Evolution of theoretical and practical basics of transition from beard tillage to beardless and surface soiltillage in Ukraine untill the first half of 20<sup>th</sup> century
The idea of the positive effect of maximum deep soil plowing began was suggested in Russia and European countries since the second half of the 18th century. Deep soil plowing was recommended by A.T. Bolotov (1738-1833), I.M. Komov (1750-1792), O.O. Yizmaiilskyi (1851-1914), D.I. Mendeleiev (1834-1907), S.M. Usov (1796-1859), K.A. Timiriazev (1843- 1920). According to I.O. Stebuta and P.A. Kostychev, plowing provides a very rapid mineralization of organic matter and good soil aeration, nutrients desorption, and destroys wild grass. V.V. Dokuchaev and O.O. Yizmaiilskyi emphasized the interrelation of the erosion problem with the problem of drought in their early papers. Scientists suggested that soil moisture preservation along with erosion soil persistence is achieved due to its cloddy granulated structure. The majority of domestic agronomists of the 19th and early 20th centuries propagated intensively the fallow system of farming for the chernozemic areas of the country, as they can not think of any another alternative to the disappearing long fallow system. Plowing at the end of the 19th century, which replaced tillage with a wooden plow, was considered the main measure of crop growing intensification, which aimed to accelerate the desorption of ash and nitrogen nutrition elements of plants to obtain high yields. O.M. Shyshkin recommended adding manure for deep under winter plowing in arid areas. P.A. Kostychev always spoke in prize of surface tillage. The scientist recommended adding manure under a surface tillage, which created mulch, preventing the bottom layers of the soil from drying out. I.Ye. Ovsinskyi suggested cultivating fields to not deeper than 5 cm in order to destroy wild grass and loosen the top layer of soil for seeds placement. According to the farmer, both drought and excessive rainfall under deep plowing is equally dangerous for tilled soil. Surface tillage of soil was carried out by I.Ye. Ovsinskyi with cut cultivators of his own design or with multyframed plows. I..Ye. Ovsinskyi believed that deep plowing disturbed the course of capillaries in the soil and itdried. I. Ovsinskyi believed that soil top layer, being more fertile, should remain on the top, and the manure plowed in to two-inch depth under plowing, would give better results. A. Kh. Evan, V. Rotmistrov, F. Grauzdin supported the scientists, D.M. Prianishnikov spoke in favor of his recommendations, however, the majority of scientists did not accept his conclusions (O.O. Iizmaiilskyi, A.P. Modestov, A. Zanes, A.I. Neverov, F. Kosorotov, F. Kryshtofovych, etc.). High potential weeds infestation and inevitable increase of actual infestation of agrophytocenoses under the surface and beardless tillage became the main obstacle for introducing these types of tillage into cultivating practices. In the middle of the first half of the 20th century, the majority of scientists considered 18-22 cm to be the optimum depth of plowing of chernozemic soils and only in some cases they considered 25-27 cm depth to be acceptable.