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Tilling of soils prone to water erosion

The cause of water erosion is the runoff of rainwater and meltwater, which washes away and erodes the arable layer and destroys soil fertility. Water currents carry away on the most valuable silty and colloidal fractions of soil, soluble humus and nutrients. 

The main tasks of tillage of soils subject to water erosion are:

  • imparting a fine lumpy structure and friable soil condition to improve water permeability and moisture absorption;
  • creating a certain micro-relief on the slope surface;
  • reducing soil washout with surface water runoff and its accumulation in the soil;
  • deepening of the arable layer;
  • destruction of plow pan.

Erosion control techniques can be divided into two groups:

  • techniques increasing water permeability and filtering water;
  • techniques that create micro-relief on the surface to retain water runoff and soil washout.

Erosion control treatments that increase water permeability and infiltration into the soil

The erosion control techniques of tillage that increase water permeability and water infiltration include:

  • plowing across the slope;
  • plowing with ploughs with deepeners or notched mouldboards;
  • deep non-moldboard tillage;
  • slitting;
  • molling.

Methods of main tillage of slope lands depend on moisture, properties of arable soil layer and underlying rocks, soil flush, slope angle.

Plowing across the slope direction is carried out at a slope of up to 3° with rectangular configuration of the field. On complex slopes plowing is carried out along the horizontal contours of the slope, also called contour tillage.

According to the Volga Research Institute of Hydrotechnics and Land Reclamation, even ordinary plowing across the slope prevents water runoff. The amount of runoff largely depends on the depth of plowing. At deep transversal plowing due to greater water retention in the soil, cereal crops yields increase by 0.2-0.3 t/ha.

At contour-meliorative organization of field area is tilled in the direction of linear water-regulating boundaries, for example, shafts-terraces, roads, watercourses, forest belts, etc.

Agrotechnical requirements for plowing of sloping lands:

  • maintaining the contour of furrows and ridges;
  • maintenance of designed height of windrows (0,4-0,5 m) and their normal profile;
  • maintenance of tillage depth;
  • providing of good crumbling of layer;
  • preventing from mechanical damage to watercourses sown with grass;
  • hydro-forest-melioration and other constructions.

Quality of embedding of fertilizers, turf, plant residues, as well as leveling of furrows are of great importance.

The ridges and furrows formed during plowing across the slope serve as an obstacle in the way of water runoff down the slope, slowing down its speed. As a result of water retention and penetration into the soil, surface runoff is reduced by 3.5 times. According to generalized experimental data runoff of melt water is reduced by 77-94 m3/ha, in years with prolonged snowmelt and insufficient soil moisture – up to 200 m3/ha in comparison with plowing along the slope. At the same time cereal crops yield increases by 0.15-0.2 t/ha.

The depth and method of tillage depend on the slope. Plots located in the lower part of the slope, where the angle is smaller and the top layer is more humusy, plowing is carried out to the depth of humus horizon. Soil of the upper part of the slope is more washed out, therefore plowing with soil deepening or non-moldboard is used.

One-sided slopes are ploughed on rectangular paddocks, located across the slope. Fields with difficult slope relief break into irregularly shaped areas, taking into account the direction and steepness, which plowed separately mounted or turnover plow. At the same time the turnover of layer should be in the direction of the upper part of the slope, and the soil did not move down the slope.

Plowing with ploughs with deepeners, with notch and non-moldboard bodies is effective on medium- and highly washed away soils with a thin humus layer up to 20 cm.

When contour plowing, additional loosening of the subsoil layer is carried out without bringing it to the surface. Studies conducted on dark-gray heavy loamy forest soils of the state farm “Kashirsky” in the Moscow region showed that plowing with a deepening to 27 cm allowed to reduce soil washing out on the fields with a 3-5° slope by 5 times and to increase barley yield by 0.3 t/ha compared with plowing at 20-22 cm. The best results (120 m3/ha) this method gives on the sloping lands of the Central Black Earth zone.

