J Arid Land (2018) 10(2): 292–303 https://doi.org/10.1007/s40333-018-0098-7 Science Press Springer-Verlag ∗ Corresponding author: TONG Ling (E-mail: tongling2001@cau.edu.cn) Received 2017-05-22; revised 2017-12-06; accepted 2017-12-22 © Xinjiang Institute of Ecology and Geography, Chinese Academy of Sciences, Science Press and Springer-Verlag GmbH Germany, part of Springer Nature 2018 http://jal.xjegi.com; www.springer.com/40333 Planting density affected biomass and grain yield of maize for seed production in an arid region of Northwest China JIANG Xuelian 1,2 , TONG Ling 1* , KANG Shaozhong 1 , LI Fusheng 3 , LI Donghao 1 , QIN Yonghui 1 , SHI Rongchao 1 , LI Jianbing 4 1 Center for Agricultural Water Research in China, China Agricultural University, Beijing 100083, China; 2 Key Laboratory of Biochemistry and Molecular Biology in Universities of Shandong, Weifang University, Weifang 261061, China; 3 College of Agriculture, Guangxi University, Nanning 530005, China; 4 Environmental Science and Engineering Program, University of Northern British Columbia, Prince George BC V2N 4Z9, Canada Abstract: Field experiments were conducted from 2012 to 2015 in an arid region of Northwest China to investigate the effects of planting density on plant growth, yield, and water use efficiency (WUE) of maize for seed production. Five planting densities of 6.75, 8.25, 9.75, 11.25 and 12.75 plants/m 2 were conducted in 2012, and a planting density of 14.25 plants/m 2 was added from 2013 to 2015. Through comparison with the AquaCrop yield model, a modified model was developed to estimate the biomass accumulation and yield under different planting densities using adjustment coefficient for normalized biomass water productivity and harvest index. It was found that the modified yield model had a better performance and could generate results with higher determination coefficient and lower error. The results indicated that higher planting density increased the leaf area index and biomass accumulation, but decreased the biomass accumulation per plant. The total yield increased rapidly as planting density increased to 11.25 plants/m 2 , but only a slight increase was observed when the density was greater than 11.25 plants/m 2 . The WUE also reached the maximum when planting density was 11.25 plants/m 2 , which was the recommended planting density of maize for seed production in Northwest China. Keywords: planting density; yield model; biomass accumulation; grain yield; water use efficiency; Northwest China Citation: JIANG Xuelian, TONG Ling, KANG Shaozhong, LI Fusheng, LI Donghao, QIN Yonghui, SHI Rongchao, LI Jianbing. 2018. Planting density affected biomass and grain yield of maize for seed production in an arid region of Northwest China. Journal of Arid Land, 10(2): 292–303. https://doi.org/10.1007/s40333-018-0098-7 1 Introduction Planting density is one of the most important agronomic factors affecting crop grain yield and water use efficiency (WUE). An increased planting density usually improves the seasonal interception of solar radiation (Harper et al., 1979; Papadopoulos and Pararajasingham, 1997; Westgate et al., 1997) that leads to increased canopy photosynthesis and biomass accumulation (Loomis and Connor, 1992; Coetto et al., 2013), and thus a higher grain yield and water productivity would be reached (Lang et al., 1956; Holt and Timmons, 1968; Fulton, 1970; Qiu et al., 2013). However, the