No description available.

No description available.

Master of Science / Department of Agronomy / P. V. Vara Prasad / In many countries producers have been growing varieties of hard white winter (HWW) wheat since decades. The cause of concern is most varieties of HWW wheat are susceptible to pre-harvest sprouting (PHS) which affects grain quality. Environmental conditions like high humidity, precipitation, heavy dew and hormonal activity at physiological maturity stimulate PHS in HWW. To alleviate these conditions research was carried out at KSU. KS01HW163-4, a sprouting tolerance line was crossed with Heyne, a sprout susceptible cultivar. A total of 224 doubled haploid (DH) lines thus produced were phenotyped in the present study through experiments conducted in controlled environments. The objectives of this research were to (i) characterize and phenotype the doubled haploid lines for PHS in controlled environments; (ii) understand the impact of growth environment (high temperature and/or drought) and; (iii) impact of exogenous application of growth hormones on tolerance to pre-harvest sprouting in the parental lines of the doubled haploid population. The phenotypic data collected from this research will be ultimately combined with the genotypic data to identify DNA markers related to PHS tolerance and provide DNA markers for marker assisted selection. Based on my results of the germination percentages from the 224 DH lines, the population was distributed as susceptible, and tolerant to PHS showing a bimodal distribution and X[superscript]2 analysis indicating a complimentary gene action. From the study of the influence of environmental factors on PHS, my results confirmed a definite influence of stress on sprouting. Under optimum temperature (OT), KS01HS163-4 was tolerant to PHS, but at HT and/or drought it became susceptible to PHS. Growth under stressed conditions changed the tolerance levels to PHS. Seed dry-weight, and harvest index were also influenced negatively due to stress. Therefore multi-location tests must be conducted with variable environments to test the stability of a variety to PHS. From the study of the influence of phytohormones on PHS, the results suggest that tolerance to sprouting was seen in seeds from plants sprayed with abscisic acid (ABA) and paclobutrazol (GA-inhibitor) treatments where as those from gibberellic acid (GA) treatment showed susceptibility to sprouting.

Master of Science / Department of Plant Pathology / William Bockus / Barley yellow dwarf (BYD) is one of the most important wheat diseases in the state of Kansas. Despite the development of cultivars with improved levels of resistance to BYD, little is known about the impact that this resistance has on yield loss from the disease. The intent of this research was to estimate yield loss in winter wheat cultivars in Kansas due to BYD and quantify the reduction in losses associated with resistant cultivars. During seven years, BYD disease incidence was visually assessed on numerous winter wheat cultivars in replicated field nurseries. Cultivars were planted about three weeks early to promote disease. When grain yields were regressed against BYD incidence scores, negative linear relationships significantly fit the data for each year and for the combined dataset covering all seven years. The models showed that, depending upon the year, 19-48% (average 33%) of the yields was explained by BYD incidence. For the combined dataset, 29% of the relative yield was explained by BYD incidence. The models predicted that cultivars showing high disease incidence had 25-86% (average 49%) less yield than a hypothetical cultivar that showed zero incidence. Using the models, the moderate level of resistance in the cultivar Everest was calculated to reduce yield loss from BYD by about 73%. Therefore, utilizing visual BYD symptom evaluations in Kansas, coupled with grain yields, is useful to estimate yield loss from the disease. Furthermore, linear models that incorporate those parameters can be used to calculate the impact of improving cultivar resistance to BYD on yield losses.

<p>Kvantifikovanjem uticaja klimatskih promena na biljnu proizvodnju stiče se mogućnost obrazovanja dugoročnih planova u poljoprivrednoj proizvodnji kako bi se održao visok i stabilan prinos ključnih gajenih kutura (p&scaron;enice, kukuruz). Najpre su urađene analize klime i agroklimatskih pokazatelja za sada&scaron;nje uslove 1971-2000. i očekivane uslove za 2030. i 2050. godinu za 11 lokaliteta Republike Srbije. Tek nakon analize klime uzima se u obzir poznata činjenica da postoji međusobna interakcija između meteorolo&scaron;kih uslova, zemlji&scaron;ta i biljke. Na ovoj interakciji zasnivaju se modeli biljne proizvodnje i upotrebljavaju se u cilju kvantifikovanja uticaja klimatskih promena na biljnu proizvodnju tj. na dinamiku vegetacije i prinos.<br />U radu su kori&scaron;ćeni osmotreni dnevni meteorolo&scaron;ki podaci sa jedanaest stanica sakupljenih u Republičkom Hidrometeorolo&scaron;kom Zavodu Srbije. Za buduće stanje klime kori&scaron;ćeni su izlazni podaci globalnih klimatskih modela (ECHAM, HadCM, NCAR) i njihovom statističkom regionalizacijom Met &amp; Roll vremenskim generatorom dobijeni su podaci o budućem stanju klime na području jedanaest izabranih lokaliteta. Podaci o zemlji&scaron;tu (mehaničke i hemijske osobine) preuzeti su od Agencije za za&scaron;titu životne sredine iz Beograda. Ulazni podaci o biljnoj vrsti i njenoj agrotehnologiji, neophodni u radu sa modelom biljne proizvodnje (kalibraciji i validaciji), obezbeđeni su sa vi&scaron;egodi&scaron;njih ogleda zasnovanih na oglednim poljima Rimskih &Scaron;ančeva Insituta za ratarstvo i povrtarstvo u Novom Sadu.