Institut für Pflanzenbau und Grünland (bis 2010)

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Nachfolgeinstitut ab 2011: Institut für Landschafts- und Pflanzenökologie

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Management of Fusarium graminearum-inoculated crop residues
effects on head blight, grain yield and grain quality of subsequent winter wheat crops
(2001) Yi, Cuilin; Aufhammer, Walter
On the experimental station Ihinger Hof of Hohenheim University field experiments with artificial inoculation were conducted. An isolation-strip experiment included strips of winter rape crops, separating non-inoculated test plots of wheat from inoculated wheat plots. For the main field experiment, maize or spring wheat were planted as pre-crops in rotations with winter wheat and different crop residue treatments were applied. Additional residue management greenhouse tests were conducted and treated equivalent to the field experiment. Results of isolation-strips field experiments with wheat showed that. Isolation strips of 2 m width reduced disease incidence on neighbour plots by more than 50%. A further increase in isolation strip width did improve the isolation effect, but the differences between isolation strip widths were comparatively small. The infection in test plots was not completely eliminated even with 8 m wide strips. Greenhouse tests of residue management showed that deeper residue incorporation effectively reduced the F. g. populations on residues. The application of nitrolime reduced the population level of F. g. On the contrary, fertilization with calcium ammonium nitrate promoted F. g. populations. Soaking the residues in a fungicide preparation eliminated F. g. on the residues completely. Residue management field experiments with artificial inoculation of pre-crops, there were no significant differences in infection level after either maize or wheat, and the infection level of winter wheat was especially high after maize for silage use in one year. The reductions of FHB incidence due to ploughing or nitrolime application were 27-32% or 31-59% compared with residues remaining on the surface or calcium ammonium nitrate fertilization, respectively. But at that moderate FHB infection level, the residue management hardly influenced wheat grain yield and technological grain quality.
Optimierung und Bewertung der Produktion von Getreidekorngut als Rohstoff für die Bioethanolerzeugung
(2001) Rosenberger, Alexander; Aufhammer, Walter
Varied cultivation of high yielding winter cereals to be used as bioethanol grains were examined regarding agronomic and fermentation traits as well as with respect to energetic, economic and environmental aspects. Empirical data were taken from biennial factorial field trials with winter cereals at two different experimental sites of Hohenheim University. These are the central conclusions: A-state-of-the-art conversion process presupposed, the cultivation of high-yielding cereals in crop rotations including previous legume crops is an energetically and economically efficient option to optimize the production of bioethanol grain and hence of bioethanol. From the ecologic view, crop production aligned to high grain yields is conflicting with respect to the enhancement of fossil primary energy conservation and thus the avoidance of greenhouse gas emissions relative to the reference fossil fuel and incremental releases of other ecologically relevant substances as compared to low-input crop management.
Ertragsbildung und Konkurrenzverhalten perennierender Körnerfruchtarten in Rein- und Mischbeständen auf marginalen Standorten
(2002) Weik, Lena; Aufhammer, Walter
Cultivation of perennial grain crops in pure and mixed stands was examined as a possibility for preserving marginal arable land. The following questions were investigated: - Which dry matter and grain yield potential do these species display on marginal lands? - Are the examined species able to persist on marginal sites? - Can effects of competition be identified in mixed stands of perennial grain crops by commonly used static and dynamic parameters? - Which competitiveness do the examined species show in mixed stands compared to pure stands? In field experiments perennial species of rye (Secale cereale x S. montanum), intermediate wheatgrass (Elymus hispidus), lupine (Lupinus polyphyllus) and linseed (Linum perenne) were grown in pure and different mixed stands. Intermediate wheatgrass reached with a maximum at almost 13 t ha-1 highest dry matter yields. Grain yields were on a low level, maximum yields were obtained with 2.7 t ha-1 in pure stands of rye. Intermediate wheatgrass and lupine demonstrated the best ability for perennialism. Rye showed a satisfactory ability to persist only when grown in mixture with legumes. The persistence of linseed was very low. The relative yield total (RYT) was found to be a suitable static indicator of resource complementarity. Competitive ability was appropriately described by the competitive balance index (Cb). Regression models derived from Lotka-Volterra equations rendered a good description of dynamic growth and competition. Both grass species were in most cases stronger competitors than the companion species. The experiments showed, that using grain cop mixtures of grasses and legumes seem to be most promising for cultivation on marginal lands.
Einfluss der Bearbeitungsintensität beim Umbruch von Luzerne-Kleegras auf die Stickstoffmineralisation zur Folgefrucht Winterweizen im organischen Landbau
(2003) Wald, Fabian; Claupein, Wilhelm
In the crop rotation of organic farming grass-legume mixtures play an important role due to the legumes´ ability to assimilate N. Ploughing-in of established grass-legume mixtures results in releasing the assimilated N by mineralisation of organic matter. In practice the mineralisation can only be controlled by means of soil cultivation. The aim of the present study is to analyse the relations between different intensities of soil cultivation and N-mineralisation. The data were used to test the simulation model CANDY. The field experiment of each 0.1 ha was set up at three sites in two different locations, which were cultivated from 1999 to 2001: Hohenheim (with trials 610 and 611) and Kleinhohenheim (with trial 660). In the beginning all sites had a three-year old grass-clover-alfalfa mixture, which was ploughed-in for trial 610 and 660 in the late summer of 1999 and in the year 2000 for trial 611. The factor soil tillage was varied in three stages as follows: RT+RT+plough: double rototill cultivation (RT, 10 cm deep) in intervals of approx. 2 weeks, followed by ploughing (plough, 25 cm deep); RT+plough: single rototill cultivation, followed by ploughing (depths as mentioned above); Plough: ploughing without any preceding cultivation (depth 25 cm). After uniform seedbed preparation with a rotary harrow, wheat was sown on all trial sites in autumn, and in trials 610 and 660 it was followed by oat in 2001. Nitrogen content in the soil was determined by repeated sampling at a depths of 0-10, 10-20, 20-30, 30-60 and 60-90 cm. Monitoring boxes were installed in 1 m depth in an undisturbed soil body from September 2000 until April 2001 to record nitrate leaching. Ploughing-in of the grass-clover-alfalfa by means of rototiller cultivation (treatments RT+RT+plough and RT+plough) was followed by a significant increase of mineralisation, which in case of the plough treatment was less pronounced. In this case the date of cultivation, 6 weeks after the rototilling, may have had an influence. Nmin-contents in autumn 1999 were higher after RT+RT+plough than after RT+plough. It has to be taken into consideration that there was a time gap between both treatments of 9 days. But also in the following year (611), when both treatments were cultivated the same date, there was a significant, slight difference of the Nmin values depending on the treatment. Nitrate leaching was only measured in trial 611. Quantities of 86, 84 and 64 kg N/ha were observed in treatments RT+RT+plough, RT+plough and plough, respectively during winter. Due to high Nmin-contents in autumn, for the rototill treatments higher nitrate losses can be assumed compared to the plough treatment for both years of experiment. Depending on the location, nitrogen uptake and yields of wheat turned out to be different. In Kleinhohenheim they were lower in treatments RT+RT+plough and RT+plough than in the plough treatment. It was the other way round in Hohenheim on a higher production level. Due to strong hail impact, this relation between the treatments was not to be proved in trial 611. Oat was the second crop. In this case no effects of intensity of soil cultivation on nitrogen uptake and yield could be observed between treatments and locations. The CANDY model was used for simulating the results of trials 610 and 611. First, the model seemed to be inadequate because it could not model the N-dynamic after soil cultivation. Adding fictitious organic material to the system helped to overcome this problem and then, on average, the N-dynamic model fit was satisfying. An estimate to overcome the general insufficient fit of the model could be mineralisation of parts of the physically protected organic matter (SOS), which is already implemented in the model, right at the moment of cultivation. Data of soil moisture of trial 611 served to calibrate the model successfully. With amended soil parameters the model was then easily applied to the corresponding data of trial 610. In contrast, CANDY did not predict well the nitrate leaching - possibly because the model did not consider preferential flow.
