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Sowing (planting)

Sowing (planting) – placement of seeds, grains, tubers or seedlings over the area of the field at a certain depth, taking into account the provision of optimal nutrition area for plants. Sowing should ensure uniform distribution of seeds over the area of the field and in the soil, taking into account the depth to create favorable conditions for germination and appearance of good sprouts, good illumination of plants and the possibility of mechanized care.

The main requirements for sowing:

the use of zoned varieties;
use of seeds of high reproductions with the best varietal and sowing qualities;
observance of optimal norms of seeding, depth and terms of sowing;
choice of seeding method taking into account the type of culture, moisture zone and other conditions.

Nutrition area

Nutrition area is the area occupied by one plant, which provides optimal conditions for growth and development, hence the highest yield.

It depends on:

  • the species and density of the plants, i.e. their number per 1 m2 or 1 ha;
  • the degree of tillering and branching;
  • the moisture content of the area;
  • the duration of the growing season.

Thus, late-ripening varieties require a larger nutrition area compared to early-ripening varieties. In warm and arid climates, the nutrition area should be larger, and hence the seeding rate. For example, for the Non-Black Soil Zone, the optimal feeding area per plant of winter wheat is 20 cm2, for the left bank of the Volga region – 25 cm2. On soils with a high level of fertility the nutrition area is less than on less fertile soils. In conditions of irrigated agriculture it is possible to increase the density of plant standings.

The highest productivity of plants is achieved with the optimal nutrition area, which is close to a square in shape.

Nutrition area is determined for each crop and variety experimentally in relation to specific conditions of cultivation.

Sowing depth

Sowing depth is the distance from the soil surface to the bottom of the seeds sown. The optimal sowing depth is the one that provides the greatest completeness of uniform and unweakened seedlings.

The sowing depth depends on:

  • biological characteristics of plants,
  • granulometric composition of the soil,
  • soil moisture,
  • the size of seeds.

The larger the seeds, the greater the sowing depth. Legumes that bring their cotyledons to the soil surface, for example, lupine, require shallow sowing to a depth of 4-5 cm. Cereals and fine seeds are sown to a depth of 2-3 cm, such as clover, flax, and cereal grass seeds.

Sowing depth is:

When sowing in dry soil, sowing depth is increased to improve moisture availability of germinating seeds. Deep seeding on heavy overcrust soils leads to thinning and delayed emergence of weakened seedlings. Therefore, sowing depth on heavy loamy and clayey soils is less than on light loamy and sandy loam soils.

Sowing rate

Sowing rate is the number of seeds capable of germination, or their mass, taking into account the sowing suitability, sown per 1 hectare, providing normal density of germination and good yields. It is expressed by the number of germinating seeds (mln, thousand pieces) and mass of seeds (kg) per 1 ha.

Sowing rate of different crops is determined by the requirements of plants for food area and size of seeds (1000 seeds weight), the purpose of cultivation, for example, for grain or silage, cultivated soils, moisture conditions, method of sowing. Seeding rate of small-seeded crops is usually higher than that of large-seeded crops. For example, for peas it is 1.2 million pieces/ha at a mass of 1000 grains of 250 g, winter wheat – 5 million pieces/ha at a mass of 1000 grains of 44 g.

At wide-row method of sowing, the sowing rate is less than in the usual row method; in arid conditions it is reduced, and in areas with sufficient moisture or irrigation, on the contrary, it is increased.

Approximate sowing rates were experimentally determined for different natural and climatic zones, taking into account the biological characteristics of the variety, meteorological and other conditions. Changing the sowing rate makes it possible to regulate the density of plants standing and, consequently, the conditions of plant life.

Sowing rate depends on the germination, purity and weight of 1000 seeds. To calculate sowing rates by weight, first calculate the sowing capacity of seeds, i.e. the content (in %) of clean and simultaneously germinating seeds:

where Sc – sowing capacity of seeds, %, C – seed purity, %; G – germination capacity of seeds, %.

For example, if the purity of winter wheat seeds is 98% and their germination is 95%, the sowing capacity is:

Sowing capacity example

Weighted sowing rate, taking into account the sowing capacity, is calculated by the formula:

Weight sowing rate

where Rw – weight sowing rate, kg/ha; N – number of seeds, mln/ha; W – weight of 1000 seeds, g; Sc – sowing capacity, %.

Example. In the Central Black Earth zone recommended seeding rate of winter wheat seeds is 5 mln/ha; weight of 1000 seeds – 44 g with seed suitability 93,1%. The weight rate of seeding would be:

Weight sowing rate example

The number of sugar beet seeds N, sown per 1 m of the row in a punctuated method of sowing is determined by the formula:

Number of seeds for sowing

where m is the number of sprouts per 1 m of the row; Gf is the field germination of seeds, %; K is the coefficient of the number of sprouts from one seed.

The sowing rate also depends on the weed infestation of the fields and the preceding crop. Thinning of crops under unfavorable conditions may lead to an increase in weed infestation. Therefore, sowing rates increase by 10-12% on weedy fields and when sowing after crops which leave weedy fields behind, e.g. winter crops following non-fallow predecessors. It is also increased when sowing lodging-resistant and less bushy varieties, such as winter wheat Bezostaya 1.