<br />Kao metod kori&scaron;ćeni su modeli za određivanje agroklimatskih parametara Agriclim i model biljne proizvodnje DSSAT v. 4.2.<br />4<br />Analizom buduće klime, temperature vazduha i padavina, utvrđeno je da se može očekivati porast temperature vazduha na godi&scaron;njem nivou i tokom svih delova vegetacinog perioda, a količina padavina se očekuje da bude vi&scaron;a tokom zimskog perioda, dok u prolećnom periodu (mart &ndash; april - maj) ne&scaron;to niža do 10 mm, a tokom letnjih meseci jun-jul-avgust značajno niža.<br />Analizom rezultata DSSAT 4.2 modela biljne proizvodnje, utvrđeno je da u očekivanim klimatskim uslovima 2030. i 2050. godine pri koncentraciji CO2 od 330 ppm prinos zrna ozime p&scaron;enice ostaje nepromenjen u većini lokaliteta izuzev Kru&scaron;evcu, Somboru i Vranju gde prinos opada do 12% u 2030. i do 11% u 2050. godini. Uzrok visokih i stabilnih prinosa su povećane količine padavina i povećanje temperature vazduha u zimskom periodu, manji broj mraznih i ledenih dana. Jedan od najvažnijih faktora stabilnosti prinosa je i dovoljna količina rezerve vlage u zemlji&scaron;tu za prolećni period i količina padavina za prolećni period, koji je u literaturi određen kao kritični period potrebe p&scaron;enice za vodom. U budućim uslovima analizom rezultata broja dana potrebnih od setve do cvetanja i od setve do zrelosti, ustanovljeno je da se očekuje manji broj dana, tj. da će fenofaze kraće trajati do cvetanja i zrelosti &scaron;to je posledica očekivanih vi&scaron;ih temperatura vazduha i suma efektivnih temperatura. U uslovima 2030. i 2050. godine i očekivane koncentracije CO2 po IPCC izve&scaron;taju iz 2007. godine, uticaj povi&scaron;ene koncentracije CO2 na prinos zrna p&scaron;enice je pozitivan. Prinosi kod većine lokaliteta ostaju nepromenjeni dok je mali pad prinosa zrna bio primećen na lokalitetima Kru&scaron;evac i Sombor, gde neznatno opada do 7% u 2030. godini i 2050. godini. U Somboru se očekuje nepromenjena količina padavina za mart &ndash; april - maj period i mnogo manja količina padavina u periodu jun &ndash; jul - avgust, a u Kru&scaron;evcu ne&scaron;to manja količina padavina u periodu mart &ndash; april &ndash; maj i do 40% manja količina u periodu jun &ndash; jul - avgust u 2050. godini.<br />Analizom rezultata prinosa zrna kukuruza za 2030. i 2050. godinu pri koncentracije CO2 od 330 ppm dobijen je veoma značajan pad prinosa i u uslovima bez navodnjavanja i u uslovima navodnjavanja normom od 180 mm za sve lokalitete. U 2030. i 2050. godini u uslovima povi&scaron;ene koncentracije CO2 uticaj očekivane koncentracije CO2 na prinos zrna kukuruza simulacijama ocenjen je kao negativan, jer je dobijeni prinos zrna kukuruza bio jo&scaron; niži nego pri koncentraciji CO2 od 330 ppm.<br />Veoma značajan pad prinosa posledica je vi&scaron;ih temperatura vazduha u JJA periodu, povećanja fiziolo&scaron;kog stresa kod biljaka usled povećanja broja letnjih i tropskih dana, značajno smanjenje količine padavina, posebno u periodu jun &ndash; jul &ndash; avgust i povećanje broja su&scaron;nih dana tokom istog perioda. Analizom dužine trajanja vegetativne sezone za oba režima uzgajanja kukuruza moglo se zapaziti da se u budućim uslovima očekuje skraćenje perioda vegetacije zbog vi&scaron;ih temperatura vazduha i sume temperatura. Analizom rezultata simulacije prinosa zrna soje za 2030. i 2050. godinu pri koncentraciji CO2 od 330 ppm, očekuje se nepromenjen prinos zrna u lokalitetima Ćuprija, Ni&scaron;, Vranje i Prizren, ili neznatno vi&scaron;i do 9 % u lokalitetima Kraljevo, Kru&scaron;evac, Novi Sad, Sombor i Zaječar. Samo u istočnom lokalitetu Dimitrovgrad i centralnom Požega se očekuje značajno vi&scaron;i prinos do 14% u 2030. godini i do 23% u 2050. godini. U 2030. i 2050. godini pri povi&scaron;enoj koncentracije CO2 po IPCC izve&scaron;taju iz 2007. godine očekuje se veoma značajno vi&scaron;i prinos u svim lokalitetima, a posebno je nagla&scaron;eno u lokalitetima Dimitrovgrad i Požega gde su dobijene najniže srednje temperature vazduha za AMJ i JJA period, najmanji broj letnjih i tropskih dana. Nakon dobijenih rezultata prinosa zrna za izabrane biljne kulture, rezultati prinosa zrna kukuruza ukazivali su na potrebu definisanja i uvođenja mera adaptacija u dosada&scaron;nju agrotehnologiju. DSSAT model biljne proizvodnje je izabran u istraživanju i kvantifikovanju mera adpatacija, jer se potrebe i fiziolo&scaron;ke reakcije biljke u simulacijama mogu pratiti na dnevnom nivou (Wang et al., 2011). Kao mere adaptacije analizirane su adaptacija roka setve i navodnjavanje. Adaptacija roka setve urađena je za kukuruz u uslovima bez navodnjavanja, da bi se ocenio isključivo uticaj primene ranijeg roka setve na prinos, a ne i navodnjavanje. Na osnovu analize<br />5<br />rezultata relativne promene prinosa za sve lokalitete, pokazalo se da se u uslovima ranijeg roka setve očekuju vi&scaron;i prinosi nego u uslovima uobičajenog datuma setve. Međutim, u svim lokalitetima i dalje se očekuje veoma značajan pad prinosa, izuzev u Dimitrovgradu, Vranju i Prizrenu, gde se očekuje značajan porast u odnosu na prinose perioda 1971-2000. godina.