Projects

Background: Low supply of essential trace metals such as zinc (Zn) and copper (Cu) can impair crop yields and quality. Other trace metals like cadmium (Cd) are non-essential for plants and potentially detrimental for human health. To cope with trace metals, plants can synthesize small and large organic molecules with chemically reduced sulfur groups called thiols that can bind to metals detoxifying Cd. Thiols bind more tightly to soft metals such as Cd compared to the less soft metal Zn. Hence, thiols not only detoxify Cd, but they also act as a filter to separate non-essential from essential metals in plants. Thiols may also have such ‘filter effect’ in arable soils as they are also present in oxic soils. These soils are relevant to grow staple crops like wheat and maize but also crops for oil production such as rapeseed. Although thiols are a minor fraction of all sulfur (S) forms in the soil, a few studies showed that they bind a significant fraction of trace metals, particularly Cd. However, the effectiveness of thiols in agricultural soils to act as a filter for trace metals is largely unexplored.

Objectives and approach: The overarching goal of the project is to contribute to the development of agricultural strategies that increase crop quality by optimizing their trace metal composition. To achieve this goal, a soil survey of Swiss agricultural soils will be conducted to quantify total and plant available pools of S and trace metals and to do S speciation. Furthermore, a soil incubation and a plant growth experiment will be conducted to investigate the effect of S fertilizer on the phytoavailability of the trace metals and their soil-to-crop transfer. We will use ICP-MS/MS to quantify metals and S and synchrotron X-ray techniques for their speciation. The phytoavailability of trace metals will be determined using isotope dilution techniques, analyzing plant metal uptake, and quantifying the dynamic fraction of trace metals in the soil solution.

Background: According to FAO (Food and Agriculture Organization; United Nations), a quarter of the global surface of agricultural land is already degraded, therefore maintaining long-term soil health gains importance. Nevertheless, there are currently no easy, fast, and reliable ways to assess the effects of soil management on soil health and in particular on soil biology.

Objectives: Our goal at the Digit Soil project, is to develop an easy-to-use, portable sensor, measuring the activity of soil enzymes as a soil health indicator. We innovate by miniaturizing existing technology resulting in the replacement of big, expensive laboratory equipment with a light, hand-sized device. By enabling users to measure enzyme activity in-situ, in natural conditions, without sampling and transportation bias we enable more reliable and faster measurements. Such a portable device is addressing several markets including the academic market, agro-business, and government agencies as well as the rapidly growing agricultural sensors market.
 

Part of the International Training Network: FertiCycle, New bio-based fertilizers from organic waste upcycling.

Background: European agriculture is strongly dependent on the import of fertilizers: more than 90% of the phosphorus and synthetic nitrogen are supplied from overseas. This poses environmental and economic consequences. Local farmers and the industrial sector are in the need of alternatives that allow a local supply of crop nutrients. This is possible via the recovery of phosphorus and other vital nutrients that are present in waste products, such as sewage sludge, animal manures, and other biogenic waste products. However, for a cost-effective recovery, new research is needed. FertiCycle aims to fill the gaps in knowledge and contribute to a more sustainable fertilizer supply.

Objective and approach: The overall research objective of FertiCycle is to contribute to the development of new processes for production fertilizers, based on the recovery of nutrients from bio-based materials and recycling wasted resources. Another component is to estimate the market potential and sustainability challenges of their production and use.

The Group of Plant Nutrition at ETH Zurich will focus on the study of the fate and crop uptake of nutrients, especially phosphorus, from waste and bio-based fertilizers. The fate of P in the soil and soil-plant system will be studied with a variety of analytical techniques, including novel isotopic tracing methods.

Early stage researcher: Mario Álvarez Salas (ETH Zurich)
Supervision: Astrid Oberson (ETH Zurich), Federica Tamburini (ETH Zurich)
Collaborations: Jakob Magid, Dorette Müller-Stöver (University of Copenhagen)

 

Background: Yam (Dioscorea sp) is an important tuber crop for the livelihood of many people in West Africa. However, traditional yam cropping systems have low productivity and negative impacts on the environment. Current practices of applying manure and mineral fertilisers have resulted in higher tuber yields, but simultaneously, have led to a decrease of soil organic matter and soil degradation. The application of biochar is a potential strategy to prevent the degradation of soil fertility in highly weathered tropical soils.