Sowing methods

The following sowing methods are distinguished:

  • row:
    • narrow-row;
    • cross-row;
    • wide-row;
    • taped;
    • dotted;
    • furrowed;
    • ridged;
    • striped
  • scattered;
  • striped.

The row methods are the most widespread. Seeds by this method are distributed in rows with varying row spacing, often from 10 to 25 cm, and are sown into the soil with the help of seed drill coulters. Row methods are used for sowing crops that do not require a large nutrition area: cereals, peas, buckwheat, annual and perennial grasses.

For cereal crops, the distance between the rows is 15 cm. For their sowing, conventional row planters are used, such as СЗЗ-6, СЗТ-3,6, СЗС-2,1 and others.

In areas prone to wind erosion, the width of the row spacing is 22.8 cm.

The disadvantage of the conventional row method is the high density of plants in the rows at high sowing rates of seeds, which can be more than 6 million/ha.

With the scatter method of sowing the seeds are placed on the surface of the soil without rows and sown into the soil with harrows or other implements.

In case of strip sowing the seeds are placed in narrow strips with their chaotic distribution in the strip.

In addition to the above methods, there are also combined and direct methods of sowing.

Combined sowing is sowing of two or more crops simultaneously, for example, corn mixed with broad beans, sorghum or sunflower; vetch with oats; clover with timothy. In this method, the seeds of two crops are sown in different rows and embed them at different depths or sow in between the rows of one crop of the seeds of the other. This method is often used for sowing intercrops. Combined sowing allows you to increase the productivity of the field and reduce the sowing period.

Direct sowing of cereal crops – sowing without pre-tillage using special direct sowing machines, for example, СЗПП-4. It is used on soils with few weeds and with a high level of fertility. Particular attention during direct seeding is paid to the location of the rows of culture, which should be placed from north to south to obtain higher yields. Due to the better illumination at the same cost yields are increased by 10-28% per hectare.

The choice of sowing method is determined by taking into account the requirements of crops to the nutrition area, illumination, moisture and methods of mechanized care of plants.

Narrow-row method

Narrow-row method of sowing – row sowing with placement of seeds with a row spacing of up to 10 cm. Reducing the width of cereal crops row spacing to 7.5 cm allows for a more uniform distribution of seeds over the area of the field. The shape of the nutrition area of each plant is an elongated rectangle in the usual row sowing approaches a square. This improves illumination in the rows, enhances photosynthesis and increases resistance to lodging. It is used for sowing cereal crops, grasses and flax.

Cross-row method

Cross-row method of sowing – row sowing with placement of seeds over the area of the field in two overlapping directions. Seeding rate for one pass of the seeder is half of the specified. In this case, a uniform distribution of seeds is achieved, the best conditions for plants to use light, moisture and nutrients are created. Cross-row method of sowing contributes to the alignment of the surface of the field at two passes of the unit, which leads to an even maturation of grain and qualitative harvesting. This method is more suppressed weeds and reduces its harmfulness.

Cross-row method is used for sowing cereal crops, grasses and small-seeded technical crops.

The disadvantages are doubling the number of machine passes on the field, and as a consequence, additional compaction of the soil, increasing labor costs, fuel and time for sowing. However, the increase in yields, provided the timely and quality performance of sowing works outweighs the additional costs.

Wide-row method

Wide-row method of sowing – row sowing with placement of seeds with a row spacing of more than 25 cm. It is used in cultivation of row crops. Wide row spacing, often 45, 60, 70 cm, allows to carry out inter-row tillage during vegetation, to apply fertilizers, herbicides and plant protection means. However, the wide-row seeding method leads to an uneven distribution of seeds, which can adversely affect plant growth.

Taped method

Taped sowing method is a row sowing, in two or more rows with a distance between them of 7.5 to 15 cm, forming ribbons, and alternating with wide inter-row spaces of 45-70 cm for the passage of machinery. Taped method is used for sowing carrots, onions and other vegetable crops, as well as medicinal and plants with a small nutrition area. Due to the slow growth in the initial phases of vegetation, they can be suppressed by weeds and require inter-row cultivation without damaging the plants.

The taped method of cultivation makes better use of the nutrition area and gives greater yields than the wide-row method. Depending on the number of lines in the band there are two-, three-line, etc. methods. Vegetable and grain-grass seeders are used for sowing with appropriate placement of coulters.

Dotted method

The dotted method of sowing – row sowing with a single uniform distribution of seeds in the rows, that is, the seeds are located in the row one by one at a given distance from each other. Row spacing can be 45, 60, 70 cm.

Accuracy of seeding is achieved by calibrating the seeds and the use of special precision seeders. The dotted method is used in the cultivation of sugar beets, corn and vegetable crops. The advantage of the method is uniform, precise distribution of seeds in the row and over the area, which eliminates thinning of plants in rows and increases crop yields.

