relation entre nutrition et état de santé pour cette population préindustrielle. Des informations directes sur l’alimentation ont été recueillies par l’analyse des isotopes stables du carbone et de l’azote du collagène des os, et des informations indirectes ont été obtenues par une quantification de l’état de santé des individus. Les méthodes paléopathologiques utilisées sont celles de l’« indice de santé » (Steckel et al., 2002) pour la comparaison interpopulationnelle, puis des méthodes comprenant des degrés de sévérité plus précis afin d’étudier les variations intrapopulationnelles. L’analyse de ces données atteste d’un état de santé relativement mauvais par comparaison avec d’autres groupes nord-américains contemporains, malgré une alimentation similaire. Des différences alimentaires ont été observées en fonction des données paléodémographiques (âge, sexe), mettant notamment en évidence une variabilité temporelle dans la réalisation du processus de sevrage. De plus, un régime alimentaire moins riche en ressources C4 (maïs, sucre de canne) et en ressources animales (viande, poissons, produits laitiers) a été constaté pour les enfants entre 2 et 7 ans par rapport aux individus plus vieux. Enfin, une relation possible entre la sévérité de certaines pathologies (cribra orbitalia et périostite) et la consommation des ressources alimentaires en C4 et/ou marines et riches en protéines a été observée.
Ninety-five human skeletons from archaeological excavations at the protestant Saint-Matthew burial ground (Quebec City, 1771-1860) were studied with respect to two major aspects of palaeonutrition: palaeochemistry and palaeopathology. The aim of this study was to explore the relationship between nutrition and health in this preindustrial population. Direct information on the types of food consumed was obtained from stable carbon and nitrogen isotope analyses of bone collagen, and indirect information was acquired by quantifying health status. Palaeopathological methods used are the “health index” method (Steckel et al.,2002) for interpopulational comparison, and then quantifications using more precise severity degrees for assessing intrapopulational variation. Data analysis revealed a relatively bad health status compared to other contemporary North-American groups despite a relatively similar nutrition. Food differences in relation to palaeodemographical data (age, sex) were noted, in particular about the variability of weaning process achievement. Furthermore, a diet depleted in C4 (corn, sugarcane) and in animal resources (meat, fish, dairy products) was noted for children between two and seven years old in comparison to older individuals. Finally, a possible relationship between pathologies severity (cribra orbitalia, periostitis) and the consumption of C4 and/or marine resources and animal products rich in protein was highlighted while comparing all the data.