Plants, Soils, Climate and Agriculture In Europe : From the Neolithic Revolution to the Internal Combustion Engine Revolution.

Agriculture was born of necessity to a certain extent in that climate change in the Near East forced mankind to find a stable means of sustenance in a world of diminishing natural resources.  The initial steps of what is called the Neolithic revolution combined agriculture, domestication of grazing animals (sheep and goats), use of polished stones as axes and pottery.  This last discovery allowed the transformation of raw food into that more edible form and one much more nutritive. These tools allowed the formation of concentrations of human populations in stable communities.  Further climate change induced these communities to seek areas of higher rainfall to the north along the eastern parts of the European mountains and eventually along the Danube corridor into Northern Europe in one vector and along the Mediterranean coast in the other.  The major problem to overcome in these migrations, especially to the north, was that the biological plant cover was hostile to the introduction of steppe – derived plants used for the agricultural process, grasses and legumes.  Forests were dominant in these cooler and more moist climates at the time.  The problem was not one of trees blocking out the sun but of the chemistry engendered in the soils by trees, low pH, thin humic layers and aluminium ions in soil solutions.  These characteristics are antithetic to steppe-derived plants which engender thick humic layers, higher pH and low free alumina content. 

            In order to overcome this obstacle to the agriculture known in the early Neolithic era in the Near East, farmers had to transform the chemistry of the soils in the forest areas.  First, burning of felled trees (stone axes) increased pH when the trees ashes were spread on the soil.  This allowed 6 – 7 years of culture of grain crops.  However this did not stabilize a lower pH and alumina free soil.  The use of grazing animals to destroy new tree shoots and to encourage grasses and prairie plants maintained the soil characteristics necessary for grain culture.  Use of natural animal manure increased fertility also, but the land use was restricted to 14 year periods of grazing, diminishing grain production.  Alternating prairie and grain culture became a stable of agriculture for 6 – 7000 years.  It is described in detail by Roman agronomists.

            Eighteenth century science introduced the use of alfalfa and other leguminous plants in order to shorten the prairie cycles to one year thus increasing the grain producing productivity of the land.  This use of leguminous plants helped maintain the clay mineralogy which stores and releases potassium and probably nitrogen, via the smectie- illite association.  Forest to prairie plant regime change induces the clays in the soils to change from soil vermiculites (hydroxy interlayerd minerals) to smectite – illites.  Potassium and phosphorous fertilizers were introduced in the 19^th century but not on a large scale. Productivity gradually increased through plant selection techniques.

             Essentially the motive force remained that of animals from the Bronze Age until the 1950’s where about 20% of the productivity went to feeding the animals which were used to work the land and which provided plentiful fertilizing agents. The massive introduction of tractors changed the agricultural practice radically, eliminating the source of natural fertilizer, potassium and nitrogen, The decreased need of pasture also changed the cycles of natural fertility induced by prairie or prairie-derived plants.   Thus natural fertility induced by age old farming practice was brought an end.  The tractor introduced the need to add fertilizing agents to the soil, for the most part those made in factories.  The Neolithic revolution ended in the 1950’s.