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A single application of polymer-sulfur coated urea (PSCU) and conventional urea (U) blends can supply nitrogen (N) throughout the maize (Zea mays L.) cycle but it could become harmful for plants if not properly placed in the soil due to a possible salt stress which would reduce dry weight (DW) and N uptake (NU) in maize. DW and NU in maize plant as well as soil pH and electrical conductive (EC) were evaluated in a greenhouse pot trial. Treatments consisted of different placements (0.05, 0.1 and 0.15 m below and 0, 0.05 and 0.1 m to the side of seed row) of fertilizers (70%PSCU + 30%U, and 100%U) applied at maize sowing in band at a rate equivalent to 180 kg N ha−1 in a Rhodic Eutrustox soil. Control treatment (without N) was also included. At V7 (vegetative leaf stage 7), N fertilizers placed 0.15 m below of seed row provided higher total DW, total NU, EC and pH (in fertilizer row) than 0.05 m and 0.1 m. 70%PSCU + 30%U provided higher total DW and total NU than 100%U in placement 0 m. In addition, 70%PSCU + 30%U placed 0.1 m to the side of seed row provided lower total NU and EC (in fertilizer row) than 0 m. 70%PSCU + 30%U and 100%U placement can negatively interfere maize in vegetative stage when applied incorporated in band at sowing. The proper placement for this condition was 0.15 m below and 0.1 m to the side of seed row. [ABSTRACT FROM AUTHOR]

Urea treated with urease inhibitors (UI) in association with humic substances (HS) is expected to improve urea efficiency by reducing ammonia losses and also provide the benefits of HS such as improve nitrogen (N) recovery by plants. Ammonia volatilization (AV), 15N recovery efficiency in the soil (NRE) and 15N use efficiency (NUE) were evaluated in maize (Zea mays L.) in a greenhouse pot trial. Treatments consisted of 15N-urea treated with UI (0, 0.4% boron (B) +0.15% copper (Cu), 0.64% B, and NBPT (N-(n-butyl) thiophosphoric triamide)) and three levels of HS (0%, 0.6%, and 1.2%). A control treatment (without N) was also included. N treatments were applied at V4 (vegetative leaf stage 4) on soil surface. HS was not efficient on AV reduction, NBPT had the greatest reduction in AV, and B had higher efficiency on AV reduction than Cu. At V8 (vegetative leaf stage 8), NBPT had the greatest NUE followed by B. At VT (tassel fully emerged), NUE from urea treated with NBPT reduced when increased levels of HS, and NBPT had the greatest NRE. UI in association with HS treated-urea does not reduce AV and it does not improve NUE by maize in vegetative stages. [ABSTRACT FROM AUTHOR]