Die Ökobilanz zur Abschätzung von Umweltwirkungen in der Pflanzenproduktion - dargestellt anhand von Praxisversuchen zur konservierenden Bodenbearbeitung und von unterschiedlich intensiv wirtschaftenden konventionellen Betrieben
(2003) Arman, Beate; Claupein, Wilhelm
In the agricultural field difficulties in life-cycle assessment result from the fact that the methods of life-cycle assessment were developed in techno-industrial production. Agricultural production, however, differs from industrial production in that it depends more strongly on natural resources and, moreover, has a direct influence on them. Hence, apart from preparing data for the used production goods, the expansion of environmental impact categories to include specific effects from agriculture is focused on in the adaptation of ecobalances as an agricultural method. Among others deficiencies here include the balancing of effects in agriculturally utilized soil. The ecobalances at hand were carried out with two different goals in mind. For one, the impact of conventional and conservational cultivation methods were to be balanced. The goal of this ecobalance was to show whether life-cycle assessment have adequate selective power in order to be used as a decision criterion in the optimisation of cultural methods and their environmental impact. For another, the intensity of cultivation of three agricultural enterprises was compared. It was to be shown here whether life-cycle assessment can provide transparency as to the environmental effects of various production methods, which would enable the consumer to obtain information on the environmental relevance of these methods. A further goal of this work was the development of a method for the recording of effects on the soil in life-cycle assessment. The examined farms are situated in the Hohenlohe region and were integrated in the subproject "Conservation Tillage" of the "Cultural Landscape Hohenlohe" project group. In order to balance soil working methods, the three methods plow, cultivator and mulch sowing were examined. The data was obtained from two test fields with the same crop rotation on one of the farms. Balancing of the intensity of cultivation was carried out on three conventionally working farms using varying levels of fertilizer, crop protectants and tillage. The balanced crop rotation of the three farms did not vary (sugar-beets, winter wheat, winter barley). When developing methods for balancing environmental effects on agriculturally utilized soil three aspects were decisive in the selection of balanced effects: 1. What soil properties are there? 2. Which of these properties are influenced directly by cultivation measures? 3. For which properties are relevant negative effects caused by agriculture known? Based on the indicated methods the impact was assessed for the following soil properties: - Soil depth is influenced by soil loss. Soil loss was calculated with the universal soil loss equation. - Impact on the nutrient content was assessed with the help of a nutrient field balance, humus content with the help of a humus balance. - Variations in soil density caused by loading were assessed with the help of the weighted soil load. - Soil life is affected by pollutant input, modelling of the effect potential was carried out with the help of the Critical-Surface-Time model. All in all the results show that in order to differentiate between the tillage variants with respect to their environmental impact, it is necessary to also consider effects on the soil. Comparison of the farms showed that life-cycle assessment can reflect the environmental relevance of different cultivation intensities and can make them visible for the consumer.
Genotypische Variation der Überdauerungsneigung von transgenem und konventionell gezüchtetem Raps und Möglichkeiten der Beeinflussung durch Bodenbearbeitung als Beitrag zur Sicherheitsforschung bei transgenen Kulturpflanzen
(2004) Gruber, Sabine; Claupein, Wilhelm
High losses during harvesting of oilseed rape in combination with secondary dormancy of the seeds can result in a large soil seed bank which may persist for several years. Volunteers emerging from this seed bank cannot be controlled completely, particularly when they develop in another rapeseed population. In addition to well known agricultural problems, the risk of temporal and spatial gene dispersal by persistent seeds and volunteers gets more significant. With regard to genetically modified (GM) cultivars, seed dormancy and persistence of oilseed rape volunteers have to be reconsidered. The aim of the current study was to investigate the chances for a reduction of seed persistence and gene dispersal by growing specific genotypes and by the implementation of appropriate tillage operations. Four publications describe and discuss experiments in the laboratory and the field on the aspects ?genotype? and ?soil tillage?. One central point was the characterisation of the genotypic variation of secondary dormancy and seed persistence in GM (herbicide tolerant) and conventionally bred oilseed rape. A gradual approach towards field conditions was performed by three experiments. The first experiment examined potential seed persistence by artificial induction of secondary dormancy in the laboratory. The second experiment was a burial of seeds in the soil for six months on a field. The third experiment examined persistence of seeds actually lost during harvest and exposed afterwards to different tillage operations in a field experiment. All three experiments showed a high genotypic variability in seed dormancy and persistence. In the laboratory the level of secondary dormancy of conventional cultivars was a total of 3?76% and of the GM cultivars 1?31%. The number of persistent seeds in the burial experiment was 7?90% in the conventional and 12?79% in the GM assortment. Seeds from the seed rain of the four conventionally bred cultivars in the field experiment persisted in the soil from 0?11% over six months. A significant, positive correlation was found between the laboratory results for cultivars from two crop years as well as between the results from laboratory and burial experiments. This is an indication for a genetic background of seed dormancy and persistence of oilseed rape. It has been demonstrated that a laboratory method for induction of secondary dormancy can describe differences of seed persistence in the field. This result gives a chance for screening new cultivars in the laboratory to identify desired, low persistent genotypes. The other focus of the study was the effect of various tillage treatments on seed persistence and seedling recruitment in the field. Four differently intensive tillage operations incorporated the seeds of two near-isogenic cultivars at different times and soil depths, or left the soil untilled. Winter wheat was sown as following crop in all treatments whereby no weed control was performed. The highest number of seeds generally entered the soil seed bank when seeds were incorporated into the soil by stubble tillage immediately. After six months 1?14% of the initial seed input was found again in the soil in these treatments, and in one isolated case about 28%. Delaying the stubble breaking, the soil seed bank was 0?3%. Leaving the seeds undisturbed on the soil surface until direct drilling resulted in a soil seed bank of 0?17%. Therefore, the first tillage operation after harvest of oilseed rape should be performed with some time delay to avoid large soil seed banks. Soil inversion by a mouldboard plough shifted the majority of seeds into deep soil horizons from where a successful germination was restricted. In contrast, primary tillage by a rigid tine cultivator or zero tillage mainly distributed the seeds within the upper soil layer. Thus the number of flowering volunteers in the first spring was highest in these treatments, with a maximum of one volunteer m-2. Gene dispersal from oilseed rape volunteers to other rape crops and feral relatives was possible because their flowering periods overlapped. The volunteers were able to produce viable seeds, despite high levels of damage by pests and diseases. Overall, a high genotypic variability was found for seed persistence of oilseed rape. Tillage operations, particularly the time of stubble tillage, can also influence seed persistence and the occurrence of volunteers. Combined with a thorough knowledge of the processes involved, the selection of low persistent genotypes and adequate tillage operations offer chances to limit or even to avoid undesired gene dispersal from oilseed rape volunteers, and to make gene dispersal a predictable factor.
Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses
(2005) Link, Eva Johanna; Claupein, Wilhelm
The aim of this study was the "Investigation and Modeling of the Optimization Potential of Adapted Nitrogen Fertilization Strategies in Corn Cropping Systems with Regard to Minimize Nitrogen Losses". The background for the investigation could be seen in the increasing number of environmental pollution by agricultural land use. The dissertation was embedded in the context of the Graduiertenkolleg "Strategies to Reduce the Emission of Greenhouse Gases and Environmental Toxic Agents from Agriculture and Land Use" at the University of Hohenheim. The objective of this Graduiertenkolleg was to develop methods for quantifying and modeling the origin and the emission of greenhouse gases and environmentally toxic agents from agriculture and land use and for assessing them economically in the sense of practicable avoidance strategies. In order to determine the optimization potential of adapted nitrogen fertilization strategies in corn the study was organized in the following parts: 1. Investigation of the spatial variability and temporal stability of corn grain yield on three fields in the Upper Rhine Valley. 2. Determination of underlying yield-limiting factors in each field by the use of simple and complex models. 3. Development of adapted nitrogen fertilization strategies in consideration of the yield variability and the underlying yield-limiting factors. The area of investigation was located in the Upper Rhine Valley, which is characterized as a region with intense corn cultivation. At the same time this region belongs to the most important water protection areas in Europe. Thus, a conflict between agricultural land use associated with high fertilizer inputs on one hand and the protection of water bodies on the other hand rose, because measured nitrate concentrations in the groundwater increased constantly within the last decades. The study was conducted on three farm fields in the boundary of Weisweil, which is located northwest of Freiburg, Germany. Since 1998 the three fields were planted continuously with corn. In a 7-year field experiment spatial variability and stability of yield could be indicated. The determined yield pattern in each field raised assumptions about varying growth conditions within and among the fields. Thus, on the one hand the corn yield seemed to be influenced by temporal variations in cultivar, climate and management and by spatial and temporal variation of possible yield-limiting factors like nutrient availability or water supply on the other hand. In order to optimize management strategies the underlying yield-limiting factors causing the spatial and temporal yield variability needed to be determined in these three fields. Whereas plant yield parameters did not explain the existing yield variability very well, soil characteristics were identified as the major factors affecting the observed yield variability in all three fields. Significant relationships were found between combinations of soil nutrient levels, soil characteristics and yield. Based on these results, it appeared that soil characteristics were the primary factor affecting spatial yield variability in the three farmer fields in the Upper Rhine Valley. However, some of the spatial yield variability remained unexplained by simple regression analysis. In a more complex approach crop growth models were implemented to simulate the spatial yield variability within the field and to get information about the underlying yield-limiting factors. Therefore the process-oriented crop growth model APOLLO was implemented to evaluate the causes of spatial yield variability of corn in the three fields. APOLLO (Application of Precision Agriculture for Field Management Optimization) is a precision farming decision support system, which is based on the CERES and CROPGRO family of crop growth models and includes different soil parameter to calibrate the model. In general the APOLLO model performed well in simulating spatial yield variability in the fields. The results indicated that the spatial yield variability was mainly affected by a varying restrictive layers and reduction of root growth within the three fields. The correlation between simulated and measured yields provided information about the strength of the soil parameter affecting the yield within these fields. The calibration results were influenced by the grid size. Whereas smaller grids provided more random monitor yield data, larger grids provided a more representative set of yield monitor data, due to the coverage of a larger area. Consequently, the APOLLO model performed better when yields belonging to larger grids were used for model calibration. The applicability of the APOLLO model can be extended by developing prescriptions for different management strategies and thus enhancing the possibilities of successfully implementing site-specific management strategies. Thus, APOLLO was used to simulate the current uniform nitrogen management strategy of the producers in Weisweil over a 28-year period. Additionally an optimum uniform management and an optimum variable-rate management were developed and simulated. For these strategies also the different weather pattern were taken into account. All three strategies were evaluated based on the simulated yield, the simulated leaching potential and the simulated economics. It was obvious, that variable-rate nitrogen fertilization strategies were most advantageous compared to the other strategies, especially, when the nitrogen application rates were differentiated for dry, normal and wet weather scenarios. Adapted nitrogen fertilization strategies, as optimum uniform management and variable-rate management indicated a potential to reduce the amount of nitrogen, which is left in the soil after harvest, and associated that the potential nitrate leaching was reduced. In a case study the cumulative denitrification under these weather and fertilization scenarios over the growing season was simulated. The results indicated a reduction of cumulative denitrification under adapted fertilization strategies when compared to current uniform management. Summarizing, the results of this study suggest, that the implementation of adapted fertilization strategies (especially the variable-rate management of nitrogen) could lead to a reduction of nitrogen losses, as nitrogen leaching and nitrogen emissions could be minimized. Generally, the optimization potential for adapted nitrogen fertilizer strategies (optimum uniform management and variable-rate management) could be improved for cropping systems that were associated with higher risk for nitrogen losses.
