Reconstructing Sustainable Agrarian Conditions: Examples from three field experiments in Spain.

Malaga Experimental Field. Photo by Guiomar Gallego

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Editor’s Note: This is part of a monthly series showing the work of the Sustainable Farm Systems project

Stripped of much of its traditional knowledge, modern western agricSFS logoulture based on fossil fuel mechanization is responsible for a number of environmentally destructive processes, including the rise of greenhouse gas emissions, loss of biodiversity, an increase of farm soil erosion, and aquifer pollution. In this context, and with a majority of the global population depending on modern
agriculture for food production, it is necessary to study preindustrial agro-ecosystems comparatively with those that emerged during the second half of the twentieth century in order to draw conclusions about the development and design of sustainable farm systems in the future.

The international and interdisciplinary project “Sustainable Farm Systems: Long-Term Socio-Ecological Metabolism in Western Agriculture, 1700-2000”, aims to reconstruct patterns of sustainability in farm systems and explore possible options for long-term sustainability. As part of this project, the Agro-ecosystems History Laboratory of University Pablo de Olavide in Seville (Spain) is studying how factors such as fertilization, farm management, and crop varieties shaped the transition between preindustrial, solar-based, traditional agriculture to industrial and fossil fuel-based agriculture.

Ronda Experimental Field. Photo by Guiomar Gallego
Ronda Experimental Field. Photo by Guiomar Gallego

Failure to consider the historical context of the socio-metabolic transition in western agriculture can lead to mistaken and unfair conclusions about traditional farming systems. Deep and extended studies of renewable energy and animal fertilizers in past agro-ecosystems are essential in designing sustainable organic farming systems for the future. Agrarian History provides us with useful knowledge about how farming systems were organized, which allows us to recognize important factors for future sustainable farming system patterns. But, Agrarian History faces some problems related to the lack of information or the uncertainty related to historical data sources. Since it is impossible to get close to older farming systems, we must recreate ecological and farming conditions in the present that closely approximate those of the past. This involves not only employing methods and technologies from earlier periods, but also using older varieties of seeds. To fill this knowledge gap we have begun to carry out field experiments that reconstruct traditional agriculture management conditions.

Some of the research questions that guide these field experiments include:

How did different types of varieties and management affect productivity, biodiversity, and nutrient cycles (principally carbon, nitrogen, phosphorus, and potassium)?

What are the implications of these results for accounting procedures in agrarian metabolism studies?

What are the implications for the study of ecosystem services in the past?

And, what are the agronomic implications for past organic farming practices?

The field experiments take place at three different locations in Andalusia. Two represent traditional management, while the third represents modern monoculture agriculture. The location and basic agro-climatic characteristics of the three farms are:

Location of Three Experimental Field sites, Andalusia, Spain
Location of Three Experimental Field sites, Andalusia, Spain

Farm 1. One third rotation (wheat‐fallow‐fallow) reproducing traditional management at low productivity dry lands and without manure amendments. Rain fed cereal within dehesa landscape at Ronda (Málaga). Poor soils and average rainfall of 635 mm/year.

Farm 2. Wheat‐fava beans rotation representing traditional management of Ruedo, typical of better quality soil and higher precipitation areas that allow productivity intensification. Located at Sierra de Yeguas (Málaga), with fertile soils and an average rainfall of 492 mm/year. Supplementary irrigation at seeding is possible to guarantee seed germination if a dry autumn is expected. Manure amendments are biannual.

Farm 3. Conventional wheat monoculture, representing current management based on fossil fuel inputs. Located at La Zubia (Granada), with very fertile soils and an average rainfall of 395 mm/year. As at Farm 2, supplementary irrigation at seeding is possible. The experimental design is split-plot with four repetitions. Whole plot factor is common/durum wheat, and subplot factor is old/modern varieties. Plot size is  6 × 4 m2 and a total of 48 subplots. The seed ratio is 200 kg/ha. We measure wheat spike and straw biomass, micro- and macronutrients. We also measure weed biomass and biodiversity.

Harrowing Ronda Experimental Field. Photo by Guiomar Gallego
Harrowing Ronda Experimental Field. Photo by Guiomar Gallego

In order to simulate traditional conditions, farms selected have been under certificated organic management for a minimum of fifteen years to ensure that soil conditions such as organic matter, biological activity, and natural fertility are as close as possible to that of traditional agriculture conditions. Additionally, several aspects of the field experiments involve recreating historical management and practices, such as the use of a fallow season, ruminant mechanical tillage, rotation with legumes to preserve soil fertility, and the absence of fossil fuel-based inputs, including fertilizers and pesticides.

Twelve wheat varieties have been sown in each of the farms, six are modern and six are traditional Andalusian varieties collected before 1930. Our hypothesis is that the crop variety is a structural component of agro-ecosystems that affect their functioning, and that modifications to  agro-ecosystem functioning produced by the variety could depend on farm management. Varieties should show relevant performance differences and applications for fertility system, biodiversity or yield, and nutritional harvest data. And we expect to find organic system, agronomic, and agro-ecological transition implications.

Wheat is sampled at harvest time. Weeds are sampled at weeding and harvest time. Two types of weeds, spike and straw samples, are taken in each plot. Straw and weed fresh matter is weighed and dried at 70ºC for 48 hours. Dry matter is then weighed to calculate moisture values. Spike fresh matter is also weighed after harvest, but then is threshed. Grain and husk fresh matter is weighed then and dried at 70ºC.

The results from these field experiments will allow us to reconstruct wheat crop biomass and macronutrients flows since the eighteenth century. In this way we will be able to:

  1. Assess traditional Mediterranean agro-ecosystem sustainability with different levels of intensification in terms of soil quality and biomass relocation to satisfy human needs and maintain ecosystem services.
  2. Assess contemporary monoculture wheat crop sustainability. Applying the knowledge gained from the field experiments to model different circumstances, mixing management practices and variety types, can help agro-ecologists and historians identify strategies that succeeded in reaching acceptable levels of grain yields while maintaining ecosystem services.
Harvesting Wheat at La Zubia Experimental Field. Photo by Juan Infante
Harvesting Wheat at La Zubia Experimental Field. Photo by Juan Infante

Agro-ecology can further help to improve our knowledge about traditional farming systems by informing adjustments to field experiment designs that reflect conditions prior to the Green Revolution. Termed experimental history (González de Molina et al., 2010), this way of doing Agrarian History has become a methodological tool that allows us to reproduce past conditions in a controlled way, as an indirect means of substituting for missing variables in historical sources. To this end, our investigation group has planned a field experiment to compare cereal systems before and after the rise of industrial agriculture. We chose cereal crops because they are the basis of the human diet, the most extensively grown crops, and likely the most affected by agrarian intensification and varietal modernization. A comparison between moderns and older varietals allows us to draw conclusions between differences in productivity, biodiversity, and nutritional composition harvest values. The loss of biodiversity, the disproportionate production increases in response to market demands, the depletion of soil fertility produced by harvest extractions, and the nutrient cycle breakdown are major problems facing modern agrarian systems. In this sense, the field experiments are connected with the SFS Project, as we are reconstructing past agrarian conditions to learn more about past agro-ecosystem sustainability with an aim to understanding long-term sustainability of present agriculture.

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Guiomar Gallego

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