<br />Na osnovu analize rezultata simuliranih prinosa za ozimu p&scaron;enicu, kukuruz i soju, konstatovano je da se p&scaron;enica može proizvoditi u uslovima bez navodnjavanja, a prolećni usevi kukuruz i soja bi morali da se navodnjavaju zbog očekivanog velikog smanjenja količine padavina u letnjem periodu. Da bi se procenila adekvatna norma navodnjavanja u proizvodnji kukuruza u simulacijama u DSSAT modelu biljne proizvodnje izabrana je opcija 50 % dostupne vode biljci. Simulacije proizvodnje kukuruza u uslovima 50% dostupne vode biljci dale su pozitivne rezultate prinosa. Prinosi su bili nepromenjeni u lokalitetima Ćuprija, Kru&scaron;evac, Kraljevo, Ni&scaron;, Novi Sad, Sombor, Vranje, Zaječar u 2030. godini i 2050. godini izuzev u Kraljevu gde je prinos bio niži do 17% u 2050. godini. U lokalitetima Dimitrovgrad, Požega i Prizren prinos je bio vi&scaron;i oko 9% u 2030. godini i nepromenjen u 2050. godini. Uvećanje norme navodnjavanja je bilo veoma značajno na većini lokaliteta od 20% do 30% sa maksimumom u Požegi do 45% u 2030. i 84% u 2050. godini. Lokalitet Požega imao je zemlji&scaron;te tipa ilovasti fluvisol i izmeren visok procenat peska, iznad 50% u svom mehaničkom sastavu, &scaron;to je uslovilo i veću propusnost vode, njeno kraće zadržavanje u profilu zemlji&scaron;ta i potrebu za većom količinom vode u navodnjavanju. Simulacije prinosa soje odmah su urađene u uslovima navodnjavanja od 50% dostupne vode biljci, jer je opcija u uslovima bez navodnjavanja davala jako niske prinose, a opcija 50% dostupne vode je davala takve norme navodnjavanja koje su bile slične u na&scaron;im uslovima na Institutu za ratarstvo i povrtarstvoPri takvoj opciji navodnjavanja u svim lokalitetima norma navodnjavanja je u budućim uslovima veoma značajno rasla od 10 do 40% u 2030. godini i od 13 do 110% u 2050. godini, a rezultati relativne promene prinosa ukazivali su na veoma značajno povećanje prinosa u budućim&nbsp;uslovima.</p> / <p>DSSAT 4.0 is a crop model commonly used to quantify the climate change impact on agriculture production. The model predictions are very important for long term planning in agriculture to keep high and stable yield production. At the first, the climate was analysed for 1971-2000 period, 2030 and 2050 year. After these analyses the crop model was run. Crop model is based on interaction between climate, soil and plant. Simulations were predicted the yield and dynamic in vegetation for 2030 and 2050 climate conditions. As input parameters were used observed daily weather data from eleven weather stations for 1971-2000 period. For 2030 and 2050, the data were used from global climatology models ECHAM5, HadCM3 and NCAR-PCM for two scenarios A1B and A2. Before crop simulations, the out results from global climatology models had to be regionalised and downscaled with Met &amp; Roll weather generator. The soil input data were assumed from Agency for Environmental Safety from Belgrade. The data were consist of mechanical and chemical characteristics of soil which were chosen near the weather station. The crop input data were collected from the literature and personal communication of Institute of Field and Vegetable Crops and their long term period experiments. A current and future agroclimatic indices were calculated with Agriclim model. As a crop model, DSSAT v. 4.2. was chosen for crop simulations of major field crops: winter wheat, maize and soybean.<br />The results of climate shown that the air temperature should be higher in all vegetation phases, and precipitation should be higher during winter months, lower for 10 mm in spring and significantly lower in summer months June- July-August.<br />In 2030 and 2050 year (CO2=330 ppm) simulations shown that winter wheat yield might be the same as in 1971-2000 period in most locations except in Krusevac, Sombor and Vranje where yield might be lower for 12% in 2030 year and lower for 11% in 2050 year. It is a consequence of expected higher precipitation and higher air temperatures during winter period, less frosty and frozen days, higher precipitation during spring, which is a critical period for winter wheat production. It was analysed the dinamyc in vegetation in future<br />9<br />conditions. The results showed the shorter vegetation, less number of days from seeding to anthesis and seeding to maturity. These changes in vegetation duration were caused by expected higher air temperatures and higher effective temperatures.<br />The yield results were also analysed for expected conditions under future CO2 concentration from IPCC report 2007, and shown that winter wheat yields were not changed for most locations except in Krusevac and Sombor in 2030 and 2050 year.<br />The maize yield results for 2030 and 2050 under CO2 concentration of 330 ppm shown a significant decrease in yield in non irrigated conditiond and irrigated conditions with 180 mm water added per vegetation season. Also, the results given under expected CO2 concentration from IPCC Report 2007, shown great decrease in 2030 and 2050 and lower yield than under CO2 was set on 330 ppm. The significant decrease in yield was caused by expected higher temperatures in JJA period, higher physiologicaly stress caused by more days with extreme high temperatures (summer and tropical days) and very significant decrease in precipitation during JJA period. The results showed the shorter vegetation, less number of days from seeding to anthesis and seeding to maturity. These changes in vegetation duration were caused by expected higher air temperatures and higher effective temperatures.<br />The soybean yield analyses for 2030 and 2050 under CO2 concentration of 330 ppm shown no changes in yield for Cuprija, Nis, Vranje and Prizren, a little higher to 10% in Kraljevo, Krusevac, Novi Sad, Sombor, Zajecar and up to 24% higher in Dimitrovgrad and Pozega. In 2030 and 2050 under future CO2 concentrations from IPCC Report 2007, it is expected a significantly higher yield in all locations especially for Dimitrovgrad and Pozega, where the air temperatures were lowest in AMJ and JJA period. The results showed the shorter vegetation in soybean production, less number of days from seeding to anthesis and seeding to maturity. These changes in vegetation duration were caused by expected higher air temperatures and higher effective temperatures. After all simulations for winter wheat, maize and soybean, it is concluded that maize production need some adaptation measures