Polyolefin-coated urea decreases ammonia volatilization in a double rice system of southern china

Published in Agron. J. 105:277–284 (2013) doi:10.2134/agronj2012.0222 Copyright © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. R a major crop in China, accounts for 25% (~30 million ha) of China’s total cultivated area and 37% of the world total inorganic N fertilizers use in rice production. Applications of N fertilizers, including urea, in China accounts for one-third of the world total N use (FAOSTAT, 2009). However, urea applied to fl ooded paddy soils usually is rapidly hydrolyzed to ammonia (NH3), which can easily volatilize into the atmosphere (Harrison and Webb, 2001; Pacholski et al., 2008; Reddy et al., 1990). Studies showed that up to 60% of applied fertilizer N could be lost through NH3 volatilization in fl ooded soils (Xing and Zhu, 2000), depending on type of N fertilizer, tillage practices, and soil properties (temperature and pH) (Duan and Xiao, 2000; Gioacchini et al., 2002; Hayashi et al., 2011; Zhang et al., 2011a). Th e gaseous ammonia in the atmosphere can cause environmental problems such as soil acidifi cation and change of biodiversity (Eerden et al., 1998; Emmett 2007; Stevens et al., 2004). Recently the use N fertilizer has been greatly increased with the intensive rice cultivation in paddy soils of southern China. Nitrogen use effi ciency (NUE) is relatively low (20– 40%) in Chinese paddy soils and the excess of N can cause environmental problems (Ju et al., 2009; Wang et al., 2007; Zhu and Chen, 2002). Various attempts have been made to increase NUE and reduce N losses through applications of polymer coated N fertilizers (Shoji et al., 1991, 2001; Shoji and Kanno, 1994; Xu et al., 2005). For instance, studies found that NUE was higher when POCU was used compared to NCU. Th e oily or waxy texture of the added polyolefi n (a polymer from a simple olefi n in the formula CnH2n) slows down the dissolution of urea in water, resulting in less N loss (Shoji et al., 1991, 2001; Shoji and Kanno, 1994). Th e Chisso and Chisso-Asahi Co. in Japan has developed a series of POCU forms under the trade name MEISTER. By adding surfactants to urea and coating the mixture with a thermoplastic resin, the release of urea from the coated materials could be controlled by changing the ratio of the additives to the coating materials. Th e N release from POCU should be aff ected by only soil temperature (Shoji et al., 1991, 2001; Shoji and Kanno, 1994). Meanwhile, compared to the NCU, the POCUs generally maintained higher NH4 + but lower NO3 – in the soil, and resulted in a higher plant N accumulation and less N2O emission (Chen et al., 2008; Shoji et al., 1991; Shoji and Kanno, 1994; Soon et al., 2011). Polyolefi n-coated urea has been extensively applied to paddy fi elds and horticultural crops in Japan and tested in Australia and Canada. (Chen et al., 2008; Shoji and Kanno, 1994; Soon et al., 2011). Eff ects of POCU and their optimal application rates on the N loss need more evaluation. However, little information is available on the eff ect of the MEISTER (POCU) products on N loss through NH3 volatilization in paddy fi elds of southern China, particularly under the double rice cultivation (Li et al., 2011). A 2-yr fi eld experiment was conducted to compare the diff erence of NH3 volatilization between NCU and POCU ABSTRACT