Journal of Agricultural Science; Vol. 12, No. 11; 2020 ISSN 1916-9752 E-ISSN 1916-9760 Published by Canadian Center of Science and Education 98 Yield Response of Upland Rice as Influenced by Enhanced-Efficiency Nitrogen Fertilizers in the Brazilian Cerrado Vinícius Almeida Oliveira 1 , Eliana Paula Fernandes Brasil 2 , Welldy Gonçalves Teixeira 2 , Felipe Corrêa Veloso dos Santos 3 & Atila Reis da Silva 4 1 Faculdade Central Cristalinense, Cristalina, GO, Brazil 2 Federal University of Goiás, Goiânia, GO, Brazil 3 School of Engineering, Pontifical Catholic University of Rio de Janeiro, Goiânia, GO, Brazil 4 Instituto Federal Goiano, Goiânia, GO, Brazil Correspondence: Welldy Gonçalves Teixeira, Campus Samambaia, Agronomy School, Federal University of Goiás, Goiânia, Goiás, Brazil. Tel: 55-62-991-711-481. E-mail: welldygteixeira@gmail.com Received: June 22, 2020 Accepted: August 5, 2020 Online Published: October 15, 2020 doi:10.5539/jas.v12n11p98 URL: https://doi.org/10.5539/jas.v12n11p98 Abstract Nitrogen (N) fertilizers have their use efficiency adversely affected by the rate and source of N. A two-year field experiment was conducted to examine the yield response of upland rice by using NBPT (urease inhibitor), PCU (polymer-coated urea) and uncoated urea under different N application rates. It was hypothesized that either NPBT or PCU may result in increased yield components of upland rice when compared to conventional urea. The experiment was set up in a randomized block design in a 3 × 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha -1 ) of N, in addition to a control treatment (no fertilizer application). Nitrogen fertilizers were applied in two split doses: 50% at the seedling stage, and 50% at the tillering stage (~80 days after planting). The results revealed that the use of enhanced-efficiency N sources increased the productivity and plant height of upland rice crop when compared to conventional urea. As compared to when it is untreated or polymner-coated, treating urea with NBPT resulted in increased 100-grain weight. Keywords: grain yield, fertilizer efficiency, Oryza sativa L. 1. Introduction Rice (Oryza sativa L.) is one of the major food crops for more than 3.5 billion (> 50%) people in the world (CGIAR, 2016). It is a staple food in the diet of many developing countries, particularly in Asia, Latin America and Africa (Fageria et al., 2011). Based on FAO’s forecasts for cereal production, 516.8 million tonnes of rice was harvested in 2019, led by China and India (FAO, 2019). Brazil s among the ten largest rice producers worldwide, accounting for 7.2 million tonnes, down 11.7% from the previous year’s output because of the reduction in the planted area (FAO, 2019). The traditional methods for cultivating rice are known as upland rice and irrigated lowland rice, which are distinguished by the soil’s water availability. Due to lower yield as compared with flooded rice, upland rice contributes less than 40% of total rice production in Brazil (Barbosa Filho & Yamada, 2002). To produce high grain yields, modern rice cultivars require adequate amount of essential nutrients. Nitrrogen (N) fertilizers are extensively used by farmers to enhance rice crop production, as N is usually the most limiting nutrient except in soils containing high content of organic matter (V. B. Singh & V. K. Singh, 2017). Rice crops use 1 kg of N to produce 68 kg of grain (Witt et al., 1999). Deficiency of N in plants rapidly slows shoot growth and lead to severe nutritional disorders. Fertilizer N-use efficiency by the crops is typically low. In general, plants assimilate less than 50% of the N applied (Tilman et al., 2002; Dobermann & Cassman, 2004), turning the N losses into a potential source of environment pollution. The supply of to crop plants comes from various sources, including native soil N crop residues, animal manure, and inorganic or mineral fertilizers (Ladha et al., 2005). In the case of rice, N fertilizers have their use efficiency adversely affected by the rate and source of N. Inadequate rate of N fertilizer