Maximum Contact Time of “Piatã Grass” Brachiaria brizantha (Poaceae) Seeds with Fertilizer for Germination

Data regarding the mixing of palisade grass seeds with fertilizers are scarce and contradictory. The aim of this study was to evaluate the maximum contact time without significant damage on physiological quality of Piatã grass seeds when mixed with 05:25:15 NPK fertilizer. The experiment was conducted in a completely randomized design with six treatments and four replications. Treatments consisted of six contact times of the seeds with the fertilizer: 0, 24, 48, 72, 96 and 120 hours. The variables following variables were evaluated: water content, germination percentage, first germination count, seed viability, eletrical conductivity, accelerated aging, emergence percentage and emergence speed index. Except for the water content, there was an effect of the fertilizer contact times with the seeds over all variables. There was a decreasing linear effect of the contact time of the seeds with the fertilizer for all variables, except for electrical conductivity. The average water content of 10.09% was observed. After 120 hours of the fertilizer/seeds mixture, a reduction of 36.4% was observed in germination, of 36.7% in the first germination count, of 25.0% in seed viability, and of 65.0% in the germination of seeds subjected to the accelerated aging. There was an increase of 170.0% in the electrical conductivity of the Piatã grass seeds. The minimum standard of 60% germination, viability or emergence, required for the commercialization of forage seeds, should be maintained to ensure the ideal forage population in the establishment of the crop. Based on the emergence and viability tests, the commercialization levels can be maintained by performing the fertilizer/seeds mixture up to 63 hours before sowing. After 63 hours of seed and fertilizer mixing, a reduction of the initial vigor of the seeds can be observed, although not compromising the crop establishment or causing degradation of soil. Therefore, Piatã grass seeds can be mixed with the 05:25:15 NPK fertilizer up to 63 hours before sowing.