Impacts of seeding speed

Increasing seeding speed can be an alternative to increase the operational capacity of the seeder tractor set. However, a study shows that this practice greatly reduces the profitability obtained per hectare.

With the increase in population, food production also had to increase. However, the expansion of areas did not grow in proportion to the increase in demand. As a result, farmers are increasingly seeking to increase crop productivity, producing more in the same area.

What is also noticeable is a reduction in the planting window, due to climate changes that altered the characteristics of the seasons. One of the ways used by producers is to increase the sowing speed, thus increasing the number of hectares sown per hour/day to stay within the window. However, before making this decision, some points must be evaluated, such as the impact on productivity and consequently on profitability due to higher speed sowing being carried out without corrective mechanisms, which may cause a reduction in productivity, directly affecting the producer's net income.

Among the seeders on the market, those that use the pneumatic system have better seed distribution due to the construction characteristics of this dosing system. With better seed distribution we have a higher percentage of acceptable spacing between plants, thus reducing the Coefficient of Variation (CV), reducing losses caused by poor distribution at the time of sowing.

Increasing sowing speed has a direct influence on the number of plants distributed per linear meter, as well as on their arrangement, that is, with increasing speed, distribution between plants tends to be uneven due to greater vibration of seed deposition mechanisms. . This non-uniformity is not desired, as the corn crop is very sensitive to changes in spacing. Sowing at high speed, without adequate and correctly adjusted compensation mechanisms, can cause failures (too long spacing between plants) and/or double seeds, which can generate dominated plants, that is, plants that do not show the expected development due to competition for nutrients.

To determine the quality of a sowing, a mathematical index is used, called Coefficient of Variation (CV). This index represents in % how much seed arrangement varies depending on the average spacing, thus a better distribution is related to a lower CV value. The smaller the CV means that there was less variation in the size of the spacings and consequently greater productivity.

This work was carried out at Fatec Shunji Nishimura de Tecnologia, located in Pompéia (SP), in the experimental area of ​​the Mechanized Harvest Study Group (Gecom) and aimed to evaluate the impact of increasing speed on productivity and profitability. Soil amendment consisted of 500 kg/ha of gypsum and 1000 kg/ha of limestone. Fertilization in the furrow was 200 kg/ha of simple superphosphate and top dressing carried out 28 days after emergence, with application of 90 kg/ha of urea. The total experimental area was 1ha. Sowing was carried out with MORGAN 30A37 hybrid corn seeds in a direct planting system on spontaneous vegetation straw. A fertilizer seeder from the Jumil brand, model JM3090, with seven rows, at a spacing of 0,5 m, with a pneumatic vertical disc doser, was used.

The treatments consisted of two sowing speeds V1= 5,5 km/h and V2=6,5 km/h calculated using the gear scaling table, where the speed variation was made as shown in Table 1.

Two assessments of the spacing between plants were carried out, the first post-emergence and the second pre-harvest. Each sampling was composed of two 5-meter lines from a georeferenced central point, 2,5m to the right and 2,5m to the left. The plant count was always carried out on the 5 central lines, in order to prevent any line located closer to the other area from suffering any type of interference.

The harvest was carried out manually 5 months after planting, making it possible to weigh each sample separately and check the humidity at the time of weighing.

With data collection and processing, the following data were obtained.

Analyzing Graph 1, we can conclude that when sowing is carried out at a speed of 5,5 km/ha, there is an increase of 10500 plants in the stand obtained compared to a speed of 6,5 km/ha (an increase of 14,38%).

Analyzing the coefficient of variation, a variation in productivity (SC/ha) was noted, as shown in graph 2. With a speed of 5,5 km/ha, productivity was 83,72 sc/ha and the coefficient of variation in distance among plants it was 28,96%. At a speed of 6,5 km/ha, productivity was 77,136 sc/ha, 7,87% lower when compared to a speed of 5,5 km/ha. It was also noted that at a speed of 6,5 km/ha the coefficient of variation was 41,67%, an increase in the coefficient of variation by 12,71 percentage points (an increase of 30,05%).

Analyzing Graph 3, it was found that there was a reduction in the producer's profit with sowing at a speed of 6,5 km/ha of R$ 263,93 per hectare in relation to sowing at 5,5 km/ha (7,87 .XNUMX% less in profit).

With the knowledge of the results obtained, it was concluded that the increase in speed resulted in an increase in the coefficient of variation (30,05%) and consequently a reduction in the population of plants per hectare (14,38%), thus demonstrating that the control system was not able to adapt the number of plants per linear meter in order to maintain the stand's initial speed.

With the higher coefficient of variation and the smaller number of plants per hectare, consequently lower productivity (7,87%) and return to the producer, the only advantage that can be seen with the increase in speed was the greater operational capacity of the studied set.

The compensation mechanisms described above are linked to the vertical displacement of the seeding line, therefore the pressure springs of the seeding units must be adjusted correctly, to minimize the impacts of speed on the line (shaking in the carts). In seeders that use the vertical disc system, special attention must also be paid to the vacuum pressure in order to hold the seeds in the disc even with the increase in the seeder's travel speed.

Lara Marie Guanais Santos, Vinicius Andrade Favoni, Danilo Tedesco de Oliveira, Edson Massao Tanaka, FATEC Pompeii

Article published in issue 181 of Cultivar Máquinas, February, 2018.