Objectives: The aim of this project is to assess the use of biochar produced from different agricultural wastes as a soil amendment for sustainable yam production. The specific objectives are: i) to characterise and quantify available agricultural residues for biochar production at farm and local agro-industry level; ii) to analyse the impact of biochar produced from locally available agricultural residues on crop production and soil properties at field scale; and iii) to assess the early adoption and acceptance of biochar production by yam farmers. The research is conducted at two sites in Côte d’Ivoire where yam is grown as a cash and/or staple crop.

Background: Zn is an essential micronutrient for both human nutrition and plant systems. Wheat grown in Zn-limiting conditions can exhibit Zn deficiency, which can limit biomass yields. This can also decrease the nutritional value of the resulting food products, and ultimately lead to malnutrition in communities in which cereal grains are a significant component of the diet.
We are interested in studying two important strategies that can be used to increase the Zn content in wheat grains. The first is the application of organic fertilizers, which have the potential to increase the pool of available Zn in soils. The fertilizer may facilitate the release of Zn from the soil solid phase into the soil solution and may also directly add available Zn to the soil. The effect of the organic fertilizer on Zn availability for plant uptake will depend on the chemical properties of the treatment – for example, certain organic fertilizers contain high levels of available Zn, while others contain very little.
The second strategy is genetic biofortification, which is a powerful tool that can be used to allow healthy plant growth in soils with low Zn availability. This may either be achieved through plant breeding or through genetic modification. Biofortified plants grown in soils with low Zn availability have been shown to have higher biomass yields and a higher Zn density in edible plant parts than their non-biofortified counterparts, due to their increased ability to uptake nutrients from the soil as well as the increased efficiency of their use of these nutrients.
However, in performing these strategies, their effects on Cd availability and uptake by wheat crops must be considered. Cd is a toxic trace element, and a major source of Cd intake by humans is consumption of food produced from cereal crops, such as wheat. Because Cd has similar reactivity and biological uptake pathways as Zn, strategies that increase plant uptake of Zn can also correspond to increased plant uptake of Cd. Still, differences in the complexation chemistry between Zn and Cd could also influence the (im)mobilization of Cd in soils and/or non-edible plant components, and may allow for increased Zn uptake without increasing Cd concentrations in the edible portions of the plant.
Thus, the purpose of this study is firstly to examine the processes that lead to the release of bioavailable Zn and Cd in soils with Zn-limiting conditions that have been treated with organic fertilizers. We are interested in studying the effect of different types of organic fertilizers, with wide ranging chemical compositions, on the mechanisms that govern Zn and Cd (im)mobilization. In addition, we hope to gain information on how the speciation of the released Zn and Cd affects the uptake and transport of Zn and Cd within the wheat plant, and to examine how the genetic modification of a wheat cultivar to increase its resistance to Zn deficiency will impact its uptake and internal distribution of Cd.

Full Project title: Biophysical and socio-economic drivers of sustainable soil use in yam cropping systems for improved food security in West Africa (YAMSYS)

Background: Yams are tuber crops essential for food security in West Africa. They are an important source of income for the actors involved in the yam chain value (producers, traders, processors) as their tubers are highly appreciated by urban populations. They are also a very important part of West African culture and are present in many rites and ceremonies. Traditionally yams are grown without input as the first crop after a long-term fallow or natural vegetation with strong negative impacts on the environment. However, the traditional cropping systems have very low tuber productivity. Given the high prevalence of food insecurity, poverty and environmental degradation in West Africa, measures to improve the sustainability of yam cropping systems should be developed and implemented as soon as possible

Objectives and approach: YAMSYS aims at developing sustainable methods for soil management that will allow settling yams in long-term crop rotations, increase tuber yields and increase income of the actors working along the yams chain values. To reach these goals we will carry out research both on biophysical aspects to assess the effects of soil management options on soil fertility and yams yield and on the socio-economic and institutional settings to understand the drivers of soil use and the role of these crops. Innovation platforms gathering the most important stakeholders of the project will be installed at each of the 4 pilot sites (2 in Côte d’Ivoire and 2 in Burkina Faso). Based on continuous discussions and on results delivered by the research, these platforms will elaborate and validate innovations that will have a sustainable impact in the region.

