Sowing (planting)
Sowing (planting) — placement of seeds, grains, tubers or seedlings over the field area at a certain depth, taking into account providing plants with an optimal feeding area. Sowing must ensure uniform distribution of seeds over the field area and in the soil at a depth that provides favorable conditions for germination and uniform emergence, good illumination of plants and the possibility of mechanized care.
Main requirements for sowing:
- use of zoned varieties;
- use of seeds of high reproductions with the best varietal and sowing qualities;
- observance of optimal seeding rates, depth and timing of sowing;
- selection of a suitable sowing method for the crop, moisture conditions of the zone and other conditions.
Feeding area
Feeding area — the area occupied by one plant and providing optimal conditions for growth and development, consequently, the highest yield.
The feeding area depends on:
- the species and density of plant stand, that is, their number per 1 m2 or 1 ha;
- the degree of tillering and branching;
- moisture conditions of the zone;
- duration of the growing season.
Thus, for late-ripening varieties, a larger feeding area is required compared to early-ripening varieties. In a warm and dry climate, the feeding area should be larger, and consequently, the seeding rate should also be higher. For example, for the Non-Chernozem zone, the optimal feeding area of one plant of winter wheat is 20 cm2, for the left-bank Volga region — 25 cm2. On soils with a high level of fertility, the feeding area is smaller than on less fertile soils. Under irrigated farming, an increase in plant stand density is possible.
The highest plant productivity is achieved with an optimal feeding area close in shape to a square. The feeding area is determined for each crop and variety experimentally in relation to specific cultivation conditions.
Sowing depth
Sowing depth — the distance from the soil surface to the lower part of the sown seeds. The optimal sowing depth is the one that ensures the greatest completeness of uniform and non-weakened seedlings.
Sowing depth depends on:
- biological characteristics of plants;
- soil texture;
- soil moisture;
- seed size.
The larger the seeds, the greater the sowing depth. Leguminous plants that carry cotyledons to the soil surface, for example, lupine, require shallow placement to 4-5 cm. Cereals and small-seeded crops are placed at a depth of 2-3 cm, for example, seeds of clover, flax, and cereal grasses.
Sowing depth is:
- winter cereals — 5-7 cm;
- spring cereals — 4-5 cm;
- maize — 6-8 cm;
- sugar and fodder beet — 3-4 cm.
When sowing in dry soil, the sowing depth is increased to improve moisture supply for germinating seeds. Deep placement on heavy, slaking soils leads to thinning and delayed emergence of weakened seedlings. Therefore, the sowing depth on heavy loamy and clayey soils is less than on light loamy and sandy loam soils.
Seeding rate
Seeding rate — the number of viable seeds or their mass, taking into account sowing quality, sown per 1 ha, ensuring normal stand density and good yield. It is expressed as the number of viable seeds (million, thousand pcs.) and seed mass (kg, c) per 1 ha.
The seeding rate of various crops is determined respectively by the requirements of plants for feeding area and seed size (mass of 1000 seeds), the purpose of cultivation, for example, for grain or silage, soil cultivation level, moisture conditions, and sowing method. The seeding rate of small-seeded crops, as a rule, is higher than that of large-seeded crops. Optimal seeding rates and plant stand densities are given in reference books and depend on the cultivation level of the soil. Within one plant species on the same soil, these rates vary depending on varieties, lodging resistance and quality of sowing material.
With wide-row sowing, the seeding rate is lower than with ordinary row sowing; in arid conditions it is reduced, and in zones of sufficient moisture or under irrigation it is increased.
For different natural-climatic zones, approximate seeding rates have been experimentally determined taking into account the biological characteristics of the variety, meteorological and other conditions. Changing the seeding rate allows regulating the plant stand density, and consequently, the living conditions of plants.
The seeding rate depends on germination, purity and mass of 1000 seeds. To calculate weight seeding rates, the sowing quality of seeds is first calculated, that is, the content (in %) of pure and simultaneously viable seeds:
where
- SQ
- — sowing quality, %;
- P
- — seed purity, %;
- G
- — seed germination, %.
For example, with a purity of winter wheat seeds of 98% and their germination of 95%, the sowing quality will be:
The weight seeding rate taking into account sowing quality is calculated by the formula:
where
- SR
- — weight seeding rate, kg/ha;
- Q
- — number of seeds, million/ha;
- M
- — mass of 1000 seeds, g;
- SQ
- — sowing quality, %.
Example.
