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Post-sowing tillage

Post-sowing tillage is a complex of practices for care of crops, aimed at creating favorable conditions for seed germination, emergence of seedlings and providing optimal conditions for plant growth and development.

Post-sowing tillage allows to improve seed contact with soil, break the soil crust, thereby improving soil aeration, keep the sowing layer of soil in a friable state to reduce moisture loss by evaporation and increase moisture supply of cultivated crops, conduct effective weed control.

The tillage after sowing and before emergence of seedlings consists of rolling and harrowing, after emergence – post-emergence harrowing, inter-row loosening of tilled crops, hilling and thinning of plants in the rows.

Rolling

Rolling is carried out simultaneously with sowing or after it, before sprouting in dry weather, especially on loose soils. Rolling allows to compact the soil of the sowing layer and improve the contact of seeds with the solid phase of the soil. Excessive looseness of the sowing layer prevents water absorption by seeds, the top layer dries up quickly, which reduces field germination of seeds and slows down the emergence of seedlings. Lack of moisture in the period of bushing node formation negatively affects the formation of the secondary root system of cereal plants.

Post-sowing packing also reduces air content in the soil; it improves its warming, which ensures earlier sprouting. It is especially effective for sowing leguminous crops as well as cereals and grasses when they are sown in dry soil. Post-sowing consolidation of tilled crops, such as corn and sunflower, increases field germination and accelerates seedling emergence.

Rolling has negative features: continuous soil rolling also stimulates weed seed germination, soil compaction reduces its water permeability and moisture absorption of precipitation, soil crust is formed when drying. Therefore, with sufficient soil moisture and good pre-sowing tillage, rolling is inexpedient. When sowing small-seeded crops, packing is combined with sowing.

In order to avoid continuous rolling grain seeders СЗС-2,1, СЗП-3,6А are used, equipped with special rollers, which compact the soil only in the rows of sowing and well close the rows. As a result, a dense seed bed is created and field germination of the seeds increases.

Post-sowing rolling is carried out by smooth rollers of ЗКВГ-1,4, СКГ-2 type with additional loosening of the surface by light seed harrows or ploughs. This creates a loose layer on the surface and prevents emergence of soil crust. In legume crops that bring the cotyledons to the surface, the soil crust hinders emergence of seedlings. For this reason, rolling is carried out during the pre-sowing cultivation or combined with sowing.

In the steppe arid zone, the soil is rolled after sowing, while in regions with sufficient moisture the soil is rolled before sowing.

Harrowing

Pre-sowing harrowing is used to destroy soil crust, which worsens the gas exchange between soil and atmosphere, hampers the emergence of seedlings.

Surface hard crust increases moisture evaporation, reduces water and air permeability, worsens conditions for seed germination and further plant growth. It is formed after abundant precipitation on poorly structured heavy and saline soils when they dry up.

Soil crust is loosened by light tooth, wire or net harrows before sprouting. On grain crops harrowing is carried out before the appearance of the first crop leaves, on beet fields – when the beet sprout is 1 cm long. It is important that the tines of the harrow do not reach the germinating seeds and do not damage the seedlings. Light rotary hoes are used for this purpose.

Post-sowing harrowing destroys up to 70-80% of sprouts of small weeds in the phase of “white thread”.

Especially effective is harrowing on tilled crops with long period from sowing (planting) to sprouting of crops, for example, on potato crops.

Post-sowing harrowing is used to loosen the soil between the plants, destroy crust and kill the weeds. Harrowing improves the air regime of the upper soil layer and accelerates microbiological processes. Timely harrowing of mature soil allows you to create a mulching layer that prevents moisture evaporation and protects the soil from overheating.

The timing of harrowing depends on the condition of the soil and crops, as well as weather conditions. Spring and winter crops are harrowed in the tillering stage when the plants are well rooted. On beetroot fields, harrowing is carried out in the phase of the first pair of true leaves; on corn crops – in the phase of 3-4 leaves. To reduce damage to plants, processing is carried out at low speeds of no more than 4-5 km/h, and the harrow passive side of the tooth must be set in the direction of the unit movement. On solid crops harrowing is carried out across the rows or along the diagonal of the field.

Sprouts of legumes, potatoes, beets and other crops are harrowed in the afternoon when plants are less turgor and less damaged.

Inter-row tillage

Inter-row cultivation on row crops is designed to loosen compacted soil, destroy soil crust and cut down weed sprouts. Periodic loosening and leveling of the soil between the rows contributes to soil aeration and water permeability, moisture supply of plants, activates the activity of microorganisms, increases the availability of nutrients.

The timing of inter-row loosening is determined depending on soil compaction in the rows, the formation of soil crust or the time of weed emergence.