for future conditions. As an adaptation measure it were chosen two measures: the shift in sowing date and irrigation quantity. The adaptation in sowing date was set for maize under non irrigated conditions, to analyse only the time of sowing not irrigation. The sowing date was set 15 days earlier, on the 5th of April. The yield results shown less decrease than results given at usual sowing date (20th of April), but in all locations the predicted yield decreased except in DM, VR and PR where the yield shown significant increase in a comparison with 1971-2000 yield. The change in irrigation quantity was more efficient for yield. It was done for maize production and soybean, because winter wheat irrigation was estimated as non economic. The irrigation method was set on 50% available water for plant. The maize yield was stable in Ćuprija, Kru&scaron;evac, Kraljevo, Ni&scaron;, Novi Sad, Sombor, Vranje, Zaječar in 2030 and 2050 year except in Kraljevo where the yield decreased up to 17% in 2050 year. In Dimitrovgrad, Požega and Prizren the yield was higher for 9% in 2030 year and not chaged in 2050 year. The water requirements had significantly higher values than in 1971-2000 period up to 20-30% in 2030 year with maximum in Požega up t 45% in 2030 year and 84% in 2050 year. The location Požega has soil with a high percent of sand in structure, above 50%, what caused quick water filtration and more water in irrigation. The soybean simulations were done in irrigation option of 50% available water at the begining, because the non irrigated method did not gave the satisfied yield results in crop model. The 50% irrigation method gave adequate yield and water requirements as in experiments on Institute. The water requirements had significantly higher values in 2030 year from 10-40% and from 13% to 110% in 2050 year than in 1971-2000 period.<br />Key words: climate change, CO2 fertilization, DSSAT v. 4.2. crop model, effective irrigation, maize yield, soybean yield, vegetation, winter wheat yield.</p>

Lhumectation des surfaces végétales, due principalement aux précipitations sous forme de pluie ou de rosée, joue un rôle déterminant lors de la phase de contamination des plantes par de nombreux agents phytopathogènes. La connaissance de la pluie et de la rosée constitue un élément fondamental pour létude et la compréhension du fonctionnement des modèles de simulation des épidémies et des systèmes d'avertissements agricoles. Lobjectif de cette recherche est de contribuer à lamélioration du système davertissement des principales maladies cryptogamiques affectant le blé dhiver au sud de Belgique et au G-D de Luxembourg. Notre démarche a consisté, dans un premier temps à évaluer les potentialités du radar météorologique de Wideumont. Nous avons décrit son fonctionnement général ainsi que son principe de mesure et nous avons détaillé les différentes sources derreur qui affectent les estimations de précipitations dérivées des observations radar. Les mesures radar sont moins précises que les mesures de précipitations par des pluviomètres. Néanmoins, le radar permet dobserver en temps réel les précipitations sur un large domaine avec une très bonne résolution spatiale et temporelle. La comparaison quantitative et qualitative des précipitations mesurées au sol avec celles estimées par le radar a été faite sur une période de trois ans (2003, 2004 et 2005). Les résultats de la validation des cumuls mensuels font apparaître que le radar a tendance à sous-estimer les précipitations. Lerreur calculée pour lensemble des stations varie entre -50% et +12%. La validation qualitative du radar a été réalisée sur des occurrences de cumuls horaires. Les indices calculés à partir des tables de contingence donnent des valeurs de POD (Probability Of Detection) entre 0.44 et 0.80 durant la période étudiée. Limpact des estimations radar sur les périodes dinfection de Septoria tritici simulées par PROCULTURE a été évalué durant trois saisons culturales (2003, 2004 et 2005) par comparaison entre les données de sortie du modèle (alimenté par des estimations radar de précipitations horaires) et les estimations visuelles du développement des symptômes de la maladie sur les trois dernières feuilles. Les outputs de PROCULTURE via les données radar ont montré un grand accord entre la simulation et lobservation. Le radar météorologique devrait dès lors être bénéfique pour des régions où le réseau des pluviomètres est inexistant (ou moins dense) et où lincidence de la septoriose est importante. Dans un deuxième temps, sur base dune recherche bibliographique, un modèle dhumectation a été choisi. Le modèle sélectionné, appelé SWEB, se base sur le bilan énergétique et le bilan hydrique. Il simule la durée dhumectation due à la pluie et à la rosée sur lensemble du couvert végétal à partir des données issues des stations agrométéorologiques. Le modèle a été ensuite testé et validé sur différentes variétés de blé dhiver. Les données de sortie du modèle ont été comparées statistiquement aux mesures des capteurs (préalablement calibrés) et aux données dobservation obtenues sur des parcelles expérimentales et au champ durant les saisons culturales 2006 et 2007. Sur base des résultats obtenus, le modèle SWEB semble sous-estimer la durée dhumectation et plus particulièrement pour les événements de la fin dhumectation (dryoff). Lerreur moyenne en général est inférieure à 90 minutes. Dans un troisième temps, afin dobtenir une relation entre les périodes dhumectation et le développement de la septoriose sur les trois dernières feuilles, les périodes dhumectation simulées par SWEB ont été comparées dune part aux périodes dinfection de Septoria tritici simulées par PROCULTURE et dautre part aux estimations visuelles. Le modèle de la durée dhumectation