Institut für Kulturpflanzenwissenschaften

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Nonadditive gene expression contributing to heterosis in partially heterozygous maize hybrids is predominantly regulated from heterozygous regions
(2025) Pitz, Marion; Baldauf, Jutta A.; Piepho, Hans‐Peter; Hochholdinger, Frank; Pitz, Marion; Institute of Crop Science and Resource Conservation, Crop Functional Genomics, University of Bonn, Bonn, Germany; Baldauf, Jutta A.; Institute of Crop Science and Resource Conservation, Crop Functional Genomics, University of Bonn, Bonn, Germany; Piepho, Hans‐Peter; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Hochholdinger, Frank; Institute of Crop Science and Resource Conservation, Crop Functional Genomics, University of Bonn, Bonn, Germany
Hybrids often perform better than their homozygous parents, a phenomenon that is commonly referred to as heterosis. Heterosis is widely utilized in modern agriculture, although its molecular basis is not very well understood. In this study, we backcrossed an intermated recombinant inbred line population of maize ( Zea mays L.) with its parental inbred lines B73 and Mo17. The resulting hybrids exhibited different degrees of heterozygosity and heterosis. We identified nonadditively expressed genes, which are expressed differently from their mid‐parental level. In addition, we surveyed their regulation by investigating expression quantitative trait loci (eQTL). Nonadditively expressed genes explain up to 27% of heterotic variance in the backcross hybrids. Furthermore, nonadditively expressed genes are regulated almost exclusively from heterozygous regions of the genome. We observed that nonadditive expression patterns are distinctly regulated depending on the genetic origin of the higher expressed parent. As a consequence, these regulatory regimes lead to higher gene activity in most nonadditively expressed genes in the hybrids. We demonstrated that nonadditive expression patterns contribute to heterosis and their mode of regulation might translate phylogenetic distance into vigorous hybrids. Based on our results, we hypothesize that diverging regulatory preferences in inbred lines are beneficial for selecting parental combinations for hybrid breeding.
Subsurface drip irrigation reduces weed infestation and irrigation water use while increasing inflorescence and cannabinoid yield in an outdoor tunnel Cannabis sativa L. production system
(2025) Büser, Christian; Hartung, Jens; Graeff-Hönninger, Simone; Büser, Christian; Institute of Crop Science Dept. of Agronomy (340a), Stuttgart, Germany; Hartung, Jens; Institute of Crop Science Dept. of Biostatistics, Stuttgart, Germany; Graeff-Hönninger, Simone; Institute of Crop Science Dept. of Agronomy (340a), Stuttgart, Germany
Cannabis ( Cannabis sativa L.) has served as a valuable medicinal plant for thousands of years and is experiencing a resurgence in cultivation and research due to recent legal changes. However, the resource-intensive nature of cannabis cultivation, particularly water and energy demands, poses significant environmental challenges. Outdoor cultivation in a semi-controlled environment can reduce those energy demands but necessitates irrigation. Drip irrigation (DI) is the most commonly used irrigation method but is often criticized for its susceptibility to water losses through evaporation and the risk of surface runoff. Subsurface Drip Irrigation (SDI) provides a sustainable solution by minimizing evaporation losses while maintaining or increasing yields, thereby enhancing water use efficiency. In this study, we compared the effects of DI and SDI on weed infestation, total water usage, inflorescence yield, and water use efficiency of three CBD-rich cannabis chemotype III genotypes (Kanada, Terra Italia, FED) in an outdoor foil tunnel cultivation system. SDI resulted in a reduction of irrigation water usage by 18.6% compared to DI. Remarkably, weed dry biomass was reduced by 93.2% in SDI. Concomitantly, inflorescence yield increased by 5% and CBD concentration by 9%. Overall, the water use efficiency of inflorescence yield and CBD concentration was significantly higher in SDI than in DI. Our results indicated that implementing SDI instead of DI can significantly decrease irrigation water use and reduce weed infestation while increasing inflorescence and CBD yield, thus reducing the environmental challenges associated with cannabis cultivation.
Sustainable growth of organic farming in the EU requires a rethink of nutrient supply
(2024) Reimer, Marie; Oelofse, Myles; Müller-Stöver, Dorette; Möller, Kurt; Bünemann, Else K.; Bianchi, Silvia; Vetemaa, Airi; Drexler, Dóra; Trugly, Bence; Raskin, Ben; Blogg, Hugh; Rasmussen, Anton; Verrastro, Vincenzo; Magid, Jakob; Reimer, Marie; Institute of Crop Science, Fertilization and Soil Matter Dynamics, University of Hohenheim, Fruwirthstr. 20, 77593, Stuttgart, Germany; Oelofse, Myles; Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark; Müller-Stöver, Dorette; Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark; Möller, Kurt; Institute of Crop Science, Fertilization and Soil Matter Dynamics, University of Hohenheim, Fruwirthstr. 20, 77593, Stuttgart, Germany; Bünemann, Else K.; Department of Soil Sciences, Research Institute of Organic Agriculture FiBL, Box 219, Ackerstrasse 113, 5070, Frick, Switzerland; Bianchi, Silvia; Department of Soil Sciences, Research Institute of Organic Agriculture FiBL, Box 219, Ackerstrasse 113, 5070, Frick, Switzerland; Vetemaa, Airi; Estonian Organic Farming Foundation (EOFF), Kungla 1a, 50403, Tartu, Estonia; Drexler, Dóra; Hungarian Research Institute of Organic Agriculture, Miklós Tér 1, 1033, Budapest, Hungary; Trugly, Bence; Hungarian Research Institute of Organic Agriculture, Miklós Tér 1, 1033, Budapest, Hungary; Raskin, Ben; Soil Association, Spear House, 51 Victoria Street, BS1 6AD, Bristol, UK; Blogg, Hugh; Soil Association, Spear House, 51 Victoria Street, BS1 6AD, Bristol, UK; Rasmussen, Anton; Innovation Centre for Organic Farming, Agro Food Park 26, 8200, Aarhus, Denmark; Verrastro, Vincenzo; Mediterranean Agronomic Institute of Bari, Valenzano (IAM-B), Italy; Magid, Jakob; Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg, Denmark
The European Commission recently set a target of increasing the area of organic agriculture to 25% by 2030. To achieve this, it is imperative to understand current nutrient use patterns and identify sustainable nutrient supply opportunities. To that end, this study assessed the sustainability of the current nutrient origin and supply of 71 arable organic farms in 8 European regions. Deficient nutrient supply was found on 24%, 66%, and 56% of farms for nitrogen, phosphorus, and potassium, respectively. On average, we show a moderate surplus for nitrogen (28 kg ha −1 ), while phosphorus and potassium balances were close to zero (− 1 and 2 kg ha −1 , respectively). Large variation between countries and farm types shows a divide between more intensive systems relying on external inputs, and less intensive systems facing nutrient deficits and lower outputs. We show, for the first time, the extent of current use of external input types, where conventional manures supplied 17–26% of external nutrients and inputs from non-agricultural origin supplied 31–41%. A large proportion of nutrient sources within the last group are materials derived from urban wastes. The sustainable expansion of the organic sector will require increased use of locally available recycled fertilizers from urban wastes, and acceptance of such sources by organic farmers is shown to be high, provided they are considered safe.