Pflanzenbauliche Untersuchungen zum ökologischen Anbau von Körnerleguminosen an sommertrockenen Standorten Südwestdeutschlands
(2007) Poetsch, Jens; Claupein, Wilhelm
Grain legumes, as nitrogen fixing crop, protein rich animal feed and marketable product are of great importance for organic agriculture. Due to staged abolition of the possibility to add non-organic products in organic animal feeding, the EU?s demand for organically produced protein feed is further increasing. Field bean (Vicia faba) and field pea (Pisum sativum) are large-scale crops but feature a limited feeding value. Lupin species (Lupinus spp.) excel by protein contents of up to 40% in the seed and higher protein value. At warmth favoured locations in southwestern Germany the valuable soybean (Glycine max) can be grown successfully and obtain above-average proceeds in natural food industry. Constraints of yield stability of grain legumes result amongst other things from frequently high weed infestation in organic cropping systems and suboptimal water supply at summer-dry locations. For lupins, moreover, particular soil requirements and the seed-borne fungal disease anthracnosis are problematic. Nitrogen residues after harvest are relevant for subsequent crop as well as groundwater protection. The presented work aimed at defining preconditions and developing cropping strategies to optimise yield stability and level of organically grown grain legumes with a main focus on summer-dry locations, to increase diversity of cultivatable crops and provide information on disposition of nitrogen residues. For this purpose from 2003 to 2005 trials at several locations as well as in greenhouse and laboratory were accomplished. Field trials on organic weed control in soybean as well as white and narrow-leafed lupin (Lupinus albus und L. angustifolius) were conducted at organically managed commercial sites in the upper rhine valley. At the same time agronomic measures for optimisation of competitiveness and machinery implementation were varied. Early high soil coverage and crop height contributed considerably to grain legumes? competitiveness. Delayed sowing at elevated temperatures supported rapid juvenile development and allowed for pre-sowing weed control. At optimum sowing date these effects may be used without yield depression or maturity problems. Reduced row distance was beneficial for optimum space utilisation and early crop closure, but effectiveness of mechanical means was highest at high row distance and large areal proportion for interrow cultivation. As an optimum compromise for grain legumes row distances of 30 - 35 cm are recommended. Optimum impact of mechanical means against weeds was achieved by combining interrow cultivation with harrow or fingerweeder. Forgoing interrow cultivation may be considered in strongly competitive crops like field bean. Lupin species appeared rather poor in competitiveness compared to other crops. Field trials on effects of cultivar and cropping strategy on overwintering and yield performance of autumn-sown field bean, field pea and white lupin were conducted at three locations. Summer drought caused substantial yield advantages of autumn-sown compared to spring-sown cultivars due to superior water supply at earlier flowering. With sufficient water supply a head start was not yield effective. Differing coincidence with pests and diseases could account for advantages (head start on aphid infestation) or disadvantages (fungal infections during winter period) of autumn-sown cultivars. Overwintering was excellent for winter field bean and good for winter field pea. For winter white lupin further trials are required. Temperatures down to -12°C were well endured by all of the three crops. The most important cropping parameter was the sowing date. Winter field bean permitted a relatively wide sowing window. Winter white lupin required strong development before winter and preferably early sowing. Sowing date of winter field pea presented an optimisation problem, because sowing too early leads to overdevelopment and reduced cold-tolerance, while sowing too late may reduce yield potential. Optimum sowing dates for southwestern Germany according to experimental results are in the range of early September (winter white lupin), mid-October (winter field bean) and late October (winter field pea). Water use efficiency may gain significantly in importance in the future. A two-year trial on cultivation prospects and yield performance of the notably drought tolerant chickpea (Cicer arietinum) in the upper rhine valley resulted in successful crop development, but problems with empty pods and inadequate grain quality. Further trials are considered promising. A field trial with white and narrow-leafed lupin confirmed that anthracnosis of lupin spreads less rapidly and yield effectively at summer-dry locations, and narrow-leafed lupin frequently stays unaffected. Laboratory studies for optimising detection methodology of the causative organism Colletotrichum lupini showed advantages of using sectioned petri dishes (quad plates), which confined propagation of disturbing organisms. A trial on seed storage under different temperatures, seed moisture contents and CO2-atmosphere produced no distinct treatment effect, but could confirm the general decrease of seed infection by storage. According to literature hot air (approx. 4 days at 65°C) also reduces seed infection effectively. Thus, storage or hot air treatment of basic seed and propagation at summer-dry locations appear as a viable over-all strategy. Difficult soil requirements of white and narrow-leafed lupin were studied by a pot trial as well as a comprehensive literature analysis. It is concluded that the so-called lime chlorosis is caused by HCO3--induced inactivation of physiologically relevant Fe(II) in the plant. Accumulation of HCO3- is basically caused by insufficient soil aeration and promoted by the presence of lime in the clay fraction. Furthermore, especially in narrow-leafed lupin, disturbances of root development are caused by high Ca-content or high and at the same time strongly buffered pH of soil solution. These conditions are often but not necessarily caused by lime. Analyses of harvest residues and soil were consulted for estimation of nitrogen dynamics. Immobilisation due to degradation of residues with high C:N ratio as well as uptake by catch crops contributed substantially to nitrogen conservation. Risk of leaching is predominantly site dependent. The over-all nitrogen balance of grain legumes when exporting the seed may be low or even negative. In conclusion, results of the presented work indicate that site adapted cropping systems with agronomic measures in the areas of crop rotation, choice of cultivar, sowing date or space allocation can still contribute considerably to yield stability in organic cultivation of grain legumes.
Comparative performance of annual and perennial energy cropping systems under different management regimes
(2007) Böhmel, Ute Constanze; Claupein, Wilhelm
The theme of this thesis was chosen against the background of the necessary substitution of fossil fuels and the need to reduce greenhouse gas emissions. One major solution for these topics may be the energy generation from domestically produced biomass. The overall aim of this thesis was the identification of one or more efficient energy cropping systems for Central Europe. The target was set to supply high quality biomass for existent and currently developing modern conversion technologies. Renewable energy production is thought to be environmentally benign and socially acceptable. The existence of diverse production environments necessitates further diversification and the identification of several energy crops and the development of energy cropping systems suited to those diverse environments. This thesis starts with an introductory essay (chapter 1), which provides the background for renewable energy production, its features, demands and potentials, and the scientific basis of this thesis. Chapters 2 to 6 consist of five manuscripts to be published in reviewed journals (Papers I, II, IV and V) or in a multi-author book (Paper III). Subsequently, the results from all papers are discussed in a general setting (chapter 7), from which a general conclusion is formulated (chapter 8). The basis of the research formed four field experiments, which were conducted at the experimental sites Ihinger Hof, Oberer Lindenhof and Goldener Acker of the University of Hohenheim, in south-western Germany. Paper I addresses the overall objective of this thesis. Selected cropping systems for this experiment were short rotation willow, miscanthus, switchgrass, energy maize and two different crop rotation systems including winter oilseed rape, winter wheat and winter triticale with either conventional tillage or no-till. The systems were cultivated with three different nitrogen fertilizer applications. An energy balance was calculated to evaluate the biomass and energy yields of the different cropping systems. Results indicate that perennial lignocellulosic crops combine high biomass and net energy yields with low input and potential ecological impacts. Switchgrass, which produced low yields at the study site, may better perform on marginal sites. Switchgrass is an example of the need to grow site-adapted energy crops. The annual energy crop maize required the highest input, but at the same time yielded the most. The two crop rotation systems did not differ in yield and energy input, but the system with no-till may be more environmentally benign as it has the potential to sequester carbon. The objective of Paper II was the optimization of crop cultivation through the differentiation of input parameters to enhance the quality of the energy crop triticale, without influencing the biomass yield. The intention was to minimize the content of combustion-disturbing elements (potassium and chlorine) and the ash residue of both aboveground plant parts (grain and straw). It was done through different straw and potassium fertilizer treatments. It could be shown that the removal of straw from the previously cultivated crop and no additional potassium fertilizer could reduce the amount of combustion-disturbing elements. A high influence must also be expected from site and weather conditions. Papers III to V address the supply of different high quality biomasses, with the focus on maize for anaerobic digestion. The objective of Paper III was the assessment of the requirements of biogas plants and biomass for anaerobic digestion. It introduces potential energy crops, along with their advantages and disadvantages. Alongside maize, many other biomass types, which are preserved as silage and are high in carbohydrates and low in lignocelluloses, can be anaerobically digested. The development of potential site-specific crop rotation systems for biomass production are discussed. The objective of Papers IV and V was the identification of suitable biomass and production systems for the anaerobic digestion. The focus lay on the determination of (i) suitable energy maize varieties for Central Europe, (ii) optimal growth periods of energy crops, (iii) the influence of crop management on quality parameters and (iv) environmentally benign crop rotation systems. Differently maturing maize varieties were grown in six different crop rotation systems (continuous maize with and without an undersown grass, maize as a main crop partially preceded by different winter catch crops and followed by winter wheat) and tested at two sites. Additional factors were sowing and/or harvest dates. Maize and cumulative biomass yields of the crop rotation systems were compared. Specific methane yield measurements were carried out to evaluate the energy performance of the tested crops. Quality was assessed either by measurements of the dry matter content or by using the near infrared reflectance spectroscopy for the determination of chemical composition. Results indicate that an environmentally benign crop rotation system requires nearly year-round soil cover to minimize nitrogen leaching. This can be achieved through the cultivation of undersown or catch crops and additional main crops alongside maize, such as winter wheat. Late maturing maize varieties can be cultivated at a site where the maize can build adequate dry matter contents due to a long growth period (late harvest date). The energy generation in terms of methane production was primarily dependent on high biomass yields. It could be further shown that the specific methane yield of maize increased with increasing starch content, digestibility and decreasing fiber content. To conclude, selected site-specific energy crops and crop rotation systems, with suitable crop management, (fertilizer and soil tillage) can produce high quality biomass and the highest net energy return. Lignocellulosic biomass can be optimized for combustion. Wet biomass is an optimal substrate for anaerobic digestion. Profitable energy production is characterized by a high land and energy use efficiency and especially high net energy yields.