In the Central Chernozem zone, the recommended seeding rate of winter wheat seeds is 5 million/ha; the mass of 1000 seeds is 44 g with a sowing quality of 93.1%. The weight seeding rate will be:
The number of seeds of sugar beet N sown per 1 m of row with precision sowing is determined by the formula:
where
- m
- — number of seedlings per 1 m of row;
- FG
- — field germination of seeds, %;
- K
- — sprouting coefficient of seeds.
The seeding rate also depends on the weed infestation of fields and the preceding crop. Thinning of crops under unfavorable conditions can lead to increased weed infestation, therefore on weedy fields and when placed after crops that leave sufficiently weedy fields, for example, winter crops after non-fallow predecessors, the seeding rate is increased by 10-12%. It is also increased when sowing lodging-resistant and less tillering varieties, for example, winter wheat of the Bezostaya 1 variety.
Sowing methods
The following sowing methods are distinguished:
- row;
- broadcast;
- strip.
In turn, row sowing methods are:
- narrow-row;
- cross;
- wide-row;
- band;
- precision;
- furrow;
- ridge;
- strip;
Row sowing method
Row sowing methods are the most widespread. With this method, seeds are distributed in rows with different row spacings, most often from 10 to 25 cm, and are placed into the soil using seed drill openers. Row methods are used for sowing crops that do not require a large feeding area: cereals, pea, buckwheat, annual and perennial grasses.
The disadvantage of the ordinary row method is the crowding of plants in rows at high seeding rates, which can be more than 6 million/ha.
With the broadcast sowing method, seeds are placed on the soil surface without rows and are incorporated into the soil with harrows or other implements.
With the strip sowing method, seeds are placed in narrow strips with a chaotic distribution within the strip.
In addition to the above methods, there are also combined and direct sowing methods.
Combined sowing — sowing in which two or more crops are sown simultaneously, for example, mixtures of maize with faba beans, sorghum or sunflower; vetch with oats; clover with timothy. With this method, seeds of two crops are sown in different rows and placed at different depths, or sowing is carried out in the interrows of one crop with seeds of another. This method is often used for sowing intermediate crops. Combined sowing allows increasing field productivity and shortening sowing time.
Direct sowing of cereal crops — sowing without preliminary tillage using special direct sowing drills, for example, SZPP-4. It is used on slightly weedy soils with a high level of fertility. Particular attention in direct sowing is paid to the arrangement of crop rows, which should be placed from north to south to obtain higher yields. Due to better illumination at the same costs, yield increases by 10-28% per 1 ha.
The choice of sowing method is determined taking into account the requirements of crops for feeding area, illumination, moisture and methods of mechanized care of plants.
Narrow-row method
Narrow-row sowing method — row sowing with placement of seeds with row spacings up to 10 cm. The shape of the feeding area of each plant from an elongated rectangle in ordinary row sowing approaches a square. At the same time, illumination in the rows improves, photosynthesis intensifies and lodging resistance increases. It is used for sowing cereals, grasses and flax.
Cross method
Cross sowing method — row sowing with placement of seeds over the field area in two intersecting directions. The seeding rate per one pass of the drill is half of the specified one. At the same time, uniform distribution of seeds is achieved, better conditions are created for plants to use light, moisture, and nutrients. The cross sowing method is facilitated by the evenness of the field surface with two passes of the unit, which leads to uniform ripening of grain and high-quality harvesting. With this method, weeds are suppressed more strongly and their harmfulness is reduced.
The cross method is used for sowing cereals, grasses and small-seeded industrial crops.
The disadvantages include doubling the number of passes of the unit across the field and, as a consequence, additional soil compaction, increased labor, fuel and time costs for sowing. However, the increase in yield, provided timely and high-quality sowing operations, covers the additional costs.
Wide-row method
Wide-row sowing method — row sowing with placement of seeds with row spacings more than 25 cm. It is used in the cultivation of row crops. Wide row spacings, most often 45, 60, 70 cm, allow inter-row tillage during plant vegetation, application of fertilizers, herbicides and plant protection products. However, the wide-row sowing method leads to uneven distribution of seeds, which can negatively affect plant growth.
Band method
Band sowing method — row sowing in two or several rows with a distance between them from 7.5 to 15 cm, forming bands, and alternating with wide row spacings of 45-70 cm for the passage of machinery. The band method is used for sowing carrot, onion and other vegetable crops, as well as medicinal plants and plants with a small feeding area. Due to slow growth in the initial phases of vegetation, they can be suppressed by weeds and require inter-row cultivation without damaging the plants.
With the band method, crops use the feeding area more fully and give a higher yield than with the wide-row method. Depending on the number of rows in a band, two-, three-row and so on methods are distinguished. For sowing, vegetable and grain-grass seed drills are used with the appropriate arrangement of openers.