Impact of different storage conditions with combined use of ethylene blocker on ‘Shalimar’ apple variety
(2024) Khera, Kartik; Büchele, Felix; Wood, Rachael Maree; Thewes, Fabio Rodrigo; Wagner, Roger; Hagemann, Michael Helmut; Neuwald, Daniel Alexandre; Khera, Kartik; Lake of Constance Research Centre for Fruit Cultivation (KOB), Schuhmacherhof 6, Ravensburg, Germany; Büchele, Felix; Lake of Constance Research Centre for Fruit Cultivation (KOB), Schuhmacherhof 6, Ravensburg, Germany; Wood, Rachael Maree; Horticulture and Product Physiology, Wageningen University and Research, Droevendaalsesteeg 1, 6708 PB, Wageningen, The Netherlands; Thewes, Fabio Rodrigo; University of Santa Maria, v. Roraima n 9702 1000 Cidade Universitaria, Bairro - Camobi, Santa Maria, RS 97105-900, Santa Maria, Brazil; Wagner, Roger; University of Santa Maria, v. Roraima n 9702 1000 Cidade Universitaria, Bairro - Camobi, Santa Maria, RS 97105-900, Santa Maria, Brazil; Hagemann, Michael Helmut; Department Production Systems of Horticultural Crops, University of Hohenheim, 70593, Stuttgart, Germany; Neuwald, Daniel Alexandre; Lake of Constance Research Centre for Fruit Cultivation (KOB), Schuhmacherhof 6, Ravensburg, Germany
This research investigates the impact of storage conditions on the quality and preservation of 'Shalimar' apples, a relatively new cultivar known for its resistance to apple scab and powdery mildew. The study explores the efficacy of different storage techniques such as regular atmosphere (RA), controlled atmosphere (CA), and dynamic controlled atmosphere with CO2 Monitoring (DCA-CD), as well as the integration of 1-methylcyclopropene (1-MCP) at different storage temperatures (1 °C and 3 °C). Various fruit quality parameters were monitored under different storage conditions, including firmness, titratable acidity, total soluble solids, background color, respiration, ethylene production, and volatile compounds. The results indicate that the controlled atmosphere (CA) at 1 °C emerges as an efficient method for long-term storage. However, it is noted that CA storage may impact the apple aroma, emphasizing the need for a balance between preservation and consumer acceptability. On the other hand, DCA-CD at variable temperatures (approximately 2.5 °C) offers a promising approach for maintaining fruit quality and a higher concentration of volatile compounds. Integrating 1-MCP enhances firmness, but its impact varies across storage conditions. Principal component analysis (PCA) provides insights into the relationships between storage conditions, fruit quality, and volatile compounds. This study contributes valuable insights into optimizing storage strategies for ‘Shalimar’ apples, addressing sustainability and quality preservation in apple production.
Impact of calibration strategy and data on wheat simulation with the DSSAT‐Nwheat model
(2025) Shawon, Ashifur Rahman; Attia, Ahmed; Ko, Jonghan; Memic, Emir; Uptmoor, Ralf; Hackauf, Bernd; Feike, Til; Shawon, Ashifur Rahman; Institute for Strategies and Technology Assessment, Julius Kühn Institute (JKI)–Federal Research Centre for Cultivated Plants, Kleinmachnow, Germany; Attia, Ahmed; Institute for Strategies and Technology Assessment, Julius Kühn Institute (JKI)–Federal Research Centre for Cultivated Plants, Kleinmachnow, Germany; Ko, Jonghan; Department of Applied Plant Science, Chonnam National University, Gwangju, Republic of Korea; Memic, Emir; Department of Agronomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Uptmoor, Ralf; Department of Agronomy, University of Rostock, Rostock, Germany; Hackauf, Bernd; Institute for Breeding Research on Agricultural Crops, Julius Kühn Institute (JKI)–Federal Research Centre for Cultivated Plants, Groß Lüsewitz, Germany; Feike, Til; Institute for Strategies and Technology Assessment, Julius Kühn Institute (JKI)–Federal Research Centre for Cultivated Plants, Kleinmachnow, Germany
Cropping system models (CSMs) are valuable tools for analyzing genotype, environment, and management (G × E × M) interactions in crop production. To apply a CSM in a new region with specific soils, climate, and cultivars, proper calibration and evaluation are required. However, calibration methods vary widely, often depending on modelers' expertise and approach. This study compares three calibration strategies for the DSSAT‐Nwheat model using two datasets: one including yield components (1000‐kernel mass, ears per m 2 , grain number per m 2 ) alongside phenology and grain yield, and another excluding yield components. The datasets cover ∼100 site‐years of winter wheat ( Triticum aestivum ) data from German pre‐registration trials and field experiments. The calibration approaches were (1) stepwise calibration of phenology, biomass, and yield, (2) simultaneous calibration of multiple genetic coefficients, and (3) a hybrid approach combining elements of both. The Time‐Series cultivar coefficient estimator tool was used for implementation. Including yield component data improved model accuracy, reducing root mean square error (RMSE) by up to 10% for key variables such as phenology (3.4–5.5 days). Future wheat yield projections under selected climate scenarios varied by strategy and dataset, ranging from 6376 to 7473 kg ha −1 in fertile, wet soils and 6108 to 6757 kg ha −1 in poorer, dry soils. These results highlight the impact of calibration strategy and dataset choice on model performance. Transparent calibration practices are essential for improving CSM reliability in regional agricultural analysis under diverse environmental conditions.