Biometrical approaches for analysing gene bank evaluation data on barley (Hordeum spec.)
(2007) Hartung, Karin; Piepho, Hans-Peter
This thesis explored methods to statistically analyse phenotypic data of gene banks. Traits of the barley data (Hordeum spp.) of the gene bank of the IPK-Gatersleben were evaluated. The data of years 1948-2002 were available. Within this period the ordinal scale changed from a 0-5 to a 1-9 scale after 1993. At most gene banks reproduction of accessions is currently done without any experimental design. With data of a single year only rarely do accessions have replications and there are only few replications of a single check for winter and summer barley. The data of 2002 were analysed separately for winter and summer barley using geostatistical methods. For the traits analysed four types of variogram model (linear, spherical, exponential and Gaussian) were fitted to the empirical variogram using non-linear regression. The spatial parameters obtained by non-linear regression for every variogram model then were implemented in a mixed model analysis and the four model fits compared using Akaike's Information Criterion (AIC). The approach to estimate the genetical parameter by Kriging can not be recommended. The first points of the empirical variogram should be explained well by the fitted theoretical variogram, as these represent most of the pairwise distances between plots and are most crucial for neighbour adjustments. The most common well-fitting geostatistical models were the spherical and the exponential model. A nugget effect was needed for nearly all traits. The small number of check plots for the available data made it difficult to accurately dissect the genetical effect from environmental effects. The threshold model allows for joint analysis of multi-year data from different rating scales, assuming a common latent scale for the different rating systems. The analysis suggests that a mixed model analysis which treats ordinal scores as metric data will yield meaningful results, but that the gain in efficiency is higher when using a threshold model. The threshold model may also be used when there is a metric scale underlying the observed ratings. The Laplace approximation as a numerical method to integrate the log-likelihood for random effects worked well, but it is recommended to increase the number of quadrature points until the change in parameter estimates becomes negligible. Three rating methods (1%, 5%, 9-point rating) were assessed by persons untrained (A) and experienced (B) in rating. Every person had to rate several pictograms of diseased leaves. The highest accuracy was found with Group B using the 1%-scale and with Group A using the 5%-scale. With a percentage scale Group A tended to use values that are multiples of 5%. For the time needed per leaf assessment the Group B was fastest when using the 5% rating scale. From a statistical point of view both percent ratings performed better than the ordinal rating scale and the possible error made by the rater is calculable and usually smaller than with ratings by rougher methods. So directly rating percentages whenever possible leads to smaller overall estimation errors, and with proper training accuracy and precision can be further improved. For gene banks augmented designs as proposed by Federer and by Lin et al. offer themselves, so an overview is given. The augmented designs proposed by Federer have the advantage of an unbiased error estimate. But the random allocation of checks is a problem. The augmented design by Lin et al. always places checks in the centre plot of every whole plot. But none of the methods is based on an explicit statistical model, so there is no well-founded decision criterion to select between them. Spatial analysis can be used to find an optimal field layout for an augmented design, i.e. a layout that yields small least significant differences. The average variance of a difference and the average squared LSD were used to compare competing designs, using a theoretical approach based on variations of two anisotropic models and different rotations of anisotropy axes towards field reference axes. Based on theoretical calculations, up to five checks per block are recommended. The nearly isotropic combinations led to designs with large quadratic blocks. With strongly anisotropic combinations the optimal design depends on degree of anisotropy and rotation of anisotropy axes: without rotation small elongated blocks are preferred; the closer the rotation is to 45° the more squarish blocks and the more checks are appropriate. The results presented in this thesis may be summarised as follows: Cultivation for regeneration of accessions should be based on a meaningful and statistically analysable experimental field design. The design needs to include checks and a random sample of accessions from the gene pool held at the gene bank. It is advisable to utilise metric or percentage rating scales. It can be expected that using a threshold model increases the quality of multivariate analysis and association mapping studies based on phenotypic gene bank data.
