**3.1 Materials and methods**

*Applied Geochemistry with Case Studies on Geological Formations, Exploration Techniques…*

enough data over long periods of time. The ability to detect slow drifts and weak noises is needed to forecast tipping points that can eventually modify or jeopardize

In fact, the interest of geochemistry is to produce scalar-type information that obeys the universal laws of chemistry, whatever the place and time in the Earth's surface conditions. It offers remarkably robust concepts and models that are valid for several orders of magnitude on space and/or time scales (e.g., from nanometer to megameter and from picosecond to millennium). Thus, we have used it in the study of different agro-systems and exploring long-time (up to 1000 years), mediumtime (around 60 years), and short-time (1 hour to 3–4 months) phenomena.

In the present chapter, geochemical data are processed to gain this information.

Agriculture appeared almost concomitantly in the Middle East, particularly in the Euphrates Valley, in Central America, and in Asia. With the global warming ending the last quaternary ice age, agriculture spread to Europe, West Africa and South America, and then North America and Oceania. From a historical perspective, we can observe (**Figure 1**), firstly, that the development of agrarian systems is directly linked to the growth of human population and, secondly, that each positive inflection of the curve corresponds to significant improvements and innovations in

During the evolution of agricultural practices, we distinguish a first period from

less than −10,000 years to 1850, called organic agriculture, in which progresses rested mainly on the improvement of the use of internal energy of the agriculture system. It thus starts with manual farming where only the farmer's labor force counts. Then the lightly hitched agriculture appears in which the animal force is introduced but with animals not specifically dedicated to work in the fields (soil tillage) and, finally, the heavily hitched agriculture, with animals selected for their physical strength, in which the farmers could maintain them during winter, because they became able to stock a stable surplus of fodder grown during the summer season. In the middle of the nineteenth century, with organic farming, a farmer could work a maximum of 5 ha with a yield remaining below 50 quintals per hectare.

*The development of agrarian systems is linked to the growth of the human population (from [1]).*

the present steady state.

agricultural practices.

**2. Short historical evolution of agriculture**

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**Figure 1.**

For isotopic and palynological characterizations, soil and/or sediment cores were drilled and sampled as continuously as possible. One core was drilled on the delta of Mirna River (Gulf of Venice) in coastal Croatia continuously at 720 cm depth [2].

The chronology of the core is based on accelerator mass spectrometry 14C dating of short-lived terrestrial samples (seeds and small leaves). No botanical macroremains were found in the middle core, but the use of marine shells (involving the radiocarbon-dating reservoir effect) and bulk samples (involving potential contaminants) was strictly avoided in order to minimize chronological biases in the age-depth model. Dated samples were calibrated (1 sigma (σ) and 2σ calibrations, respectively, 68 and 95% confidence interval) using CALIB REV 7.0.4 [3]. The average chronological resolution for the core stratigraphy is 7 years per cm<sup>−</sup><sup>1</sup> (1.43 mm per year<sup>−</sup><sup>1</sup> ). **Figure 2** shows some examples of micro-botanical remains like pollen and macro-botanical remains like seeds, kernels, and wood pieces.
