Review article

Improving nitrogen fertilization in rice by site-specific N management. A review^*

¹ Crop and Environmental Sciences Division, International Rice Research Institute, DAPO Box 7777, Metro Manila, Philippines
² Crop Physiology and Production Center, MOA Key Laboratory of Huazhong Crop Physiology, Ecology and Production, Huazhong Agricultural University, Wuhan, Hubei 430070, China
³ Rice Research Institute, Guangdong Academy of Agricultural Science, Guangzhou, Guangdong 510640, China
⁴ Crop Physiology, Ecology, and Production Center, Hunan Agricultural University, Changsha, Hunan 410128, China
⁵ Agronomy Department, Agricultural College, Yangzhou University, Yangzhou, Jiangsu 225009, China
⁶ College of Environmental and Natural Resources Sciences, Zhejiang University, Hangzhou, Zhejiang 310029, China
⁷ College of Resources and Environmental Sciences, Northeast Agricultural University, Harbin, Heilongjiang 150030, China
⁸ Centre for Chinese Agricultural Policy, Institute of Geographical Sciences and Natural Resource Research, Chinese Academy of Sciences, Beijing 100101, China
⁹ College of Resources and Environmental Sciences, China Agricultural University, Beijing 100094, China

^** Corresponding author: s.peng@cgiar.org

Accepted: 21 December 2009

Abstract

Excessive nitrogen (N) application to rice (Oryza sativa L.) crop in China causes environmental pollution, increases the cost of rice farming, reduces grain yield and contributes to global warming. Scientists from the International Rice Research Institute have collaborated with partners in China to improve rice N fertilization through site-specific N management (SSNM) in China since 1997. Field experiments and demonstration trials were conducted initially in Zhejiang province and gradually expanded to Guangdong, Hunan, Jiangsu, Hubei and Heilongjiang provinces. On average, SSNM reduced N fertilizer by 32% and increased grain yield by 5% compared with farmers’ N practices. The yield increase was associated with the reduction in insect and disease damage and improved lodging resistance of rice crop under the optimal N inputs. The main reason for poor fertilizer N use efficiency of rice crop in China is that most rice farmers apply too much N fertilizer, especially at the early vegetative stage. We observed about 50% higher indigenous N supply capacity in irrigated rice fields in China than in other major rice-growing countries. Furthermore, yield response of rice crop to N fertilizer application is low in China, around 1.5 t ha⁻¹ on average. However, these factors were not considered by rice researchers and extension technicians in determining the N fertilizer rate for recommendation to rice farmers in China. After a decade of research on SSNM in China and other Asian rice-growing countries, we believe SSNM is a matured technology for improving both fertilizer N use efficiency and grain yield of rice crop. Our challenges are to further simplify the procedure of SSNM and to convince policy-makers of the effectiveness of this technology in order to facilitate a wider adoption of SSNM among rice farmers in China.