Die Auswirkungen einer einmalig variierten Bodenbearbeitung auf Ertragsbildung, Verunkrautung und Bodennitratgehalt unter ökologischen Produktionsbedingungen
(2007) Häberle, Annette; Claupein, Wilhelm
Although organic farming is a very non-polluting kind of agriculture, nitrate leachate losses can also be found under this management. Restrictions in organic fertilization have the purpose to keep the nitrate leachate with soil tillage and crop rotation on a low level. Due to this aim field experiments were conducted to investigate the short-term effect of timing and method of cultivation after the harvest of legumes and crops with high-N crop residues on N mineralization, nitrate leaching, crop growth, diseases and weeds in wheat crops. The study was designed to compare the effects of the ?Schutz- und Ausgleichsverordnung? (SchALVO) in Baden-Württemberg and tillage strategies which are normally used in practice, like reduced and conventional tillage in autumn and to compare different times of conventional tillage in winter and spring in three different areas of Baden-Württemberg with typically soil types. The areas were located in the Main-Tauber-Kreis with soils from Keuper and shell lime, in the Gäu-Region with soils from löss and the Schwäbische Alb with soils of limestone. Especially organic farms use, for the admancement of yield und for the regulation of weed population, a timely and increased requirement of soil tillage. In the results of October 2002 till summer 2005 there was no significant influence of timing and method of cultivation, for example reduced tillage in autumn or tillage in winter or spring, on the productivity of organic farms. In the most cases the conditions on the experimental fields were very good resulting of a low weed density and a good farming management. On fields with a high density of perennial weeds the risk of multiplication of weed population persists even after a short-term variation of tillage. There were only a few, not significant differences in the development of wheat growth because of different soil tillage. The most differences were seen between the growth of winter wheat and summer wheat. The yield of summer wheat was not significantly lower than the yield of winter wheat. Summer wheat reached nearly the same yield potential with higher amounts of crude protein. Especially in areas with strong winters and low N-input the yield of summer wheat was higher than the yield of winter wheat. Because of a second peak of mineralization in spring there was a better adaptation of NO3-release to the growth of summer wheat after soil tillage in November, December and February. Because of the better utilization of soil-N from summer wheat the lower yield potential in comparison to winter wheat was relativised in the most areas. With regard to N mineralization a time displacement of soil tillage in winter or spring didnt reduce the N-mineralization before winter in all cases. But in this time displaced treatments there was a second peak in N-mineralization additional to the first peak in autumn. Short-term practice of reduced soil tillage did not reduce N-release in the field experiments. Altogether a time displaced soil tillage in winter or spring could be, based on the experiments, a practical alternative for N-conservation through winter with regard to N-mineralization as well as with regard to corn yield. With the cultivation of a fast-growing catch crop farmers could reach an additional reduction of mineralised N amount over winter. In the farming practice a well timed sowing of catch crops is not always possible, like it is shown in the experiments, but it should be kept in mind for N conservation.
Reducing irrigation water supply to accomplish the goal of designing sustainable cropping systems in the North China plain
(2007) Binder, Jochen; Claupein, Wilhelm
An International Research Training Group (IRTG) of the University of Hohenheim and the China Agricultural University, entitled ?Modeling Material Flows and Production Systems for Sustainable Resource Use in the North China Plain? was launched in 2004. The major hypothesis was ?that adjustments in cropping systems and management practices provided potential for sustainable resource protection on a high yield level?. The research program was conducted in one of the most important economic and agricultural regions in China, the North China Plain (NCP). The NCP is one of the major maize (Zea mays L.) and wheat (Triticum aestivum L.) growing areas. A literature review indicated that over the last two decades yields for wheat and maize increased by more than 20%, which had mainly been achieved by augmenting the amount of irrigation water and fertilizer. Besides the positive effects on yield an increasing amount of these input factors leads to many environmental problems. Field experiments were carried out to compare different cropping systems. Currently, the double cropping of winter wheat and summer maize is the common cultivation system in the NCP. It consists of growing two crops mostly winter wheat and summer maize in one year. The winter wheat production depends on a supplemental irrigation, because rainfall is concentrated in the summer months during the maize growing season. An alternative to the intensive double cropping system could be the single cultivation of spring maize. Relative less irrigation water is required for spring maize production, because the rainy season coincides with the main part of the maize growing season. Due to the longer growing season spring maize normally realises higher yields in comparison to summer maize. However, the total yield of a double copping system of wheat and maize is higher. The evaluated system three harvests in two years (winter wheat and summer maize in the first year followed by spring maize in the second year) forms a balance between the double cropping system and the single cropping of spring maize. Due to the fact that three crops are grown in two years total yield is higher in comparison to single cropping of spring maize (two harvests in two years) but lower in comparison to the traditional double cropping system (four harvests in two years). However the lower cropping index in contrast to the double cropping of wheat and maize results in a lower demand of the input factors irrigation water and N-fertilizer whereas in comparison to the single cropping of spring maize a higher amount of input factor is required. Besides the conduction of field experiments for the collection of empirical datasets, the CERES-Maize and CERES-Wheat models were used to quantify the effects of different irrigation management practices on crop growth, productivity and sustainability of agricultural production. Results indicated that there is a considerable potential for reducing the irrigation amount for winter wheat. However, the results also showed that a supplemental irrigation at critical growth stages seems to be essential to maintain high yields and to ensure an adequate gross margin. In a more complex approach the CERES-Maize model was used to simulate the yield of summer maize and spring maize across the NCP. The spatial and temporal climate variability was taken into account by using up to 30 years of weather data from 14 meteorological stations. The simulated results were linked to a Geographic Information System (GIS). Results indicated that the yield distinction between summer maize and spring maize was partially very low as a result of water shortage at flowering stage. A delay in sowing and the use of adapted cultivars with a later flowering date could help to increase spring maize yields. Summarizing, the results of this study indicate that water is one of the most limiting factors for crop production in the NCP. Further, the reduction of total water consumption will become more and more important with water becoming increasingly scarce and thus costly. Consequently agriculture has to undergo and is already undergoing dramatic changes. The results of this study indicated that there are several possibilities optimize cropping systems in the NCP, focussing on a more sustainable use of water while maintaining high yields. In this context, crop models are valuable tools for e.g. irrigation planning or evaluating different cropping designs in the NCP.
Use of sensor technologies to estimate and assess the effect of various plant diseases on crop growth and development
(2008) Gröll, Kerstin; Claupein, Wilhelm