simule avec succès des périodes dhumectations, dues à la fois à la rosée et à la pluie, qui ont déclenché linfection de la septoriose observée sur des parcelles expérimentales. Une durée minimale dhumectation favorable à linfection des feuilles de blé par Septoria tritici a été déterminée. Il est donc désormais nécessaire délaborer un système opérationnel intégrant le radar météorologique, le modèle de la durée dhumectation et le modèle épidémiologique. Notre travail a permis dacquérir via lanalyse des données agrométéorologiques et des données phytopathologiques, les connaissances nécessaires à lélaboration dun tel système et de participer ainsi à lamélioration des modèles davertissements existants. En effet, nous avons analysé les avantages et les limites du système radar comme données dentrée aux modèles et son aptitude dans la spatialisation des données. Nous avons également testé le modèle dhumectation pour la détermination des périodes dinfection nécessaires au développement de la septoriose. Dans une perspective dune meilleure opérationnalisation du système, lapproche envisagée pourrait facilement être intégrée dans le système existant pour la simulation dautres maladies comme les rouilles, loïdium et la fusariose à léchelle régionale. En définitive, ce travail aura prouvé une fois de plus lintérêt du "mariage" entre lagrométéorologie et la phytopathologie. [en] Summary - Weather-Radar Rainfall Measurement and Simulated Surface Wetness Duration for Septoria Leaf Blotch Risk Assessment. The persistence of free moisture on leaves, mainly as a result of precipitation in the form of rainfall or dew, plays a major role during the process of plant infection by most fungal pathogens. Acquiring rainfall and leaf moisture information is needed for accurate and reliable disease prediction and management. The objective of this research is to contribute to improve forecasting Septoria leaf blotch and other fungal pathogens on winter wheat in Belgium and Luxembourg./In the first part of this work, the potential of weather-radar rainfall estimates for plant disease forecasting is discussed. At first step, we focused on assessing the accuracy and limitations of radar-derived precipitation estimates, compared with rain-gauge data. In a second step, the Septoria leaf blotch prediction model PROCULTURE was used to assess the impact on the simulated infection rate of using, as input data, rainfall estimated by radar instead of rain gauge measurements. When comparing infection events simulated by PROCULTURE using radar-derived estimates and reference rain gauge measurements, the probability of detection (POD) of infection events was high (0.83 on average), and the false alarm ratio (FAR) of infection events was not negligible (0.24 on average). FAR decreased to 0 and POD increased (0.85 on average) for most stations, when the model outputs for both datasets were compared against visual observations of Septoria leaf blotch symptoms. Analysis of 148 infection events observed over three years at four locations showed no significant difference in the number of simulated infection events using either radar assessments or gauge measurements. This suggests that, for a given location, radar estimates are just as reliable for predicting infection events as rain gauges. As radar is able to estimate rainfall occurrence over a continuous space, unlike weather station networks that do observations at only a limited number of points, it has the great advantage of being able to predict the risk of infection at each point within an area of interest with an accuracy equivalent to rain gauge observations. This gives radar an important advantage that could significantly improve existing warning systems. In the second part, a physical model based on the energy balance, known as the Surface Wetness Energy Balance (SWEB), was applied for the simulation of Surface Wetness Duration (SWD) on winter wheat canopy. The model, developed in the United States on grapes canopies, was adapted for the winter wheat cultivars and was applied for use with agrometeorological data easily available from standard weather stations and weather-radar rainfall estimates. The SWEB model simulates surface wetness duration for both dew and rain events. The model was validated with data measured by sensors and with visual observations of SWD conducted in experimental plots during two cropping seasons in 2006 and 2007. The wetness was observed visually by assessing the presence or absence of surface water on leaves. Based on the results, the SWEB model appeared to underestimate surface wetness duration and especially for the dry-off events when compared statistically to visual observations. The error, on average, is generally less than 90 minutes. In order to establish a relationship between the surface wetness periods and Septoria leaf blotch development risk on the top three leaves, the SWEB model SWD outputs were compared with the number of hours of high probability of infection simulated by PROCULTURE as well as with visual plant diseases observations. A minimal surface wetness duration of favourable infection conditions for Septoria tritici was established. It is now required to develop an operational system that would integrate weather radar, surface wetness duration and foliar epidemic model. In this work, we have analyzed the advantages and limitations of the radar system as input to models and its ability for spatial interpolation of rainfall. We also tested the model for the determination of surface wetness periods required for Septoria Leaf Blotch Risk development. The proposed approach could be integrated in the existing system. Finally this approach shows once more the "happy marriage" between agrometeorology and plant disease management.

