Sowing(redirected from sowings)
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in crop production, the distribution of seeds in the top layer of soil so that they will germinate; an important farming procedure in raising many crops. The selection of one or another sowing method takes into account the crop’s requirements for space, light, moisture, and the need for mechanized plant cultivation, in particular interrow tillage.
Broadcast seeding is the most primitive method of sowing. The seeds are scattered on the soil surface and are imbedded to different depths by a harrow. As a result, the sprouts appear at different times. Row seeding, with interrow spacing from 10–25 cm, usually 15 cm, is used chiefly for grain crops. A grain drill places the seeds at the bottom of a furrow and covers them with a loose layer of soil; this promotes simultaneous appearance of the sprouts. Narrow-row seeding, with interrow spacing from 7–8 cm, and crossed sowing of such crops as grain, grass, and flax are preferable to row seeding because they permit a more uniform distribution of seeds. Wide-row seeding, with interrow spaces of more than 25 cm, is used for such row crops as corn, sugar beets, sunflowers, buckwheat, and feed and food root crops.
In strip sowing, used for such crops as carrots and radishes, wide interrow spaces between strips, or groups of rows, alternate with narrow interrow spaces. In cluster seeding, several seeds are placed in each hole, or cluster. If the clusters are distributed in the corners of a rectangle, the sowing method is called checkrow planting. In square planting, one seed is planted at each corner of a square. In single-seed planting, individual seeds are planted at equal distances from one another. In regions with severe winters and little snow, furrow sowing is used for winter crops: the seeds are planted at the bottom of furrows where retained snow protects the sprouts from freezing. Ridge planting is carried out along the crests of ridges, which receive more heat from the sun; this method is common in regions with excess moisture and in polar crop cultivation. Sowing is usually done with seeding machines, and sometimes by airplane, as in the seeding of forests.
Spring crops are sown in spring, and winter crops in autumn. For a second harvest, sowing takes place in summer, and to obtain early sprouts sowing is done in early winter. There are optimal sowing times for each crop. In the European part of the USSR, early planting of spring crops ensures the best utilization of spring moisture, nutrients, and light. Uniform growth permits weed control and reduces susceptibility to diseases and pests. In Siberia and Northern Kazakhstan, spring crops are planted later because more harm from weeds and June drought occurs if such crops as grains are planted early. In such areas as Azerbaijan and the republics of Middle Asia, early spring crops, especially barley, may be sowed in February and even in January. For late spring crops the sowing time is determined by the temperature of the soil and air.
The sowing time for winter crops is set so that the sprouts will be able to develop and become hardy before the early autumn frosts begin. Thus, these crops are sowed in August in the northern regions of the USSR, while in such areas of the south as Krasnodar Krai and Crimean Oblast sowing takes place from around September 10 to the end of the month. It is important to keep the sowing period as short as possible. Raising early and late varieties of the same crop permits some extension of the sowing period without loss of yield.
The depth of seed placement depends on the biological characteristics of the plants and on the soil’s composition. As a rule, the larger the seed the deeper it must be planted. Corn, for example, is planted 10–12 cm deep, while eared grains are planted 4–6 cm deep, and cereal grasses and Indian tobacco (makhorka) 1–2 cm deep. In heavy loams and clayey soils, seeds are planted at levels shallower than in sandy and average loams. Soil moisture is also considered: the seeds must not be in a dry layer of soil. The depth of seed placement is sometimes increased to protect the seeds from birds, as in the case of corn and peas, and to prevent them from being carried away by the wind.
The determining of the seeding rate takes into account soil and climatic conditions, the purpose for which the crop will be used, the plants’ space requirements, the time and methods of sowing, and the soil’s cultivability.
Preparation for sowing begins with procuring and storing the seed and testing it for germination and cleanliness. Each farm draws up a plan that establishes the schedule for sowing. In evaluating the quality of sowing, the factors taken into account are correct timing, uniform depth of seed placement, observance of seeding norms, straightness of rows, and accuracy of squares.
The word “sowing” (posev) also refers to a field planted with a crop.
REFERENCESRubtsov, M. I., and V. P. Matveev. Ovoshchevodstvo. Moscow, 1970.
Rastenievodstvo, 3rd ed. Moscow, 1971.
Zemledelie, 2nd ed. Edited by S. A. Vorob’ev. Moscow, 1972.
S. A. VOROB’EV