# Simulation of Sowing Precision in Laboratory Conditions
###### Abstract
Experimental research on the seed meters precision planners has highlighted the following ideas:  
* Mechanical seed meters require a much more precise adaptation of hole sizes to the seed sizes of the crops to be sown [9];
* The diameters of the holes in the distributing discs of mechanical seed meters must be approximately 10% larger than the seed diameters [10];
* Sowing precision is higher for pneumatically assisted seed meters [10];
* Seed meters' drive can be mechanical, electrical or hydraulic [11];
* Eliminating seed surplus from the holes of the distributing discs is done by means of a singulator of different shapes;
* The removal of broken seeds and residues that can clog the holes of the distribution discs is done by means of: ejector wheels that are interchangeable depending on the crop to be sown [12]; ball rod devices actuated by means of a spring which enters the holes of the distributing disc after passing the seed release area into the guiding tube [13; 14]; and controlled penetration of free air into the depression chamber [15];
* Elimination of seed compaction inside the seed meters is ensured by mechanical means (agitators mounted on the drive shaft of the distributing disc, and vibrating mechanisms) and pneumatic means [16];
* To avoid collision of the seeds with the walls of their guiding tube towards the furrow and to manage the speed of seed inside the guiding tube, row units were built where the seed guiding tube was replaced with a brush belt that places the seeds at the bottom of the furrow according to agrotechnical norms [17; 18];
* The modular construction of the seed meters allows: rapid replacement of the distributing discs when different crops are sown, hence the distribution of various types of seeds; quick check of seed meters when disturbances of the optimal sowing process are found; easy filling and emptying at the beginning and end of sowing work; and the rapid cleaning of seed meters [19; 20]. Through their informational content, qualitative and quantitative in nature, the experimental research in the field of precision sowing aims to increase the efficiency of different constructive variants of seed meters by determining their qualitative working indices [21; 22; 23; 24; 25]. The factors that influence the sowing precision can be evaluated by comparative studies between various types of seed meters through laboratory research (on a specialized stand) [26; 27; 28]. In order to obtain a uniform distance between plants in a row, the precision planners manufactured thus far were equipped with different types of seed meters (mechanical and pneumatic). The efforts to continuously improve seed meters have been aimed at maximizing weed plant production [29; 30; 31]. To obtain a perfect spacing between plants, each seed must be separated and then launched from the seed meter into the seed guide tube in the furrow opened by the coulter, after a precise and repeatable period of time and trajectory [32; 33]. Studies showed that the sowing accuracy achieved by precision planners at traditional working speed falls within the agrotechnical norms, and the problems that appear with its increase were caused mainly by sliding and vibrations from drive chains [34; 35]. The influence of the planter working speed on the qualitative parameters of the sowing process was evaluated in theoretical research by dynamic and mathematical modeling of the oscillating system of the row units and experimental research carried out both on stand (in the laboratory) and under field conditions [36]. The sowing work can be done with or without the previous processing of the seedbed, and the placement of the seeds is done at a constant depth, at the base of a loose soil layer and above a more compact soil layer [37]. Sowing depth and seed spacing, in turn, play an important role in the amount of sunlight received; any delay in seedling development may be of major importance in competition with neighboring weeds or plants, which may adversely affect the yield of future crops [38; 39; 40].