The topic of this study was ?Use of sensor technologies to estimate and assess the effect of various plant diseases on crop growth and development?. The background of the investigation can be seen in the challenge of developing a sensor system for the site-specific identification of plant diseases. The most widely used practice in disease control is still to spray fungicides uniformly over fields at different times during the vegetation period. However, most diseases are not distributed uniformly across a field, but occur in patches. During the early stage of epidemics large areas of the field are disease free. Excessive use of fungicides increases costs and can increase fungicides residue levels on agricultural products. As there is an increasing pressure to reduce their use by targeting fungicide spraying only on those places in the field where they are needed, the challenge is to provide farmers the the appropriate technological solutions. A simple and cost-effective optical device, based on the measurement of canopy reflectance in several wavebands, would allow disease patches to be identified and thus controlled. The implementation of these reflectance measurement data into crop growth models would allow for the development of site-specific decision rules whether to spray or not to spray. The specific objectives of the Ph.D. thesis were to: develop and test reflectance measurements as a possible technology to identify reflectance signatures of various plant diseases; develop suitable sets of calibrations that can be used for the identification and quantification of plant diseases; test different sensor systems at different spatial resolutions for their ability to identify plant diseases; develop a strategy to use plant disease information gained from sensor measurements as input dataset for the simulation of wheat growth under disease pressure in CERES-Wheat. In greenhouse experiments at the University of Hohenheim and in field experiments at the experimental station ?Ihinger Hof? of the University of Hohenheim the influence of the diseases powdery mildew, septoria leaf blotch and wheat eyespot on the reflectance of winter wheat was analyzed. To measure the reflectance of the plants three different sensor systems were used. Plant reflectance was measured with a digital camera (LEICA S1 PRO, LEICA Kamera AG, Solms, Germany) at leaf scale (0.5 cm²) and with the spectroradiometer Field Spec® Hand Held (ASD, Inc. Boulder, CO, USA) (0.5 m²) and the Yara N-Sensor in the field-scan modus (12 m²) 2 m above the canopy. The diseases powdery mildew, septoria leaf blotch and wheat eyespot have been analyzed. In a first approach it was tested if it is possible to detect plant diseases using reflectance measurements. The greenhouse studies showed that powdery mildew could be identified especially in the visible wavelength range. Also a correlation between powdery mildew pustules and reflectance changes was possible. Powdery mildew is a leaf disease and changes could directly be detected by a sensor system (Chapter 5). Out of this the second approach was to analyze if a stem disease that cannot directly be detected could be identified using a sensor system. The influence of wheat eyespot was investigated in a field experiment with winter wheat. The results showed that wheat eyespot could not be detected with the digital camera and the spectroradiometer. The problem was the low infection level and the distance between the measuring place and the infection place (Chapter 6). In a next step common vegetation indices were tested for their ability to identify plant diseases. Different vegetation indices were selected out of the literature to detect powdery mildew and septoria leaf blotch in the field using a spectroradiometer. Results indicated that the common vegetation index REIP was able to detect powdery mildew at an infection level of 7 %. With the common vegetation indices septoria leaf blotch could be detected only at a late infection level of 13.7 %. Out of this the new vegetation index DII was developed, which was able to detect septoria leaf blotch at an early infection level of 4 % (Chapter 7). Not only the place of infection but also the spatial resolution seems to play an important role in the identification of plant diseases. In a further approach different sensor systems with different spatial resolutions were tested in a field experiment for the identification of septoria leaf blotch. The results showed in general that septoria leaf blotch could be identified especially in the infrared wavelength range compared to powdery mildew that could especially identified in the visible wavelength range. The results showed further that the lower the spatial resolution , the more difficult it gets to identify plant diseases site-specifically. With a spatial resolution of 0.5 cm² a identification and quantification was possible. With a spatial resolution of 0.5 m² only a identification was possible and with a spatial resolution of 12 m² not identification and quantification was possible. That might be because of the resulting mixture of healthy and diseased plants (Chapter 8). The last step of this work was then to show how reflectance measurements could be implemented into crop growth models to calculate decisions whether to spray or not to spray fungicides on a site-specific level. Summarizing, the overall results of this study indicated that an identification of plant diseases was possible under certain conditions. An identification was possible if the infection place was also the measuring place and if a sensor system was used with a high spatial resolution. The results also showed that it was possible in a certain way to differ between biotroph and necrotroph plant diseases. For a holistic farming concept it is necessary in the future that reflectance measurements are integrated in a crop growth model to give farmers a decision tool that decides whether the infection is critical enough to spray or not.
Use of modeling to characterize phenology and associated traits among wheat cultivars
(2008) Herndl, Markus; Claupein, Wilhelm
Predicting phenology of wheat is important for many aspects of wheat production as for example facilitating accurate timing of pesticides, fertilizers and irrigation, avoiding stress at critical growth stages, and adapting cultivar characteristics to specific environmental constraints or global changes in climate. The aim of the dissertation was to characterize and test the impact of wheat phenology on agronomic traits through integrated use of crop models and information on the genetic makeup of cultivars. In an initial study, cultivar differences in vernalization requirement, photoperiod response and earliness per se were distinguished by field-based indices and compared with corresponding model parameters in CSM-Cropsim-CERES-Wheat model Version 4.0.2.0. To determine whether field-based indices can provide accurate characterization of vernalization requirement, photoperiod response and earliness per se, 26 winter wheat cultivars were evaluated under field conditions at Ihinger Hof, Germany using two natural photoperiod regimes (from different transplanting dates) and vernalization pre-treatments. Results indicated that combining planting dates with vernalization pre-treatments can permit reliable, quantitative characterization of vernalization requirement, photoperiod response and earliness per se of wheat cultivars. Furthermore, genotypic model parameters appeared to be reliable estimates of cultivar differences in response to vernalization and photoperiod. In a second study, the model parameters for vernalization requirement (P1V) and photoperiod response (P1D) were estimated using gene information. To estimate these model parameters through integrating effects of Vrn and Ppd loci, flowering data obtained for 29 cultivars tested in the International Winter Wheat Performance Nursery (IWWPN) were used. Summarizing, results indicated that gene-based estimation of model coefficients was effective for prediction of phenology over a wide range of environments and appears feasible for studying wheat response to environment. To assist plant breeding with crop models, a possibility could be to assess model parameters for designing improved plant types (ideotypes). CMS-Cropsim-CERES-Wheat was used in a third study to test model parameters concerning plant development and grain yield. In ideotyping sequences, the parameters were varied and the model was run in four different scenarios in the North China Plain. The parameter G1 (corresponding trait: kernel number per spike) showed the highest influence on yield over all scenarios followed by G2 (corresponding trait: kernel weight). Results obtained in this study could help breeders to select the relevant traits and integrate them in their breeding program for a specific population of environments. To investigate the coherences between pre-anthesis phenology and grain protein content in a fourth study the statistical analysis of causal relationships with genotypic model parameters was used. It was tested whether model-based characterizations of vernalization requirement, photoperiod response and earliness per se can help explain genotype x environment interactions for grain protein content. Twenty four winter wheat and five spring wheat cultivars (IWWPN) and twelve winter wheat cultivars (of a two year field study at Ihinger Hof, Germany) were characterized using CSM-Cropsim-CERES-Wheat. Covariance analyses indicated that vernalization requirement, photoperiod response, and earliness per se all influenced grain protein content, but their effects varied with site and year within region. Path analyses using data from two seasons in Germany confirmed that grain protein content increased with a shorter pre-anthesis phase and indicated in accordance with the covariance analyses the environmental dependence of this trait. The results proposed that efforts to improve grain protein content should target levels of vernalization requirement, photoperiod sensitivity and earliness per se to specific populations of environments and seek to reduce the apparent large influence of environment on grain protein content. The improved understanding of traits affecting phenology and the linkage with genotypic model parameters can be applied e.g. in China to solve arising and existing agricultural challenges. Model-based analyses can help adapting cropping systems to global warming. In the North China plain a more accurate timing of N-fertilizers and irrigation, as a result of modeling, can ensure a sustainable resource use while maintaining high yields. Summarizing, the findings of this dissertation showed that traits affecting phenology in wheat can be successfully characterized by field-based indices, genotypic model parameters and gene-based estimates of genotypic model parameters. Furthermore, the research showed how genotypic model parameters can be used for breeding purposes, and to test causal relationships both at regional and local geographic scales.