Table. Meltwater runoff during plowing across the slope with deepening, m3/ha (according to Rozhkov, 1983)

Zone
Number of years/experience
Soil type
Ploughing across the slope by 20-22 cm
Plowing with a deepening at 28-30 cm
Reduced runoff
Non-Black Earth
16
Sod-podzolic and gray forest
186
113
73
Central Black Earth
9
Black earth and gray forest soils
377
257
120
Middle Volga region
45
Black earth and light chestnut soils
197
126
71

Humus layer of small thickness on sloping lands is exposed to water erosion and constantly decreases, so annually include a small part of the underlying soil-forming rock, usually of heavy granulometric composition, into the cultivated arable layer. Involvement of clay admixture of bedrock leads to deterioration of soil properties, increasing its density, reducing water permeability. On such soils it is expedient to use plowing with ploughs with notched blades, providing continuous loosening of subsoil layer.

With deep loosening the soil freezes to a shallower depth and thaws earlier in spring. Melt water is absorbed by the soil, thus reducing flushing, water runoff, and its reserves are increased by 120-150 t/ha compared with plowing.

On soils subjected to strong washing away, the turnover of the layer is undesirable, so for processing plow-riders type ПРК-4-40, chisel tools, subsurface (flat-cut) deep tillers are used. Non-moldboard loosening is combined with plowing and polydisc-tilling. Performed it on the autumn plowing strip width of 4-6 m every 15-20 cm to stable freezing of the soil. This method increases the filtration capacity of the soil. According to the data of the Soil Institute named after V.V. Dokuchaev, deep strip loosening decreases washing away of sod-podzol soil on the slopes of 2-4 ° in 2 times, the cereal crops yield increases by 0.6 t/ha.

Deep non-moldboard tillage is carried out on heavily washed out slopes that are not weeded. On weedy areas, alternation of non-moldboard loosening and plowing is used. On poorly-washed slopes with a steepness of 2-4°, conventional plowing with soil deepening is used.

Special methods of tillage – slitting and molling are carried out for regulation of surface water runoff on slopes with angle of 3-10°, which reduce soil washing out, increase water supply by 370-550 m3/ha due to transfer of surface runoff into intra-soil one. Nitrogen, phosphorus and potassium losses with water are reduced by 3-4 times.

Slitting is used on heavy soils with poor permeability in the system of autumn tillage, on crops of winter crops, perennial grasses, hayfields and pastures. Slits 3-8 cm wide and 40-60 cm deep are cut in pairs (tapes) at a distance of 1.4 m between them. The distance between the tapes depends on the slope and is 5-10 m. On difficult slopes the strips are made discontinuous. Slitting is carried out in late autumn when the top layer of soil freezes to a depth of 5-7 cm to protect the slits from swamping.

Slitting makes it possible to increase moisture reserve in meter layer of soil up to 1000-2500 m3 of water per 1 hectare. In a number of farms in Podgoreny district of Voronezh region slitting of sloping lands allowed to increase moisture reserves in the soil up to 1600-2500 tons per 1 ha, which increased the yield of perennial grasses by 2.5 times.

For better water permeability and preservation of slits, they are filled with loose soil of humus layer mixed with stubble. Open slits are filled with water, which freezes and prevents the absorption of melt water. The greatest effect of this technique is achieved by cutting slits at the end of winter on still thawed soil and, if possible, covering them with a roll of snow.

Mounted slitters such as ЩН-3-70 and ЩН-4 or re-equipped ploughs, subsurface (flat-cut) deep tillers are used for crevicing. For slitting the ploughed autumn soil, they are equipped with roller-makers, which form water-retaining rollers of 10-12 cm in height over the slit. On crops of winter crops and grasses on slitters a disc knife is installed in front of each stand cutting through the turf and reducing damage to plants.

On hayfields and pastures located on the slopes of 8-10°, molling is carried out simultaneously with slitting, using slitter-moler ЩН-2-140 equipped with chisels and mole cutters. To prevent damage to plants of winter crops, grasses, ripping chisels are set at an angle of 10°, and when working on the autumn plowing field – at an angle of 30°.

On soils of heavy granulometric composition with poor permeability for regulation of surface runoff mole cutting (molling) is used. Mole cutting is creation on depth of 35-40 cm of parallel drains-moles with diameter of 6-8 cm on distance of 70-140 cm from each other. It is carried out by mole ploughs, mole-makers, on steep slopes – by rotary and shuttle ploughs. In steppe and forest-steppe regions in the spring period mole cutting contributes to the accumulation of water in the subsoil layer. In Kursk region mole cutting of soils increased the yield of winter and spring wheat by 0.27 t, barley – by 0.22, potatoes – by 3.7 t/ha, sugar beet – by 3.3 t in comparison with the ordinary plowing.

