ºthe Principles of Rational Agricultureº by Albrecht Daniel Thaer (1752±1828)
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J. Plant Nutr. Soil Sci. 2003, 166, 687±698 DOI: 10.1002/jpln.200321233 687 ºThe principles of rational agricultureº by Albrecht Daniel Thaer (1752±1828). An approach to the sustainability of cropping systems at the beginning of the 19th century Christian L. Feller1*, Laurent J.-M. Thuris1,2, Raphal J. Manlay1, Paul Robin3, and Emmanuel Frossard4 1 Institut de Recherche pour le DØveloppement (IRD), Laboratory MOST (Organic Matter in Tropical Soils), BP 64501, F-34394 Montpellier Cedex 5, France 2 Phalippou-Frayssinet SA, Organic Fertilizers, La Mothe, F-81240 Rouairoux, France 3 Institut National de la Recherche Agronomique (INRA), UMR 1123-System, Cirad-Lavalette, TA 179/01, F-34395 Montpellier Cedex 5, France 4 Swiss Federal Institute of Technology (ETH Zurich), Institute of Plant Sciences, Group of plant nutrition, P.O. Box, Eschikon 33, CH-8315 Lindau, Switzerland Accepted 13 October 2003 Summary ± Zusammenfassung The identification of quantitative fertility indicators for evaluatingthe sustainability of croppingand farmingsystems has become a major issue . This question has been extensively studied by the German agronomist Albrecht Daniel Thaer at the beginning of the 19h century. In this paper Thaer's work is set in its historical background, from the end of the 16th century (Palissy, 1580) to the middle of the 19th century (Liebig, 1840). Then the paper focuses on Thaer's quantitative and complex fertility scale (expressed in ªfertility degreesº), which was based on soil properties, on the requirement of nutrients by plants, and on the croppingsystem (includingcrop rotation). Thaer expressed soil fertility and economic results as a function of rye production in ªscheffel of rye per journalº (ca. 200 kgper hectare). He also proposed a scale to describe the intrinsic fertility of soil. Thaer used this approach to assess the effect of major German croppingsystems on soil fertility. He applied it to eighttheoretical systems and nine existingsystems in a true modelingapproach. Thaer completed the fertility evaluation for the nine existingsystems with a detailed economical analysis commentingthe limits and potentialities of each system. Thaer's approach was used with success duringhalf a century as it combined numerous empirical findings on soils and fertilization with organic substances in a sophisticated model. Unfortunately and despite effective practical applications, the scientific foundations of Thaer's ªHumus Theoryº proved definitively false as soon as 1840 when Sprengel and Liebig published on mineral nutrition of plants. Thaer's work deserves to be rediscovered since it approaches the modern issue of the sustainability of croppingand farmingsystems. ¹Grundsätze der rationalen Landwirtschaftª von Albrecht Daniel Thaer (1752±1828). Ein Ansatz zur Nachhaltigkeit von Anbausystemen zu Beginn des 19. Jahrhunderts Die Identifizierung von quantitativen Fruchtbarkeitsindikatoren, mit denen die Nachhaltigkeit von Anbau- und Bewirtschaftungssystemen evalu- iert werden kann, ist ein wichtiges Thema geworden. Diese Frage wurde zu Beginn des 19. Jahrhunderts von dem deutschen Agronomen Albrecht Daniel Thaer intensiv untersucht. In diesem Beitragwird die Arbeit von Thaer in ihren historischen Zusammenhanggestellt,d.h. vom Ende des 16. Jahrhunderts (Palissy (1580)) bis zur Mitte des 19. Jahrhunderts (Liebig (1840)). Anschlieûend wird Thaers komplexe quantita- tive Fruchtbarkeitsskala (ausgedrückt in ªFruchtbarkeitsgradenº) vorgestellt, die auf Bodeneigenschaften, dem Nährstoffbedarf der Pflanzen und dem Anbausystem (einschlieûlich der Fruchtfolge) basierte. Thaer formulierte die Bodenfruchtbarkeit und ökonomische Resultate einer Kultur oder einer Fruchtfolge in ªScheffel Roggen pro Morgenº (ca. 200 kg pro Hektar). Thaer schlug auch eine Skala vor, um den inhärenten Wert des Bodens zu beschreiben. Er benutzte diesen Ansatz, um die Auswirkungen von in Deutschland verbreiteten Anbausystemen auf die Bodenfruchtbarkeit zu bestimmen. Er wandte diesen Ansatz auf acht theoretische und neun reale Systeme an, d.h. mit einem echten Modellie- rungs-Ansatz. Er vervollständigte die Beurteilung der Fruchtbarkeit der neun existierenden Systeme mit einer detaillierten wirtschaftlichen Ana- lyse, wobei er die Grenzen und die Leistungsfähigkeit jedes Systems kommentierte. Thaers Ansatz wurde ein halbes Jahrhundert lang mit Erfolg benutzt, da er zahlreiche empirische Beobachtungen über Böden und Düngung mit organischen Substanzen in einem komplexen Modell vereinigt. Trotz erfolgreicher praktischer Anwendung erwiesen sich die wissenschaftlichen Grundlagen von Thaers ªHumustheorieº schon 1840 definitiv als falsch, als Sprengel und Liebig ihre Arbeiten über die mineralische