Shelterbelt for Fields

a barrier of trees and shrubs established along fields planted in crop rotation; in some very large fields, shelterbelts are planted among the crops.

The planting of such shelterbelts is part of the system of protective afforestation that constitutes the basis of land reclamation through forest planting. Shelterbelts prevent soil erosion and check surface runoff. They also improve the water, temperature, and nutrient regimes; reduce wind velocity; and retain snow on fields. As a result, soil fertility is increased; the climatic and hydrologic conditions of the locality are improved by reducing the effects of drought and dry winds, and crop yields are increased. According to long-term experimental data, fields situated between shelterbelts have yields 20–25 percent higher than those in the open steppe. Protected winter grains, industrial crops, grasses, and root crops show the greatest increase in yield.

In Russia, tall trees were planted for the first time around plowed fields by V. Ia. Lomikovskii in Poltava Province in 1809. At the end of the 19th century, V. V. Dokuchaev and G. N. Vysotskii worked out the scientific principles of protective afforestation. At this time shelterbelts were planted along fields in the steppes of European Russia—in the Kamennaia Steppe (in present-day Talovaia Raion, Voronezh Oblast), near Mariupol’ and in Starobel’sk (in present-day Starobel’sk Raion, Voroshilovgrad Oblast).

In the USSR great importance is attached to protective afforestation. The decree On Drought Control, which was issued by the Council of Labor and Defense and signed by V. I. Lenin on Apr. 29, 1921, stated: “The Central Forestry Section is charged with the responsibility for developing on a national scale work on (a) reinforcing gullies and sands by planting trees, especially in Saratov, Samara, Tsaritsyn, Astrakhan’, Tula, and Don oblasts; (b) constructing snow-retention strips and enclosures; and (c) afforesting cut-over areas, sites of slash fires, and other treeless stretches in arid regions, in the upper courses of rivers, and along the riverbanks” (Resheniia partii i pravitel’stva po khoziaistvennym voprosam 1917–1928, vol. 1, 1967, p. 224).

In the period of the first five-year plan (1929–32), 21,000 hectares (ha) of shelterbelts were planted, and in the second (1933–37), 278,000 ha. The decree On Measures to Stabilize Yields in the Arid Regions of the Southeastern USSR, which was issued by the Council of People’s Commissars and the Central Committee of the ACP(B) on Oct. 26, 1938, introduced a new program for afforestation, including the establishment of shelter-belts for fields in the steppe. In October 1948 the Council of Ministers of the USSR and the Central Committee of the ACP(B) issued a decree dealing with the creation of a system of large state shelterbelts and with other matters related to protective afforestation. The decree On Urgent Measures to Protect Soils From Wind and Water Erosion, issued in March 1967 by the Central Committee of the CPSU and the Council of Ministers of the USSR, also emphasized the intensification of protective afforestation. In 1974, shelterbelts for fields and orchards occupied about 1.3 million ha in the USSR (810,000 ha in the RSFSR, 360,000 ha in the Ukraine, 70,000 ha in Kazakhstan, and 20,000 ha in Moldavia). Between 1971 and 1974, 414,000 ha of kolkhoz and sovkhoz land were planted with shelterbelts.

Shelterbelts for fields are planted on flat watersheds and gentle slopes (about 1.5°). Longitudinal shelterbelts are planted opposite to the direction of the prevailing winds (with a possible deviation from the perpendicular of no more than 30°) along the long sides of the fields or in parallel lines within the fields. Transverse shelterbelts are established along the short sides of the fields. On gray forest soils, podzolized chernozems and leached chernozems the distance between longitudinal strips are no more than 600 m; on typical, ordinary, and Ciscaucasian chernozems, 500 m; on southern and other eroded chernozems, 400 m; and on dark chestnut and chestnut soils, 350 m. The distance between transverse shelterbelts is twice to four times the distance between longitudinal ones but no more than 2,000 m. Breaks 25 m long are left at the places where the longitudinal and transverse strips meet. Shelterbelts for fields have a width of 7.5 to 15 m.

In protective afforestation, three- to five-row wind-penetrable strips of tall, rapidly growing trees are planted to help distribute snow evenly on the fields, slow wind velocity 40 to 50 percent and evaporation from the soil surface 20 to 30 percent, and increase air humidity 5 to 10 percent over that in the open steppes. There are three types of shelterbelts: some are narrow and have small openings throughout, others have large openings between the lower part of the trees, and still others have small gaps above and large openings below. The last type is widespread in the Trans-Volga Region, Western Siberia, and northern and western Kazakhstan. Shelterbelts with large openings below are widely encountered in the Ukraine and the Central Chernozem Zone, and those with small openings throughout are common in the Northern Caucasus, Moldavia, and Middle Asia.

Shelterbelts for fields consist of two types of tree species. The principal species (oak, larch, pine, white birch, green ash, European ash, poplar, black locust) contribute to the height, stability, and long life of the stand, whereas the secondary species (linden, maple, Russian elm, English elm, wild pear, apple, cherry plum, mulberry, white beech) create conditions for the best growth and development of the principal species, ensure the necessary compactness of the upper story of the shelterbelt, and help to shade the soil and protect it against weeds.

Shelterbelts for fields are grown by the row or cluster method. The row method is the more common. The distance between rows in the forest steppe and in the northern and central parts of the steppe zone is 2.5 to 3 m; in the southern part of the steppe zone the distance is 3 to 4 m. The trees in each row are 1 to 3 m apart. The cluster method is sometimes used when oak is grown from seeds. Five or six acorns are placed in a hole. The nourishment range for young oaks is the same as when oak seedlings are planted in rows, that is, 60 × 75 cm. The shelter-belts are established with seedlings and cuttings that are planted in the spring (for the best results) or in the fall by tree-planting machines in deeply cultivated soil (plowed to a depth of 40–60 cm).

Various methods are used in managing shelterbelts. The soil between the rows is loosened with cultivators, and the soil between the trees with tractor-mounted rippers. Weeds are destroyed with herbicides (simazin with prometrin and trisberi) at the rate of 2–4 kg/ha of active substance. Pesticides are used to control pests and diseases. Young shelterbelts are watered. The soil is cultivated, and the weeds are destroyed until the tree crowns touch (after five to ten years). In shelterbelts consisting of principal species only, the lower branches are pruned to a height of 1–2 m, and sick trees are removed. Some trees, mainly sick ones, of both the principal and secondary species are cut down, and their shoots destroyed with chemical substances.

Shelterbelts for fields are common in such foreign socialist countries as Yugoslavia, Poland, Rumania, Hungary, and Bulgaria. They are also widespread in the United States (especially on the Great Plains), Canada (Manitoba, Saskachewan, Alberta), Italy, France, Great Britain, Denmark, and other capitalist countries.