Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute) University of Hohenheim Crop Water Stress Management (490g) Prof. Folkard Asch Effects of temperature and vapor pressure deficit on genotypic responses to nitrogen nutrition and weed competition in lowland rice Dissertation submitted in fulfillment of the requirement for the degree “Doktor der Agrawissenchaften” (Dr. in Agricultural Sciences) to the Faculty of Agricultural Sciences presented by Duy Hoang Vu born in Vietnam Stuttgart, 2021 Printed and published with the support of the German Academic Exchange Service (DAAD). This thesis was accepted as a doctoral thesis (Dissertation) in fulfillment of the regulations to acquire the doctoral degree “Doktor der Agrarwissenschaften” by the Faculty of Agricultural Sciences at University of Hohenheim on 22 July 2021.
Date of the oral examination: 22 July 2021. Examination Committee Chairperson of the oral examination Prof. Uwe Ludewig Institute of Crop Science Supervisor and Reviewer Prof. Fokard Asch Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute) Co-Reviewer Prof.
Mathias Becker The Institute of Crop Science and Resource Conservation (University of Bonn) Additional examiner Jun. Sandra Schmöckel Institute of Crop Science “Ở đây một hạt cơm rơi Ngoài kia bao hạt mồ hôi thấm đồng” (Don't waste a grain of rice from your bowl, as each comes from the hard labor of a farmer) ------------------Vietnamese folk verses----------------- Acknowledgements To complete this dissertation, I received a great deal of support and assistance. First of all, I would like to express my sincere gratitude to my supervisor, Prof. Folkard Asch, who gave me the opportunity to build and develop my skills in scientific work.
He always gave me valuable advice in formulating research questions and methodology, which was especially helpful for the times when plans met the reality of practice. His insightful feedback pushed me to sharpen my thinking and take my work to a higher level. My deepest gratitude goes to Dr. Sabine Stürz for her patient supervision, and in particular her invaluable and constructive suggestions.
I greatly appreciated her generosity concerning her time. She also gave me the freedom to develop and implement my own research ideas. Whenever I faced difficulties, she was always behind me with enthusiastic encouragement and gave me the best advice with her excellent experience and in-depth expertise. Without her persistent help, this study would not have been possible.
My thanks to Julia Asch for her constant assistance. With her excellent knowledge and skills in the laboratory, she helped me to develop analytical methods, and above all, supported me throughout my experiments. I would like give special thanks to Dr. Jens Hartung for his invaluable advice on methods of statistical analysis.
With his help, I was able to build statistical models and methods suited to the experimental design. I would like to thank Dr. Alejandro Pieter for sharing his expertise, and helping me in the laboratory. My thanks to Marc Schmierer for his invaluable advice and help in the greenhouse.
Thanks to Kristian Johnson and Shimul Mondal for their help, encouragement, company, and very helpful technical discussions. My thanks to my colleagues, HiWis at the Department of Crop Water Stress Management, especially Oliver, Marc Neuberger, Benedikt, Tabea, Pia, Kevin, Benjamin, Tanja, Bayuh, Sarah, Van, Thuong, Reza, Marc Cotter, and Marc Giese for their encouragement, help, and hard work during my experiments. A very special thanks to Gabriele Kircher and Gabriele Schmid for their excellent organization, cheerfulness, and enthusiasm. I would also like express my gratitude to professors, staff, and colleagues at the Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg-Institute), who assisted me in my research and gave me help (usually) at the right time.
i I would like to express my sincere gratitude to the DAAD (German Academic Exchange Service) for supporting me and my research with a PhD scholarship as part of the study program “Agricultural Economics, Bioeconomy and Rural Development”. I would also like to acknowledge the support of the program manager, Prof. Regina Birner, and coordinators of the program at the University of Hohenheim, who made everything possible for me during my study in Germany. I would like to thank the Faculty of Agricultural Sciences and the Graduate Academy (University of Hohenheim) for enabling me to complete my PhD program.
I would like to thank my professors and my colleagues at the Faculty of Agronomy (Vietnam National University of Agriculture), especially at the Department of Cultivation Science, who gave me the push to come to Germany and always encouraged me to complete this study. My special thanks go to my friends for the support and laughter, and also for the many unforgettable memories of my life in Germany. Last but not least, I would like to thank the great support and love of my family: my parents, my wife, my children, my brothers, and my sisters. I am extremely grateful to my parents for their love, prayers, and sacrifices which made my education possible and prepared me for a bright future.
This dissertation is especially dedicated to my wife, who has always been with me in the most challenging times, and always knew how to motivate me from afar. I give all of my love to my dear son and daughter, who give me countless moments of happiness and are my greatest inspiration to overcome all difficulties I face. I would like to acknowledge all your invaluable help and will cherish all moments during my PhD study! Stuttgart, July 22, 2021 Duy Hoang Vu ii Table of Contents SUMMARY. 1 Chapter 1 General Introduction .1 Global rice production and demand .2 Global warming challenging rice production .3 Water-saving irrigation technologies and new concerns in rice production.1 Alternate wetting and drying .2 Root zone temperature in alternate wetting and drying system .3 Nitrogen dynamics in the soil under alternate wetting and drying .4 Weed dynamics in water-saving rice systems .4 Vapor pressure deficit.
