Back to overview

How to decrease phosphate (P) losses from upland crops while maintaining optimum crop yields on acid sulfate soils of the lower Mekong delta? (acronym P-ASS)

English title How to decrease phosphate (P) losses from upland crops while maintaining optimum crop yields on acid sulfate soils of the lower Mekong delta? (acronym P-ASS)
Applicant Frossard Emmanuel
Number 203317
Funding scheme Resource not found: '8595bf37-0545-46ef-8729-36f87f6b0611'
Research institution Plant Nutrition Environmental Systems Science (D-USYS) ETH Zurich
Institution of higher education ETH Zurich - ETHZ
Main discipline Pedology
Start/End 01.11.2021 - 31.10.2024
Approved amount 249'591.00
Show all

All Disciplines (2)

Agricultural Engineering

Keywords (7)

Vietnam; phosphate; pineapple; acid sulphate soils; yam; water quality ; Mekong Delta

Lay Summary (French)

L’agriculture du delta du Mékong s’est fortement intensifiée pendant les dernières décades. Les rendements atteints sont maintenant très élevés. Ces agrosystèmes sont cependant installés sur des sols sulfatés acides qui sont très difficiles à gérer. En effet étant donné leur formation en absence d’oxygène et leur richesse en sulfides, dès que ces sols sont mis en contact avec de l’oxygène, ils émettent de fortes quantités d’acide sulfurique et de métaux toxiques. La mise en valeur de ces sols s’est accompagnée d’apports de grandes quantités d’intrants y compris d’azote et de phosphore. Or non seulement les engrais sont chers, mais en plus une fraction de ces éléments est perdue vers l’environnement. Il est donc important de développer des bases qui permettront aux producteurs et productrices du delta d’apporter des quantités plus faibles d’engrais de telle façon à maintenir les rendements élevés en limitant les pertes vers l’environnement.
Lay summary

Contenu et objectifs du travail de recherche

Notre principal objectif est de développer et d’évaluer des options adaptées aux sols sulfatés acides (SSA) permettant de diminuer les pertes en phosphore (P) des sous cultures d’ignames et d’ananas tout en maintenant des rendements élevés. Ces cultures ont été choisies comme modèles car la production agricole se diversifie fortement dans le delta mais que peu de choses sont connues sur ces cultures par rapport au riz. Ce travail sera effectué en collaboration entre l’ETH de Zurich, l’université internationale de Ho Chi Minh City. Plus précisément i) nous étudierons les pratiques de fertilisation dans les plantations d’igname et d’ananas du delta en fonction des contraintes pédologiques, hydrologiques et de la perception des agriculteurs et agricultrices; ii) nous analyserons la dynamique du P dans les SSA et nous développerons des options permettant d’augmenter l’efficacité d’utilisation du P par les cultures ; et iii) nous évaluerons l’impact des options les plus intéressantes sur les transferts de P des sols vers les eaux.


Contexte scientifique et social du projet de recherche

Notre travail générera des informations qui permettront aux producteurs et productrices d’ignames et d’ananas du delta du Mékong d’utiliser les éléments nutritifs et plus particulièrement le P de façon efficace et de diminuer les pertes en P vers les eaux. Ce travail devrait permettre de démarrer une discussion pour générale dans le delta du Mékong pour le développement d’une agriculture plus durable et respectueuse de l’environnement.

Direct link to Lay Summary Last update: 07.09.2021

Responsible applicant and co-applicants

Gesuchsteller/innen Ausland


Name Institute

Project partner

Associated projects

Number Title Start Funding scheme
152017 Biophysical, institutional and economic drivers of sustainable soil use in yam systems for improved food security in West Africa (YAMSYS) 01.12.2014 r4d (Swiss Programme for Research on Global Issues for Development)
64135 Preferential flow and nutrient/contaminant accessibility for plants. 01.07.2001 Project funding (Div. I-III)
118103 Composition and dynamics of bacterial phosphorus in phosphorus deficient soils: relevance for crop nutrition 01.10.2007 Project funding (Div. I-III)
153600 Phosphorus availability and its interaction with plant belowground carbon, nitrogen and phosphorus input to soil 01.09.2014 Project funding (Div. I-III)
171170 Impacts of N/P inputs on organic P dynamics and P status in soils and plants along anutrient gradient 01.02.2017 Project funding (Div. I-III)
162422 Forms and dynamics of soil phosphorus along a climosequence on basalt-derived soils (CLIMP) 01.11.2015 Project funding (Div. I-III)
194252 Can organic farming practices increase nitrogen (N) use efficiency and decrease N losses in mature tea (Camellia sinensis L. (O.) Kuntze) plantations in Sri Lanka? (Acronym N-tea) 01.08.2021 SPIRIT
131310 Nutrient Use and Dynamics in Conservation Agriculture Including Legumes in the Midwest of the Malagasy Highlands 01.09.2010 Resource not found: 'bd31932a-e257-46d9-9dba-079f6f2c77c6'
50528 Evaluation of phosphorus availability in swiss agricultural soilsFertility status for an optimal crop production and an environmentally sound management 01.01.1998 Project funding (Div. I-III)
177584 Biophysical, institutional and economic drivers of sustainable soil use in yam systems for improved food security in West Africa (YAMSYS) 01.12.2017 r4d (Swiss Programme for Research on Global Issues for Development)
149130 The phosphorus cycle in forest ecosystems as revealed by analysis of the isotopic composition of oxygen associated to phosphate 01.10.2013 Project funding (Div. I-III)


