Stefan Siebert

Stefan Siebert
Georg-August-Universität Göttingen | GAUG · Department of Crop Sciences

Dr. agr. (PhD)

About

179
Publications
154,316
Reads
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21,524
Citations
Introduction
Stefan Siebert currently works at the Department of Crop Sciences, Georg-August-Universität Göttingen, as a Professor for Agronomy / Crop Science. Stefan does research in Agronomy, Environmental Science and Geoscience with focus on strategies for sustainable resource use and management in plant production. Specific emphasis is on water and nutrient management. Another research focus is on the impact of abiotic stress (heat, drought) on crop growth, development and productivity.
Additional affiliations
October 2017 - present
Georg-August-Universität Göttingen
Position
  • Professor
March 2016 - September 2017
University of Bonn
Position
  • Chair
April 2009 - February 2016
University of Bonn
Position
  • Senior Researcher
Education
April 2009 - April 2015
University of Bonn
Field of study
  • Crop Science and Resource Conservation
May 2002 - December 2005
Universität Kassel
Field of study
  • Agricultural Sciences
October 1999 - April 2002
Universität Kassel
Field of study
  • Agricultural Sciences

Publications

Publications (179)
Article
Full-text available
Increasing population and consumption are placing unprecedented demands on agriculture and natural resources. Today, approximately a billion people are chronically malnourished while our agricultural systems are concurrently degrading land, water, biodiversity and climate on a global scale. To meet the world's future food security and sustainabilit...
Article
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Achieving sustainable global food security is one of humanity’s contemporary challenges. Here we present an analysis identifying key “global leverage points” that offer the best opportunities to improve both global food security and environmental sustainability. We find that a relatively small set of places and actions could provide enough new calo...
Article
Full-text available
Irrigation intensifies land use by increasing crop yield but also impacts water resources. It affects water and energy balances and consequently the microclimate in irrigated regions. Therefore, knowledge of the extent of irrigated land is important for hydrological and crop modelling, global change research, and assessments of resource use and man...
Article
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Climate change will increase the number and severity of heat waves which may negatively affect crop yields. Here we show for wheat and maize across Europe that heat stress is considerably reduced by irrigation due to surface cooling for both current and projected future climate. We demonstrate that crop heat stress impact assessments should be base...
Article
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Snowpack stores cold-season precipitation to meet warm-season water demand. Climate change threatens to disturb this balance by altering the fraction of precipitation falling as snow and the timing of snowmelt, which may have profound effects on food production in basins where irrigated agriculture relies heavily on snowmelt runoff. Here, we analys...
Article
A c c e p t e d M a n u s c r i p t 3 Highlight An ensemble of 29 wheat crop models simulates seasonal wheat growth well under locally recommended sowing conditions, but needs improvements to capture the yield response to early sowing, especially under high sowing density. Abstract Crop multi-model ensembles (MME) have proven to be effective in inc...
Article
Crop multi-model ensembles (MME) have proven to be effective in increasing the accuracy of simulations in modelling experiments. However, the ability of a MME to capture crop response to changes in sowing dates and densities has not yet been investigated. These management interventions are some of the main levers for adapting cropping systems to cl...
Article
Unmanned aerial vehicle (UAV) remote sensing and machine learning have emerged as a practical approach with ultra-high temporal and spatial resolutions to overcome the limitations of ground-based sampling for continuous crop monitoring. However, little is known on the suitability of distinct sensing indices for different crop management and distinc...
Preprint
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Although extreme weather events recur periodically everywhere, the impacts of their simultaneous occurrence on crop yields are globally unknown. In this study, we estimate the impacts of combined hot and dry extremes as well as cold and wet extremes on maize, rice, soybean, and wheat yields using gridded weather data and reported crop yield data at...
Article
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This study investigates the main drivers of uncertainties in simulated irrigated maize yield under historical conditions as well as scenarios of increased temperatures and altered irrigation water availability. Using APSIM, MONICA, and SIMPLACE crop models, we quantified the relative contributions of three irrigation water allocation strategies, th...
Article
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Advances in estimating actual evapotranspiration (ETa) with remote sensing (RS) have contributed to improving hydrological, agricultural, and climatological studies. In this study, we evaluated the applicability of Vegetation-Index (VI)-based ETa (ET-VI) for mapping and monitoring drought in arid agricultural systems in a region where a lack of gro...
Article
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Since the onset of human societies, settlement patterns and social structures have been shaped by access to water. This review covers historical and recent examples from Cambodia, Central Asia, India, Latin America and the Arabian Peninsula to analyze the role of water resources in determining the rise and collapse of civilizations. Over recent dec...
Article
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The regular drought episodes in South Africa highlight the need to reduce drought risk by both policy and local community actions. Environmental and socioeconomic factors in South Africa's agricultural system have been affected by drought in the past, creating cascading pressures on the nation's agro-economic and water supply systems. Therefore, un...
Preprint
