Abstract:In agricultural production within arid and semiarid regions, common practices involve rhizobium bacteria inoculation and nitrogen application to promote soybean growth and increase seed yields. However, there has been limited research on the interaction between rhizobium inoculation and nitrogen application and their impact on soybean growth and yield. This twoyear field experiment aimed to address this gap by investigating four nitrogen application levels (N0: 0kg/hm2, N1: 60kg/hm2, N2: 120kg/hm2, N3: 180kg/hm2) and two inoculation levels: rhizobium inoculation (R) and water mixed with no inoculation (unmarked). Various parameters related to soybean growth, including nodule number, nodule dry weight, leaf area index (LAI), biomass accumulation and root characteristics, were measured at different growth stages. Additionally, physiological indicators such as chlorophyll content, photosynthetic parameters, fluorescence parameters and nitrogen uptake, along with nitrogen use efficiency calculations were assessed. The results demonstrated that soybean growth reached its optimum under the RN2 treatment, with maximum nodule number of 241.47, maximum nodule dry weight of 1.30g,maximum root length density of 15.00cm/cm3, maximum LAI of 5.44cm2/cm2, maximum biomass accumulation of 17530.51kg/hm2, maximum chlorophyll content of 53.55, maximum net photosynthesis rate of 32.75μmol/(m2·s), and maximum seed yield of 4659.4kg/hm2. In conclusion, reducing nitrogen fertilizer application (N2) while concurrently inoculating with rhizobium (R) was essential for enhancing the physiological growth of soybeans in the Guanzhong Plain, improving nitrogen use efficiency and increasing soybean yields. The research result can provide both theoretical underpinning and practical experience to elevate soybean production in arid and semi-arid regions.
