Why is the soil on the river bank fertile

Soil fertility

A One of the most important properties of soils in terms of their management is fertility. Sustainable high-quality plant products (e.g. grain, vegetables, fodder crops, energy crops) can be produced by the farmer on fertile soil. As a synonym for soil fertility, terms such as productivity of the soil, productivity or yield potential are often used.

A distinction can be made between natural soil fertility and acquired soil fertility. Natural soil fertility depends solely on the location factors that control soil development. These include the starting substrate of soil development, the climate, the relief, flora and fauna as well as the time, without the influence of the economic people. As a result of the agricultural use of a soil, the natural soil fertility changes. The way of cultivation can affect the natural soil fertility positively and negatively, which is reflected in the yield performance. Natural influences also play a not insignificant role here. These include, for example, the course of the weather or the infestation of a crop with pests.

Naturally very fertile soils are suitable from an agricultural point of view for arable farming, vegetable growing or fruit crops. While less fertile soils or very fertile soils, which in the middle and lower reaches of streams and rivers are exposed to episodic flooding and often high groundwater levels (e.g. brown floodplain or Vega), are more likely to be used for grassland use (meadow, pasture), provided that these are not diked on larger rivers. If they are, the floodplain soils are plowed, which harbors the risk of pollutants and fertilizers entering the nearby river via the groundwater.

Properties of the soil that determine its fertility:

Thoroughness, (mightiness of the solum)
Soil type
Soil structure
Pore ​​volume, pore size distribution (water and air balance)
Soil activity (Edaphon)
pH value and redox potential
Soil temperature
Nutrient and pollutant content
Content, quality and composition of the humus and clay fraction

The type of cultivation can improve or worsen these properties. In the course of natural soil development, fertility increases to a certain level, depending on the location factors. In the case of naturally fertile soils (e.g. Parabraunerde from loess), but also in soils that are poor in nutrients (e.g. Pararendzina from sand-lime bricks), the yield can be increased through cultivation (fertilization, crop rotation). Soils that are naturally rich in nutrients can deliver high yields even for many years without fertilization (= harvested cultivation), since the cultivated plants receive abundant nutrients from the soil reserves, while the yield decreases sharply in less fertile soils without fertilization (= exhaustion cultivation). So-called soil fatigue can be observed in long-term monocultures, which can lead to a marked decrease in yields. Fertilization does not help either. Soil fatigue in long-term monocultures is a. attributed to root exudates (excretions), which in higher concentrations inhibit plant growth and disrupt the biological balance of the soil. Crop rotations can eliminate this problem. An irreversible destruction of soil fertility occurs through soil erosion.

Processes that lead to a reduction in the fertility and productivity of agriculturally cultivated soils:

Failure to fertilize less fertile soils
Underbody compaction due to high wheel loads
Soil erosion
Unfavorable weather conditions (frequent wetness or dryness)
Wrong or no crop rotation (catch crop)
Bad humus balance
Bad conditions for the Edaphon (e.g. low or changed pH value)

The importance of organic matter (dead, living) for soil fertility was already emphasized by researchers such as the founder of agricultural science Albrecht Daniel Thaer (1752-1828) and Charles Darwin (1809-1882). Thaer wrote in his work “Principles of rational agriculture”: “Just as humus is a production of life, it is also the condition of life.” And Darwin: “The plow is one of the oldest and most valuable human inventions; but long before it existed the land was regularly plowed by earthworms. "

Literature:

Sauerbeck, D. (1985): Functions, quality and resilience of the soil from an agricultural chemical point of view - Stuttgart.