Loss reducer in the fertilizer spreader

Loss-reducing mechanism in the fertilizer distributor helps maintain flow in different vertical working inclinations and humidity conditions.

Brazilian agriculture is increasingly technological, both in the area of ​​seeds, manifested by cultivars with high productive potential in adverse conditions, and - and especially - in the area of ​​agricultural mechanization, with machines and agricultural implements equipped with sensors and increasingly autonomous. . Each year the country's production increases without expanding the area, however, the genetic potential of the main commodities is not yet being reached.

The productive potential of a crop is directly related to the condition of the environment in which the plant will develop, being closely related to its sowing. Therefore, problems in this operation compromise productivity, resulting in a reduction in the profitability of the activity. When sowing, one of the problems is the variation in fertilizer dosage using helical screw type dosers. According to Frantz et al (2011), of 292 seeder models analyzed, 89,38% use a helical screw type doser, thus qualifying as the most used in the country.

Fertilizer dosing in this system takes place through the rotational movement of a helical screw, in which the transported material fills the space between the helicoid, after which it is moved from the reservoir to the conductor tube and from there to the groove in the soil. This doser is found on the Brazilian market in basically three models: gravity screw (which we will call DRHg), overflow (which we will call DHt) and/or side overflow. Research shows variations in DRHg of up to 50% (Portella et al, 1998), this in the laboratory, when taking measurements in the field, our research demonstrated variations of up to 71,62%. Some research points to a drastic reduction in variation when using overflow dosers, by up to 30%, compared to gravity. The variation in screw dosers is due to variations in rotation speed, terrain slope and fertilizer moisture, especially the fertilizer particle size.

In view of this scenario, the Center for Soil and Agricultural Machine Studies (Nesma), of the Federal Institute of Education, Science and Technology of Rio Grande do Sul Campus Sertão, has been developing research for five years with such dosers, and sought in this work to evaluate the performance of this helical screw type fertilizer doser for overflow with a loss reducing mechanism working at different vertical working inclinations and fertilizer moisture conditions.

HOW WAS THE TEST CARRIED OUT?

The experiment was developed at Nesma at IFRS - Campus Sertão. The test was carried out in the laboratory, on a fertilizer doser test bench equipped with inclination adjustments in longitudinal and transverse directions. At the bottom of the bench there was a treadmill, which was driven by an induction motor with a constant speed of 5,04 m/s. The doser used for the test was the helical screw type for overflow, commercially called Fertisystem, working with a rotation of 60rpm.

A loss-reducing mechanism was developed, which reduces the internal space of the screw, which is one of the influencers of fertilizer distribution variation. Therefore, the treatments under study were the presence of this loss reduction mechanism, which we will use the acronym Mred, and its absence, SMred, working at three working inclinations, thus simulating sowing at 0°, +11° and - 11°, level, slope and slope, respectively, with dry and wet fertilizers. The granulated fertilizer used had the formula 2-23-23, in normal conditions it had a moisture content of 4,9%, and was then moistened up to 9,8%.

The fertilizer doser was equipped with an internal filling mechanism made of one piece, manufactured in technology, containing an exact internal dimension to the thread transmission shaft, thus eliminating any play. The dosed fertilizer was collected to evaluate distribution in a gutter with collection pots, thus simulating a linear displacement.

The coefficient of variation of fertilizer distribution was analyzed, as well as the amplitude of the data (difference from largest to smallest), with a statistical evaluation carried out using the Tukey test at 5%.

WHAT WERE THE RESULTS

The loss reducing mechanism demonstrated lower distribution amplitude indexes (Ad), as shown in Table 1, being 5,35g versus 8,59g for the doser without this mechanism, this difference will cause a variation of up to 150kg of fertilizer per hectare, considering sowing with a spacing of 0,40m between rows. 

Regarding humidity, one of the items that generate the most problems in the field due to the crusting of fertilizers on the dosing screws, it is clear that with the use of the loss reduction mechanism there was a reduction in amplitude from 9,16g to 7,35g, that is, dose peaks along the distribution line were reduced by 19,8%. It is necessary to emphasize that in these humid conditions fertilizer application should be avoided due to operational problems, although many times in the field some problems are beyond management.

The coefficient of variation (CVd) provides us with very important information when evaluating fertilizer dosers, as it is the value that tells us how the linear distribution of fertilizers is. We can see in Graph 1 a trend contrary to the amplitude data, in which the loss reduction mechanism (Mred) on average presented higher CVd rates. This will result in non-uniformity of plants, as there will be places with greater fertility and others with lower fertility.

In the different fertilizer moisture conditions, it is clear that the greatest variations occurred with the addition of moisture on the slope, 34,8% against 23,4% of the level and 10,8% on the slope. This fact is explained by the action of gravity, which is in favor of gravity, as seen in the drawing in Figure 1, where the exit nozzle is at a lower level than the supply.

When the loss reducing mechanism is removed, the slope is no longer the biggest problem, because as the fertilizer is more aggregated it ends up “holding itself”. The increase in CVd was 1,1% between dry and wet conditions, and the working condition that had the worst distribution was slope, in the order of 30,6%, compared to 23,6% in the level condition. This result must be related to the fact that the wet fertilizer aggregates in a larger volume under slope conditions and results in dosages of larger aggregates (acorns), which was seen in practice, instead of dosing in granules.

RESULTS

The loss reduction mechanism was efficient in reducing dosage peaks, however, there was a greater variation in fertilizer dosage along the line, thus leading to considerations that reducing the screw's internal space alone is not the solution technique.

In relation to the humidity condition of the fertilizer, with the doser working normally without the mechanism under study, in the dry condition there are greater variations in the slope, and with high humidity all conditions are worsened.

David Peres Da Rosa, Roger Toscan Spagnolo, Alisson Alves, Cesar Augusto Cansian, Marcos Longaretti, Nesma, IFRS – Campus Sertão

Article published in issue 170 of Cultivar Máquinas