Effect of genetic improvement of grain yield and nitrogen efficiency of mid-season indica rice cultivars
Lijun Liu1*, Yiwei Xiong1, Jinglong Bian1, Hao Zhang1, Junfei Gu1, Zhiqin Wang1, and Jianchang Yang1 1 Department of Agronomy, College of Agriculture, Jiangsu Key Laboratory of Crop Genetics and Physiology/Co-Innovation Center for Modern
Production Technology of Grain Crops, Yangzhou University, 12 Wenhui East Road, Yangzhou 225009, China
Genetic improvement (GI) of mid-season indica rice (Oryza sativa L.) in China has been experienced four typical plant types during the past several decades, i.e., early tall cultivars (ET), dwarf cultivars (DC), semi-dwarf cultivars (SDC) and super rice cultivars (SR). However, little is known about the changes in fertilizer nitrogen (N) efficiency and their relationships with grain yield during the GI. With 12 representative mid-season indica cultivars of the four types during GI, the effects of GI on grain yield and nitrogen efficiency were investigated. The results show that GI significantly increased grain yield and agronomic efficiency (AE) of N fertilizer but had no significant effect on recovery efficiency (RE) of N fertilizer. The low percentage of filled grains in modern SR limited its yield potential and the further increase in AE. GI decreased the N uptake from heading to maturity, leading to lower RE in modern rice cultivars. The rapid decline of the activities of root oxidation and nitrate reductase in SR during grain filling might be the physiological reasons for the lower percentage of filled grains and lower N uptake from heading to maturity.
Key words: dwarf cultivars / genetic improvement / Oryza sativa / root activity /super rice
Accepted January 08, 2015 1 Introduction
China accounts for about 30% of the global rice (Oryza sativa
L.) production and is the largest rice producing country in the world. Rice is also one of the most important cereal crops in
China as it produces more than 40% of the total cereal output.
The average rice yield in China has exceeded 6 t ha–1 at present, about 65% higher than the world average (FAOSTAT, 2012), which plays an important role in food supply and social stability for China and even for the whole world. To meet the increasing population growth, improving rice yield will be still an important issue and a long term target in China and the whole world.
Increase in fertilizer input, especially nitrogen (N) fertilizer, contributed significantly to the improvement of crop yields (Cassman et al., 2003). China’s national average N application rate for rice was 193 kg ha–1 in 2006 (Peng et al., 2010), about 90% higher than the world average (FAOSTAT, 2012;
Heffer, 2008). N application rates ranged from 150 to 250 kg ha–1 depending on rice planting areas (Wang et al., 2001;
Peng et al., 2006). For the most high-yielding counties in
Jiangsu Province, China, the average N rate reached 300 kg ha–1 (Liu et al., 2006). The high application rates and improper application timing of N fertilizer have led to low agronomic
N efficiency (AE) and poor recovery efficiency (RE) in China.
Earlier studies showed that the RE of rice in China was around 30–35% (Li, 1997). However, it was only18–20% in
Jiangsu Province and Zhejiang Province (Li, 2000; Wang et al., 2001). Peng et al. (2006) found that the RE of rice was 20–30% under farmers’ N fertilizer practice in four provinces in China. Agronomic efficiency was 15–20 kg grain kg–1 N from 1958 to 1963 and declined to only 9.1 kg grain kg–1 N between 1981 and 1983 (Lin, 1991). Then, it further decreased because of the increase in N application rate in China (Peng et al., 2002). Peng et al. (2006) reported that rice yield was increased by only 5–10 kg for each kg of N fertilizer input under farmers’ N fertilizer practice in China. High N rates and low nitrogen efficiency not only pollute the environment directly or indirectly, but also aggravate grain yield loss by diseases and lodging, and harm grain quality in rice (Li et al., 2014).
Many endeavors have been undertaken for opimizing N fertilization and improving nitrogen efficiency in China in the past.
These include: (1) N application methods, such as application rates and timing, deep placing of fertilizer (Li et al., 2014;
Zhang et al., 2012); (2) research, development and application of new-type N fertilizers (Yan et al., 2008); (3) computerbased decision support system for fertilizer management (Chen et al., 2004; Bouman and Van Laar, 2006; Liu et al., 2010); (4) site-specific nutrient management and real-time N management by using chlorophyll meter (SPAD) or leaf color chart (Peng et al., 1996; 2010), and (5) precise and quantitative N application in rice (Ling et al., 2005; Zhang et al., 2010). All of the above-mentioned studies have contributed greatly to an increase in nitrogen efficiency of rice production in China.
Many earlier studies showed that there are significant differences in nitrogen efficiency among various rice cultivars (De
Datta and Broadbent, 1990; Wu and Tao, 1995; Piao et al., ª 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.plant-soil.com
J. Plant Nutr. Soil Sci. 2015, 000, 1–9 DOI: 10.1002/jpln.201400304 1 *Correspondence: L. Liu; e-mail: firstname.lastname@example.org 2003; Koutroubas and Ntanos, 2003; Li et al., 2009; Dong et al., 2009), which provides great opportunities to increase grain yield with low N input by selecting rice cultivars with high nitrogen efficiency. During the past several decades in
China, Mid-season indica rice cultivars have been evolved from early tall cultivars, dwarf cultivars, semi-dwarf cultivars to modern super rice cultivars. The genetic improvement (GI) has contributed greatly to improving the rice yield. However, little is known about the changes in yield response to N and nitrogen efficiency during the GI. In this study, 12 typical midseason indica rice cultivars (including hybrid combinations) during the GI were grown in the paddy fields, and the changes in grain yield and nitrogen efficiency were investigated.