Chloride application enhances photosynthesis and facilitates nitrate translocation while driving chloride translocation into roots
(2025) Wei, Guanghui; Zhang, Xudong; Franzisky, Bastian L.; Geilfus, Christoph‐Martin; Zörb, Christian; Wei, Guanghui; Institute of Crop Science, Quality of Plant Products, University of Hohenheim, Stuttgart, Germany; Zhang, Xudong; Institute of Crop Science, Quality of Plant Products, University of Hohenheim, Stuttgart, Germany; Franzisky, Bastian L.; Department of Soil Science and Plant Nutrition, Hochschule Geisenheim University, Geisenheim, Germany; Geilfus, Christoph‐Martin; Department of Soil Science and Plant Nutrition, Hochschule Geisenheim University, Geisenheim, Germany; Zörb, Christian; Institute of Crop Science, Quality of Plant Products, University of Hohenheim, Stuttgart, Germany
Chloride and nitrate are essential mineral elements for crop growth. Due to their similar physical and electrochemical properties, their uptake and translocation interact antagonistically. This suggests that applying chloride to the leaf canopy during the late grain‐filling stage of cereals might enhance nitrate use efficiency. Hence, it remains uncertain whether foliar‐applied chloride at the late growth stage stimulates nitrate translocation from mature to younger leaves. To explore this possibility, two contrasting faba bean varieties were grown in a climate‐controlled chamber. Nitrate concentrations of approximately 50 and 93 μg mg FW −1 , respectively, were established in leaves by depleting nitrogen in the rooting medium. Based on these two nitrate concentrations in mature leaves, chloride was applied to the leaf canopy. Measurements of biomass, photosynthesis, and nitrate and chloride concentrations in both young and mature leaves revealed that chloride foliar application raised nitrate levels in younger leaves from 7.1 to 9.5 μmol g FW −1 and boosted photosynthesis by approximately 35%. However, one of the two faba bean varieties did not respond significantly to the chloride foliar application. These findings indicate that chloride application facilitates nitrate translocation from mature to younger leaves, potentially improving grain nitrogen supply. As a result, nitrate use efficiency might be increased by chloride application during late growth stages, although this effect is genotype‐dependent.
A computer vision approach for quantifying leaf shape of maize (Zea mays L.) and simulating its impact on light interception
(2025) Otto, Dina; Munz, Sebastian; Memic, Emir; Hartung, Jens; Graeff-Hönninger, Simone; Otto, Dina; Institute of Crop Science, Agronomy Department, University of Hohenheim, Stuttgart, Germany; Munz, Sebastian; Institute of Crop Science, Agronomy Department, University of Hohenheim, Stuttgart, Germany; Memic, Emir; Institute of Crop Science, Agronomy Department, University of Hohenheim, Stuttgart, Germany; Hartung, Jens; Department Sustainable Agriculture and Energy Systems, University of Applied Science, Freising, Germany; Graeff-Hönninger, Simone; Institute of Crop Science, Agronomy Department, University of Hohenheim, Stuttgart, Germany
The precise determination of leaf shape is crucial for the quantification of morphological variations between individual leaf ranks and cultivars and simulating their impact on light interception in functional-structural plant models (FSPMs). Standard manual measurements on destructively collected leaves are time-intensive and prone to errors, particularly in maize ( Zea mays L.), which has large, undulating leaves that are difficult to flatten. To overcome these limitations, this study presents a new camera method developed as an image-based computer vision approach method for maize leaf shape analysis. A field experiment was conducted with seven commonly used silage maize cultivars at the experimental station Heidfeldhof, University of Hohenheim, Germany, in 2022. To determine the dimensions of fully developed leaves per rank and cultivar, three destructive measurements were conducted until flowering. The new camera method employs a GoPro Hero8 Black camera, integrated within an LI-3100C Area Meter, to capture high-resolution videos (1920 × 1080 pixels, 60 fps). A semi-automated software facilitates object detection, contour extraction, and leaf width determination, including calibration for accuracy. Validation was performed using pixel-counting and contrast analysis, comparing results against standard manual measurements to assess accuracy and reliability. Leaf width functions were fitted to quantify leaf shape parameters. Statistical analysis comparing cultivars and leaf ranks identified significant differences in leaf shape parameters (p < 0.01) for term alpha and term a . Simulations within a FSPM demonstrated that variations in leaf shape can alter light interception by up to 7%, emphasizing the need for precise parameterization in crop growth models. The new camera method provides a basis for future studies investigating rank-dependent leaf shape effects, which can offer an accurate representation of the canopy in FSPMs and improve agricultural decision-making.
Microbial inoculants modulate the rhizosphere microbiome, alleviate plant stress responses, and enhance maize growth at field scale
(2025) Francioli, Davide; Kampouris, Ioannis D.; Kuhl-Nagel, Theresa; Babin, Doreen; Sommermann, Loreen; Behr, Jan H.; Chowdhury, Soumitra Paul; Zrenner, Rita; Moradtalab, Narges; Schloter, Michael; Geistlinger, Joerg; Ludewig, Uwe; Neumann, Günter; Smalla, Kornelia; Grosch, Rita; Francioli, Davide; Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Kampouris, Ioannis D.; Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, Braunschweig, Germany; Kuhl-Nagel, Theresa; Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops (IGZ), Großbeeren, Germany; Babin, Doreen; Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, Braunschweig, Germany; Sommermann, Loreen; Department of Agriculture, Ecotrophology and Landscape Development, Anhalt University of Applied Sciences, Bernburg, Germany; Behr, Jan H.; Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops (IGZ), Großbeeren, Germany; Chowdhury, Soumitra Paul; Helmholtz Zentrum München—German Research Center for Environmental Health, Neuherberg, Germany; Zrenner, Rita; Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops (IGZ), Großbeeren, Germany; Moradtalab, Narges; Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Schloter, Michael; Helmholtz Zentrum München—German Research Center for Environmental Health, Neuherberg, Germany; Geistlinger, Joerg; Department of Agriculture, Ecotrophology and Landscape Development, Anhalt University of Applied Sciences, Bernburg, Germany; Ludewig, Uwe; Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Neumann, Günter; Department of Nutritional Crop Physiology, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Smalla, Kornelia; Institute for Epidemiology and Pathogen Diagnostics, Julius Kühn Institute (JKI)—Federal Research Centre for Cultivated Plants, Braunschweig, Germany; Grosch, Rita; Plant-Microbe Systems, Leibniz Institute of Vegetable and Ornamental Crops (IGZ), Großbeeren, Germany
Background: Field inoculation of crops with beneficial microbes is a promising sustainable strategy to enhance plant fitness and nutrient acquisition. However, effectiveness can vary due to environmental factors, microbial competition, and methodological challenges, while their precise modes of action remain uncertain. This underscores the need for further research to optimize inoculation strategies for consistent agricultural benefits. Results: Using a comprehensive, multidisciplinary approach, we investigate the effects of a consortium of beneficial microbes (BMc) ( Pseudomonas sp. RU47, Bacillus atrophaeus ABi03, Trichoderma harzianum OMG16) on maize ( Zea mays cv. Benedictio) through an inoculation experiment conducted within a long-term field trial across intensive and extensive farming practices. Additionally, an unexpected early drought stress emerged as a climatic variable, offering further insight into the effectiveness of the microbial consortium. Our findings demonstrate that BMc root inoculation primarily enhanced plant growth and fitness, particularly by increasing iron uptake, which is crucial for drought adaptation. Inoculated maize plants show improved shoot growth and fitness compared to non-inoculated plants, regardless of farming practices. Specifically, BMc modulate plant hormonal balance, enhance the detoxification of reactive oxygen species, and increase root exudation of iron-chelating metabolites. Amplicon sequencing reveals shifts in rhizosphere bacterial and fungal communities mediated by the consortium. Metagenomic shotgun sequencing indicates enrichment of genes related to antimicrobial lipopeptides and siderophores. Conclusions: Our findings highlight the multifaceted benefits of BMc inoculation on plant fitness, significantly influencing metabolism, stress responses, and the rhizosphere microbiome. These improvements are crucial for advancing sustainable agricultural practices by enhancing plant resilience and productivity.
