Biotemas (Dec 2009)
Maize initial development as affected by nitrogen sources and rates at sowing time
Abstract
The growth of notillage has stimulated an increase in nitrogen applied at maize sowing time. This work was carried out aiming to evaluate the effects of nitrogen fertilizer sources and rates on maize germination. Two nitrogen sources (urea and ammonium sulfate) and four nitrogen rates (0, 50, 100 and 200kg ha-1) were tested in five soils with contrasting textures. The experimental units were plastic boxes that were 50cm long, 22cm wide and 13cm in deep. Four rows with 10 seeds sown 2.5cm apart from each other were used per box. Nitrogen fertilizers were applied 5cm deep in the sowing row. The addition of N in the form of urea at doses greater than 50kg ha-1 decreased maize germination in four of the five tested soils. The addition of ammonium sulfate only reduced maize germination in the soil with lowest clay content. Crescent N rates increased the soil’s electrical conductivity. This increment was higher with ammonium sulfate addition. Ammonia volatilization was more important than salinity to decrease maize germination when high rates of N fertilizers were used at sowing time.
