What is soil science

Soil science

Soil science, Pedology, is the science of the properties and functions, of the development and distribution of soils. It belongs to the natural body sciences, namely to the geosciences with close links to the biosciences. Soil science also deals with soil pollution and its avoidance, i.e. soil protection, or its elimination, i.e. soil remediation. It is responsible for soil research and soil theory.

At around 120 years of age, soil science is a young, independent natural science; however, the knowledge of the importance of soil for human nutrition is very old. 10,000 years ago people began to farm, i.e. to work the soil, initially with a digging stick and hoe. Later they learned to improve soil fertility with manure and 3000 years ago people started fertilizing with pests on the North Frisian Islands. A similar technique has been practiced with loess in China since that time. The first land terraces to prevent soil erosion have also been laid out in China and the Middle East since then; At the same time, irrigation agriculture began in the river plains. The experience gained empirically over a long period of time was in China as early as 400-300 BC. put down in writing. A first classification of different soils in China according to color, grain size and moisture regime was given and presented as a map. Something similar is known from India and classical antiquity. In the Roman literature (from Cato the Elder, the young Plini, Varro Collumella, Palladius and Virgil) there are practical tips for agriculture, using 40 terms to describe soil properties, as well as the distinction between ten different soils or arable soils. Statements that go beyond the pure usability for agriculture can be found for the first time in the Greek philosopher and botanist Theophrastus (327-287 BC), who made theoretical considerations about the importance of the soil for plant nutrition, but remain the exception. That changed in the 19th century, when two directions developed, the agricultural chemical and the agrogeological-pedological. It was J. Liebig who established agricultural chemistry as the scientific basis for high-yield and sustainable land use. Professorships for agricultural chemistry have been established at many universities and the effect of mineral fertilizers on crop growth has been studied in many field tests since then. Agricultural chemistry developed from agricultural chemistry, especially under the influence of M. E. Wollny, in the years 1878-1898, later soil physics, after the water conductivity was described as early as 1853 and the first sludge apparatus for particle size analysis was developed in 1867. Soil physics was and is fertilized by soil mechanics and hydrology and has made its research more precise through modeling over the past decades. The agrogeological direction goes back to F. Senft (1810-1893) and F. A. Fallou (1794-1877), who, under the influence of geology, understood soils as weathering products of rocks. F. Senft gives the first profile descriptions in his books on forest soil science, while F. A. Fallou calls for dealing with the soil for its own sake in his works and has introduced the term pedology for it. W.W. Dokuchayev (1846-1903), EW Hilgard (1833-1916) and E. Ramann (1851-1926) then discovered that soils are formed from rock by soil-forming processes (factors of soil formation) under the influence of climate, relief, organisms (possibly . also humans) have arisen in the course of time. You have made soil science an independent natural science. At the same time, the first soil classifications on a genetic basis were also developed. The first maps of pedological content (apart from the Chinese ones mentioned) were made in England at the end of the 18th century. Under the influence of A. Orth, geological maps with an assessment of soils for agricultural use have been drawn up in Germany since 1870. The first small-scale soil map of Europe was created in 1927 under the direction of H. Stremme.

Soil science covers different areas:

Soil physics deals with the forms of the solid phase of the soil, i.e. the morphology, as well as the proportions and the physical behavior of the liquid phase and vapor phase, i.e. with soil water and soil air, and also with soil heat. The macrostructure of the soil structure is described by the field soil scientist on the profile wall of a soil outcrop. The fine structure or the microstructure is described and measured by the micromorphologist with a reflected light, polarization, phase contrast and / or electron microscope, usually of partial or thin sections, which were created from small soil monoliths after consolidation by impregnation with synthetic resin . The structure of the terrain is described with the shape, size and stability of the soil aggregates. The same applies to the humus shape and the proportion of litter and humic substances in the humus layer or peat, which is classified as the degree of humification (often incorrectly the degree of decomposition) in ten levels (1 = not, 10 = completely humidified). The size and number of macropores are also recorded in the area. The size distribution of the soil particles is only measured under the microscope in exceptional cases: As a rule, the proportion of the soil skeleton (gravel and stones) on the open profile wall is estimated in the field and the soil type or grain size of the fine soil is estimated as the proportion of sand, silt and clay by means of a finger test . The quantitative determination takes place in the laboratory with the sludge analysis, in which after dispersion (often beforehand removal of cement substances) the sand fractions are determined by means of sieving, the silt and clay fractions by means of sedimentation. The pore size distribution or pore size is usually derived indirectly from the water content with different water binding.

Soil hydrology deals with soil moisture and soil water content and their changes over the course of the year, with water conductivity (or permeability) and water movement (seepage as saturated, unsaturated or preferential river, groundwater flow) in the soil and soil landscape. Ground temperatures are mostly determined by meteorology.

Soil chemistry explores the material properties of soil minerals, humus, soil solution (including pH value, redox potential) and soil air as well as the interactions at interfaces, e.g. ion exchange. She also studies changes in space and time. Humus chemistry now forms a separate branch of science, which also includes water, coal and peat chemists: In addition to wet chemistry, nuclear magnetic resonance (NMR) and pyrolysis field ionization mass spectrometry are also used.