PhD – New insights into organic fertilization from the perspective of agricultural soil quality (OT100)

PhD – New insights into organic fertilization from the perspective of agricultural soil quality (OT100)

Supervisor name and surname:

Iñigo Virto (

Description of the research project:

The organic by-products of agri-food origin and others, far from being considered a waste that has to be disposed of, are increasingly seen, in the frame of circular economy, as an opportunity to be re-used as organic fertilizers and amendments, improving the productivity of crops, but with the challenge of maintaining or increasing the sustainability of the system and in particular, soil quality.

Traditionally, studies on organic fertilization have focused mainly on investigating the dynamics of nitrogen. However, organic fertilization incorporates micro- and macronutrients other than N, which may affect soil functioning. Also, the addition of other wastes as those from livestock also incorporate significant amounts of micronutrients and other trace elements. The negative impact of some of these elements, such as heavy metals, will depend (in addition to their concentration) on soil properties (as pH, mineralogy or organic matter). The interaction processes between the added organic compounds and the soil components are still not completely understood. In addition, although it is well known that organic matter is at the heart of soil functioning, and not only of its chemical fertility, little is known on the effect of organic amendments on the soil physical properties, including those affecting water storage and dynamics, such as hydrophobicity or porosity. In the search of agricultural systems closer to circular economy strategies and climate change adaptation, gaining knowledge on the net effect of organic fertilization in the sustainability of the whole system, and not only on yields, is strategic. This is of special importance in organic farming systems, since organic fertilizers are the only ones allowed.

This project aims to explore these issues in a range of experimental fields across the Ebro Valley, with the aim of advancing in the assessment of the consequences of different organic amendments on soil quality.

The research goals of this project are focused on studying the effect that the continued application of organic amendments or fertilizers has on the environment and soil quality, by studying the physical quality (water retention capacity, hydraulic conductivity, compaction, porosity, stability of aggregates, structure) chemistry (granulodensimetric fractionation and physical-chemical characterization of organic matter; macro-, micronutrient and heavy metal contents; or P retrogradation) and/or biological (macro and microfauna) of the soil.

For such goals, a network of long-term trials exists under different pedoclimatic conditions within the Ebro Valley (NE Spain), including plots with more than 20 years of amendments from wastewater treatment plant by-products and more than 15 years with fertilization with livestock waste in different management systems (tillage, rotations, with or without irrigation). In addition to the universities involved in the project, a public company (INTIA) in Navarra, leads some of these actions. Also, training will be provided in France (École Normale Supérieure de Paris) for specific analyses (Rock-Eval pyrolisis), following previous successful experiences and under the supervision of a international reference group in the field.

This Project fits squarely into the Action Plan of Campus Iberus as it falls at the intersection of the three challenges posed within the Agro-food and Nutrition field: the social (need to generate healthy food with high added value), economic (cover the requirements to starting from optimizing primary production in the region) and environmental (guaranteeing the non-degradation of ecosystems in relation to agricultural production) challenges.

These materialize in the research trends identified in the Plan: valorization of by-products of the sector, strategic improvements that allow to reduce toxic waste in food, and improvements in the strategy of agricultural production processes (soil, water, etc.).

PHD Programme:

Programa Agroalimentación (Universidad Pública de Navarra)
Public University of Navarra

Supervisor short biography:

Agricultural Engineer (UPNA, 1998) and PhD in Soil Science (UPNA, 2004). Associate professor at the Department of Sciences (Area Soil Science) of the Public University of Navarre (UPNA, Spain). He has a broad scientific background as agronomical engineer, including post-doctoral experience in France (AgroParisTech) and the US (University of Pennsylvania).

He works in the research group: Sustainable Soil management, integrated into the Institute on Innovation & Sustainable Development in Food Chain (IS-FOOD, ). Part of his activity as researcher can be found in ORCID and at the UPNA directory

His teaching activities cover different subjects (Geology, Climatology, Erosion, Soil Quality, Educational Projects) in BSc and MSc degrees at UPNA and U. of Lleida

Gross annual salary:

22.000-26.000 €

The employment contract in each recruiting institution will apply internal rules so final retribution might slightly differ.

Working hours:

37,5 hours a week


Full time

Deadline for application 01/31/2019

More information and application on

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