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(soil cultivation), the practice of working the soil to raise its fertility and to bring about better conditions for plant growth. Tillage breaks the topsoil up into loose, small clumps and improves the water, air, and thermal regimes of the soil. Microbiological processes are activated in the soil, and the fields are cleared of weeds, pests, and disease pathogens. During tillage, fertilizer is applied to the soil. The choice of a method of tillage is determined by climatic conditions, by the biological features of the crops raised, and by the intended use of the plants. The effectiveness of soil cultivation greatly depends on the properties of the soil.
One of the basic procedures of tillage is the turning over of soil layers that differ in agronomic properties. For example, the dusty, structureless upper horizon of soil is covered with the structured soil of the lower horizon. The procedure covers over crop residue, the sod, fertilizers, fractured weed seeds, and the vestiges of pests and diseases of agricultural crops. The soil is turned by plowing and scuffling.
Tillage also involves breaking up, or crumbling, large masses of soil into small clumps, which increase the porosity and aeration of the soil. As a result, biological activity is intensified, and plant nutrients are accumulated. The procedure breaks up the soil crust, which would otherwise impede plant growth and increase water loss. It is done separately or simultaneously with the other operations (turning over or inverting). The surface soil is loosened by harrowing. Soils at depths of 10–12 cm are loosened by cultivation, and those at depths of 20 cm and more are worked with plows whose moldboards have been removed, with subsoil deep rippers, and with other implements. The soil may be turned and loosened simultaneously by using plows with skim colters and by scuffling. Crumbling and partial inversion is achieved by rototilling the soil.
Inversion creates a uniform layer with an even distribution of organic matter, inorganic fertilizers, and lime or gypsum. This procedure is used with subsoiling. Inversion is done by plows without skim colters, as well as by implements that loosen the soil but do not turn it.
Soil compaction—the pressing together of soil particles—increases capillary porosity and reduces noncapillary porosity. The clumps of soil are broken up, and the plowed land settles somewhat. There is less aeration of the soil and less evaporation of moisture. Better conditions are created for seed germination. The soil is compacted by rollers.
Leveling provides better conditions for sowing, tending, and harvesting the crops. It also reduces water evaporation from the soil. Leveling is achieved by harrowing, cultivating, rolling, and smoothing. In irrigated areas, the surface soil is leveled. The removal of weeds may be done at the same time as the previously mentioned procedures or may be carried out separately, using various cultivators. Under conditions of excess moisture, furrows, ridges, and furrow crowns are made to regulate the air, thermal, and nutritional conditions of the soil. They are also used on fields that have been subject to water erosion. They retain thaw waters and prevent the washing out of soil. Furrows are also important in irrigation farming (furrow irrigation).
A distinction is made between basic, special, and surface tillage. Basic tillage consists of ordinary plowing. Special tillage involves plow planting, deep loosening, rototilling, mole plowing, slotting, and the banking of slopes. Surface tillage includes rolling, harrowing, smoothing, scuffling, disking, cultivating, hilling, and furrowing. The various sequentially executed procedures for working the soil constitute a tillage system. In the USSR there are tillage systems for spring and winter crops, for lands subject to water and wind erosion, for newly developed lands, and for irrigated lands.
The tillage system for spring and winter crops consists of basic, presowing, and postsowing tillage. Basic tillage for spring crops is done in the summer and autumn of the year preceding planting. Weedy soils from which grain crops have been harvested undergo stubble scuffling and autumn plowing after the sprouting of weeds. The soil in regions with an extended and warm autumn is cultivated two or three times as the weeds sprout. For winter crops, basic tillage is begun in the autumn preceding planting (bare fallow) or in the spring and summer of the year the winter crops are sown (early, occupied, green-manured, and strip fallow). Presowing tillage takes place in the spring for spring crops and in the spring-summer for winter crops. Surface tilling predominates presowing tillage for spring and winter crops; procedures include harrowing, cultivation, and rolling. For potatoes, cotton, and certain other crops, deepsoil loosening is also used. In regions having sufficient or excessive moisture, the fall-plowed field is replowed. Postsowing tillage encompasses the period from sowing to harvesting and consists primarily of rolling the soil, harrowing the plantings, interrow cultivating, and hilling.
The tillage of land that has been subjected to water and wind erosion includes special procedures. To combat water erosion deep plowing with a subsoiler plow is used, as is deep loosening with a plow without a moldboard. All types of tillage are carried out across the slope (along the horizontals), that is, perpendicular to the direction of the water runoff. On slopes above 2°, procedures include banking the underwinter fallow, dibbling, slotting, and other moisture-retaining methods. To prevent wind erosion, moldboardless tillage is conducted with rippers, and the stubble is retained.
Different tillage systems for newly developed lands are used in the various natural zones of the USSR. Thus, in the northwestern and northern regions of the nonchernozem zone, the system for developing the virgin lands, many of which have undergone reclamation, includes plowing with special high-powered plows with helical moldboards or with brush-moor plows, disking with heavy harrows, and rototilling with bog cutters. In the forest-steppe and steppe zones, where the land is generally very fertile, various types of deep plowing, disking, and cultivation are employed.
The tillage system under irrigated conditions is determined by the type of irrigation. In the necessary instances, the field is prepared during plowing for water supply irrigation; after the water has been supplied, with the onset of physical maturity, the soil is tilled again in the autumn to retain moisture and destroy weeds. Tillage includes leveling of the field, autumn cultivation, the creation of a temporary irrigation network, presowing cultivation, tending of the plants, and preparation of the soil for resowing.
REFERENCESZemledelie, 2nd ed. Edited by S. A. Vorob’ev. Moscow, 1972.
Teoreticheskie voprosy obrabotki pochv. Leningrad, 1968.
S. A. VOROB’EV