Papildomas augalų tręšimas per lapus žinomas jau prieš 140 metų. Tai labai efektyvus būdas norint greitai panaikinti nepalankių augimo sąlygų žieminiams kviečiams sukeltą stresą purškiant gydomaisiais tirpalais ir siekiant suformuoti optimalius derliaus struktūros elementus. Tai pasiekus galima tikėtis didesnio ir geresnės kokybės grūdų derliaus. 2005 – 2006 metais LŽŪU bandymų stotyje daryti lauko bandymai, kuriuose buvo tiriama tręšimų per lapus gydomaisiais tirpalais Atgaiva-1 (50 l ha-1), Amistar (0,7 l ha-1) ir jų mišinio įtaka žieminių kviečių (Triticum aestivum L.) derliui ir jo struktūros elementų rodikliams, esant trims, skirtingiems pagrindinio tręšimo fonams: 1) netręšta; 2) N90P60K90 ir 3) N180P120K180. Nustatyta, kad labiausiai žieminių kviečių grūdų derlių ir jo struktūros elementų reikšmes didino tręšimas Atgaiva-1 (50 l ha-1) ir tręšimas gydomųjų tirpalų Atgaiva-1 (50 l ha-1)+Amistar (0,7 l ha-1) mišiniu. Taip pat nustatyta, kad tręšimas per lapus didina mineralinių trąšų efektyvumą ir šių faktorių sąveika 2005 m. davė 3,84 t ha-1, o 2006 m. - 2,28 t ha-1 derliaus priedą. / Supplementary leaf-feed fertilization of plants was known about 140 years before. It is very effective way on purpose fast to remove winter wheat stress because of disadvantageous growth conditions, spraying leaf-feed fertilizers and settling optimum elements of yield. When these points gained, it is possible to expect the major and better quality grain yield. During the period of 2005 – 2006 field-site experiments were carried out at the experimental station of the Lithuanian University of Agriculture. The aim of investigation was to determine leaf-feed fertilizers Atgaiva-1 (50 l ha-1), Amistar (0,7 l ha-1) and their mixture solutions influence on winter wheat (Triticum aestivum L.) grain yield and its elements of yield, under different fertilization types: 1) unfertilized; 2) N90P60K90 and 3) N180P120K180. The biggest winter wheat grain yield and elements of yield values obtained after fertilization with leaf-feed fertilizers Atgaiva-1 (50 l ha-1) and Atgaiva-1 (50 l ha-1) + Amistar (0,7 l ha-1) mixture solution. Leaf-feed fertilization increased efficiency of mineral fertilizers and this factors interaction gave 3,84 t ha-1 yield increase in 2005 and 2,28 t ha-1 in 2006.