Design evaluation and predictive accuracy of multi-environment trials in plant breeding
(2025) Gudata, Diriba Tadese; Piepho, Hans-Peter
In plant breeding, predictive accuracy of genotype means in the target population of environment (TPE) can be improved through proper experimental design and statistical analysis. During experimentation, blocking and randomization are expected to handle the major source of heterogeneity in the field. When heterogeneity exist in both directions, across row and column, two-way blocking is necessary to ensure homogeneity within blocks. Several trials need to be conducted in the TPE to generalize information. The TPE can be divided to form zonation that allows for borrowing information between zones when fitting genotypes as random and to allow for the zone-specific recommendation. The multi-environment trials (MET) data analysis can follow either one-stage or stage-wise analysis where in the latter case, information from individual trials is forwarded to the next stage of analysis. The linear mixed models (LMM) is commonly used in the MET data analysis. Furthermore, auxiliary information from the locations, particularly soil information and weather data can be integrated to MET data analysis to improve predictive accuracy. In general, the objective of this thesis was to improve predictive accuracy of modeling MET data based on different approaches of integrating ECs and pedigree information. Different spatial model selection and design evaluation was conducted in the second chapter using existing MET data from dry lowland sorghum breeding program of Ethiopia. Randomization based model, augmenting randomization-based model with linear variance and exponential spatial variations were compared in partially replicated and fully replicated row- column designs using Akaike information criterion (AIC). The baseline model with a two- dimensional nonlinear spatial model plus nugget improved the fitted model in many trials. In addition, the randomization-based plus two-dimensional linear variance model was also a good candidate model. According to the AIC, it is difficult to find a specific model that suits all the trials. Therefore, trying different spatial models and select the best fit model per trial could be a solution. Evaluation of the current design practice was also assessed in the same chapter through generating alternative designs by restructuring the blocking units and computing the relative efficiency. The relative efficiency results indicate most of the alternative alpha designs with block sizes of five, six, ten, fifteen, and the alternative row-column designs were more efficient when compared to the current practice. In the third chapter, a method of extracting and fitting synthetic environmental covariates (SCs) and pedigree information in multi-location trials data analysis was investigated. The main goal of this chapter was comparing predictive accuracy of LMM without pedigree information and SCs and with pedigree or/and SC to predict genotype performances in untested locations. The SCs were extracted from the actual ECs by using multivariate partial least squares (PLS) analysis. Then, subsequently we fitted in the LMM assuming the random coefficients of genotypes. An unstructured variance-covariance matrix of the random intercept and slope(s) was considered to ensure translational invariance. For the model with pedigree information, the baseline model with the independent genotype effect was modified to allow correlation between genotype through parents. For the GEI effect, the identity, the diagonal and the FA variance-covariance structures were considered. The mean squared error of prediction differences (MSEPD) and Spearman rank correlation shows that integrating the SCs in MET improve predictive accuracy of the model compared to the model without SCs. In all different variance-covariance structures of the GEI models, integrating SC was beneficial. There is also improvement with modelling pedigree information using diagonal and FA variance-covariance structures for genotype-environment effects. The diagonal variance-covariance structure of the GEI with the SC is the most accurate model in predicting genotype means to the new locations. In Chapter 4, the predictive accuracy under different approaches of fitting ECs in predicting genotypic performance in new environments was evaluated. The kinship matrix based on ECs, reduced rank regression and extended Finlay-Wilkinson approaches were evaluated and compared in predicting genotype means. Among the others, the reduced rank regression approach showed the smallest MSEPD. The limitation with this approach is that there are singularity problems when the number of ECs exceeds the number of environments. For this reason, a variable selection by using multivariate PLS was conducted to consider only the very important covariates in the subsequent modelling. Over all, there is a substantial gain in predictive accuracy in considering ECs compared to the model without ECs. In addition, we evaluated the importance of fitting the geographic zone factor, however, the result shows less improvement compared to the model without the zone factor. This result may be related to a smaller number of trials in some of the zones. One limitation with the data set when considering the zone effect is that only few trials remained in the western and northern zones after removing trials with zero genotype variances during individual trials analysis. The southern zone comprises the majority of the trials. The optimum allocation of trials to the zones was also tried based on the variance-covariances of the genotype -by-zone interactions. In chapter 3 and 4, when predicting genotype performance to new environments, the drop-out-one-environment at a time cross-validation (CV) mechanism was considered. This type of CV mimics the prediction for new environments and assesses uncertainty in model prediction. In conclusion, this study developed methods for improving the accuracy of genotypic performance prediction models in METs by improving the design efficiency in ongoing breeding programs through post-blocking mechanism, by fitting spatial models to capture spatial field trends in an experiment, and by using ECs, SCs and pedigree information.