Studies on water-soluble carbohydrates in wheat (Triticum aestivum L.): regulating traits, model analysis, early chilling effects, and future perspectives
(2009) Valluru, Ravi; Claupein, Wilhelm
Wheat is one of the major staple food crops of the world. Although a wealth of research has been made a significant progress in wheat productivity through genetic interventions in the last two decades, there remains an untapped potential for further yield gain. Water-soluble carbohydrates (WSCs) are excess carbohydrates stored in vegetative organs such as stem, sheaths, and tiller base during vegetative period. They are highly heritable agronomic trait that regulates plant growth and development as well as grain yields. In addition, WSCs also contribute to plant adaptation to abiotic stresses. Improving current understanding of the multi-faceted roles of WSCs is therefore essential for future crop improvement. The present thesis provides information on WSCs, its associated traits and future perspectives that derived from several experiments conducted under field and glasshouse conditions. Typically, the thesis has four objectives dealing with a specific set of questions. The first objective explains the traits regulating WSCs under three N levels (0, 100 and 200 kg ha-1). N concentration in the plant is negatively correlated with WSCs storage. The traits associated with total WSCs storage are also influenced by N levels. Three vegetative traits, viz., total biomass, flag-leaf width, root: shoot ratio and two physiological traits, viz., radiation use efficiency, and leaf N concentration were considered. Under high N level, lower biomass, flag-leaf width and root: shoot ratio is beneficial to increase total WSC storage. In contrast, increasing biomass and flag-leaf width is advantageous under lower N level. However, a specific set of traits, rather than a single trait, appeared to evolve under N-specific selection maximizing total WSC storage. The second objective describes the simulation model for WSC accumulation under three N levels. A simple phenological model for carbon accumulation, in the form of WSCs, during vegetative period in four wheat genotypes was developed. This model was integrated and evaluated under crop management factors such as low (0 kg ha-1), medium (100 kg ha-1), and high (200 kg ha-1) nitrogen supply. The proposed model predicted higher rate of WSC accumulation in the early stages of crop growth and lower rates in the later stages. Overall, the model predicted the rate of WSC accumulation with a RMSE of 6.58, suggesting that the proposed model simulated well. Nevertheless, the predicted rate of WSC accumulation was close to the observed data only in low and high N level. The model predicted total WSCs well with the observed data; however, it overestimated total WSCs at early stages and underestimated total WSCs at later stages, largely due to the respective rate of WSC accumulation. Overall, evaluation of the model with the predicted dataset indicated that the prediction errors for the rate of WSC accumulation were more with RMSE between 20-30% in all N levels. For total WSC accumulation, the prediction errors were less, and the RMSE, in most cases, was less than 20% in all N levels. The third objective reveals the plasticity of the phenotypic expression of two primitive wheat species (Triticum monococcum L. and T. dicoccum S.) in response to early chilling stress (4 oC). Early chilling stress resulted in lower total WSCs, in addition to lower flag leaf size, total biomass, specific leaf area and early flowering. While lower specific leaf area may reduce the early chilling stress effects at an individual leaf level, a higher leaf mass ratio and utilization of reserve carbohydrates indicated that the compensatory growth of chilled plants during the recovery period relied on the concerted action of altered resource allocations and reserve carbohydrate consumption. However, the lack of direct selection on sucrose indicates that sucrose has indirect effects on total WSCs. Thus, the total effects of reserve sucrose on relative fitness seem to be buffered via rapid growth rate in chilled plants. Nevertheless, a significant cost of plasticity was evident only for fructans. Further, a regression of daily cumulative plant biomass derived from a crop growth simulation model (CERES-Wheat) on crop growing period revealed a divergent developmental pathway for early chilled plants. These results showed that not only are the characteristic architectures in two Triticum species plastic, but the regulating mechanism of intrinsic developmental (ontogenetic) pathway is also sensitive to early chilling stress. Fourth objective provides future perspectives for WSCs, in particular fructans. Fructans can be involved in freezing tolerance by protecting cellular membranes. This opinion postulates that fructans can be transported from vacuole (site of synthesis) to apoplast (site of action) through vesicles derived from the vacuole. These results can improve the current understanding of WSCs in plant growth and development as well as grain yields. Traits can be used as WSCs markers to prescreen a large number of wheat germplasm for high total WSCs contents. However, a further understanding of different dimensions of WSCs in grain yield improvement and plant growth and development deserves more attention.
Optimizing the prediction of genotypic values accounting for spatial trend andpopulation structure
(2010) Müller, Bettina Ulrike; Piepho, Hans-Peter
Different effects, like the design of the field trial, agricultural practice, competition between neighboured plots, climate as well as the spatial trend, have an influence on the non-genotypic variation of the genotype. This effects influence the prediction of the genotypic value by the non-genotypic variation. The error, which results from the influence of the non-genotypic variation, can be separated from the phenotypic value by field design and statistical models. The integration of different information, like spatial trend or marker, can lead to an improved prediction of genotypic values. The present work consists of four studies from the area of plant breeding and crop science, in which the prediction of the genotypic values was optimized with inclusion of the above mentioned aspects. Goals of the work were: (1) to compare the different spatial models and to find one model, which is applicable as routine in plant breeding analysis, (2) to optimize the analysis of unreplicated trials of plant breeding experiments by improving the allocation of replicated check genotypes, (3) to improve the analysis of intercropping experiments by using spatial models and to detect the neighbour effect between the different cultivars, and (4) to optimize the calculation of the genome-wide error rate in association mapping experiments by using an approach which regards the population structure. Different spatial models and a baseline model, which reflects the randomization of the field trial, were compared in three of the four studies. In one study the models were compared on basis of different efficiency criteria with the goal to find a model, which is applicable as routine in plant breeding experiments. In the second study the different spatial models and the baseline model were compared on unreplicated trials, which are used in the early generation of the plant breeding process. Adjacent to the comparison of the models in this study different designs were compared with the goal to see if a non-systematic allocation of check genotypes is more preferable than a systematic allocation of check genotypes. In the third study these different models were tested for intercropping experiments. In this study it should be tested, if an improvement is expectable for these non randomized or restricted randomized trials by using a spatial analysis. The results of the three studies are that no spatial model could be found, which is preferable over all other spatial models. In a lot of cases the baseline model, which regards only the randomization, but no spatial trend, was better than the spatial models, also for the restricted or non-randomized intercropping trials. In all three studies the basic principle was followed to start first with the baseline model, which is based on the randomization theory, and then to extend it by spatial trend, if the model fit can be improved. In the second study the systematic and non-systematic allocation of check plots in unreplicated trials were compared to solve the question if a non-systematic allocation leads to more efficient estimates of genotypes as the systematic allocation. The non-systematic allocation of check plots led to an unbiased estimation in three of four uniformity trials. As well as in the third study an analysis was done, if the border plots of the different cultivars are influenced by the neighboured cultivar and if there are significant differences to the inner plot. The position of the cultivars, border plot or inner plot, had a significant influence of the yield. If maize was cultivated adjacent to pea, the yield of the border plot of maize was much higher than the inner plot of maize. When wheat was cultivated behind maize, there were no significant differences in the yield, if the plot was a border plot or inner plot. In addition to optimizing the field design for unreplicated trials and the extension of the models by spatial trend the marker information was integrated in a fourth study. An approach was proposed in this study, which calculates the genome wide error for association mapping experiments and accounts for the population structure. Advantages of this approach in contrast to previously published approaches are that the approach on the one hand is not too conservative and on the other hand accounts the population structure. The adherence of the genome wide error rate was tested on three datasets, which were provided by different plant breeding companies. The results of these studies, which were obtained in this thesis, show that by the different extensions, like integration of spatial trend and marker information, and modifications of the field design, an improved prediction of the genotypic values can be achieved.

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