DOI: 10.1094/CC-82-0588 |  VIEW ARTICLE

Nitrogen Fertilizer Increases Seed Protein and Milling Quality of Rice.

M. Leesawatwong (1–4), S. Jamjod (2,3), J. Kuo (1), B. Dell (4), and B. Rerkasem (2). (1) Centre for Microscopy and Microanalysis, University of Western Australia, Crawley 6009, Australia. (2) Agronomy Department, Faculty of Agriculture, Chiang Mai University, Chiang Mai 50200, Thailand. (3) Corresponding author: Phone: 665-394 4621. Fax: 665-321 0000. E-mail: <agosjmjd@chiangmai.ac.th>; <g4368102@cm.edu> (4) School of Biological Sciences and Biotechnology, Murdoch University, Perth 6150, Australia. Cereal Chem. 82(5):588-593. Accepted May 13, 2005. Copyright 2005 AACC International, Inc.

Rice grain breakage during milling is a problem in many parts of Asia. It has been suggested that nitrogen (N) fertilizer can improve the milling quality of rice. Therefore, this study investigates effects of N fertilization on grain N concentration, endosperm storage protein distribution, and milling quality of rice. Four Thai extra long grain commercial rice cul­tivars (KDML105, KLG1, PTT1, and CNT1) were grown at Chiang Mai University in the wet season of 2001 with 0 or 120 kg of N/ha at flower­ing. Anatomical sections showed that there was more storage protein accu­mulated in the lateral regions of polished grain of high N concentration than in grain of low N concentration. Percent (%) unbroken rice was positively correlated with relative abundance of storage protein in the lateral region of the endosperm in all cultivars. Applying N increased head rice N concentration in all cultivars, whereas % unbroken rice was increased in KLG1 and CNT1. KDML105 cultivar, on the other hand, already had high % unbroken rice and more abundant storage protein in the lateral region with the grain of low N concentration. It is hypothesized that high density of storage protein in the lateral region of the endosperm provides resilience and lessens grain breakage during milling. The addi­tional protein may increase hardness in rice grains and thus could make the rice more resistant to breakage during milling. Furthermore, N fertiliza­tion may enhance the nutritional quality of rice grain by increasing the glutelin content, which is rich in lysine.