The occurrence of seed losses in the sowing process causes serious problems in the establishment of planting areas, and is also one of the main factors for evaluating the efficiency of seeders. In this context, few studies have been concerned with continuous seeders, those that sow small seeds (rice, wheat, sorghum, etc.). Continuous seeders have the specificity of having constant-flow seed metering mechanisms, that is, they do not have the individual separation, collection and deposition action of seeds like precision seeders. Thus, the processes related to seed loss, both in terms of seed breakage or damage to the embryo, as well as poor deposition in the soil, are of great importance in the final result of sowing.
Several authors point out in their studies that the uniformity of longitudinal seed distribution is one of the characteristics that most contribute to an adequate plant stand and, consequently, to improving crop productivity. However, few studies regarding seed losses due to damage or poor deposition are available.
The experiment was conducted in the experimental field of the Department of Agricultural Engineering at the Center for Agricultural Sciences at the Federal University of Ceará (CCA-UFC), state of Ceará. The soil where the experiment was carried out is classified as a Red Yellow Argisol with a textural class classified as sandy loam (Embrapa, 1999). The continuous flow seeder used to carry out the test was the SDA³ model from the Tatu brand.
The setting was determined for the deposition of 80 rice seeds/linear meter and 2,5cm depth in experiments with speeds of 4 and 8km/h. In the lines, one-meter spaces were randomly selected for evaluation. Data analyzed using Minitab statistical software, in a completely randomized design.
At each speed, the number of broken seeds (with visible damage to the seeds), basketed seeds (those that, although they were in the furrow at the correct depth, were not in contact with the soil, but in baskets of plant residue) and exposed ( those in which the soil covering process was not carried out on them, both in the furrow and outside it). Data that did not have a normal statistical distribution were treated using the Exponentially Weighted Moving Average (EWMA) statistical technique, which made it possible to evaluate the stability of the data and thus the performance of the seeder within the recommended loss limits. The data that were normal were tested using analysis of variance (Anova) and Tukey's test, which allows evaluating the difference between the different types of losses.
Carrying out the experiment in the field, note the detail of the exposed seeds.
Table 1 contains descriptive statistics for evaluating losses in the sowing process. It is important to note the coefficient of variation (CV) which indicates how much amplitude there is between losses considering the average value obtained for each type of loss.
Table 1 - Descriptive statistics for evaluating losses in continuous flow sowing
Vel. 4 km.h-1 | Vel. 8 km.h-1 | |||||
Exposed | Baskets | Gorges | Exposed | Baskets | Gorges | |
Notes | 20 | 20 | 20 | 20 | 20 | 20 |
Media | 4,8 | 2,7 | 0,25 | 4,45 | 5,35 | 0,45 |
Standard deviation | 3,53 | 2,77 | 0,55 | 3,12 | 4,09 | 0,68 |
Variance | 12,48 | 7,69 | 0,3 | 9,73 | 16,76 | 0,47 |
Coefficient of variation (CV) | 73,61 | 102,74 | 220,05 | 70,11 | 73,53 | 152,52 |
Maximum | 16 | 8 | 2 | 10 | 16 | 2 |
Minimum | 0 | 0 | 0 | 0 | 0 | 0 |
Symmetry | 1,68 | 0,94 | 2,24 | 0,25 | 0,95 | 1,28 |
Kurtosis | 4,56 | -0,41 | 4,66 | -1,54 | 0,96 | 0,54 |
Vel. 4 km.h-1
Vel. 8 km.h-1
Exposed
Baskets
Gorges
Exposed
Baskets
Gorges
Notes
20
20
20
20
20
20
Media
4,8
2,7
0,25
4,45
5,35
0,45
Standard deviation
3,53
2,77
0,55
3,12
4,09
0,68
Variance
12,48
7,69
0,3
9,73
16,76
0,47
Coefficient of variation (CV)
73,61
102,74
220,05
70,11
73,53
152,52
Maximum
16
8
2
10
16
2
Minimum
0
0
0
0
0
0
Symmetry
1,68
0,94
2,24
0,25
0,95
1,28
Kurtosis
4,56
-0,41
4,66
-1,54
0,96
0,54
For seeds exposed and broken at 4km/h there was no normality in the data, we then continued with the Exponentially Weighted Average (EWMA) for the data in question, Figure 1 shows the results. According to Montgomery (2004), if all these points are within the specified limits, that is, upper and lower limits, it is considered that there was stability in the studied process, however, it is possible to observe that in both figures there are points outside the limits of control specified by the upper limit and lower limit, showing that the process presented great variability, which is attested by the coefficient of variation shown in Table 1, but, according to Barros (2008), if 95% of the sampling points are within the limits specified, the process is considered stable.
Therefore, in terms of exposed seeds and broken seeds at 4km/h, sowing can be considered as a stabilized process, although with great variation, which denotes the need for more precise and appropriate adjustments on the seeder.
Figure 1 - Representation of the Exponentially Weighted Moving Average (EWMA) for exposed and broken seeds at speeds 4km/h, where the data abnormality is verified
From Figure 1 it can be seen that even with an abnormality in the distribution, only one point fell outside the limits established by statistics.
The Analysis of Variance (Anova) for the basketed seeds, the speed of 4 and 8km/h in Table 2 and the Tukey test in Table 3, it is clear that there is a difference between the basketing of the seeds. The speed of 8km/h resulted in almost twice as many seeds being basketed, which means that the farmer needs to pay special attention to the pressure on the waste cutting disc at this speed, as studies indicate that the main factor that influences basketing is poor quality of cutting waste on the ground.
In relation to broken and exposed seeds by comparing Figure 1 and the values presented in Table 1, both variables can be considered stable and that in terms of exposed seeds there is no difference between the highest and lowest speed, but In relation to broken seeds, the highest speed showed almost double the number of breaks.
Tabela 2 – Anova for basketed seeds at speeds 4 and 8km/h
Source | DF | SS | MS | F | P |
Factor | 1 | 1,2 | 1,2 | 0,11 | 0,742 |
Error | 38 | 422,1 | 11,1 | ||
Total | 38 | 423,4 | |||
S = 3,497 R-Sq = 13,13% R-Sq(adj) = 10,84>#/b### | |||||
Source
DF
SS
MS
F
P
Factor
1
1,2
1,2
0,11
0,742
Error
38
422,1
11,1
Total
38
423,4
S = 3,497 R-Sq = 13,13% R-Sq(adj) = 10,84>#/b###
Table 3 - Data grouping using the Tukey test
Grouping information using the Tukey test N Mean Grouping Baskets Speed 8km/h 20 5,350 A Baskets Speed 4km/h 20 2,700 B |
Grouping information using the Tukey test
N Mean Grouping
Baskets Speed 8km/h 20 5,350 A
Baskets Speed 4km/h 20 2,700 B
Thus, the seeder proved to be suitable for planting rice seeds in the edaphoclimatic conditions of the soil in question, the dosing mechanisms are in perfect working order. The basketed seeds were influenced by the sowing speed and the losses were not severe enough to cause problems with the establishment of the rice crop.
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