Collaboration with: Emmanuel Frossard (ETH Zurich), Beatrice Aighewi (International Institute of Tropical Agriculture, Nigeria), Séverin Aké (Université Felix Houphouët Boigny, Côte d’Ivoire), Dominique Barjolle (FiBL, Switzerland), Hassan Bismarck Nacro (Université polytechnique de Bobo-Dioulasso, Burkina Faso), Daouda Dao (CSRS, Côte d’Ivoire), Lucien N. Diby (World Agroforestry Centre, ICRAF), François Lompo (INERA, Burkina Faso), Johan Six (ETH Zurich)

Funding source: YAMSYS is funded by the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation

external page http://www.r4d.ch/E/food-security/projects/sustainable-yam-cropping/Pages/default.aspx

external page www.yamsys.org

Project title: More than nitrate: the importance of phosphate and cations availability from solid biowastes to complement nitrified urine for plant growth (POMP3).
Background: The background in quotation marks will be the same for the three following projects: POMP3, POMP2, PaCMan2. “The European Space Agency’s project Micro Ecological Life Support System Alternative (acronym MELiSSA) is a research program aiming to develop a bioregenerative life support system that converts waste (CO2, urine, solid wastes) to food, water and oxygen for the astronauts for long-term space missions (www.melissafoundation.org). At the same time, this program is an excellent model for addressing terrestrial challenges such as urban agriculture using nutrients from wastes, and overall, to close nutrient cycles between food production and consumers”. Nitrate from human urine has already been studied and used as organic fertilizer in agriculture, but plants need other nutrients beside Nitrogen for a correct growth and development. Other essential nutrients for plants can be found in other solid biowastes, that could be used for space missions, such as urine precipitates or non-edible plant parts.
Objectives: The overall goal of our research contribution to the MELiSSA project is to show that nitrified urine needs to be complemented with available phosphate and cations from other biowastes, so that higher plants can be grown in closed systems (C4B: higher plants compartment) and deliver the services we expect from them. For this, we will assess the availability of P present in minerals that precipitate during urine storage and treatment, the release of cations (K, Ca, and Mg) and other nutrients from non-edible plant residues remaining after harvest, and we will quantify their impact on plant growth in hydroponic soilless systems.
 

Full project title PlAnt Characterization unit for closed life support system – engineering, MANufacturing & testing phase 2 (acronym PACMAN 2).

Background “The European Space Agency’s project Micro Ecological Life Support System Alternative (acronym MELiSSA) is a research program aiming to develop a bioregenerative life support system that converts waste (CO_*, urine, solid wastes) to food, water and oxygen for the astronauts for long-term space missions (external page www.melissafoundation.org). At the same time, this program is an excellent model for addressing terrestrial challenges such as urban agriculture using nutrients from wastes, and overall, to close nutrient cycles between food production and consumers”. As part of MELiSSA, the European Space Agency has installed at the University of Naples Federico II (Italy) a plant growth facility (the Plant Characterisation Unit, PCU) allowing to grow plants hydroponically in a completely air- and watertight system as a model for future space missions.

Objectives The project PACMAN2 aims at developing a “root observatory” for crops growing in the PCU with a root subsampling tool and a system for imaging acquisition. This observatory will be used to describe root growth and activity, including nutrient uptake, and to link root growth to shoot production and final crop yield. The “root observatory” will be then tested with experiments growing lettuce.

Collaborations: Christa Hirschvogel (POMP2, Group of Plant Nutrition, ETH Zürich) Iciar Gimenez de Azcarate Bordons (POMP3, Group of Plant Nutrition, ETH Zürich), Emmanuel Frossard (Group of Plant Nutrition ETH Zürich), Astrid Oberson (Group of Plant Nutrition, ETH Zürich), Stefania De Pascale (UniNA), Antonio Pannico (UniNA), Youssef Rouphael (UniNA), Øyvind Mejdell Jakobsen (CIRiS), Mona Schiefloe (CIRiS), Gilles Dussap (UCA), Lorenzo Buccheri (EnginSoft), and Claudia Quadri (EnginSoft)

Founding source: Melissa Foundation from the European Space Agency

How do soil process domains determined by age and water balance constrain phosphorus speciation in soils? (acronym P‐Matrix)

