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The use of 15N tracers in blends of N-fertilizers contributes to determining the N derived from each N-fertilizer in the plant, improving the recommendation in the field. However, to evaluate the contribution of two 15N-labeled fertilizers to maize nutrition is an expensive process, and it is challenging to manufacture 15N-labeled controlled-release urea (CRU) considering a polymer-sulfur coated urea (PSCU). The objective of this study was to evaluate, in a field experiment, two methods to quantify the N derived from the PSCU (NdfPSCU) in maize plant using two blends (70% PSCU + 30% urea (U) and 30% PSCU + 70% U) applied in three ways (incorporated, broadcast and split application). The first method quantifies the NdfPSCU by subtracting the total N uptake in the N treatment by the sum of the N uptake in the control treatment (without N-fertilizer application) and the N derived from the U (NdfU) in the plant quantified with 15N. The second method quantifies the NdfPSCU using 15N (precise and direct method). Despite the first method is less expensive than the second it underestimated the NdfPSCU in four maize growth stages in Rhodic Eutrustox soil, being necessary the use of 15N in the PSCU to quantify the NdfPSCU with blends of PSCU + U. [ABSTRACT FROM AUTHOR]

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]

The common bean (Phaseolus vulgaris L.) requires nitrogen (N) during its vegetative and reproductive stages. A single application of a blend of polymer-sulfur coated urea (PSCU) and conventional urea (U) treated with NBPT (N-(n-butyl) thiophosphoric triamide) can meet that demand. Broadcast application could improve yield than other N management practices. This research evaluated two blends (70%PSCU + 30%U and 30%PSCU + 70%U) and three N fertilization managements (incorporated, broadcast, and split application) on soil ammonia volatilization (AV) and N mineral content (NM); plant N uptake (NU) and 15N recovery from U (NUR); and yield (GY). Irrigated field experiments were conducted in 2018 and 2019 in Rhodic Eutrustox soil. The N application rate was 90 kg ha−1. AV reached 12% (30%PSCU + 70%U, broadcast application) and 14% of the applied N (split application at the third trifoliate leaf unfolded stage (V4)). The incorporated application resulted in higher NM in the vegetative and reproductive stages than the other management practices. Broadcast application resulted in higher NU than split application at physiological maturity. Split application resulted in higher NUR (grain) and GY than broadcast application. There was a positive correlation between NUR (grain) and GY in all N fertilization management treatments. The NUR values reached 48% (30%PSCU + 70%U) and 18% (70%PSCU + 30%U). Split N application using these blends can improve NUR in grain and GY compared to broadcast application in Rhodic Eutrustox soil. This information can help farmers improve the fertilization management practices used with these blends, and thereby avoid economic losses and environmental pollution. [ABSTRACT FROM AUTHOR]

A single application of polymer-sulfur coated urea (PSCU) and conventional urea (U) is expected to ensure nitrogen (N) throughout the maize (Zea mays L.) growth cycle being U the likely main N-fertilizer supplier at the beginning and PSCU during the maize growth cycle. This research aimed to evaluate N fertilization management (split, incorporated, and broadcast application) and fertilizer blends (30%PSCU + 70%U and 70%PSCU + 30%U) on volatilization of ammonia (AV) and soil N mineral content (NM); plant N uptake (NU) and 15N-fertilizer recovery (NR); and yield (GY). Field experiments were conducted for two growing seasons (2017–2018 and 2019–2020) in Rhodic Eutrustox soil. U was treated with NBPT (N-(n-butyl) thiophosphoric triamide). N rate was 180 kg ha−1. AV reached 12% of the applied N (broadcast-applied 70%PSCU + 30%U, 2017–2018). The 30%PSCU + 70%U application resulted in higher NM at 40–60 cm depth in vegetative and reproductive stages in both seasons. The 70%PSCU + 30%U application resulted in the highest GY in 2017–2018, and the N treatments did not affect GY in 2019–2020. NR was 3% on average at vegetative leaf stage 4 (V4), and PSCU, the main N-fertilizer supplier applying 70%PSCU + 30%U. After V4, the main N-fertilizer supplier is PSCU for 70%PSCU + 30%U and U for 30%PSCU + 70%U application. These blends (incorporated, broadcast, and split application) can ensure N during the maize growth cycle, with NR of 72.5% at maturity (R6) being 47.9% in the grain. [ABSTRACT FROM AUTHOR]