18 Chapter 2 Nutrient Uptake and Assimilation Under Varying Day and Night Root Zone Temperatures in Lowland Rice.2 Growth condition and treatments .3 Plant biomass and water and nutrient uptake .4 Nitrogen metabolism and enzyme assays .1 Day and night water and nutrient uptake at different root zone temperatures under low and high VPD .2 The correlation between root zone temperature and water and nutrient uptake under low and high VPD .3 Nitrogen assimilation in rice leaves at different root zone temperature under low and high VPD .1 Day and night nutrient and water uptake under different VPD .2 Nutrient uptake of two rice varieties as affected by root zone temperature.3 Effects of root zone temperature and VPD on N metabolism. 50 Chapter 3 Leaf Gas-Exchange of Lowland Rice in Response to Nitrogen Source and Vapor Pressure Deficit .2 Materials and methods .2 Treatments and growth conditions .3 Gas exchange measurement .1 NO3- induced higher gs and A relative to NH4+ at high VPD but not at low VPD69 3.2 Varietal variation of leaf gas exchange in response to nitrogen source at high VPD .3 Growth response of different rice varieties to nitrogen source at low and high VPD. 81 Chapter 4 Rice-Weed Competition in Response to Nitrogen Form and Vapor Pressure Deficit .2 Materials and methods .3 Nutrient uptake measurement .4 Determination of enzyme activities .5 Dry matter accumulation and competitive index .6 Total nitrogen uptake .1 Effect of nitrogen source and plant-competition on biomass accumulation of rice and weeds .2 Effect of nitrogen source on weed competitive index of two rice varieties .3 Effect of nitrogen source and plant-competition on nitrogen uptake of rice and weeds .4 Effect of nitrogen source and plant-competition on nitrogen assimilation of rice and weeds .1 Effects of nitrogen source on uptake and assimilation of nitrogen in rice and weeds .2 Effects of nitrogen source on biomass accumulation of rice and weeds.3 Effects of nitrogen source on competition between rice and weeds. 108 Chapter 5 General Discussion .1 Increasing root zone temperature in water-saving irrigation systems enhances nutrient uptake of rice plants .2 Enhanced nitrification may improve leaf gas exchange and growth of rice plants .3 Promotion of nitrification alters competition between rice and weed .4 Outlook for improving rice growth under alternate wetting and drying.
128 v List of tables Table 2.1: Analysis of variance (ANOVA) of nutrient and water uptake rates under low and high VPD at day- or night-time on 2 varieties exposed to 3 root zone temperature levels (19, 24, 29°C).2: Slope and level of significance of the linear regression between root zone temperature levels (19, 24, 29°C) and nutrient and water uptake rates (µmol g-1 FW h-1) for two varieties (IR64 and NU838) at day- and night-time under low and high VPD.3: Pearson correlation coefficients between nitrogen (NO3- and NH4+) uptake rates and amino acid concentration in the leaves for two varieties (IR64 and NU838) at day- and night-time under low and high VPD.1: Genetic background and growth characteristics of 12 rice varieties used in the study .2: Growth conditions and gas exchange measurement conditions .4: Intrinsic water-use efficiencies (WUEi) of four rice varieties at low and high VPD and the difference in WUEi between the two VPDs (%) in experiment 2 and 3.2: Nitrate reductase (NR) and glutamine synthetase (GS) activities in roots and leaves of two rice varieties (KD18 and NU838) and two weed species (E. crus-galli and S. nigrum) supplied with different N sources under low and high VPD. 98 vi List of Figures Figure 1.1: Global rice production.2: A ponded water layer under continuous flooding and aerobic soil during drained periods under alternate wetting and drying.1: Temperature scheme for day and night temperature treatments.2: NH4+ and NO3- uptake at 19, 24, and 29°C during day- and night-time of two rice varieties (IR64 and NU838) under low and high VPD.3: PO43- and K+ uptake at 19, 24, and 29°C during day- and night-time of two rice varieties (IR64 and NU838) under low and high VPD .4: Water uptake at 19, 24, and 29°C during day- and night-time of two rice varieties (IR64 and NU838) under low and high VPD .5: Activities of nitrate reductase (NR) and glutamine synthetase (GS), and amino acid (AA) concentration at day- and night-time in the leaves of rice plants at different RZT treatments under low and high VPD.2: Total dry matter of 12 rice varieties in response to nitrogen source (NH4+ or NO3-) at high VPD (“standard” greenhouse conditions; experiment 1).4: Total DM of four rice varieties fed with different N sources (NH4+ or NO3-) at low and high VPD (A, B) (Experiment 3).5: Root/shoot ratio (A, B) and specific leaf area (C, D) of four rice varieties fed with different N sources (NH4+ or NO3-) at low and high VPD (Experiment 3).6: Starch content in leaves of four rice varieties fed with different N sources (NH4+ or NO3-) at low and high VPD (A, B) (Experiment 3).7: : Linear regression between assimilation rate (A) and stomatal conductance (gs) of 12 rice varieties at high VPD (“standard greenhouse”; experiment 1).8: Linear regression between stomatal conductance (gs) and root/shoot ratio of 4 rice varieties at high VPD (experiment 3).9: Chlorophyll concentration of four rice varieties fed with different nitrogen sources (NH4+ or NO3-) at low and high VPD (Experiment 3).10: Transpiration rate of four rice varieties fed with different N sources (NH4+ or NO3-) at low and high VPD (Experiment 3).11: Dead leaf fraction of four rice varieties fed with different nitrogen sources (NH4+ or NO3-) at low and high VPD (Experiment 3).1: Total dry matter of two rice varieties (NU838 and KD18) and two weed species (E.
crus-galli and S. nigrum) as affected by neighbor plant and N source at low and high VPD.2: Competitive index of two rice varieties (NU838 and KD18) in competition with two weed species (E. crus-galli and S. nigrum) grown with different N sources at low and high VPD.3: Ammonium and nitrate uptake rates of two rice varieties (NU838 and KD18) and two weed species (E.
crus-galli and S.