On-farm use of recycled liquid ammonium sulphate in Southwest Germany using a participatory approach
(2023) Müller, Benedikt; Hartung, Jens; von Cossel, Moritz; Lewandowski, Iris; Müller, Torsten; Bauerle, Andrea; Müller, Benedikt; Biobased Resources in the Bioeconomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Hartung, Jens; Biostatistics, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; von Cossel, Moritz; Biobased Resources in the Bioeconomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Lewandowski, Iris; Biobased Resources in the Bioeconomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Müller, Torsten; Fertilization and Soil Matter Dynamics, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Bauerle, Andrea; Biobased Resources in the Bioeconomy, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany
For political and environmental reasons, there is an urgent need for alternatives to energy-intensive synthetic fertilizers. One solution is the targeted recycling of nutrients within agriculture. In this study, liquid ammonium sulphate (LAS) as a recycling product derived from digestate treatment was compared to calcium ammonium nitrate, manure and original digestates in an on-farm experiment using a participatory approach. Based on regular meetings with the farmers involved, a flexible experimental design was developed which integrated the fertilization legislation and the farmers’ operational structures already in place, such as crop rotation, available application techniques and manure management demands. The aim was to achieve both implementation practicability and acceptance of the study results by the farmers. Results from the year 2020 showed that LAS applied with three-jet nozzles in barley and wheat had significantly lower yields than the other fertilizers. Applied with a slurry tanker trailing shoe applicator in 2021, LAS had comparable yields to the other fertilizers in maize (51.2 t ha −1 ) and comparable yields to digestate in rapeseed (4.4 t ha −1 ). Application techniques that minimize environmental impacts and lower the LAS pH could potentially increase the effectiveness of the fertilizer. We recommend that farmers use this fertilizer not as a single solution but as a mineral compensatory fertilizer in addition to organic fertilizers following local fertilizer legislation. In this case, LAS could potentially substitute calcium ammonium nitrate (CAN).
Impact of construction measures and heat emissions from the operation of underground power cables on spelt (Triticum spelta L.) growth and yield
(2025) Trenz, Jonas; Ingwersen, Joachim; Schade, Alexander; Memic, Emir; Hartung, Jens; Graeff-Hönninger, Simone
Germany decided to promote the energy supply toward low or zero-carbon sources by the middle of the century. Therefore, massive infrastructural investments in grid expansion are needed. These grid expansions will be conducted with 525 kV High-Voltage Direct Current (HVDC) cables, buried at a depth of 1.5 m, passing mainly through arable land. The expected main effects of these cables on soils and crops are caused by construction measures (soil excavation and backfilling of soil material) and soil warming caused by heat dissipation using HVDC. To date, the impact of subsoil warming on crop growth and yield has not been studied in detail. This study investigates the effects of construction measures and subsoil warming on a field scale level for a 2-yr data set (2022 and 2023) in South Germany. The intricate dynamics between construction measures and subsoil heating on spelt (Triticum spelta L.) growth and yield were analyzed in three treatments: 1) Heated Trench (HT), 2) Unheated Trench (UT), and 3) Control. Construction measures were conducted by excavating the soil with a triple lift method (separated into three layers: A-, B-, and C-layer), storing them separately in ground heaps, and backfilling according to their natural layering. The triple lift method resulted in a 12.1 % decrease in bulk density (BD) for UT and 8.9 % for HT in the subsoil compared to the Control. The changes in soil properties affected spelt growth and yield, resulting in a yield increase of 14 % for the UT treatment. Additional subsoil warming in the HT treatment increased the topsoil temperature by 1.2 °C and spelt yield by 24 %. The triple lift method showed promising results, minimizing the impacts on soil compaction and maintaining the spelt growth and yield level.
Testing agronomic treatments to improve the establishment of novel miscanthus hybrids on marginal land
(2025) Lewin, Eva; Clifton-Brown, John; Jensen, Elaine; Lewandowski, Iris; Krzyżak, Jacek; Pogrzeba, Marta; Hartung, Jens; Wolfmüller, Cedric; Kiesel, Andreas; Lewin, Eva; Department Biobased Resources in the Bioeconomy, University of Hohenheim, 70599 Stuttgart, Germany; Clifton-Brown, John; Department of Agronomy and Plant Breeding, Justus Libeig University Giessen, 35392 Giessen, Germany; Jensen, Elaine; Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth SY23 3EE, UK; Lewandowski, Iris; Department Biobased Resources in the Bioeconomy, University of Hohenheim, 70599 Stuttgart, Germany; Krzyżak, Jacek; Institute for Ecology of Industrial Areas, 40-844 Katowice, Poland; Pogrzeba, Marta; Institute for Ecology of Industrial Areas, 40-844 Katowice, Poland; Hartung, Jens; Sustainable Agriculture and Energy Systems Department, University of Applied Science Weihenstephan-Triesdorf, 91746 Freising, Germany; Wolfmüller, Cedric; Department Biobased Resources in the Bioeconomy, University of Hohenheim, 70599 Stuttgart, Germany; Kiesel, Andreas; Department Biobased Resources in the Bioeconomy, University of Hohenheim, 70599 Stuttgart, Germany; Fujii, Yoshiharu
Miscanthus is considered a promising candidate for the cultivation of marginal land. This land poses unique challenges, and experiments have shown that the “establishment phase” is of paramount importance to the long-term yield performance of miscanthus. This experiment analyzes novel miscanthus hybrids and how their establishment on marginal land can be improved through agronomic interventions. Experiments took place at two sites in Germany: at Ihinger Hof, with a very shallow soil profile and high stone content, and at Reichwalde, where the soil was repurposed river sediment with low organic matter, high stone content, and a compacted lower horizon. These marginal conditions functioned as test cases for the improvement of miscanthus establishment agronomy. Four hybrids ( Miscanthus x giganteus , Gnt10, Gnt43, and Syn55) and agronomic treatments such as plastic mulch film, miscanthus mulch, inoculation with mycorrhizal fungi, and fertilization were tested in two years at both sites in 2021 and 2022. Specific weather conditions and the timing of planting were strong determinants of establishment success and no single treatment combination was found that consistently increased the establishment success. Plastic mulch films were found to hinder rather than help establishment in both these locations. Chipped miscanthus mulch caused nitrogen immobilization and stunted plant growth. At Ihinger Hof the novel seed-based miscanthus hybrid Gnt43 produced twice the biomass of other hybrids (7 t ha −1 ) in the first growing season. Gnt10 yielded well in 2021 and showed impressive tolerance to water stress in the summer of 2022. No treatment combination was found that consistently increased the establishment success of miscanthus hybrids across sites and years. Novel genotypes consistently outperformed the standard commercial miscanthus hybrid Miscanthus x giganteus . Gnt10 may be a promising candidate for the cultivation of water-stress-prone marginal lands, due to its isohydric behavior and high yield potential.
