When planning sowings, the requirements of the crops must be studied in detail. This includes their nutritional needs, the required soil pH, as well as the nature and structure of the soil and the humus content.
It is necessary to ascertain the compatibility of the crop in the rotation with the crops previously grown, as well as to identify potential biological (presence of pathogens) and chemical (residues in the soil of agents previously used) risks. Climatic conditions may be a limiting factor for the crop, such as the length of the growing season, the availability of water at particular periods of plant development, weather conditions at the expected time of harvest. Climatic conditions are not fully predictable, but it is necessary to know the probability of hazards in order to estimate the agricultural risk of a planned crop.
Soil structure is derived from the mineral composition of the soil, the amount of organic matter including humus, the biological activity of the soil, the moisture conditions and the cultivation measures used by the farmer. Aiming for an optimal soil structure (fine-textured, with high water retention and stable soil aggregates), it is necessary to create an optimal situation for the biological activity of the various soil organisms, by enriching with crop residues or organic fertilisers, regulating the pH to an appropriate level, establishing the correct water relations (water infiltration and water absorption), and limiting activities that lead to the destruction of the structure, such as trampling by animals, soil compaction as a result of equipment passes or the use of too intensive soil cultivation with high soil moisture.
The use of agricultural vehicles for many decades causes continuous compaction of the soil also below the arable layer. Long-term trampling of wet soil by animal herds has a similar effect. A layer of soil and subsoil is formed that impedes the proper downward and upward movement of water, leading to the formation of stagnant groundwater during periods of rainfall (lack of infiltration) and limited groundwater recharge during periods of drought. The layer of compacted soil, or subsoil, also acts as a barrier to plant root growth and movement of soil organisms. The use of mechanical equipment with narrow tyres, high pressure and worn tread in conditions of excessive moisture can be particularly damaging – soil compaction can be as deep as 1m.
More on soil in Area 6: Soil management.