Crop production in the lower Mekong River Delta is essential for food security and income generation in Vietnam. Most crops in this area are grown on acid sulfate soils (ASS) derived from anaerobic sediments rich in sulfide minerals such as pyrite. These soils release high levels of sulfuric acid when they are exposed to air, resulting in very acidic soils that contain high levels of toxic elements, such as free aluminum (Al). In addition, increasing sea water intrusions occurring in the delta due to the construction of hydraulic infrastructure (dams etc.) in the higher Mekong valley and to increasing sea surface levels caused by climate change are putting a further stress on crop growth. Farmers add nutrients (nitrogen N, phosphate P, and potassium K) in excess of crop needs in the form or mineral and organic fertilizers on rice, and probably on high-value upland crops like water yam (Dioscorea alata) and pineapple (Ananas comosus). The reasons for these excessive nutrient inputs are not known, but they might be done to facilitate plant growth in these hostile soils or through ignorance of what these upland crops need. However, not only are fertilizers costly for farmers, but these excessive inputs lead to P accumulation in soils and to the emission of P to surrounding water. Therefore, a search for options to minimize P losses from soils to water is timely. Solving this problem in rice might be possible as extensive information is available on nutrient management in this crop. By contrast, little information exists regarding the P input-output budgets of yam and pineapple in the delta, the soil P dynamics in tropical ASS, or the P transfer from ASS to water. The aim of this project is to develop soil management options adapted to ASS that will promote increased P use efficiency and decrease P losses to water, while maintaining yam and pineapple yields at optimum agronomic levels. We consider these crops as models in this project because they are highly appreciated by farmers and they are associated with the release of acidity and free Al to water. The project consists of four work packages (WP): analysis of the current nutrient use under the perceived crop needs and soil and water constraints at plot level (WP1); analysis of P forms and of processes controlling P availability in ASS and of options that could increase P use efficiency by these crops (WP2); analysis of the impacts of selected options on P losses to water and on P concentrations in rivers (WP3); and capacity building and outreach (WP4). More specifically, WP1 will first quantify N, P, and K inputs from mineral and organic fertilizers and outputs in crop harvests from 60 plots planted with yam and pineapple in the three types of ASS found in the delta (active ASS, potential ASS, and salt-affected ASS). Discussions with farmers will characterize the fertilization strategies they are now implementing. The 2nd part of WP1 will be dedicated to the description of soils properties on the 60 plots chosen for the nutrient input-output budget calculations. The 3rd part of WP1 will analyze the hydrology and water quality in the canals located around the studied plots, as well as the nutrients added by floods and irrigation. In the last part of WP1, we will ask farmers and other stakeholders whether they perceive a relationship between fertilization strategies and nutrient losses to water and which options they would propose to increase P use efficiency by these crops to decrease losses. WP2 will start with an in-depth characterization of P forms and availability in the three agriculturally used ASS mentioned in WP1 and in non-agricultural ASS. The next step of WP2 will be to use incubation experiments to test options that could sustainably decrease excessively high soil P availability and/or alleviate other constraints like high acidity and free Al concentrations that presently hinder efficient P uptake by crop plants (options could include addition of organic matter, biochar, carbonated minerals, combination thereof, or other measures discussed with stakeholders). Interesting options will be tested in a pot experiment using yam grown on different ASS to see how each option affects plant biomass production and P use efficiency. Finally, the most interesting options will be implemented in three field experiments, each one located on one of the three types of ASS using yam or pineapple as test crops. The 3rd WP will first explore the impact of these most interesting options on P losses by evaluating runoff from the plots of the field experiments. We will use these data to model the impact of these options on P losses from soil to water and on the transport of this P to the river canal system at the scale of 10 to 100 ha and over a year. For this modeling, we will use the SWAP model that simulates P transfer from soil to water, coupled with the Mike11-HD/Ecolab model that simulates the transport of P in rivers. This will allow us to simulate the impacts of land surface under yam and pineapple, of different nutrient managements and of different rainfall patterns on P losses from ASS and on P flux and concentration in the river canal system around the yam and pineapple plots. Finally, we will discuss the efficiency and acceptability of these options with farmers, agricultural extension agents, officers from the departments of agriculture, and of water management authorities of the different provinces. The training and education of students (PhD, MSc, BSc), the exchange of scientists between Switzerland and Vietnam, and the writing of publications and extension materials and the project outreach will be organized within the 4th WP. This interdisciplinary project will implement methods from agronomy (e.g., crop imaging, discussion with stakeholders), from soil science (isotopic and spectroscopic analyses of soil P availability and forms, soil profile description, quantification of P losses by runoff) and environmental science (coupling of a soil/water transport and of an hydrodynamic models for water flow in rivers). The project will deliver first fundamental results on P dynamics in tropical ASS and on the approach and options that could be taken to decrease P losses to water from agricultural land located on ASS. It will also raise awareness among farmers that excessive P inputs result in an inefficient P use by crops, thereby increasing P inputs to water and promoting the degradation of water needed for irrigation, household use, fishing, and biodiversity. Altogether, the results of this project will help to improve the sustainability of Vietnamese agriculture, while also addressing several of the United Nations’ Sustainable Development Goals: 6 (clean water), 12 (responsible consumption and production), 14 (life below water), and 15 (life on land). This project will be managed following the guidelines of the commission for research partnerships with developing countries of the Swiss Academy of Sciences. It will be conducted by a doctoral student, two MSc students, and three BSc students under the direction of Professor Emmanuel Frossard (Group of Plant Nutrition, ETH Zurich) and Associate Professor Hoa Pham Thi (School of Biotechnology, International University, Vietnam National University, Ho Chi Minh City) and their partners.