Furrow method

Furrow method of sowing – sowing seeds at the bottom of a specially formed furrow. It is used in the areas at risk of wind erosion for sowing cereals and corn. Furrows allow to save moisture better, retain snow, protect sprouts from blowing out and accelerate their appearance, save sprouts of winter crops from freezing.

The deeper embedding of spring crop seeds into the moist furrow layer favors their germination and moisture retention. However, a small ridge of soil in this method of sowing increases the loss of moisture to evaporation.

Ridge method

The ridge method of sowing is the placement of seeds on specially formed ridges. It is used in excessively moist heavy soils, for example, when growing potatoes and vegetables. Ridge sowing method allows a better supply of air and nutrients to the plants, promotes soil warming and drainage of excess moisture through the furrows.

Stripe method

Stripe method of sowing – scattered sowing with arrangement of seeds in strips more than 10 cm wide. The seeds in the strip are arranged chaotically, which allows crops with a small nutrition area to use the sown area rationally.

The stripe method is used for sowing some vegetable crops.

Timing of sowing

Sowing dates are determined by biological characteristics of crops, soil conditions and the level of intensification of agriculture.  The optimum sowing date is set on the basis of sufficient availability in the soil of all conditions for seed germination – heat, moisture, air, taking into account the biological requirements of crops. Sowing is always carried out in physically ripe, well warmed soil, clean of weeds.

The established terms of sowing for various crops should be adjusted depending on the emerging conditions: the nature of spring, the distribution of precipitation during the growing season, the length of the growing season, the possibility of maturation, the degree of weeds, diseases and pests.

Soil temperature, at which seeds begin to germinate, and the ability of seedlings to withstand possible spring frosts are decisive indicators of the spring sowing date of the crop.

Crops are divided into early-, medium-, and late-sown crops according to sowing dates.

Seeds of early spring crops are able to germinate at the sowing layer temperature of 1…2 ° C, sprouts can survive frosts as low as -4…-6 ° C. The optimum temperature for seed germination and formation of full-grown seedlings is 6…10 ºC. Early sowing crops include barley, oats, spring wheat, seradella, perennial grasses, carrots. They are sown in the first days of spring field work.

Early sowing of spring cereal crops allows the fullest use of spring moisture, nutrients and daylight conditions. These crops are less affected by fusarium and rust, less affected by Swedish and Hessian flies, the crops are more resistant to weeding of the fields.

In the steppe arid regions of the Volga region and Siberia, for example, spring wheat plants with early sowing time have time to develop a powerful root system before the summer drought, providing them with moisture of the lower deep soil layers. However, in the north of the Non-Black Soil Zone, the northern forest-steppe of Siberia, and the Urals, too early sowing increases the risk of damage to seedlings by spring frosts, and in some regions increases the weediness of crops.

Seeds of medium-season crops germinate at soil temperatures of 3…6 °C, and seedlings survive frosts as low as -3…-4 °C. They include flax, vetch, lupine, beets, sunflowers, chickpeas, fodder beans, etc.

Seeds of late-season crops germinate at 8…12 °C, but they sprout evenly at 16 … 18°C, so they are sown in well-warmed soil with no risk of frost. They include corn, soybeans, millet, sorghum, beans, buckwheat, castor beans, rice, etc.

Terms of sowing crops depend on the distribution of precipitation in the spring and summer period. Thus, the timing of sowing spring wheat, the leading cereal crop in Altai Krai, differs significantly by zones: for the Western Kulunda subzone, the optimal dates fall on the third decade of May, for the Priobskaya subzone – the second decade of May, for eastern and foothill areas – the first decade of May.

According to studies conducted at the Shadrinsk experimental station of Kurgan Region (Kolmakov P.P., 1981), the timing of sowing has a significant impact on the weediness of wild oat (Avena fatua) fields and the yield of spring wheat. Early sowing results in slow development and high wild oat infestation. The reason is that mass sprouts of wild oat appear later – from May 10 to 15, when the soil is well warmed. Rescheduling sowing of spring wheat for May 15-25 allows using the time freed up for combating wild oat with pre-sowing tillage. Weed infestation is reduced several times, and the yield increases by 0.49 t/ha.

The timing of sowing winter crops is determined by the frost date, before which the plants must be well rooted and develop above-ground mass. As a rule, they are sown 45-55 days from sprouting to the stop of vegetation. Poor rooting and weakened plants sown late have no time to accumulate enough plastic substances, suffer from adverse conditions of overwintering and poor resistance to severe frosts. On the contrary, sowing at the optimal time contributes to the accumulation of the required amount of carbohydrates, increases resistance to overwintering, diseases and pests.

According to summarized data of research institutions, the optimal sowing dates for winter wheat for the Non-Black Earth zone fall on August 10-25, for the Central Black Earth zone and the Middle Volga – August 20 – September 1, the Lower Volga – September 1-20, the Northern Caucasus October 15 – November 5.

Winter rye can be sown 5-7 days later, as early sowing leads to its overgrowth and rotting-out (asphyxiation). The deadline for sowing winter rye is when the average daily air temperature reaches 10 °C.

The sowing date of winter crops should be specified for specific conditions depending on the weather, soil moisture, and varietal characteristics of crops.

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.