On fields with a field slope up to 3°, slits are created under rows of row crops at a depth of 30-40 cm, in which water and roots penetrate, which promotes the absorption of water and nutrients by plants in the deep layers. In legume plants, the number of root nodules increases.

The best results of slitting are achieved on crops of winter crops with their weak development in the autumn period. After sowing winter crops on the leveled surface of the field, meltwater runoff and soil flushing increases. Thus, autumn slitting reduces the surface runoff of melt water in the black earth soils of Voronezh region by 2 times, but it is not possible to stop water erosion completely with the help of this method.

Erosion control tillage techniques that create micro-relief on the surface

Agrotechnical methods of tillage that create microrelief on its surface in the form of ridges, closed wells, intermittent furrows, microlimans, or stepped profile allow to retain water runoff and prevent soil washing out. They include ridging, staggered, combined plowing, interrupted furrowing, hollowing of ploughed fields in autumn, creation of rolls of soil, etc.

In spring, fields with created microrelief are leveled by levellers, cultivators with harrows and other tools.

Stepped plowing

Stepped differently deep plowing – tillage, which creates a stepped profile of the bottom of the furrow. Developed by the Research Institute of Agriculture named after V.V. Dokuchaev. . Prevents surface an intra-soil water runoff. It is used in the fields with a slope of 5-8 °, where other techniques do not provide sufficient erosion control soil stability. More often such plowing is made by 4-corners ploughing the second and fourth corn plow at a depth of 20-22 cm, and the first and third – to 30-34 cm. Such plowing creates ridged furrows on the surface of the soil, and a stepped profile in the depth of the soil. The ridged-stepped profile prevents soil washing out and melt water runoff and retains up to 200-300 m3 of water per 1 ha.

Experiments conducted by the Research Institute of Agriculture of the South-East, Penza Agricultural Station and in the Rostov region, confirmed the high efficiency of soil-protective step plowing, which increased water reserves in the meter layer by 90-330 m3/ha, with an increase in cereal crops yield by 0.17-0.43 t/ha.

Ridge plowing

Ridge plowing is plowing, in which a ridge is formed on the surface of the field with a 3-5° slope. It is carried out by ploughs, where one, usually the last body has an extended mouldboard or one shortened, the other extended. Other combinations of bodies are also possible.

Due to the extended mouldboard creates a ridge (windrow) height of 20-30 cm, the shorter – the furrow. Alternation of ridges and open furrows in perpendicular to the slope creates additional barriers to the flow of water, which is absorbed by the soil, thus increasing its reserves by 150-200 m3/ha. Ridge plowing is combined with subsoil loosening, using soil deepeners, non-moldboard bodies or notched mouldboards for this purpose. Ridge plowing is carried out during late autumn tillage on one-side simple slopes.

Combined plowing

Combined plowing – plowing with a three-corners plough with removed mouldboards on the second and third corps or replaced by non-moldboard, which allows combining mouldboard and non-moldboard tillage. It was developed by Voronezh agricultural institute and is effective on the fields with a slope of up to 5-6°.

The combined plowing creates strips with stubble bordered with ridges on the arable land. In winter, snow accumulates in the strips, which protects the soil from deep freezing, which in spring contributes to the absorption of melt water. Application of combined plowing increases cereal crops yields on sloping black earth by 0.01-0.41 t/ha.

Intermittent furrowing

Intermittent furrowing is a method of tillage, which consists in cutting furrows on the surface of the field with a slope of 5-8°. It is carried out simultaneously with ploughing with ploughs equipped with special devices of ПРНТ-70000, ПРНТ-80000 types, which is a body with a shortened mouldboard, behind which a three-blade impeller is installed. Impeller during plowing, forming furrows 1,0-1,2 m long and with a capacity of 95-100 liters, interrupted by rollers (crosspieces) of height 20 cm. Thus, a closed system of microlimans, numbering up to 4000-4200 per 1 ha with a total capacity of 350-400 m3 of water, is created.

Intermittent furrowing along the soil compacted after plowing is also carried out by hilling cultivators in two passes. The first pass is carried out along the slope, the second – in the direction perpendicular to the slope. In this case, a network of closed wells of 0.7 x 0.7 m is formed, preventing water runoff and soil washing out.

