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Long-term effects of fertilizers on soils: the 42-plot experiment

The 42-plot experiment, created in 1928 at INRA’s Research Centre at Versailles (France) aims at assessing the impacts of continuous application of fertilizers and amendments on the composition and structure of silty soils. The long-term trial and its historical soil sample collection are unique in the world and offer outstanding opportunities for current environmental research.

Overview of the long-term experimental facility, the 42-plot experiment, which was set up in 1928 at the INRA Research Centre in Versailles. Its initial objective was to determine the effects of prolonged applications of the principal nitrogen, phosphorus and potassium-based fertilizers, as well as organic and liming materials, on the composition and physical properties of wind-borne deposits of loamy soils, characteristic of the Paris region and northern France.  The facility also plays an important role in recording environmental quality (accumulation and fate of atmospheric fallouts of metallic micropollutants and radioelements).  The ongoing experiment involves the regular collection and archiving of soil samples.. © INRA, CROUZET Olivier
By Pascale Mollier
Updated on 10/28/2016
Published on 10/14/2016

Comparing the effects of prolonged fertilizer applications on the composition and structure of soils

The introduction of chemical fertilizers was promoted in the first years after World War I to give new impulses in agriculture, together with intensive cultivation and mechanisation. Under intensive land use, many soils are fragile, such as silty soils developed on aeolian loess that represent one third of the soil cover of France. Silt-textured soils are widely used for cereal production, due to their great chemical and physical fertility. Yet, in case of over-exploitation, such soils are subject to acidification and the formation of surface crusts enhancing surface erosion.

Based on that experience, Albert Demolon, Stéphane Hénin and Henri Burgevin started an innovative long-term research programme about the impacts of fertilizers on the structure and composition of loamy bare soils, instead of studies of their impacts on crop production being widely conducted elsewhere.

In 1928, they initiated at Versailles the long-term bare fallow experiment, also designated as the 42-plot trial, including 16 duplicated fertilization treatments and 10 unamended reference plots. Soil samples have been collected annually from the surface layer since March 1929, forming today a huge historical soil archive. We can compare, for equal fertilizer inputs, their effects on soil properties:

  • nitrogen, phosphate and potassium fertilizers, used to supply nutrients to cultivated crops
  • basic and organic amendments, favourable to soil structure stability

Soils may strongly acidify within one decade

Under application of ammonia-based fertilizers (nitrate, phosphate, sulphate, or chloride), the pH of the soil surface layer dropped in a short time span of 10 years by almost two pH-units, from about 6.5 to 4.3, a value more frequently observed for forest soils.

By contrast, the ancestral “liming” practice by application of quick-lime or calcium carbonate produced an opposite effect: today the soil pH reaches values comparable to those observed for soils developed on carbonate rocks. Such practices lead to increased soil aggregate stability with respect to heavy rain events and favour soil aeration and water infiltration.

Effects of road traffic, rain and bare fallow

The experiment and soil archives are now used for purposes that are quite different from the initial objectives:

  • accumulation of metal pollutants in soils from atmospheric deposition, and in some cases, their amounts and sources may be identified (lead derived from petrol combustion)
  • soil acidification induced by acid rain (drop of 1.5 – 2 pH units in 85 years)
  • a declining organic matter content under bare soil management (no crops): mineralization of up to 75% from the initial organic carbon stock in 80 years.
Contact(s)
Scientific contact(s):

Associated Division(s):
Environment and Agronomy, Plant Health and Environment
Associated Centre(s):
Versailles-Grignon

References

- Impacts of fertilizers on soil properties:

Van Oort F. et al. 2016. Dernières nouvelles de 42 vieilles parcelles - Indicateurs d’évolutions pédologiques centenaires dans un sol limoneux nu, sous contrainte d’applications continues de matières fertilisantes. Étude et Gestion des Sols, 23, 143-162.

- Atmospheric deposition of metal elements (Pb) / radionuclides (137Cs):

Semlali RM. et al. 2004. Modeling lead input and output in soils by using lead isotopic geochemistry. Environmental Science & Technology, 38, 1513-1521.

Monna F. et al. 2009. Modelling of 137Cs migration in soils using an 80-years soil archive. Role of fertilizers and agricultural amendments. Journal of Environmental Radioactivity, 100, 9-16.

- Decomposition dynamics of organic matter:

Barré P. et al. 2010. Long-term bare fallow experiments offer new opportunities for the quantification and the study of stable carbon in soil. Biogeosciences, 7, 3839-3850.

Read the 2013 report: The 42-plot experiment at Versailles

Collection d'échantillons de terre prélevée régulièrement dans les parcelles du dispositif expérimental de longue durée, dit « les 42 parcelles », mis en place en 1928 sur le site de Versailles (78). Archivage de la collection historique des échantillons de sol, avec les premiers prélèvements du 14 mars 1929…
Ce dispositif a pour objectif de déterminer les effets de l'application prolongée des principaux engrais à base d’azote, de phosphore et de potassium, ainsi que d’amendements organiques et calcaires sur la composition et les propriétés physiques des sols de limons éoliens, caractéristiques du Bassin parisien et du Nord de la France. Il joue également un rôle dans l’enregistrement de la qualité environnementale (accumulation et devenir de retombées atmosphériques de micropolluants métalliques et de radioéléments).. © INRA, BREUIL Sébastien

A sample collection unique in the world

A total of around 2500 samples have been archived since the experiment started in 1928. Several national and international research projects are still using these recent or historic samples in order to carry out chronological studies on different types of inputs.

The 42-plot trial is also a pedagogic tool that is frequently used to teach farmers, teachers and students from primary and secondary schools.