Background: Despite the importance of phosphorus (P) as a macronutrient serving ecosystem nutrition, the pedogenetic factors and processes determining the development of P species and their ecosystem availability are not yet well understood. It is acknowledged that soils can undergo slow and rapid pedogenic processes that alter soil P status in terms of quantity and quality. Slow pedogenesis prevails when changes in soil properties are buffered by, for example, carbonates such as calcium (Ca), aluminum (Al) oxides, or iron (Fe) oxides – the soil is then considered to be in a soil process domain. However, once the dominant buffer is exhausted, rapid changes in soil properties can be observed. The transition between domains is called a pedogenic threshold.
Objectives and approach: The aim of this project is to understand how soil process domains determined by age and water balance constrain P speciation in soil. Since each soil domain reflects a very constrained system, we can assume clear biogeochemical reactions within each domain. As P can react with Ca, Al, and Fe and be included in organic compounds, changes in the soil P species composition should reflect the pedogenesis along the different soil process domains – a hypothesis that will be tested.
As a result of unique plate tectonics and topographically driven precipitation dynamics, the Hawaiian archipelago has different chrono-climatic sequences that form distinct soil domains. Due to the uniform parent material (basalt) and constant temperature, Hawaiian soils are ideal to study the relationships between soil P forms, respectively availability as a function of the two state factors of pedogenesis, which are rainfall and age.
State-of-the-art spectroscopic techniques (e.g. 31P-NMR, XANES, XRD) will be used to identify and quantify P species in different soil horizons where soil process domains and pedogenic thresholds are well known. Isotopic methods will be used to analyze the corresponding functional soil properties. This approach aims to significantly improve the understanding of the relationships between P speciation and pedogenesis. This has been done a few times on specific soil sequences yielding results on the impact of rainfall or age on soil P forms in given environments, but this has never been done on a full rainfall x age matrix of sites located on the same parent material, showing large variations in both rainfall (200 mm/m² up to 7000 mm/m²) and age (200 years up to 4 million years) while maintaining other soil‐forming factors constant.

Full Title: N-tea: Can organic farming practices increase N use efficiency and decrease N losses in tea plantations in Sri Lanka?

Background: Nitrogen (N) losses from agriculture present a significant threat to the environment and human health. Yet, sufficient agricultural N inputs are necessary to attain optimal crop yield and quality. Accordingly, there is a trade-off between N losses and crop production, and addressing it remains a complex challenge.

Navigating this balance is particularly crucial for leaf crops of socio-economic importance, such as tea (Camellia sinensis L. (O.) Kuntze). As the second most consumed beverage globally, tea is the top agricultural export for Sri Lanka, supporting over a million livelihoods. Expectedly, tea planters often apply excess mineral N fertilizers for increased yields and quality, which can lead to extensive N losses. While many have turned to more sustainable organic practices, little information exists regarding N dynamics in organic tea systems. Further research is therefore required to deliver science-based understanding to stakeholders for better N usage.

Objectives: Our project aims to assess whether implementing organic cropping practices can improve N use efficiency and decrease N losses by tea without compromising yield and quality. The specific areas of study include: i) fertilization practices, N balances, and tea quality on selected smallholders and estate plantations, ii) sources, uptake and use of N by tea plants in a long-term trial comparing conventional and organic tea cropping systems, iii) forms and dynamics of soil carbon and N in this trial, and iv) losses of N from tea systems. The research site is located at the Tea Research Institute ORganic CONventional (TRIORCON) field in Sri Lanka, where the impact of organic agriculture on tea production has been studied since 1997.
 

Background: Zinc (Zn) and Iron (Fe) deficiency in human nutrition are caused by low meat consumption and staple crops that contain little bioavailable Zn and Fe. These deficiencies are widespread in low and middle income countries. However, growing environmental and animal welfare concerns in wealthy societies such as Switzerland shift their diets towards less meat consumption, which can increase the prevalence for Zn and Fe deficiencies. We are looking for motivated BSc and MSc students that assess the potential of CH (and European) wheat cultivars to fill this Zn and Fe gap in selected vegetarian and vegan diets.

