Yield, economic benefit, and key impact factors in the strip intercropping system of soybean and maize

China’s soybean industry is heavily dependent on imports, as limited domestic production capacity restricts industry development and poses risks to national food security. Enhancing soybean production capacity is therefore essential to improving supply-demand self-sufficiency. As a key agronomic technology promoted by the Ministry of Agriculture and Rural Affairs in recent years, soybean-maize strip intercropping plays a critical role in expanding soybean cultivation areas and increasing yields. This study is based on 1012 valid questionnaires collected in 2024 from a nationwide survey on soybean-maize strip intercropping conducted across 19 provinces (municipalities and autonomous regions). This study systematically analyzes the yields of soybeans and maize, planting costs, economic benefits, the land equivalent ratio (LER), as well as the effects of planting row ratios, densities, and varieties on yields. Results show that the national average yields were 1642 and 6916 kg∙hm⁻² for soybeans and maize, respectively. The combined yield of soybean and maize in the Huang-Huai-Hai Region was 9 905 kg∙hm⁻², which were 13% and 45% higher than those in the Northwest and Southwest regions, respectively. The national average LER was 1.55, ranging from 1.42 to 1.70. The highest LER was observed in the Huang-Huai-Hai Region (1.63), followed by the Southwest (1.56) and Northwest (1.55) regions. Regarding planting row ratios, the 6∶4 soybean to maize configuration was most common in the Huang-Huai-Hai Region, accounting for 39% of cases. Under this ratio, the proportion of soybean planting density of 1.28×10⁵−1.50×10⁵ plants∙hm⁻² was the highest (40%), with a corresponding maize density of 4.2×10⁴−1.05×10⁵ plants∙hm⁻². In the Northwest Region, the 4∶4 ratio was dominant (35%), with soybean density of 12.75×10⁴−1.5×10⁵ plants∙hm⁻² (48%) and corresponding maize densities of 3.75×10⁴−8.25×10⁴ plants∙hm⁻². In the Southwest Region, the 3∶2 ratio was the most prevalent, with the proportion of 60%, where soybean planting densities of 1.05×10⁵−12.45×10⁴ plants∙hm⁻² (36%) and maize planting densities of 3.75×10⁴−6.75×10⁴ plants∙hm⁻² were most common. Cultivar selection also varied by region. ‘Yundou 1’ had the highest percentage in the Huang-Huai-Hai Region, followed by ‘Qihuang 34’ and ‘Jidou 12’. ‘Huangjinliang MY73’ had the highest percentage for maize cultivar in this region, followed by ‘Liangyu 99’ and ‘Denghai 605’. ‘Dongdou 339’ had the highest percentage for soybean cultivar in the Northwest Region, followed by ‘Zhonghuang 13’ and ‘Qihuang 34’; ‘Youdi 919’ ‘Xianyu 1483’, and ‘Denghai 605’ were the first three maize cultivars in the Northwest Region. ‘Qihuang 34’ had the highest percentage for soybean cultivar in the Southwest Region, followed by ‘Qiandou 12’ and ‘Diandadou 2’. ‘Chuandan 99’ ‘Xianyu 1171’, and ‘Chengdan 716’ were the first three maize cultivars in the Southwest Region. Overall, this study provides important empirical evidence to support further development and technological extension of soybean-maize strip intercropping systems.