Abstract: To explore the effects of different types and proportions of organic fertilizers instead of chemical ones on wheat yield, photosynthetic rate and soil nutrient utilization under the same contents of nitrogen, phosphorus and potassium, a field positioning experiment was conducted at the wheat experiment base of the Millet Research Institute of Shanxi Agricultural University from September 2020 to June 2022. The experiment adopted a split-plot design. The main plot was organic fertilizer type, including bio-organic fertilizer (A1) and decomposed sheep manure (A2). In the subplots, five treatments (CK, B25, B50, B75, B100) were used to replace chemical fertilizers with organic ones. The results showed that replacing chemical fertilizer by 25% and 50% of bio-organic fertilizer and decomposed sheep manure could significantly improve net photosynthetic rate, chlorophyll relative content, normalized difference vegetation index, and nutrient uptake and utilization rate of flag leaves in the middle and late stages of wheat filling compared with sole application of chemical fertilizer. The bio-organic fertilizer and decomposed sheep manure (B25, B50) instead of chemical fertilizer promoted the synergic development of panicle number and kernel number per spike per unit area and 1000-grain weight, and significantly increased yield by 5.5%-23.1%. The average yield of bioorganic fertilizer treatment was 3.4% higher than that of decomposed sheep manure. The contents of alkali-hydrolyzed nitrogen, available phosphorus and organic matter in 0-20 cm soil layer treated with organic fertilizer replacing chemical fertilizer were significantly increased by 11.3%-50.9%, and the available potassium (B75, B100) was also significantly increased by 11.9%-24.6%. Except for organic matter, the contents of other nutrients in the 20-40 cm soil layer were higher in treatments with higher the proportion of organic fertilizer replacement. In the 40-60 cm soil layer, only the content of alkali-hydrolyzed nitrogen increased significantly. The alkali-hydrolyzed nitrogen and available phosphorus contents were higher in the 0-20 cm soil layer under the treatments of bio-organic fertilizer replacing chemical fertilizer, while the organic matter contents were higher in the 0-40 cm soil layer under the treatments of decomposed sheep manure replacing chemical fertilizer. The comprehensive analysis of wheat yield, photosynthetic rate, nutrient utilization rate and soil nutrient indices of different treatments showed that the substitution of chemical fertilizer with 50% bio-organic fertilizer was the best treatment, which could be used as an important technical model for green and efficient production of wheat fields of the same type.

Key words: substitution of chemical fertilizer with organic fertilizer, wheat growth, photosynthetic characteristic, nutrient uptake and utilization, soil nutrient