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Several safe boundaries of critical Earth system processes have already been crossed by human perturbations. Recent research indicates that not accounting for the interactions between these processes may further narrow the safe operating space for humanity. Yet existing work accounts only for transgression of single boundaries and only a few studie...
Preprint
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Many animal feeds compete for resources with human food production. The current use of food system by-products and residues as feed could potentially be increased to reduce the competition. We gathered a harmonised global food system material flow database for crop, livestock and aquaculture production including the availability of food system by-p...
Article
The uncertainties associated with crop model inputs can affect the spatio-temporal variance of simulated yields, particularly under suboptimal irrigation. The aim of this study was to determine and quantify the main drivers of irrigated potato yield variance; as influenced by crop management practices as well as climate and soil factors. Using a lo...
Preprint
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Droughts are among the most damaging and least understood of all so-called natural hazards. Droughts often lead to long-lasting and cascading impacts on different sectors across multiple spatial scales. Because the impacts of drought are less direct and immediately visible than the impacts of events such as floods or storms, drought has, for a long...
Article
Phosphorus (P) is an essential plant nutrient. However, our understanding of the complex interactions between soil P availability, environment, management and crop growth is still limited. We used unique historic and recent soil and crop data spanning more than a century combined with a process-based crop model to analyze the impact of P fertilizer...
Article
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Increasing population and a severe water crisis impose growing pressure on cropping systems of Iran to increase crop production meeting the rising demand for food. Little is known on the separate contribution of trends and variability of the harvested area and yield on crop production in severely drought-prone areas such as Iran. In this study, we...
Article
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Crop models were originally developed for application at the field scale but are increasingly used to assess the impact of climate and/or agronomic practices on crop growth and yield and water dynamics at larger scales. This raises the question of how data aggregation approaches affect outputs when using crop models at large spatial scales. This st...
Article
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One of the major sources of uncertainty in large-scale crop modeling is the lack of information capturing the spatiotemporal variability of crop sowing dates. Remote sensing can contribute to reducing such uncertainties by providing essential spatial and temporal information to crop models and improving the accuracy of yield predictions. However, l...
Article
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Yield stability is important for food security and a sustainable crop production, especially under changing climatic conditions. It is well known that the variability of yields is linked to changes in meteorological conditions. However, little is known about the long-term effects of agronomic management strategies, such as the supply of important n...
Article
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Drought is one of the extreme climatic events that has a severe impact on crop production and food supply. Our main goal is to test the suitability of remote sensing-based indices to detect drought impacts on crop production from a global to regional scale. Moderate resolution imaging spectroradiometer (MODIS) based imagery, spanning from 2001 to 2...
Article
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Multiple cropping, defined as harvesting more than once a year, is a widespread land management strategy in tropical and subtropical agriculture. It is a way of intensifying agricultural production and diversifying the crop mix for economic and environmental benefits. Here we present the first global gridded data set of multiple cropping systems an...
Article
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Various environmental challenges are rapidly threatening ecosystems and societies globally. Major interventions and a strategic approach are required to minimize harm and to avoid reaching catastrophic tipping points. Setting evidence-based priorities aids maximizing the impact of the limited resources available for environmental interventions. Foc...
Article
Early vigour in wheat is a trait that has received attention for its benefits reducing evaporation from the soil surface early in the season. However, with the growth enhancement common to crops grown under elevated atmospheric CO2 concentrations (e[CO2]), there is a risk that too much early growth might deplete soil water and lead to more severe t...
Conference Paper
Full-text available
Drought is a recurrent global phenomenon considered one of the most complex hazards with manifold impacts on communities, ecosystems, and economies. While many sectors are affected by drought, agriculture's high dependency on water makes it particularly susceptible to droughts, threatening the livelihoods of many, and hampering the achievement of t...
Article
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PUBLISHED IN NATURE FOOD; OPEN ACCESS (VIEW ONLY) ARTICLE AVAILABE AT: https://rdcu.be/b3C3K. The distance between the origin and end-point of food supply chains, and the ‘localness’ of food systems, are key considerations of many narratives associated with sustainability. Yet, information on the minimum distance to food crops is still scarce at t...
Article
Input data aggregation affects crop model estimates at the regional level. Previous studies have focused on the impact of aggregating climate data used to compute crop yields. However, little is known about the combined data aggregation effect of climate (DAEc) and soil (DAEs) on irrigation water requirement (IWR) in cool-temperate and spatially he...
Article
Full-text available
Droughts continue to affect ecosystems, communities and entire economies. Agriculture bears much of the impact, and in many countries it is the most heavily affected sector. Over the past decades, efforts have been made to assess drought risk at different spatial scales. Here, we present for the first time an integrated assessment of drought risk f...
Presentation
Full-text available
