# Simulation of Sowing Precision in Laboratory Conditions
## 2 Materials and Methods
### Tests under Laboratory Conditions
By means of accelerometers, the vibrations (accelerations) induced in the row unit were measured and the rubber hemispheres were repositioned on the belt until the vibrations power spectrums were similar to the ones of the plots actually sown. The operation was repeated to simulate the vibrations measured on the two other plots, determining, at the same time on the stand, the sowing precision in three repetitions for the row unit of the studied planter (according to ISO 7256/1-92) [68]. Thus, the sowing precision was determined, using as a reference element the theoretical (adjusted) interval between seeds in the row \(x_{r\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\!\! Figure 10: Power spectrum of vibrations during sowing on plot P2 at the working speed of 4 km\(\cdot\)h\({}^{-1}\). Figure 9: Vibration evolution during sowing on plot P2 at the working speed of 4 km\(\cdot\)h\({}^{-1}\). It was observed that the row unit had a slight tendency to reduce the interval between the seeds sown below the adjusted one \(X_{average}<1\), with the sowing precision being 95.36%. For the sowing precision diagram of the BV row unit, for the density of 50,000 corn plants-ha\({}^{-1}\) and the working speed of 4 km-h\({}^{-1}\) (determined in stationary conditions without vibration), and using the Mathcad program, the equation for the sowing precision variation curve was obtained (Figure 11), with the number of seeds, \(n_{i}\), reported to the sowing intervals \(X_{i}\). The equation represents a Gaussian distribution of the sowed seeds, desirable for this type of process. It should be noted that the sowing precision determined in stationary conditions on the stand decreased (from 95.36% to 92.55%) with the increase of the working speed (from 4 km-h to 6 km/h), however, reaching the imposed quality limits. Based on the recorded vibrations under exploitation conditions, the stand was calibrated and tests were performed on the same row unit. Table 6 presents the results of seed distribution and determination by simulating the operating conditions of the quality indices of the BV row unit, for a density of 50,000 corn  
Figure 11: Diagram of the studied row unit’s sowing precision (in stationary conditions) for the density of 50,000 corn plants-ha\({}^{-1}\) and the working speed of 4 km-h\({}^{-1}\), repetition 1. \begin{table}
\begin{tabular}{l c c c} \hline \hline \multicolumn{1}{c}{**Characteristics**} & \multicolumn{3}{c}{**Repetitions**} \\ \cline{2-4}
**According ISO 7256/1-92** & **R1** & **R2** & **R3** \\ \hline I 0 \(<X_{i}\leq 0.5\) & (double sowing) & 8 & 5 & 8 \\ II 0.5 \(<X_{i}\leq 1.5\) & (correct sowing) & 482 & 482 & 480 \\ III 1.5 \(<X_{i}\leq 2.5\) & (missing sowing) & 4 & 7 & 9 \\ IV 2.5 \(<X_{i}\leq 3.5\) & (missing sowing) & 6 & 6 & 3 \\ V 3.5 \(<X_{i}\) & (missing sowing) & 0 & 0 & 0 \\ Real intervals & 500 & 500 & 500 & 500 \\ Theoretical intervals & 508 & 514 & 507 \\ Doubles & 8 & 5 & 8 \\ Normally sown seeds & 484 & 490 & 484 \\ Missing planting holes & 16 & 19 & 15 \\ \(X_{average}\) & 0.987 & 0.996 & 0.992 \\ \hline Feeding quality index \(A\) (\%) & 95.27 & 95.33 & 95.46 \\ Doubles index \(D\) (\%) & 1.57 & 0.97 & 1.58 \\ Missing planting holes index \(M\) (\%) & 3.16 & 3.70 & 2.96 \\ Theoretical deviation \(\sigma\) & 0.091 & 0.091 & 0.092 \\ Coefficient of variation \(CV\) (\%) & 9.055 & 9.132 & 9.255 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Seed distribution and determination, in stationary conditions, of the quality indices of the studied row unit, for a density of 50,000 corn plants-ha\({}^{-1}\) and a working speed of 4 km-h\({}^{-1}\). plants-ha\({}^{-1}\) and the working speed of 4 km\(\cdot\)h\({}^{-1}\), on the plot with appropriate degree of seedbed processing. It was observed that the row unit had an increased tendency to reduce the interval between the seeds sown below the adjusted one \(X_{average}<1\), and the sowing precision was 92.51%.