Darbo objektas – segetinė flora Kazliškių ekologinės gamybos ūkyje. Darbo tikslas – ištirti Kazliškių ekologinio ūkio žieminių kviečių lauko segetinės floros dinamiką priklausomai nuo sezoniškumo bei meteorologinių sąlygų. Darbo uždaviniai. • Nustatyti, kaip kinta segetinės floros kiekis žiemkenčių lauke priklausomai nuo sezoniškumo bei meteorologinių sąlygų. • Nustatyti piktžolių žaliosios ir orasausės masės kitimą žiemkenčių lauke priklausomai nuo sezoniškumo bei meteorologinių sąlygų. • Nustatyti piktžolių skaičiaus bei masės priklausomybę nuo hidroterminio koeficiento. Darbo metodai. Atliekant tyrimą iš žieminių kviečių lauko buvo išskirta 10 tyrimo laukelių po 0,25 m2, t.y. 2,5 m2. Tyrimo laukeliai pažymėti, kad butų galima sugrįžti į tą pačią vietą ir suskaičiuoti piktžoles prieš pjūtį. Atliekant tyrimą buvo suskaičiuotos išdygusios piktžolės, nustatyta piktžolių botaninė sudėtis ir nustatyta orasausė masė. Piktžolės buvo raunamos su šaknimis, nuo jų nupurtomos žemės, sudedamos į atskiras krūveles pagal tyrimo laukelio numerį. Tą pačią dieną suskaičiuojamas piktžolių kiekis, nustatoma kiekvieno laukelio piktžolių botaninė sudėtis ir pasveriama žalioji masė. Po to piktžolės buvo džiovinamos saulės neapšviestoje patalpoje keletą dienų, kol pasiekė orasausę masę. Darbo rezultatai. Nustatyta, kad tyrimo metu agrofitocenozėje vyravo šios piktžolės: pelkinė notra (Stachys palustris L.), paprastasis varputis (Agropyron repens L.), dirvinė usnis (Circium arvense L), trikertės... [toliau žr. visą tekstą] / The theme of thesis paper – is segetical flora of Kazliškiai ecological farm. The aim of thesis paper – is to analyze segetical flora dynamic of winter wheat of Kazliškiai ecological farm depending on meteorological and seasonal conditions. The tasks of thesis paper. • To define the variation of segetical flora of winter wheat depending on seasonal and meteorological conditions. • To analyze the variation of fresh and dried mass of winter wheat depending on seasonal and meteorological conditions. • To define the number of weed and mass dependence on hydrothermal coefficient. Work methods. During the research, every field was divided into small research fields (0.25x0.25). The research fields were marked so that it would be possible to find them as well as to calculate the weeds before the harvest. The botanical composition as well as air dry content was determined. The weeds were grubbed up with their roots, then the weeds were shaked to eliminate the soil, and finally the weeds were sorted to the separate heap according to the same day the botanical composition and green mass of weeds of every field was determined. Later the weeds were dried in a place not subjected to the direct sunlight for few days until the air – dry content was researched. Work results. During the research there dominated in agro phi to community these weeds: Agropyron repens L., Circium arvense L., Capsella bursa-pastoris L., Viola arvensis L., Tripleurospermum perforatum L., Taraxacum officinale L... [to full text]

La productivité et la qualité des céréales biologiques sont soumises à deux principaux facteurs limitants dans les systèmes sans élevage : des déficits chroniques en azote (N) du sol et des infestations par les adventices. Des légumineuses telles que les trèfles ou les luzernes peuvent servir à la fois de plantes de couverture et d'engrais verts grâce à leur fixation symbiotique d'N atmosphérique. Cependant, leur substitution aux céréales présente un moindre intérêt économique dans les systèmes de grandes cultures en l'absence d'animaux pour les valoriser. L'association relais de couverts de légumineuses dans un blé d'hiver nous a semblé être une option intéressante pour à la fois enrichir le système sol-plante en N, couvrir le sol dès la récolte du blé associé et limiter le risque de compétition avec le blé en décalant au printemps la date de semis des légumineuses sous couvert de blé. Pour évaluer l'efficacité de ces associations, quatre espèces de légumineuses (Medicago lupulina L., M. sativa L., Trifolium pratense L. et T. repens L.) ont été semées au tallage du blé d'hiver sur huit parcelles réparties dans la région Rhône-Alpes. Leurs effets sur la maîtrise des adventices, l'enrichissement, la préservation et la restitution d'N au système sol-plante et les performances des cultures ont été observés, durant une succession blé d'hiver-culture de printemps. Les résidus des couverts ont été enfouis à la fin de l'hiver, 9 à 12 semaines avant le semis d'une culture de printemps. Nos travaux ont montré l'absence d'effet des couverts associés sur le rendement en grains du blé d'hiver. Mais des diminutions du taux protéique des grains sont apparues dans un tiers des situations d'association notamment avec M. lupulina et T. pratense, les espèces les plus développées à la récolte du blé. Notre suivi de la disponibilité des ressources trophiques principales (eau, N, lumière) nous a permis d'identifier une compétition pour l'eau et l'N du sol. Nous avons également noté l'efficacité des couverts de légumineuses dans le contrôle de la densité des adventices dès le stade de floraison du blé et de leur biomasse durant l'interculture. Le meilleur contrôle des adventices a été permis par M. lupulina et T. pratense, à la récolte du blé, et T. pratense et T. repens, à la fin de l'automne, associé aux biomasses aériennes observées les plus importantes. Enfin, nous avons observé une forte proportion d'N issu de la fixation symbiotique dans la biomasse aérienne des légumineuses à la fin de l'automne (80 à 94%), représentant un apport d'N exogène au système sol-plante évalué entre 37 et 77 kg N ha-1. Cet enrichissement en N n'a pas entrainé d'aggravation de la lixiviation d'N durant l'hiver. Les couverts de légumineuses n'ont pas non plus diminué la lixiviation comparativement à l'absence de couvert. Après leur destruction, les résidus des couverts ont restitué une partie de l'N accumulé (+28 à +42 kg ha-1 d'N minéral sur les 90 premiers centimètres de sol par rapport au témoin à l'émergence de la culture de printemps, 12 semaines après leur destruction). Cette restitution a permis un enrichissement en N des pailles et grains de la culture de printemps et une augmentation de 30% du rendement lorsqu'il s'agissait de maïs. Finalement nous concluons sur l'intérêt des couverts de légumineuses associés en relais dans un blé d'hiver pour apporter une réponse positive aux problèmes principaux des rotations de grandes cultures biologiques (adventices, déficits d'N et diminutions des performances des cultures). Nous terminons en proposant des voies d'évolution des associations testées, notamment pour limiter