Contents lists available at ScienceDirect Journal of Environmental Management journal homepage: www.elsevier.com/locate/jenvman Research article Controlled-release urea reduced nitrogen leaching and improved nitrogen use efficiency and yield of direct-seeded rice Shugang Zhang a,1 , Tianlin Shen a,b,1 , Yuechao Yang a,b,* , Yuncong C. Li b , Yongshan Wan b , Min Zhang a , Yafu Tang a , Samuel C. Allen c a National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources, National Engineering & Technology Research Center for Slow and Controlled Release Fertilizers, College of Resources and Environment, Shandong Agricultural University, Taian, Shandong 271018, China b Department of Soil and Water Sciences, Tropical Research and Education Center, IFAS, University of Florida, Homestead, FL 33031, USA c Department of Plant and Environmental Sciences, Agricultural Science Center, New Mexico State University, Farmington, NM 87401, USA ARTICLE INFO Keywords: Nitrogen release Recycle plastics Root zone Soil water ABSTRACT The use of controlled-release urea (CRU) has become one of best management practices for increasing crop yield and improving nitrogen (N) use efficiency (NUE). However, the effects of CRU on direct-seeded rice are not well understood while direct-seeding has gradually replaced transplanting due to increasing labor cost and lack of irrigation water. The objective of this two-year field experiment was to compare the effects of the CRU at four rates (120, 180, 240 and 360 kg N ha -1 , CRU1, CRU2, CRU3 and CRU4, respectively) with a conventional urea fertilizer (360 kg N ha -1 ; U) and a control (no N fertilizer applied; CK) on yield, biomass, NUE of direct-seeded rice and soil nutrients. The results indicated that the successive release rates of N from CRU corresponded well to the N requirements of rice. The use of CRU3 and CRU4 increased rice grain yields by 20.8 and 28.7%, re- spectively, compared with U. In addition, the NUEs were improved by all CRU treatments compared to the U treatment. Concentrations of NO 3 - -N and NH 4 + -N in the soil were increased, especially during the later growth stages of the rice, and the leaching of N was reduced with CRU treatments. In conclusion, applying CRU on direct-seeded rice increased the crops yields and NUE, increased nitrogen availability at the late growth stages, and reduced N leaching. 1. Introduction In traditional rice production systems, rice seedlings are trans- planted, a labor-intensive and high costs process (Pan et al., 2017; Song et al., 2017). It has been the trend to move from traditional rice transplanting to the direct-seeding method in recent years (Tao et al., 2016). Many new types of N fertilizers were developed to meet crop N requirements and increase crop yield and NUE (Fang et al., 2006; Yuan et al., 2016). The CRU has been strongly advocated recently because of the many advantages it brings to various crop systems (Yang et al., 2012a, 2012b; Wang et al., 2016), but not as often in direct-seeded rice systems (Shaviv, 2001; Ye et al., 2013; Zhang et al., 2016). There are also currently no studies on how CRU application influences N levels in the plough layer and N leaching after fertilizer application during the growth period of direct-seeded rice. Most CRU fertilizers are coated with polymers which slowly release N for plant use (Chen et al., 2018; Zhou et al., 2018), thereby reducing nutrient loss while improving NUE and decreasing groundwater pollution (Yang et al., 2013; Wei et al., 2014; Wang et al., 2015). The entire growth period of direct-seeded rice lasts about 120 days (Tang et al., 2007; Yang et al., 2012a) and the N needs of rice follow an S-shaped curve during this period of time (Peng et al., 2010; Liu et al., 2016); N demand is low during the nursery and maturity stages, and high from the tillering to milk stages (Golden et al., 2009; Chen et al., 2015; Shi et al., 2017). To fit the gap of information on using CRUs for direct-seeded rice, a factorial experiment was conducted to compare a newly developed CRU with conventional fertilizer (urea). The specific objectives of this study https://doi.org/10.1016/j.jenvman.2018.05.010 Received 13 March 2018; Received in revised form 26 April 2018; Accepted 5 May 2018 * Corresponding author. National Engineering Laboratory for Efficient Utilization of Soil and Fertilizer Resources; National Engineering & Technology Research Center for Slow and Controlled Release Fertilizers, College of Resources and Environment, Shandong Agricultural University, Taian, Shandong 271018, China. 1 These authors contributed equally to this work. E-mail addresses: shugangzhang2014@163.com (S. Zhang), tl_shen@163.com (T. Shen), yangyuechao2010@163.com (Y. Yang), yunli@ufl.edu (Y.C. Li), yongshan.wan@gmail.com (Y. Wan), minzhang-2002@163.com (M. Zhang), tangyafu90@163.com (Y. Tang), drsamallen@gmail.com (S.C. Allen). Abbreviations: N, nitrogen; CRU, controlled-release urea; CK, a controlled treatment with no nitrogen fertilizer; U, urea applied as basal fertilizer; CRU1, CRU was applied at 120 kg N ha -1 ; CRU2, 180 kg N ha -1 ; CRU3, 240 kg N ha -1 ; CRU4, 360 kg N ha -1 ; NUE, nitrogen use efficiency Journal of Environmental Management 220 (2018) 191–197 0301-4797/ © 2018 Elsevier Ltd. 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