The development of new technologies that aim at increasing the efficiency of nitrogen (N) fertilizers is essential for the agricultural sustainability. Thus, this study aimed at evaluating the cotton plants response to different topdressing N sources, under no-till system, in the Brazilian Savannah, in the 2008/2009 and 2009/2010 growing seasons. Treatments consisted of three N sources (urea, urea with urease inhibitor and ammonium nitrate) and two topdressing N fertilization applications (one application at V5 and two applications, as it follows: 50% at V5 + 50% at B6), plus a control (without topdressing N). The ammonium nitrate application provided the best results for both seasons, while the urea with urease inhibitor differed from urea only in the first season. The topdressing N fertilization provided different results among crops, being dependent of environmental conditions. If there is sufficient rainfall to incorporate the N to soil, better yields can be expected, when all the topdressing fertilization takes place at the V5 stage.
Gossypium hirsutum L.; urease inhibitor; topdressing fertilization