Objective and approach: The objectives of the project are to i) identify wheat cultivars with high Zn and Fe concentrations and to ii) calculate their contribution to Zn and Fe supply to subpopulations with distinct diets. To this end, samples are collected from the archive of the Field Phenotyping Platform located at the Research Station of Plant Sciences at ETHZ. Samples are analyzed for total trace metal contents (Fe, Zn, cadmium, selenium) and components that control the bioaccessability of these metals for humans (phytate, phenols, vitamin C). Finally, Swiss food data bases will be used to calculate the potential contribution of high Fe and Zn wheat cultivars to distinct diets.

Collaborators:
Isabelle Herter-Aeberli, Human Nutrition Group (ETHZ)
Andreas Hund, Crop Science (ETHZ)
Lukas Kronenberg, Molecular Plant Breeding Group (ETHZ)
Julie Tolu, Laboratory Manager in trace element analytics & Lenny Winkel, Inorganic Environmental Geochemistry Group (both EAWAG)
Funding: World Food System Center (ETHZ)
 

Full title: LysiTrace : Precise determination of trace metal leaching rates and soil mass balances with monolith lysimeters

Background: Fertilizers can be inadvertently the major pathway for trace metals into agricultural soils. In Switzerland, these trace metal inputs can lead to critical soil accumulation of cadmium (Cd), uranium (U), zinc (Zn) and copper (Cu) and eventually to elevated concentrations of these trace metals in crops and/or groundwaters. An important tool for political decision makers to assess the risk of trace metal inputs with fertilizers are soil mass balances. However, they often contain large uncertainties as it is challenging to measure trace metal outputs in soil leaching water. A way to overcome these limitations is to use monolith lysimeters which are as such pots that contain large quantities of undisturbed soils (3.3t) with an outlet to collect the leaching water.

Objective and approach: The major objective of the LysiTrace project is to determine precise trace metal leaching rates to optimize trace metal soil mass balances and thereby the risks assessments of trace metals in agriculture. By using the state-of-the-art external page lysimeter facilities of Agroscope, we can further determine precise trace metal soil mass balances and the relation of meteorological conditions and soil water fluxes on trace metal leaching in soils that are managed according to distinct agricultural practices (e.g., organic vs. conventional).

Collaborators:
Frank Liebisch and Volker Prasuhn from the Water Protection and Substance Flows Group (Agroscope)
 

Full project title: How to decrease phosphate (P) losses from upland acid sulfate soils while maintaining optimum crop yields in the lower Mekong delta? (P-ASS)

Background: The Vietnamese Mekong Delta (VMD) region is home to 17 million inhabitants and contributes greatly to Vietnam’s food security and income generation via crop export. However, one of the large constraints in crop production in this region is the large area of acid sulphate soils of 1.6 million ha, accounting for 40% region’s total land area and nearly 10% and 25% of world and Asia ASS areas, respectively. Acid sulphate soils are problem soils because when oxidized they develop high acidity and high P sorption capacity due to the high levels of Al and Fe oxides, and high levels of mobile toxic elements. In addition to that, the region is affected by floods and saline water intrusion during rainy and dry seasons, respectively. Promising crops currently grown on upland ASS are pineapple and yam because of their economic value and adaptability to these soils. It is hypothesized that high application rates of P fertilizers are often required to attain optimal crop yields. This possibly causes not only high production costs but also the risk of P losses to the water and thus water pollution risk. However, there is little available information on P dynamics and appropriate P nutrient management for yam and pineapple in ASS.
Objectives and approach: P-ASS project aims to understand P dynamics and develop science-based soil management options that will improve P use efficiency (PUE) in yams and pineapple and decrease P losses to water. To realize these goals we employ a systematic approach with analyses and experiments to be carried out in the laboratory, greenhouse and on the field. The activities are inter-connected but basically organized in three main work packages (WP) as follows:
In WP1, to understand the current nutrient use of the yam and pineapple cropping systems at plot level and/or set a baseline for the study, we first assess NPK input-output soil surface budge and NPK use efficiency (i.e., nutrient output by harvested products/nutrient inputs from all sources) via individual interview for farmers’ soil and crop management practices, analyses of production inputs and outputs and nutrients contributed by flood sediments and water quality. Moreover, soil profile description, soil sampling across soil horizons, general soil characteristic analyses will also be conducted. These activities are implemented mainly by Ho Chi Minh City International University – HCM IU, the Vietnamese project partner. In WP2, with the aim of a) understanding processes that control P dynamics and b) identifying the soil management options that improve PUE while maintaining crop yields, we: a1) measure P availability using isotope exchange kinetics or anion exchange resin method; a2) identify and quantify P forms using and state-of-the-art techniques of P K-edge x-ray adsorption near edge spectroscopy and solution state 31P NMR spectroscopy, which are supported by Hedley chemical sequential extractions and XRD and a3) link those information to the results of WP1. From then, we assess the effects of tailored soil management options on b1) P availability and dynamics in incubation and in pot experiments and on b2) soil P availability, yields and PUE in the field experiments. The latter will be conducted on farmers’ fields in either Tien Giang or Long An province of Vietnam with supporting from students registered at HCM IU. In WP3, to assess the effects of soil management options on reducing P losses from soil to water, we first evaluate P losses via runoff and via bypass flow using brilliant blue in the above-mentioned field experiments at plot level and then simulate the losses at a larger scale using SWAP model coupled with the Mike 11 HD/Ecolab model. This will be carried out in collaboration with experts from HCMC IU.