Prevalence, genetic diversity, and molecular detection of the apple hammerhead viroid in Germany
(2025) Zikeli, Kerstin; Berwarth, Constanze; Born, Ute; Leible, Thomas; Jelkmann, Wilhelm; Hagemann, Michael Helmut; Zikeli, Kerstin; Julius Kühn-Institute, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and Viticulture, Dossenheim, Germany; Berwarth, Constanze; Julius Kühn-Institute, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and Viticulture, Dossenheim, Germany; Born, Ute; Department of Production Systems of Horticultural Crops, University of Hohenheim, Stuttgart, Germany; Leible, Thomas; Julius Kühn-Institute, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and Viticulture, Dossenheim, Germany; Jelkmann, Wilhelm; Julius Kühn-Institute, Federal Research Centre for Cultivated Plants, Institute for Plant Protection in Fruit Crops and Viticulture, Dossenheim, Germany; Hagemann, Michael Helmut; Department of Production Systems of Horticultural Crops, University of Hohenheim, Stuttgart, Germany
Introduction: Apple hammerhead viroid (AHVd) is an emerging plant pathogen infecting apple orchards worldwide. Its genetic variability and geographical distribution remain poorly understood, limiting effective diagnostics and management strategies. Methods: In this study, 192 samples from German apple orchards were analyzed using reverse transcription (RT) and real-time PCR, one-step RT real-time PCR, and Sanger sequencing. Next-generation sequencing (NGS) was employed on pooled RNA extracts to explore genetic diversity. Phylogenetic relationships were inferred using maximum likelihood methods, and viroid-derived small RNAs (vd-sRNAs) were identified from small RNA sequencing data. Results and discussion: AHVd was detected in 78% of samples, with prevalence varying by region: southern (82%), eastern (90%), northern (72%), and western (70%) states of Germany. Phylogenetic analysis revealed distinct clusters linked to geographical origins, indicating isolated evolutionary pathways. NGS analysis uncovered 39% inter-sample variability and 169 polymorphic positions, while Sanger sequencing of RT real-time PCR products derived from the same samples showed only 3% variability, reflecting dominant quasispecies populations. Small RNA analysis mapped 128,388 reads to the AHVd genome, identifying hotspots within and outside the rod-like structure, suggesting structural and regulatory functions of vd-sRNAs. These findings underline AHVd’s genetic diversity. The complex relationship between AHVd genetic variability and symptom expression necessitates the development of highly sensitive diagnostic tools and adaptive management strategies to effectively monitor and control its spread in apple production.
NAC transcription factors ATAF1 and ANAC055 affect the heat stress response in Arabidopsis
(2022) Alshareef, Nouf Owdah; Otterbach, Sophie L.; Allu, Annapurna Devi; Woo, Yong H.; de Werk, Tobias; Kamranfar, Iman; Mueller-Roeber, Bernd; Tester, Mark; Balazadeh, Salma; Schmöckel, Sandra M.; Alshareef, Nouf Owdah; Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia; Otterbach, Sophie L.; Department Physiology of Yield Stability, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Allu, Annapurna Devi; Department of Biology, Indian Institute of Science Education and Research (IISER), Tirupati, India; Woo, Yong H.; Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia; de Werk, Tobias; Max Planck Institute of Molecular Plant Physiology, Potsdam-Golm, Germany; Kamranfar, Iman; Institute of Biochemistry and Biology, University of Potsdam, Potsdam‐Golm, Germany; Mueller-Roeber, Bernd; Center of Plant Systems Biology and Biotechnology (CPSBB), Plovdiv, Bulgaria; Tester, Mark; Division of Biological and Environmental Sciences and Engineering (BESE), King Abdullah University of Science and Technology (KAUST), Thuwal, Saudi Arabia; Balazadeh, Salma; Institute of Biology, Leiden University, Leiden, The Netherlands; Schmöckel, Sandra M.; Department Physiology of Yield Stability, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany
Pre-exposing (priming) plants to mild, non-lethal elevated temperature improves their tolerance to a later higher-temperature stress (triggering stimulus), which is of great ecological importance. ‘Thermomemory’ is maintaining this tolerance for an extended period of time. NAM/ATAF1/2/CUC2 (NAC) proteins are plant-specific transcription factors (TFs) that modulate responses to abiotic stresses, including heat stress (HS). Here, we investigated the potential role of NACs for thermomemory. We determined the expression of 104 Arabidopsis NAC genes after priming and triggering heat stimuli, and found ATAF1 expression is strongly induced right after priming and declines below control levels thereafter during thermorecovery. Knockout mutants of ATAF1 show better thermomemory than wild type, revealing a negative regulatory role. Differential expression analyses of RNA-seq data from ATAF1 overexpressor, ataf1 mutant and wild-type plants after heat priming revealed five genes that might be priming-associated direct targets of ATAF1: AT2G31260 (ATG9), AT2G41640 (GT61), AT3G44990 (XTH31), AT4G27720 and AT3G23540. Based on co-expression analyses applied to the aforementioned RNA-seq profiles, we identified ANAC055 to be transcriptionally co-regulated with ATAF1. Like ataf1, anac055 mutants show improved thermomemory, revealing a potential co-control of both NAC TFs over thermomemory. Our data reveals a core importance of two NAC transcription factors, ATAF1 and ANAC055, for thermomemory.
How many checks are needed per cycle in a plant breeding or variety testing programme?
(2025) Piepho, Hans‐Peter; Laidig, Friedrich; Piepho, Hans‐Peter; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany; Laidig, Friedrich; Biostatistics Unit, Institute of Crop Science, University of Hohenheim, Stuttgart, Germany
Check varieties are used in plant breeding and variety testing for a number of reasons. One important use of checks is to provide connectivity between years, which facilitates comparison among genotypes of interest that are tested in different years. When long‐term data are available, such comparisons allow an assessment of realized genetic gain (RGG). Here, we consider the question of how many check varieties are needed per cycle for a reliable assessment of RGG. We propose an approach that makes use of variance component estimates for relevant random effects in a linear mixed model and plugs them into an analysis of dummy datasets set up to represent the design options being considered. Our results show that it is useful to employ a larger number of checks and to keep the replacement rate low. Furthermore, there is intercycle information to be recovered, especially when there are few checks and replacement rates are high, so modelling the cycle main effect as random pays off.