les risques de compétition durant l'association. Nous évoquons également les implications scientifiques et pratiques de ce travail pour de futures études sur ce sujet. / Cereal productivity and quality are subject to two main problems in organic stockless systems: chronic soil nitrogen (N) deficiencies and weed infestation. Legume species as clovers or alfalfas can be used as cover crops and green manures due to their natural ability to fix atmospheric N. Nevertheless, their substitution to cereals in crop rotations is less economically viable without animals to use it. Relay intercropping of legume cover crops (RIL) in winter wheat was expected to simultaneously enrich the soil-plant system in N, cover the soil from the wheat harvest onwards and limit the risk of competition with wheat by delaying the undersowing of legumes in spring. To evaluate the efficiency of RIL, four legume species (Medicago lupulina L., M. sativa L., Trifolium pratense L. and T. repens L.) were undersown at wheat tillering stage, in eight fields organically managed in the Rhône-Alpes region, France. Their effects on weed control, on N enrichment, preservation and restitution in the soil-plant system and on crop performance were observed during the succession of the winter wheat and a spring crop. RIL residues were incorporated in soil in late winter, 9 to 12 weeks before the sowing of spring crops. Our work illustrated the absence of detrimental effect of RIL on wheat grain yield despite the decrease of the grain protein content in one third of the situations. This decrease was mainly observed with M. lupulina and T. pratense as they were the most developed legume species at wheat harvest. Our monitoring of trophic resources (water, N and light) enlightened the competition for soil water and N during the intercropping period. We also showed the efficiency of RIL in the control of weed density from wheat flowering stage onwards and of weed aerial biomass in late autumn. The best weed control was observed with M. lupulina and T. pratense, at wheat harvest, and with T. pratense and T. repens in late autumn, in relation to the highest aerial biomasses observed with these species. Finally, we noted an important proportion of N derived from atmosphere (Ndfa) in legumes' shoots in late autumn (80 to 94%), representing an input of exogenous N in the soil-plant system ranging from 37 to 77 kg Ndfa ha-1. The N enrichment of the system did not increase mineral N lixiviation during winter. However, legume cover crops did not significantly prevent any lixiviation of mineral N relative to the control without cover crop. After their ploughing in, legumes residues returned a part of the accumulated N (+28 to +42 kg ha-1 of mineral N in the first 90 cm of soil compared to the control at the emergence of the spring crop, 12 weeks after ploughing). This restitution of mineral N allowed a significant N enrichment of straw and grains of the spring crop with all previous legumes cover crop species. With maize as spring crop, the grain yield increased by 30%, on average, compared to the control treatment. We finally conclude on the interest of RIL in winter wheat to bring a positive response to the problems of weed control, N deficiency and crop performances in organic crop rotations. We then suggest possible improvements of the RIL system, especially against the competition for trophic resources during the relay intercropping period. We also mention scientific and practical implications of this work for future studies on this subject.

Understanding the spatial and temporal dynamics of soil water and crop water stress within a field is critical for effective Variable Rate Irrigation (VRI) management. Proper VRI can result in improved protection of the crop from early onset of crop water stress while minimizing runoff and drainage losses. The objectives of this study are (1) to examine zone delineation for informing irrigation recommendations from volumetric water content (VWC) and field capacity (FC) to grow similar or greater wheat yields with less water, (2) evaluate the ability to model soil and crop water dynamics within a season and within a field of irrigated winter wheat, and evaluate the sensitivity of crop water stress, evapotranspiration and soil water depletion outputs within a water balance model with Penman-Monteith evapotranspiration (ET) in response to adjusted soil properties, spring volumetric water content (VWC), and crop coefficient model input values. Five irrigation zones were delineated from two years of historical yield and evapotranspiration (ET) data. Soil sensors were placed at multiple depths within each zone to give real time data of the VWC values within each soil profile. Soil samples were taken within a 22 ha field of winter wheat (Triticum aestivum ‘UI Magic’) near Grace, Idaho, USA multiple times during a growing season to describe the spatial variation of VWC throughout the field, and to assist in modeling soil water dynamics and crop water stress through energy balance and water balance equations. Spatial variation of VWC was observed throughout the field, and on a smaller scale within each zone, suggesting the benefit of breaking portions of the field into zones for irrigation management purposes. Irrigation events were triggered when soil sensors detected low values of VWC, with each zone receiving unique rates intended to refill to zone specific FC. Cumulative irrigation rates varied among zones and the VRI approach saved water when compared to an estimated uniform Grower Standard Practice (GSP) irrigation approach. This method of zone management with soil sampling and sensors approximately represented the VWC within each zone and proved beneficial with effective reduction of irrigation rates in every zone compared to an estimated GSP. As such, there was a delay in the premature onset of crop water stress throughout some areas of the field. Variability in soil properties and spring soil moisture were key in giving accurate values to the model in order to make proper VRI management decisions. When assessing the model sensitivity, changing the inputs such as FC, wilting point (WP), total available water (TAW), spring VWC and crop coefficient (Kc) by -4 to +4 standard deviations away from their spatially average values, impacted the outputs of the model, with Kc having a large impact all three of the outputs. Further work is needed to improve the accuracy of representing VWC throughout a field, thus improving VRI management, and there is potential benefit in using a variable crop coefficient could to more accurate VRI management decisions from a soil water depletion model.