Precision method
Precision sowing method — row sowing with single uniform distribution of seeds in rows, that is, seeds are arranged in a row one at a time at a specified distance from each other. Row spacing can be 45, 60, 70 cm.
The accuracy of seed sowing is achieved by seed calibration and the use of special precision seed drills. The precision method is used in sugar beet cultivation, maize and vegetable crops. The advantage of the method is the uniform, precise distribution of seeds in the row and over the area, which allows eliminating thinning of plants in rows and increasing crop yields.
Furrow method
Furrow sowing method — sowing seeds on the bottom of a specially formed furrow. It is used in areas at risk of wind erosion for sowing cereals and maize. Furrows allow better moisture retention, snow retention, protection of seedlings from blowing out and acceleration of their emergence, and preservation of winter crop seedlings from freezing.
Deeper placement of seeds of spring crops in the moistened layer of the furrow favors their germination and moisture supply. However, slight ridging of the soil with this sowing method increases moisture losses by evaporation.
Ridge method
Ridge sowing method — placement of seeds on specially formed ridges. It is used on excessively moist heavy soils, for example, in potato cultivation and vegetables. The ridge sowing method allows better providing plants with air, nutrients, promotes soil warming and removal of excess moisture along furrows.
Strip method
Strip sowing method — broadcast sowing with arrangement of seeds in strips more than 10 cm wide. Seeds in the strip are arranged chaotically, which allows crops with a small feeding area to rationally use the sowing area.
The strip method is used for sowing some vegetable crops.
Sowing dates
Sowing dates are determined by the biological characteristics of crops, conditions of the soil environment and the level of agricultural intensification.
The optimal sowing date is established based on the sufficient presence 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 mature, well-warmed soil, free from weeds.
The established sowing dates for various crops should be adjusted depending on prevailing conditions: the nature of spring, distribution of atmospheric precipitation during the growing season, length of the growing season, possibility of ripening, degree of weed infestation, development of diseases and pests. On cultivated fertile soils, yield losses when sowing is delayed by 1 day amount to 0.10-0.15 t/ha. Sowing dates are especially important in the southern regions of the country: with optimal dates, crop resistance to drought, dry winds, as well as to early autumn and late spring frosts increases. In the Non-Chernozem zone, a delay in sowing by 10 or more days for most crops leads to yield reduction, especially with a lack of moisture during the growing season.
The determining indicator of the spring sowing date of a crop is the soil temperature at which seed germination begins, and the ability of seedlings to withstand possible spring frosts.
According to sowing dates, crops are divided into crops of early, medium and late sowing dates.
Seeds of early spring crops are able to germinate at a temperature of the sowing soil layer of 1…2 °C; seedlings tolerate frosts down to —4…—6 °C. The optimal temperature for seed germination and formation of full-fledged seedlings is considered to be 6…10 °C. Early sowing crops include barley, oats, spring wheat, serradella, perennial grasses, carrot. They are sown in the first days of spring field work.
Early sowing dates of spring cereal crops allow fuller use of spring moisture, nutrients and daylight regimes. These crops are less susceptible to fusarium and rust, are less damaged by Swedish and Hessian flies, and the crops are more resistant to weed infestation.
Seeds of medium sowing date crops germinate at a soil temperature of 3…6 °C; seedlings withstand frosts down to -3…-4 °C. These include flax, vetch, lupine, beet, sunflower, chickpea, faba beans, etc.
Seeds of late sowing date crops germinate at 8…12 °C, but uniformity of seedlings is ensured at a temperature of 16…18 °C, therefore they are sown in well-warmed soil, in the absence of danger of frost. These include maize, soybean, millet, sorghum, bean, buckwheat, castor bean, rice, etc.
The sowing date of winter crops is determined taking into account the dates of frost onset, before which plants must root well and develop aboveground mass. As a rule, they are sown 45-55 days from emergence to cessation of vegetation. Poor rooting and weakened plants of late sowing dates do not have time to accumulate a sufficient amount of plastic substances, suffer from unfavorable overwintering conditions and poorly withstand severe frosts.
The sowing date of winter crops should be specified for specific conditions depending on weather, soil moisture, and varietal characteristics of crops.
List of sources
- Bazdyrev G. I., Loshakov V. G., Puponin A. I. et al. (2000). Agriculture. Textbook for universities. Moscow: Kolos Publishing House.
- Evtefeev Yu. V., Kazantsev G. M. (2013). Fundamentals of Agronomy: textbook. Moscow: FORUM.