Ernährung der Pflanzen veröffentlichten. Thaers Werk ver- dient es, neu entdeckt zu werden, da es die aktuelle Frage nach der Nachhaltigkeit von Anbau- und Bewirtschaftungssystemen behandelt. Key words: cropping system / humus concepts and history / agricultural sciences history / soil organic matter / fertility indicators and scale / economical scale / sustainability PNSS P123/3B 1 Introduction agricultural sciences. The three components of sustainability (economic, ecological, and social) can be assessed from on- For more than a decade now designing sustainable cropping farm study cases and/or from experimental designs provided and farmingsystems has become a major research issue in that these studies are conducted over several decades. A major limitation of these studies is the strongdependence of * Correspondence: Christian L. Feller; the results on the local initial conditions. This makes it neces- E-mail: [email protected] sary to model the dynamics of croppingsystems using(gene- ã 2003 WILEY-VCH VerlagGmbH & Co. KGaA, Weinheim 1436-8730/03/0612-687 688 Feller, Thuris, Manlay, Robin, and Frossard J. Plant Nutr. Soil Sci. 2003, 166, 687±698 rally) simple, robust, and preferably quantitative parameters. only one to be present in their composition (of the plants)º The parallel with economic sciences has lead to name these (1796, vol. 1, p. 627), parameters ªindicatorsº. or, this other definition (which is closer to the present mea- The history of agricultural sciences conceals various theories ning): aimingat identifyingquantifiable fertility indicators in order to model the functioningof croppingsystems. The German º... trees have imperceptibly prepared the earth we cultivate. agronomist Albrecht Daniel Thaer, the most important and This humus or mould that insures the abundance of harvests famous one in the first half of the 19th century (see annex), is is due to the tree remains, accumulated during several centu- an exceptional pioneer of this approach. ries, ... Destroy a forest ... continually sow on this soil, bit by bit crops will absorb the mould, rains will sweep away the rest In this article a brief reminder is given on the theories in plant ... This previously black and fertile soil will change in colora- nutrition and on the role of humus in soil fertility until the tion, it will just remain a dry earth grain, arid and granularº middle of the 19th century. We then show how the ªHumus (1781, vol. 1, pp. 390±401). Theoryº developed by Thaer allowed him to elaborate a remarkably quantified evaluation system of the sustainability This quotation illustrates one of the principles of plant nutri- of croppingsystems and, from then on, to model the functio- tion at these times, namely as plants ªabsorb the mould (or ningof farmingsystems. This paper refers solely to Thaer's humus)º for the elaboration of their dry matter ± thus announ- reference work ªThe principles of rational agricultureº in four cingthe later experimental justifications that will make a basis volumes, of which the original edition was published in 1809 of the work of Thaer. and which was published in French in 1811 (Thaer, 1811). Here, all excerpts are from the French edition. When neces- In 1823, the great chemist Chaptal (1823) still refers to ªmine- sary, the German edition published in 1837 (Thaer, 1837± ral humusº. Thaer (1811±1816) is the first to define precisely 1839) and the American edition published in 1856 were con- humus as a soil constituent: ªThe usual name of this sub- sulted. We use in this report the surface and production units stance is ªterreauº (mould). This designation has been widely given in the French edition. misunderstood as it referred to the layer of vegetable earth rather than the special part of the substances forming it. This mistake has been repeated even in the writings of eminent 2 Historical summary on the concepts agronomists which led to increasing misconception of this of humus and plant nutrition before 1809 part of science. This is the reason why I adopted the termof Humus which is unequivocal. Generally, the scientific design- 2.1 Meaning of the term ªhumusº ation of ªearthº is not appropriate; properly speaking, it is not earth; it was only designated so for its powdery form... Although humus bas been the focus of debates on plant nutri- Humus is the residue of animal and plant putrefaction, it is a tion and therefore on fertility since the antiquity, its definition black body.º (Thaer, 1811±1816, vol. 2, pp. 102±114). varied strongly over time, especially in the 18th century. There is a semantic confusion that has not been entirely ruled even A much detailed and ± at this time ± complete description of today, since the term ªhumusº keeps two meanings: organic humus composition, extractability, and properties follows in constituent of soil and soil