Computing optimal allocation of trials to subregions in crop‐variety testing in case of correlated genotype effects
(2025) Prus, Maryna; Prus, Maryna; Biostatistics Unit (340c), Institute of Crop Science, University of Hohenheim, Stuttgart, Germany
The subject of this work is the allocation of trials to subregions in crop variety testing in the case of correlated genotype effects. A solution for computation of optimal allocations using the OptimalDesign package in R is proposed. The obtained optimal designs minimize linear criteria based on the mean squared error matrix of the best linear unbiased prediction of the genotype effects. The proposed computational approach allows for any kind of additional linear constraint on the designs. The results are illustrated by a real data example.
Developing marginal‐land‐based bioeconomy systems — A design and development approach for bio‐based value chains and webs
(2025) Schlecht, Valentin; Vargas‐Carpintero, Ricardo; von Cossel, Moritz; Lewandowski, Iris; Schlecht, Valentin; Biobased Resources in the Bioeconomy, University of Hohenheim, Stuttgart, Germany; Vargas‐Carpintero, Ricardo; Biobased Resources in the Bioeconomy, University of Hohenheim, Stuttgart, Germany; von Cossel, Moritz; Biobased Resources in the Bioeconomy, University of Hohenheim, Stuttgart, Germany; Lewandowski, Iris; Biobased Resources in the Bioeconomy, University of Hohenheim, Stuttgart, Germany
Industrial crops grown on marginal lands offer a potential source of low-iLUC feedstock for bio-based industries, supporting sustainable bioeconomic development. However, marginal-land-based bioeconomy systems face significant uncertainties at early stages, such as limited data, farmers' hesitancy to adopt novel crops, undeveloped markets and immature technologies. This study implements an integrated multi-criteria framework as a structured, multi-step approach to connect bio-based value chain components and stakeholders in marginal-land-based bioeconomy systems at the research level. The framework was applied within the EU Horizon project MIDAS to identify, evaluate and combine bio-based value chain components, with a case study in the Swabian Alb (southern Germany) demonstrating its potential for designing scalable bio-based value chains tailored to regional conditions. Key findings emphasise the importance of stakeholder collaboration, iterative design processes and context-specific criteria that address technical, economic, social and regulatory aspects. The approach, based on qualitative data and stakeholder input, offers critical insights into the feasibility of biomass-to-product pathways and serves as a foundation for advanced research. Future research needs to focus on expanding data availability, incorporating quantitative methods, and addressing economic and market factors, such as stakeholder willingness to produce feedstocks, to enhance the scalability and robustness of the findings and facilitate the establishment of sustainable bioeconomy systems on marginal lands.
Adapting wheat production to global warming in West Asia: facultative wheat outperforms winter and spring wheat at conventional nitrogen levels
(2025) Yousefi, Afsaneh; Koocheki, Alireza; Mahallati, Mehdi Nassiri; Khorramdel, Soroor; Trenz, Jonas; Malakshahi Kurdestani, Ali; Ludewig, Uwe; Maywald, Niels Julian; Yousefi, Afsaneh; Department of Nutritional Crop Physiology, University of Hohenheim, Stuttgart, Germany; Koocheki, Alireza; Department of Agrotechnology, Ferdowsi University of Mashhad, Mashhad, Iran; Mahallati, Mehdi Nassiri; Department of Agrotechnology, Ferdowsi University of Mashhad, Mashhad, Iran; Khorramdel, Soroor; Department of Agrotechnology, Ferdowsi University of Mashhad, Mashhad, Iran; Trenz, Jonas; Department of Agronomy, University of Hohenheim, Stuttgart, Germany; Malakshahi Kurdestani, Ali; Department of Fertilization and Soil Matter Dynamics, University of Hohenheim, Stuttgart, Germany; Ludewig, Uwe; Department of Nutritional Crop Physiology, University of Hohenheim, Stuttgart, Germany; Maywald, Niels Julian; Department of Nutritional Crop Physiology, University of Hohenheim, Stuttgart, Germany
Global warming and weather anomalies pose significant threats to cereal production in West Asia. Winter wheat, which requires vernalization to trigger reproductive growth, is particularly vulnerable to heat, while spring wheat faces limitations due to short and hot vegetation periods. Facultative wheat, which does not require vernalization and can be planted in either fall or spring, offers potential flexibility and resilience to fluctuating temperatures. This study aimed to evaluate the development and grain yield of facultative, spring, and winter wheat varieties under different nitrogen fertilization rates in current climate conditions. Facultative wheat, grown as either facultative winter (FWW) or facultative spring (FSW), along with winter (WW) and spring wheat (SW) varieties, was cultivated over two consecutive seasons (2020–2022) at Ferdowsi University of Mashhad, Iran. Developmental stages were monitored, and grain yield, protein, and nutrient concentrations were measured at four nitrogen levels (0, 100, 200, and 300 kg N ha −1 ) in both shoots and grains. Crop modeling under the RCP 8.5 climate scenario supported the experiments and projections. Facultative wheat sown in autumn exhibited a shorter tillering stage and a longer early reproductive stage compared to winter wheat. While nitrogen fertilization delayed development, it significantly increased yield. Facultative wheat achieved higher grain yields at conventional nitrogen levels (100–200 kg N ha −1 ). Additionally, increasing nitrogen fertilization improved grain protein and nutrient concentrations (N, P, and K). Crop modeling indicated that facultative varieties sown in winter could offer greater yield stability and might benefit from a more consistent phenological development. Overall, facultative wheat performed better at conventional nitrogen levels, highlighting its potential in a changing climate in West Asia. Optimizing sowing dates and nitrogen fertilization could help mitigate some of the negative effects of rising temperatures, enhancing wheat resilience and productivity.
