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in crop rotation, a field that is not occupied by crops during an entire growing period or during part of it; the soil is kept loose and weed-free. Fallowing is an effective farming technique for raising soil fertility, accumulating moisture in the soil, increasing the yield of all crops in the rotation, and improving the quality of agricultural products. It is an essential element of a scientifically based system of land cultivation.
There are two types of fallow land: true fallow and occupied fallow. True fallow includes bare fallow (tillage begins in the summer or autumn after harvesting the previous crop), early fallow (the soil is plowed in the spring of the next year), and strip fallow (with strips of corn, sunflower, mustard, and other tall-stalked plants planted in the field to retain snow). Occupied fallow is land cultivated during the first half of the summer with plants having a short growing period. Green manure fallow is land cultivated with herbaceous plants, such as lupine and serradella, which are turned under.
The introduction of true fallow is related to the development of the ley system, which existed in Europe until the 15th or 16th century and in southern and southeastern Russia until the late 19th century. As the amount of untilled land decreased, the length of the “rest time” gradually decreased to one year. Livestock grazed on the land in the spring, and in June manure was applied and plowed in for winter crops. This form of true fallow was used in Western Europe until the 19th century and in Russia until the Great October Socialist Revolution.
In the USSR, true fallow occupied 16 percent of the total arable land in 1940, 18 percent in 1950, 8 percent in 1960, and 6 percent in 1973. In the southern Ukraine, the Volga region, the North Caucasus, and Moldavia, true fallow is used most effectively before planting winter wheat and rye. In northern Kazakhstan and in Western and Eastern Siberia, spring wheat is planted on true fallow. Bare fallow for winter crops is tilled in the autumn: manure and inorganic fertilizers are applied before plowing, the field is harrowed in the early spring to preserve moisture, and in the summer the soil is cultivated at different depths and compacted. With correct management, bare fallow accumulates 100–200 mm of moisture in a 1-meter soil horizon by the time winter crops are to be planted. The soil becomes nutrient-rich (N, P, K), thus creating favorable conditions for the development of winter crop sprouts and making possible high and stable grain yields. The effectiveness of bare fallow is increased by strip plantings. The tillage for spring wheat begins with autumn or spring scuffling, which is repeated several times throughout the summer to control weeds and accumulate moisture. In late August, the primary plowing is done. Early fallow is plowed in the spring, and in the summer it is tilled the same way as bare fallow. In regions subject to wind erosion, a system of tillage using deep rippers and subsoil cultivators that leave stubble on the soil surface is used. In the 20th century, true fallow has occupied an extensive portion of the arid regions of many countries, especially the USSR, the United States, Canada, Argentina, and Australia. In these countries, true fallow is the basis of grain rotations and the chief means of combatting drought in dry farming.
Occupied fallow arose in the 18th century with the development of animal husbandry and the introduction of crop rotations for industrial crops (sugar beets and potatoes). Fallow fields were cultivated with feed crops that were harvested three or four weeks before the planting of winter crops. The system of occupied fallow was widely used first in Great Britain and France and then in Germany and other countries. The system was used on certain landlord farms in Russia.
In the USSR, occupied fallow is common in areas having adequate moisture: in the nonchernozem zone, in the northern forest-steppe of the European USSR, and in irrigated regions where it is used for fields of winter and spring grain crops. In southern forest-steppe regions that have less moisture, occupied fallow is combined with true fallow. In the autumn, the occupied fallow is tilled; during the summer, after the fallow crop has been harvested, the fields are plowed or cultivated. Occupied fallow is used extensively in Western Europe.
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K. G. SHUL’MEISTER