Isotope Fingerprints for Deciphering the Role of Chelating Thiols to separate Zinc from Cadmium in Plants (IsoThiolPrint)

Background: Cadmium and zinc occur naturally in soils and through anthropogenic activities. Due to their similar chemical properties, they are invariably found together in nature. Even though Cd plays no role in plant metabolism, it is easily absorbed by plants because of its similarity to Zn. In the plant, it can accumulate in the edible parts and eventually enters the food chain posing a severe risk to human health in the long run. Zinc is essential for plants and humans but in high concentrations is also toxic. Plants have tools to cope with these metals, such as thiols (reduced sulfur groups). Thiols are organic ligand molecules that bind to metals, chelating (i.e., detoxifying), immobilizing, and transporting them within plants. Thiols may also separate Cd from Zn by efficiently sequestering Cd into the vacuole of roots and leaves. As a result, not all metals absorbed by plants end up in edible parts. Thiols typically bind light Cd and Zn isotopes, so biochemical processes involving thiols may lead to a unique isotope fingerprint. We expect that linking the isotope fingerprint of thiols with isotope ratios in different plant organs can advance understanding of the various functions of metal-chelating thiols.

Objective and approach: The project's goal is to investigate the role of chelating thiols in separating Cd and Zn and their transport to edible parts of the plant. The system we focus on is utilizing low levels of Cd that are not critical for plant metabolism but may become a risk to human health. To achieve this goal, we will step-by-step study the Cd and Zn natural stable isotope variations in different systems, starting at a molecular level and ending at a whole plant level. We will use analytical techniques to determine isotope ratios (MC-ICPMS) and the chemical speciation of metals (SEC-ICP-MS, Syncrothron XANES). With these tools, we seek to contribute with our findings to produce highly nutritious crops with enriched Zn and minimize their Cd content.
 

Heavy Metals in Palestinian agriculture (HEMiPA)

Background: Heavy metals are toxic to all biota if they are present at elevated concentrations. In agriculture, heavy metals are inadvertently applied to soils, thereby potentially impairing the quality of soils, freshwater, and crops. Switzerland has a well-established soil data base that helps to monitor major heavy metal inputs into agroecosystems. Such a data base is a pivotal prerequisite to assess the environmental and health risks that are associated with heavy metal inputs into agroecosystems. In Palestine, there is no such data base, and it is not possible to assess the current risk of heavy metals in agricultural on the environment and health of the Palestinian society.
Objective and Approach: The HEMiPA projects aims to identify major sources and pathways of heavy metals in Palestinian agroecosystems by providing soil mass balances for distinct cropping system in the region of Jenin (West Bank). To this end, the Group of Plant Nutrition collaborates with colleagues from the Ministry of Agriculture/National Agricultural Research Centre (NARC) and the Al-Quds Open University (QOU) in Palestine.

Collaborators:
Aziz Salameh, Agricultural Research Center, Al-Quds Open University (QOU) in Palestine
Zaher Barghouthi, Ministry of Agriculture/National Agricultural Research Centre (NARC)
Lukas Kronenberg, SNF fellow at John Innes Center Norwich
Adrien Mestrot, Soil Science, University of Berne

Funding:
Research Partnership Grant funded by the Swiss State Secretariat for Education, Research and Innovation (SERI) for the Middle East and North Africa region (MENA). The funding is managed by the University of Applied Sciences and Arts Western Switzerland.
 