Improving cover crop mixtures to increase soil carbon inputs and weed suppression as a tool to promote yield potential
(2024) Groß, Jonas; Müller, Torsten
Arable cropping systems are facing challenges imposed by climate change and are, at the same time, a tool to mitigate climate change. Soils are essential in securing yield potential and acting as a carbon sink. Recognizing small-scale site-specific differences in crop management and integrating cover crops, which provide ecosystem services such as carbon sequestration and weed suppression, are two approaches to climate-smart agriculture. To investigate site-specific soil heterogeneity, soil properties were analyzed in a field trial, measuring at three soil depths in 42 plots to determine their influence on yield measures. Soil organic carbon, silt, and clay contents in both topsoil and subsoil explained 45-46% of the variability in grain yield. Additionally, a positive correlation was found between increasing clay content in the topsoil and grain yield and tiller density. A higher clay content in the subsoil resulted in a decrease in grain yield. Soil organic carbon was identified as a soil property that positively influences yield and yield formation at any soil depth through multiple regressions and cluster analysis. Soil organic carbon is a critical soil measure that can significantly improve yield potential and can be manipulated by crop management practices like cover cropping. In a second field experiment, the impacts of increasing plant diversity of cover crop mixtures on rhizosphere carbon input and microbial utilization were investigated. A comparison was made between Mustard (Sinapis alba L.) planted as a sole crop and diversified cover crop mixtures of four (Mix4) or twelve (Mix12) species. A 13C-pulse labeling field experiment traced C transfer from shoots to roots to the soil microbial community. Mix 4 doubled the net CO2-C removal from the atmosphere, while Mix 12 more than tripled it, indicating that plant diversity positively impacts carbon cycling. This is reflected in higher atmospheric C uptake, higher transport rates to the rhizosphere, higher microbial incorporation, and longer residence time in the soil environment, improving the efficiency of C cycling in cropping systems. Root C-transfer could be identified as a fast pathway for C to reach soil C-compartments, but a substantial share of atmospheric C-catch comes from shoot biomass. In a third field experiment, the influence of species combination on shoot biomass formation was systematically assessed by investigating species interactions in dual cover crop mixtures and their competitiveness to suppress weeds before winter under different growing conditions. The shoot biomass share of a cover crop species in a dual-species mixture was found to be directly linked to its shoot biomass in a pure stand. Mustard and phacelia had similar effects on the shoot biomass production of the second species added to the mixture. Cruciferous species were more competitive against weeds than other cover crop species and could suppress weeds even when mixed with a less competitive partner. Weed suppression in mixtures with phacelia depended on the second component. Our results indicate that dual mixtures containing one competitive species reduce weed shoot biomass before winter, comparable to competitive pure stands. The research in this thesis shows that C content in the soil plays a crucial role in yield formation in arable cropping systems in Germany. Finally, the study has demonstrated that implementing cover crop mixtures can enhance soil C input and represent a valuable method for preserving yield potential. It was also shown that an intelligent combination of cover crop species can determine successful development and weed suppression.
Phosphorus- and water- deficiency induced morpho-physiological and yield changes in maize (Zea mays L.)
(2024) Ning, Fangfang; Graeff-Hönninger, Simone
Phosphorus (P) is a nonrenewable and finite resource for all living things. It plays a crucial role as an essential nutrient in crop production. However, plants have low efficiency in utilizing P due to its immobility and low bioavailability. P deficiency can cause irreversible effects, particularly during the early stages of maize growth. Drought further exacerbates nutrient uptake challenges, especially for P, by limiting its diffusion in the soil. Therefore, the dual stress of drought and P deficiency restricts plants' shoot and root growth. It is necessary to investigate the interaction between P deficiency and drought and better understand the response mechanisms, as the effect of P deficiency on plant growth precedes the plant's own drought regulatory mechanisms. In Paper I, the effects of placed diammonium phosphate (DAP) and rock phosphate (RP) on the growth and development of two maize cultivars (Stabil and Ricardinio) were investigated combined with soil liming. Maize cultivars differed in their P utilization characteristics under low-P field conditions. The results showed that RP resulted in a lower leaf area index and light interception than DAP. This led to a 33% lower silage yield and a 29% lower P content at harvest. The PUE of RP was found to be 18%, which is 37% lower than that of DAP. Furthermore, soil liming reduced shoot biomass and caused a 35% decrease in shoot P content at the six-leaf stage. Maize cultivar ‘Stabil’ showed higher yield and P uptake. This paper demonstrated that placed RP could not be used as a substitute for DAP in silage maize production regardless of the application of lime to the soil. Paper II explored the impact of different types of P fertilizer (DAP and RP) on the root systems of maize. The results showed that P deficiency in the early stages of growth hindered root growth. However, in later stages, the roots exhibited enhanced lateral root growth in response to P deficiency. Although the differences in organic acids and phytohormones across different zones of the maize root system were not significant due to the delayed sampling, it is still feasible and necessary to conduct further investigations on organic acids and phytohormones in various root locations. Paper III tested deep P fertilizer placement as a strategy to alleviate combined drought and P deficiency stress in maize. It was tested under greenhouse conditions involving three factors: P fertilizer amount (low-P: LP, and high-P: HP), fertilizer placement (mixed (M, 0-18 cm), lower (L, 10-18 cm), and upper (U, 0-9 cm)), and soil water content (DS, 45% of soil water holding capacity (WHC)) and well-watered: WW, 75% WHC) and well-watered: WW). LP decreased shoot P content and both root and shoot biomass compared to HP. Under DS, root biomass increased by 50% and 95% in 0-18 and 10-18 cm depth at the fourth-leaf stage compared to WW treatment. However, root biomass decreased by at least 41% in different depths at the tenth leaf stage. Plants under DS consistently exhibited lower shoot biomass and P uptake at both stages. Although L-DS did not improve shoot growth and P uptake until the tenth-leaf stage, more than 55% higher root biomass and increased root length could be found in 10-18 cm depth compared to M-DS and U-DS treatments. This could potentially enhance P exploration in a larger soil volume and enable water absorption from deeper soil layers. However, no advantage in P uptake was observed with LP and HP until the ten-leaf stage. In conclusion, this thesis highlights the importance of optimizing P utilization strategies in maize production systems facing the dual challenges of P deficiency and drought stress. While soil liming and cultivar selection can help, high-solubility P fertilizers like DAP remain irreplaceable by RP due to their superior ability to support root development. It also discussed the possibilities and mechanisms for mitigating P and water- deficiency by promoting root growth in deeper soil layers through applying P fertilizers. This study provides a comprehensive evaluation of the feasibility of various maize cultivation and management practices under combined P deficiency and drought conditions, offering valuable references and practical guidelines for sustainable maize production in resource-limited environments.

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