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  Module 3 - Theses on the themes of the first sub-module                                         Content


Nikolai Markov - Institute of melioration and mechanization Sofia, Bulgaria

Acquaintance of the trainees with the systems of soil treatment in case of grain-corn cultures.

       A predominant characteristic of the physical state of all soil types is the thickness.
Depending on the thickness, variations are observed in water permeability, moisture evaporation, aeration, temperature, firmness, erosion resistance and a number of other soil properties.
      Autumn sowing of grain-corn cultures is preferred to the spring one both in our country and abroad because of the higher possibilities of obtaining agricultural production in a later summer period of vegetation.
      The soil climatic conditions and predecessors exert a substantial influence on choosing a suitable system and mechanization for pre-sowing treatment.
      The treatment of soil for autumn sowing is usually carried out during summer dryings and dry climatic conditions.
Tillage with plowshares as a technology of preparing the soils, especially those of average and heavy mechanical composition, is not recommended. After tillage, on the upper surface layer there are large, stiff and hard lumps formed which are hardly broken during further treatments by other soil handling machines. Under such conditions of pre-sowing treatment, especially areas relatively free of plant waste and root weeds are handled using a technology of treatment by disc harrows. Depending on the soil type and its present moisture, the requirements of quality preparation are achieved by using two - four cross treatments. The more dried and hardened the soil is the more the number of harrows is increased. The results are considerably better when the treatment with harrows is combined with rollers. The latter, mostly the combined ones break up additionally the lumps or tread them in the soil again, and they are better broken by the discs under the following cross passing. The degree of breaking up the lumps and mixing the plant wastes with the soil depends on the schemes of arranging the disc sections. In the case of modern harrow design, the front sections are fitted with discs having cuts on the periphery, while the back ones have discs of smooth periphery. Smoothing the surface is achieved through the smaller diameter of end discs using the back sections.
      The working depth of the disc harrows can be controlled within definite limits by varying the attack angle of the disc sections. The disc harrows find the largest application due to the highest reliability, performance and ability to be in aggregate with tractors widely spread and used in our agriculture.
      The use of plowshares is also desirable during the treatment of areas of large amounts of plant wastes on the surface.
      It is of utmost importance not to underestimate the quality of pre-sowing preparation of soils for winter corn cultures and it should be completed selectively, and such systems and corresponding machinery providing the best sowing conditions have to be chosen.