Influence of either operational speed and the pressure applied on compress wheels in the initial establishment of the maize crop under no-till system / Influência da velocidade operacional e da carga aplicada pelas rodas compactadoras sobre o estabelecimento inicial da cultura do milho em sistema de plantio direto

Wagner Santos Gonçalves

Since Brazil is one of the main maize producers throughout the world, this crop becomes an important target for research. To obtain the successful implantation of the crop, a good soil-seed contact should be promoted, besides to be careful about the good distribution of the plantlets. The no-till planting minimizes the undesirable effects from the preparation of the soil and can be adopted as a measure to favoring the sustainability of the productive systems. This study was carried out to evaluate the effects from the combination between displacement speeds and the loads applied by the compress wheel of the seeder-fertilizer machine upon the emergency of the plantlets and initial development of the maize crop in the no-till system. The assays were conducted on December 2006, in the Universidade Federal de Viçosa, Viçosa county MG. Twelve treatments were used under an entirely randomized experimental design, under the factorial scheme 3x4 with four replicates. Three displacement speeds of the seeder machine (V1 = 1.11, V2 = 1.67 and V3 = 2.22 m s-1) were used with four loads applied by the compacting wheels (C1 = 119.26, C2 = 131.11, C3 = 257 and C4 = 339 N). The different pressures were adjusted according to the compression pressure of two springs in each planting unit of the seeder machine. In a cambic yellow-red Argisol, the following were used: tractor Massey Ferguson, model 265 4x2 TDA (auxiliary-front drive) and a seeder-fertilizer for no-till planting, Seed-Max, model PC 2123. A pressure cell was adapted between the structures of the compression wheels and the seeder in order to measure the applied loads. The sowing depth, the percentage and emergence speed index of the plantlets, the plantlet heights, the masses of the green and dry matters in plantlets and the uniformity of longitudinal seed distribution were evaluated, by using the lacking spacing classification (when higher than 1.5 the wanted one), double (when lower than 0.5 the wanted one) and acceptable (between 1.5 and 0.5 the wanted one). Effects of the different loads were observed for depth of the seed depositions. The C4 load caused a lower deposition depth of the seeds than C2 load. This fact shows the highest flattening of the soil layer on the seed with C4 load, because the pressure by the compress wheels. No interaction occurred between factors, as well as no significant differences were found for the evaluated speeds. For the other characteristics under evaluation, no effect of the displacement speeds and the loads applied by the compress wheels were found and no interaction among them. The average emergency of the plantlets was 56% and occurred between six and 12 days after sowing. The average height of the plantlets was 0.16m, and the average mass of the green and dry matters were 67 and 7g, respectively. Under the conditions this study was carried out, the loads applied by the compress wheels and the displacement speeds used for seeding had no influence upon emergency and initial establishment of the maize crop.

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