A field experiment was conducted using asparagus lettuce as test material to study the effects of different fertilizer combinations on dry matter accumulation

nutrients absorption

fertilizer use efficiency

soil physical-chemical properties and soil microbial quantity

which could provide the scientific basis for reasonable fertilization of asparagus lettuce. The experiment used a completely randomized block design to set a conventional fertilization (CF)

reduction of 20% (F1) and 30% (F2) and combined with 3 000 kg/hm2 (B1) and 6 000 kg/hm2 (B2) bio-organic fertilizer. The results showed that compared with the CF

the accumulations of dry matter in roots

stems and leaves of F1B2 treatment were increased by 5.74%

22.19% and 17.82%

respectively

and the accumulations of N

P and K nutrients were increased by 128.81%

113.19% and 23.15%

respectively. The reduction of fertilizer combined with bio-organic fertilizer could significantly improve the fertilizer use efficiency

agronomic efficiency and partial factor productivity of N

P and K fertilizers. The soil N

P and K dependent rates of CF were the highest. The application of bio-organic fertilizer could significantly increase soil nutrients contents. Compared with CF

the contents of soil organic matter

total N

P

K and alkaline N

available P and available K were increased by 71.65%

84.53%

75.41%

19.94%

75.90%

17.06% and 24.35% respectively in F1B2

and were increased by 58.51%

70.17%

72.13%

9.28%

42.94%

13.48% and 11.42% respectively in F2B2. The combination of chemical fertilizer and bio-organic fertilizer could increase the number of bacteria and actinomycetes in the soil of asparagus lettuce

and inhibit the growth of fungi. Compared with CF

the number of aerobic azotobacter

anaerobic azotobacter

nitrifying bacteria and denitrifying bacteria were increased by 1.36

6.10

47.50 and 23.76 times

respectively in F1B2. The number of bacteria was significantly positively correlated with the contents of organic matter

alkaline N

available P and total N. There was a significant positive correlation between the number of actinomycetes and the contents of total P. The number of azotobacters and nitrogen transformational bacteria showed a significant or extremely significant positive correlation with the contents of alkaline N and total N. According to the principal component analysis and comprehensive scores

the soil quality under different fertilization treatments with the following sequence of F1B2

F2B2

F1B1

F2B1

CF and CK. The partial substitution of chemical fertilizer by bio-organic fertilizer could not only improve the amount of asparagus lettuce's nutrients accumulation and fertilizer use efficiency

but also significantly increase the contents of soil nutrients

regulate the structure of soil microbial community

and improve soil physical and chemical properties. In summary

the partial substitution of chemical fertilizer by bio-organic fertilizer had a good effect on the nutrients accumulation of asparagus lettuce

and could improve the fertilizer use efficiency and soil fertility. The F1B2was a good fertilization mode with a rational use of fertilizer resources and improved soil environment.