Hollowing

Hollowing is a method used to create closed holes in the fields with a slope of 4-6°. It is done simultaneously with plowing with ploughs equipped with devices ПРНТ-90000, or separately with devices like ПЛДГ-5, ПЛДГ-10, disc-tillers ЛДГ-5, ЛДГ-10 or hole-forming devices ЛОД-10. The latter are spherical disks, which are periodically sunk into the soil and form holes. Up to 12 000 holes with total capacity of 200-500 m3/ha of water are created per 1 ha.

Pre-sowing soil preparation, sowing and plant care on sloping lands

Pre-sowing tillage of sloping lands includes:

  • early spring harrowing of ploughed soil in the autumn,
  • slitting,
  • leveling the surface of the field,
  • pre-sowing cultivation,
  • contour sowing (planting).

Sloping lands with exposition (orientation) to the south and southwest reach physical ripeness in spring earlier than others. On such slopes the soil, dries out faster, that also concerns the top sections of slopes and fields with hollowing, furrowing. Therefore, on these soils carry out moisture closure first of all by cross harrowing with heavy tooth harrows.

Harrowing and cultivation

When sowing early spring crops harrowing is carried out simultaneously with cultivation. To do this in the fields with modified microrelief fallow heavy cultivators such as КПЭ-3,8, КПС-4, levelers ВП-8, ВПН-5,6А, ВИП-5,6, heavy levelers in coupling with tooth harrows are used. For better levelling of the surface double cultivation in cross direction with harrowing is carried out. Thus, a loose mulch layer is formed on the surface and capillary bonds are broken, which reduces moisture loss on evaporation.

Sloping lands, where non-moldboard tillage was conducted, warm up more slowly. Moisture is closed in this case by needle harrows in active loosening mode. For pre-sowing cultivation anti-erosion flat-cut cultivators such as КПШ-5, КПШ-9, etc. are used.

The depth of the first cultivation of heavy heavily leached soils prone to waterlogging is 10-12 cm with heavy cultivators КПЭ-3,8, КТС-10-1, which improve soil warming, embed fertilizers and facilitate the control of weeds. The first cultivation is carried out across the slope, the second – diagonally, as it will overlap the subsequent sowing.

Cultivation across the slope by extirpator cultivators and cultivation with simultaneous intermittent furrowing across the slope by cultivators equipped with furrow breakers are used for anti-erosion tillage of sloping lands when taking care of row crops and bare fallows.

In the crops of cereals and fallow fields as an agrotechnical method, cells with simultaneous rolling are created. For this purpose, special anti-erosion rollers are used.

Sowing (planting)

Sowing or planting on simple one-sided slopes is carried out in a perpendicular direction to the slope, on complex – along the contours, the so-called contour sowing. The rows of plants at contour seeding serve as a barrier for water runoff from atmospheric precipitation along the slope, reducing it by 25%.

Cereals are sown with ordinary row sowing method on slopes of 3-8°. If the slope is up to 3°, corn is sown with furrow method, potatoes – with ridge method, sugar-beet – with dotted method.

To increase infiltration capacity of soil in row crops, slitting or intermittent furrowing is carried out to create additional capacity of storm water absorption. Slitting to a depth of 30-35 cm is carried out simultaneously with sowing or inter-row tillage. For this purpose, tilled cultivators are equipped with slitters and chisel ripping working tools. Slit cutting is carried out along the tractor’s wheel track or through 1-2 row-spacing. For intermittent furrowing and deep loosening of row-spacing a device ППБ-0,6 is used which is hinged on tilled cultivators and consists of an hiller and a four-blade impeller. When the latter is used, up to 4 thousand furrows are formed with bridges on 1 hectare to a depth of 16 cm and a total capacity of 250-280 m3.

According to the All-Russian Research Institute of Farming and Soil Protection from Erosion, intermittent furrowing between the rows at a slope of 2-3° makes it possible to retain up to 200 m3/ha of water while increasing the yield of green mass of corn by 1.8-2.0 t/ha.

To reduce the compaction effect of heavy wheeled tractors during tillage and sowing, additional rippers, which loosen compacted soil to a depth of 14-16 cm, are installed along the wheel track.

The use of organic and mineral fertilizers on sloping lands contributes to anti-erosion soil stability and increases crops yields by 20-40%.

On slightly and medium eroded soils, row crops are sown in wide-row dotted method across the slope, on more sloping slopes, sowing is carried out with the simultaneous creation of intermittent furrows in the row spacing.

Sources

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