Formation of the optimal sowing density
Providing plants with the necessary mineral nutrition and protection from pests and diseases is only part of the technology. An extremely important aspect is the formation of the optimal plant density of the cultivated variety or hybrid recommended by the seed producer.
Each breeding institution provides recommendations on the optimal density for a particular variety or hybrid at the time of harvesting, which will maximize the yield. These data are based on experiments conducted in different soil and climatic conditions in different agricultural backgrounds.
Recommended stem density values are determined in thousands of plants per hectare (thousand plants/ha for corn, sunflower, sorghum, soybeans) or in millions of plants per hectare (million plants/ha for cereals, peas, soybeans, flax, annual and perennial grasses). The originators of crop varieties and hybrids recommend a certain plant density per hectare, but not all producers are aware that this is the recommended density at the time of harvest (especially for economically attractive corn, sunflower, soybeans, sorghum, and sugar beet).
How to determine the required quantitative rate of seeds per unit area or per linear meter and what should be taken into account?
We propose to dwell on the calculation algorithm in more detail.
In order to correctly determine the number of seeds per linear meter (or per unit area) to be sown, a number of requirements must be taken into account:
- Laboratory germination of seeds in %.
- Correction factor for field conditions (sowing suitability), %.
- Row spacing
- Required stem density recommended by the seed manufacturer at the time of harvest, thousand units/ha or million units/ha.
For small-seeded crops - annual and perennial grasses (except for vegetables), sowing is carried out taking into account the weight of 1000 seeds, laboratory germination and the coefficient for field germination in weight terms, since it is physically impossible to carry out a control count of the number of grains in a row per linear meter after sowing with a seeder due to its small size.
The seeding rate on precision seeders is set either mechanically (on a sprocket-chain mechanism) or using an electronic controller on modern seeders. For most cereals and soybeans, the seeding rate is set by weight on mechanical and pneumatic seeders. However, the control of the seed rate in a row is carried out only visually by counting the number of seeds per linear meter.
To simplify the calculations, mathematical coefficients are used, which are presented in the tables depending on the row spacing.
Calculation algorithm:
- The traditional unit of area measurement for Ukraine and Europe is 1 hectare (hectare)
- The area of 1 hectare is 10000m 2 , i.e. a conditional plot of 100m in length and 100m in width - 100m*100m
- To simplify the calculation of the number (density) of plants on an area of 1 hectare, coefficients are used depending on the row spacing of the sown crop
- To determine the calculation coefficient, a prerequisite is a fixed row spacing, which traditionally can be 12.5cm, 15.0cm, 30cm, 45cm, 70cm.
- The coefficient is determined by dividing the area of 1 ha by the row spacing in cm
Coefficients for determining the density of sowing of agricultural crops, the seeding rate of which is calculated in millions of pieces per 1 ha (million pieces/ha)
Row spacing, cm | Main crops sown (in million units/ha) | Algorithm for determining the coefficient | Coefficient for calculations |
12,5 | cereal grains | 1/12,5=0,0800 | 0,0800 |
15 | cereals, soybeans, winter rape | 1/15=0,0667 | 0,0667 |
30 | 1/30=0,0333 | 0,0333 |
Coefficients for determining the density of sowing of agricultural crops, the seeding rate of which is calculated in thousands of pieces per 1 ha (thousand pieces/ha)
Row spacing, cm | Main crops sown (in thousand units/ha) | Algorithm for determining the coefficient | Coefficient for calculations |
45 | soybeans, sugar beet, winter rape | 1/45*1000=22,2 | 22,2 |
70 | sunflower, corn, sorghum | 1/70*1000=14,3 | 14,3 |
How to use these coefficients?
Example.
The recommended stem density for one of the corn hybrids is 85 thousand units/ha.
Seed germination according to laboratory data is 95%;
Purity - 99.95%;
The quantitative seeding rate can be determined as follows:
- We calculate the sowing suitability of seeds using the formula: X=A*B/100
where X is the sowing suitability, %.
A - purity or seed of the main crop, %;
B - seed germination, %,
That is, 99.95*95/100 = 94.95%.
- The physical seeding rate is determined by the formula: N=R*100/X
where N is the physical seeding rate, thousand units/ha
R - recommended planting density, thousand units/ha
X - sowing suitability, %.
So, 85*100/94.95 = 89.5 thousand units/ha
According to the calculation, to ensure the recommended density of corn plants per 1 ha of 85 thousand units/ha, 89.5 thousand units/ha must be physically sown.
It is necessary to determine the quantitative seeding rate per 1 running meter and adjust the seeder to the specified rate:
89.5 thousand units/ha: 14.3 = 6.25 pcs./m.
We found that in order to achieve the predicted corn stalk density of 85 thousand units/ha at harvest, it is necessary to sow 6.25 seeds per 1 running meter, i.e. the distance between the seeds in the row should be:
100cm : 6.25pcs/m = 16cm.
According to this indicator, we adjust the seeder.
To control the sowing in the field, after the passage of the seeder, count the sown seeds in the row at a distance of 14.3 m. Their number should correspond to 88-91 pcs. In this case, the seeder is adjusted correctly and allows sowing with a given density.
Similar calculations are made for other crops according to the recommended seeding rates, germination and seed purity depending on the row spacing.
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