Sustainable tropical pastures: Optimize nitrogen supply through integration of legumes and grasses with biological nitrification inhibition (NiTroLeG)

Background: In South America, vast areas of tropical forest have been converted into pastures (mostly sown with Urochloa grasses) for livestock production over the past few decades. Given the unsustainable pasture management practices, the majority of pastures exist in some stage of degradation, which has dramatic economic and ecological consequences. Nitrogen (N) limitation for pasture plant growth has been identified as a major cause of pasture degradation and two strategies have been proposed to overcome this constraint. These are the introduction of N2-fixing legumes, and of grasses with the capacity of Biological Nitrification Inhibition-BNI).

Objective: The overall goal of our project is to enhance the sustainability of tropical pastures in forest margins through the integration of N2-fixing legumes and grasses with BNI capacity for reducing pressure on the forest.

Approach: In grass-legume (GL) and grass-alone (GA) pastures, containing grasses with high/low BNI capacity we will: 1) Determine N sources of legumes and grasses; 2) Assess the soil N status including abundance and diversity of archaeal and bacterial nitrifiers; 3) Measure specific N losses and determine NUE; 4) Identify, with farmer participation, the main barriers for adoption and proper management of pastures. The experiments will take place both on farms, in the Caquetá region of Colombia, and on-station under controlled greenhouse conditions.

PhD students:
Daniel M. Villegas, ETH Zurich
Mauricio Sotelo, Universidad politécnica de Madrid

Principal investigator:
Dr. Astrid Oberson, ETH Zurich, Institute of Agricultural Sciences, Group of Plant Nutrition, Eschikon, Lindau, Switzerland

Collaborators:
Prof Dr. Jaime Velasquez, Universidad de la Amazonía, Colombia
Dr. Jacobo Arango, International Center for Tropical Agriculture (CIAT), Colombia)

Partners:
Prof. Dr. Emmanuel Frossard (ETH Zurich)
Dr. Federica Tamburini (ETH Zurich)
Dr. Verenice Sanchez (Universidad de la Amazonia, Colombia)
Dr. Gelber Rosas (Universidad de la Amazonia, Colombia)
Dr. Juan Andres Cardoso (CIAT, Colombia)
Dr. Idupulapati Rao (CIAT, Colombia)
Dr. Hans Martin Krause (FiBL, Switzerland)
Eduardo Vázquez García (Universidad Politécnica de Madrid, Spain)

Funding source: Swiss national science foundation (SNSF), SPIRIT program

The Role of Organic Ligands on Cadmium Isotope Fractionation in Membrane Interfaces

Background: Cadmium (Cd) is a non-essential and toxic trace metal that can be readily taken up by crops. It can be further transported along the food chain to humans and thereby threaten human health. Hence, the understanding of biogeochemical processes that control Cd uptake and translocation in plants is important. Organic ligands play a key role for the mobility of trace metals in plants, especially for the alkaline compartments such as the cytosol and the phloem. In these compartments, trace metals are almost fully bound to organic ligands. A novel way to study the role of organic ligands on the mobility of Cd in plants could be stable isotopes. In plants, the isotope composition varies systematically. This variation is caused by physical and biochemical processes, such as membrane transport and chemical speciation for Zn and Cd. The results of theoretical calculations indicated that organic ligands have a strong effect on the Cd isotope composition. Hence, the isotope composition potentially provides a unique fingerprint on the role of organic ligands for uptake and translocation of Cd in plants. However, in plant membrane interfaces, the isotope composition may be additionally controlled by membrane transport. To date, the interplay between organic ligands and membrane transport on the Cd isotope composition and transport in plants is not well understood.

Goal and approach: The goal of this study is to advance the understanding of Cd uptake and translocation in plants. We will use Cd isotope processes tracing to investigate the role of different organic ligands in membrane interfaces. The Donnan Membrane technique (DMT) will be used to determine the change of isotope composition that is induced by distinct organic ligands. The Polymer Inclusion Membrane (PIM) technique will be used to mimic membrane transport processes of Cd in plants. With these two techniques, we will disentangle distinct isotope fractionation steps during the passage of Cd through membrane interfaces. This project will improve the use of Cd isotopes as a tool to study processes that control Cd mobility in plants and thereby improve crop quality in the long run.