Effect of nitrogen rates applying controlled-release and conventional urea blend in maize

Blending polymer-sulfur coated urea (PSCU) and conventional urea (U) for maize (Zea mays L.) fertilization can supply nitrogen (N) during the crop cycle with a single application. Proper placement of PSCU + U (0.15 m below and 0.1 m to the side of seed row) in band application at sowing is necessary to reduce salt stress that can decrease dry weight (DU) and N uptake (NU) of maize plant compromising maize yield. It is not clear the proper N rate in the proper placement for band application of PSCU + U at maize sowing to avoid salt stress. In the current literature, reduction of N rates are being recommended using PSCU + U without consider the probably salt stress provided by high rates of PSCU + U. DW and NU in maize plant as well as soil pH and electrical conductivity (EC) were evaluated in a greenhouse pot trial. N treatments were equivalent to 0, 90, 180, 360 and 540 kg N ha(-1) applied incorporated in band in two contrasting soils (Rhodic Eutrustox and Typic Haplustox) using 70%PSCU + 30%U. At V10 (vegetative leaf stage 10), DW and NU of maize aerial part had quadratic behavior in response to increase N rates in the Typic Haplustox soil. In the Rhodic Eutrustox was not observed known behavior for DW and NU in response to increase N rates. Soil pH and EC was higher in the fertilizer row than sowing row. A N rate above of 180 kg N ha(-1) using 70%PSCU + 30%U incorporated in bands can reduce DW and NU in early maize plant growth associated with salt concentration of N fertilizer in a Typic Haplustox soil, which could compromise maize yield.