Abstract: 【Objective】To determine soybean optimal growing period under the condition of increasing boron fertilizer in the southern Daxing′Anling of Inner Mongolia,and to provide technical support and theoretical basis for water and fertilizer management of soybean in this area.【Methods】Using Mengkedou No.9 as the experimental variety,the agronomic characters and yield under traditional cultivation were set as the control,increasing boron fertilizer at flowering stage(BR1),pod setting stage(BR3),seed filling stage(BR5)and flowering+seed filling stage(BR1R3),the input-output accounting was carried out,and the economic benefits were calculated.【Results】There was no significant difference in the number of growth days and main stem nodes between different treatments(P>0.05).The plant height of BR1R3 treatment was significantly higher than that of CK(P<0.05).The number of effective branches in BR1,BR3 and BR1R3 was significantly higher than that of CK(P<0.05).The results of dry matter accumulation and SPAD value of soybean under the different treatments were BR1R3>BR1>BR3>BR5>CK. The dry matter accumulation and SPAD value in BR1R3 increased most significantly(P<0.05),12.5% and 7.2% when compared with CK. There were no significant differences in protein content,fat content and total egg fat content among the treatments(P>0.05). Under the condition of increasing boron fertilizer,the yield of soybean at different growth stages was BR1R3>BR1>BR3>BR5>CK,and BR1R3,BR1 and BR3 were significantly different from CK(P<0.05),the yield increased 497,329 and 234 kg/hm² respectively.The pod number per plant,grain number per plant and grain weight per plant of BR1R3 treatment were significantly higher than CK(P<0.05). Compared with CK,the efficiency of BR1R3,BR1 and BR3 was 15.5%,12.1% and 7.0% respectively,and the income increased by 1 386.0,1 078.5 and 622.5 yuan/hm².【Conclusion】The flowering stage and pod setting stage were optimal time for boron fertilizer applying in soybean in the area for income increasing. Increasing the boron fertilizer input simultaneously at flowering stage and pod setting stage had a most significant effect in yield enhancement and a best performance in elevating economic income and efficiency, while no significant effect was observed at filling stage.

Key words: Soybean, Agronomic characters, Quality, Yield, Economic benefit