Abstract: A two-factor field experiment of randomized block design was conducted in Guangzhou to investigate the effects of reduced nitrogen application on the
yield, quality, and total biomass dynamic of sugarcane as well as the economic benefit of the sugarcane population under different sugarcane/soybean intercropping patterns. Neither N application nor intercropping pattern had significant effects on the yield and quality of sugarcane, and no significant differences were observed in the yield and quality of sugarcane among all treatments. The land equivalent ratio (LER) of sugarcane/soybean intercropping at different N application levels was from 1.36 to 2.12, suggesting that sugarcane/soybean intercropping had higher LER than monoculture sugarcane. The total dry matter (except root) of sugarcane in all treatments increased with plant growth, and the growth pattern fitted sigmoid function. At lower nitrogen application level, the eigenvalues of the dynamic dry matter accumulation model were more coordinative, compared with those at higher nitrogen application level, which meant that in the later case, sugarcane had an advanced peak growth time and shortened fast-growth duration
, and thereby, its yield decreased. Therefore, it was possible to reasonably adjust nitrogen application level to improve the eigenvalues of the sugarcane dynamic dry matter accumulation model, and accordingly, to achieve high yield. The population economic benefit under sugarcane/soybean intercropping was 3.2%-26.3% higher at lower than at higher nitrogen application level, suggesting the increase of the economic benefit of sugarcane population under reduced nitrogen application. Among the treatments, 1:2 sugarcane/soybean intercropping had the best economic benefit.

Key words: sugarcane/soybean intercropping, reduced nitrogen application, yield,  quality, economic benefit, Guangzhou