Input data aggregation influences crop model estimates at the regional level. Previous studies have focused on the impact of aggregating the climate data used to compute crop yields. Little is known about the combined data aggregation effect of climate (DAEc) and soil (DAEs) model inputs. This study explores the implications of using coarse resolut...
Conference Paper
Warmer temperature with climate change will affect crop yields by shortening growth duration and increasing water demand as well as the frequency and severity of heat stress. At the same time, elevated atmospheric CO 2 concentrations will decrease rates of water use and additionally increase growth of C 3 crops like wheat. Understanding the combine...
Article
Full-text available
Drought adversely affects vegetation conditions and agricultural production and consequently the food security and livelihood situation of the often most vulnerable communities. In spite of recent advances in modeling drought risk and impact, coherent and explicit information on drought hazard, vulnerability and risk is still lacking over wider are...
Article
Full-text available
Explicit and large-scale information on farming systems is important for many applications such as crop production estimates, drought impact assessments or water footprint analysis. This contribution investigated the possibility of optimizing harmonic functions fitted to cloud-corrected Landsat NDVI (Normalized Difference Vegetation Index) time-ser...
Article
Full-text available
Droughts continue to affect ecosystems, communities, and entire economies. Agriculture bears much of the impact, and in many countries it is the most heavily affected sector. Over the past decades, efforts have been made to assess drought risk at different spatial scales. Here, we present for the first time an integrated assessment of drought risk...
Article
Full-text available
Reducing the social, environmental, and economic impacts of droughts and identifying pathways towards drought resilient societies remains a global priority. A common understanding of the drivers of drought risk and ways in which drought impacts materialize is crucial for improved assessments and for the identification and (spatial) planning of targ...
Article
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In the version of this Analysis originally published, in the section ‘Trends in global water demand’, the percentage increase in agricultural area equipped for irrigation was incorrect: the text ‘rose by 48% from 270 to 400×106 ha’ should have read ‘rose by 50% from 220 to 330×106 ha’; this has now been corrected.
Article
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Water stress is often evaluated by scarcity: the share of available water supply being consumed by humans. However, some consumptive uses of water are more or less flexible than others, depending on the costs or effects associated with their curtailment. Here, we estimate the share of global water consumption over the period 1980–2016 from the rela...
Conference Paper
Full-text available
In times of drought, water resources are insufficient. These water shortages often have negative effects on agricultural productivity and on associated socioeconomic factors, causing reduced income, food shortages and even famines. The overall objective of GlobeDrought is to develop an integrated drought risk information system which will adequatel...
Article
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Voluntary sustainability standards (VSS) are stakeholder-derived principles with measurable and enforceable criteria to promote sustainable production outcomes. While institutional commitments to use VSS to meet sustainable procurement policies have grown rapidly over the past decade, we still have relatively little understanding of the (i) direct...
Article
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Understanding the drivers of yield levels under climate change is required to support adaptation planning and respond to changing production risks. This study uses an ensemble of crop models applied on a spatial grid to quantify the contributions of various climatic drivers to past yield variability in grain maize and winter wheat of European cropp...
Article
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For highly productive regions such as Germany, the increase of wheat grain yields observed throughout the 20th century is largely attributed to the progress in crop breeding and agronomic management. However, several studies indicate a strong variability of the genetic contribution across locations that further varies with experimental design and v...
Article
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In the hydrologic cycle, continental landmasses constitute a sink for atmospheric moisture as annual terrestrial precipitation commonly exceeds evapotranspiration. Simultaneously, humans intervene in the hydrologic cycle and pump groundwater to sustain, for example, drinking water and food production. Here, we use a coupled groundwater‐to‐atmospher...
Article
Abstract Impacts of nutrient supply and different cultivars (genotypes) on actual yield levels have been studied before, but the long-term response of yield trends is hardly known. We present the effects of 24 different fertilizer treatments on long-term yield trends (1953–2009) of winter wheat, winter rye, sugar beet and potato, with improved cult...
Poster
Full-text available
Development of a global drought information system (DIS) useful for: To comprehensively quantify (potential) droughts impacts Support possibility of better drought management and reduce drought vulnerability, especially for affected area with lower capacity drought capacity. Provide DIS capacity to all drought prone regions Background
Article
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The El Niño Southern Oscillation (ENSO) peaked strongly during the boreal winter 2015-2016, leading to food insecurity in many parts of Africa, Asia and Latin America. Besides ENSO, the Indian Ocean Dipole (IOD) and the North Atlantic Oscillation (NAO) are known to impact crop yields worldwide. Here we assess for the first time in a unified framewo...
Article
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Changing crop phenology is considered an important bio-indicator of climate change, with the recent warming trend causing an advancement in crop phenology. Little is known about the contributions of changes in sowing dates and cultivars to long-term trends in crop phenology, particularly for winter crops such as winter wheat. Here, we analyze a lon...