Plantability performance of pneumatic seeders in the soybean culture implantation in the Piaui cerrado - Brasil

The identification of limit speed to make the sowing is important to take advantage of machines with pneumatic system, but is also necessary maintain adequate plantability. Faced with this problem, the objective of this study was to evaluate the performance of plantability of the pneumatic seeders in soybean implantation in Piaui cerrado (savanna). The study was conducted in the municipality of Baixa Grande do Ribeiro, southern Piaui state. The experiment was arranged in a completely randomized design (CRD) in factorial arrangement (2x4), with three replications. Therefore, the first factor was compound by models seeders John Deere (R) (BT2117 and DB740) and the second factor, by four forward speeds of the seeder during operation (V1 = 5,6 km h(-1), V2 = 7,0 km h(-1), V3 = 8,6 km h(-1) e V4 = 10,0 km h(-1)). The plantability was evaluated by checking the number of plants / seeds distributed with seeders, uniformity of planting, spacing acceptable, flawed and double between plants. In seeder John Deere (R) model 2117, with increased speed seeding of 5.6 km h(-1) to 10.0 km h(-1), the number of plants per linear meter is close to the established regulation of the machine. As for the seeder John Deere (R) DB74 model, the plant number value is lower than expected, with an average of 8.76 plants m(-1), (possible result failed regulation / machine calibration before installing the experiment). For both seeders, the percentage of acceptable spacings decreases as increases the travel speed, and flawed spacing increase with increase in speed, thus reducing the uniformity of planting.