# Simulation of Sowing Precision in Laboratory Conditions
## 2 Materials and Methods
### Tests under Laboratory Conditions
The histogram, which characterizes the sowing precision, was obtained based on the number of used seeds and the spaces between them, but this time with vibration simulation based on real exploitation conditions. Figure 12 shows 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\(\cdot\)h\({}^{-1}\) (by simulating the operating conditions). Compared to Figure 11 (sowing precision determined in stationary conditions), Figure 12, \begin{table}
\begin{tabular}{c c c c} \hline \hline \multicolumn{2}{c}{**Characteristics**} & \multicolumn{2}{c}{**Repetitions**} \\ \multicolumn{2}{c}{**According ISO 7256/1-92**} & **R1** & **R2** & **R3** \\ \hline I 0 \(<X_{i}\leq 0.5\) & (double sowing) & 20 & 14 & 6 \\ II 0.5 \(<X_{i}\leq 1.5\) & (correct sowing) & 469 & 469 & 462 \\ III 1.5 \(<X_{i}\leq 2.5\) & (missing sowing) & 6 & 9 & 31 \\ IV 2.5 \(<X_{i}\leq 3.5\) & (missing sowing) & 5 & 7 & 1 \\ V 3.5 \(<X_{i}\) & (missing sowing) & 0 & 0 & 0 \\ Real intervals & 500 & 500 & 500 \\ Theoretical intervals & 496 & 512 & 527 \\ Doubles & 20 & 14 & 6 \\ Normally sown seeds & 460 & 472 & 488 \\ Missing planting holes & 11 & 16 & 32 \\ \(X_{average}\) & 0.878 & 1.082 & 0.998 \\ \hline Feeding quality index \(A\) (\%) & 92.74 & 92.18 & 92.59 \\ Doubles index \(D\) (\%) & 4.03 & 2.73 & 1.13 \\ Missing planting holes index \(M\) (\%) & 3.23 & 5.09 & 6.28 \\ Theoretical deviation \(\sigma\) & 0.120 & 0.128 & 0.139 \\ Coefficient of variation \(CV\) (\%) & 12.003 & 12.825 & 13.984 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Seed distribution and determination of the quality indices of the BV row unit, for a density of 50,000 corn plants-ha\({}^{-1}\) and the working speed of 4 km\(\cdot\)h\({}^{-1}\), on the plot with appropriate degree of seedbed processing. Figure 12: Diagram of the studied row unit’s sowing precision (simulation of operating conditions) for the density of 50,000 plants-ha\({}^{-1}\) and the working speed of 4 km\(\cdot\)h\({}^{-1}\), repetition 1.  
which represents sowing precision obtained by simulating the real exploitation conditions in terms of supported vibrations, better represented the actual performance of the row unit. It could be observed that there was a slight decrease in performance due to the simulated vibrations. The equation corresponding to Figure 12 showed the same Gaussian distribution and can be used to predict the sowing precision with better accuracy. Table 7 presents the values of the sowing precision by simulating the operating conditions on the stand. It was observed that there was a decrease in the sowing precision with the increase of speed, which is a common aspect for all the working speeds used during the tests. Referring to Section 2.2, it was found that:  
* In the first stage, which aimed to measure the stresses, induced in the mechanical structures of the precision plinters in contact with the soil during movement, on three work plots with a different degree of seedbed preparation: 1. The accelerations (vibrations), induced by the action of the running surface in the row unit and in the bar-frame of the seeder, registered an increasing value in amplitude at the same time as the transition to a higher gear; 2. The amplitude of the accelerations (vibrations), measured when sowing was made on a plot with a degree of inadequate seedbed preparation (plots 1 and 3), increased compared to the case of plot (2) and worked properly, having the granulation of soil particles less than 50 mm.