In humid years with frequent precipitation the soil is more compacted, so the inter-row loosening is carried out more often than in dry years.

The depth of inter-row loosening is determined by the phase of plant growth, soil moisture and its degree of compaction. The first loosening in the crops of sugar beet, fodder beet, corn and other row crops is carried out when the seedlings appear and the rows of plants appear. It is called hacking blind and performed at a depth of 4-5 cm. Hacking blind is carried out to destroy shoots of weeds, loosening of soil crust, moisture conservation and faster growth of plants. It is performed by tilled cultivators, for example, УСМК-5,4А, КРД-5,4, КРН-4,2, КРН-5,6 equipped with one- and two-sided razor-shaped tines. To prevent damage to the root system of plants in rows of row crops leave a protective zone width of 10-15 cm. To prevent damage to the plants and covering them with soil during processing, cultivators are equipped with protective discs on both sides of the row.

Cultivator section with weeding harrows
Cultivator section with row weeding harrows for soil loosening and weed control in protective zones

To eliminate weeds and loosen the soil in the protective zone of rows, additional working tools are installed on tilled cultivators: weeding harrows, double needle-shaped rotary discs or rotary harrows of БРУ-0,7 type, for tines with blades or disc bar-trailing hillers.

The depth of the second cultivation increases to 8-10 cm, all subsequent decrease to 6-8 cm and 4-5 cm to prevent damage to the root system of plants and soil drying. The protective zone near the row increases to 15-20 cm.

For deeper loosening between the rows, tilled cultivators are equipped with loosening chisel blades, feeding blades, lancet tines, and trowels. For better soil levelling, they are supplemented with needle-shaped rotary discs or weeding harrows.

In strip crops the soil is loosened in wide inter-row areas between the strips.

The use of herbicides, including narrow-directed action, allows reducing the number of inter-row cultivations on row crops to 1-2.

Cultivator section with rotary needle discs
Cultivator section with rotary needle discs for soil loosening and weed control in protective zones

Blocking-cross

When growing sugar beets, fodder beets, and some vegetable crops, inter-row tillage is combined with a specific weeding called blocking-cross. It consists in leaving several plants at the same distance from each other in rows. Such thinning is usually carried out by row-cultivators, such as УСМК-5,4А, equipped with razor blades, and carry it out across the rows of crops.

Beet blocking-cross is carried out in the phase of one or two pairs of true leaves.The most common thinning schemes are 27 and 30 cm with a block length of 18 and 15 cm. Mechanical cross-cutting of crops allows to destroy germinating weeds while ensuring the density of standing 5-6 plants per 1 m.

Hilling

When growing potatoes, corn, tomatoes, cabbage and some other crops, we use hilling.

Hilling is the covering of loose moist soil to the base of plant stems with simultaneous undercutting of underground breeding organs of perennial weeds in between the rows.

In conditions of excessive moisture and under irrigation, hilling allows to prevent excessive soil overwatering, promotes aeration, soil warming and accumulation of available nutrients. Hilling helps cover the lower part of stems with loose soil, which enhances formation of adventitious roots of tomatoes, corn, potato stolons, increasing yield by 10-15%.

Hilling helps protect plants from spring frosts.

In conditions of drought or lack of moisture, no hilling is carried out to prevent additional soil drying.

The number of hilling and the time of their implementation are determined depending on the biological features, height of plants and weather conditions. Most often, it is carried out 1-2 times after rain or watering at a height of plants 15-20 cm with simultaneous loosening of the soil. The last hilling is carried out before the tops of the plants close in the rows. It is carried out by tilled cultivators, such as KON-2,8PM, KON-2,8P, USMK-5,4 and others, equipped with loosening tines or hillers.

Slitting

In some cases, as a post-sowing tillage is carried out slitting in the soil when caring for crops of winter and perennial grasses, placed on sloping lands. Slitting prevents water runoff, soil washing out and removal of nutrients with water, contributes to accumulation of moisture in the soil profile.

It is applied to winter crops in late autumn when topsoil is frosty and to perennial grasses – after the second cutting when the soil is dry. Especially effective in winter crops, under which a minimum of surface tillage was carried out.

Slitters like ЩН-2-140, ЩН-3-70, which cut the soil to a depth of 40-50 cm and the distance between the slits 70-140 cm, are used for slitting.

Sources

Farming. Textbook for universities / G.I. Bazdyrev, V.G. Loshakov, A.I. Puponin et al. – Moscow: Publishing House “Kolos”, 2000. – 551 с.

Fundamentals of Agronomy: Tutorial/Y.V. Evtefeev, G.M. Kazantsev. – M.: FORUM, 2013. – 368 p.: ill.