Abstract: Through two consecutive years of pot experiments, the effects of different amounts of black soldier fly frass（2%, 4%, 6%）application on the growth of Brassica chinensis and soil physicochemical properties were studied, with no fertilization as the control（CK）. The results showed that compared with CK, the application of black soldier fly frass reduced soil pH, increased soil organic matter content（4.5%-49.5%）, EC value（34.4%-814.1%）, alkaline nitrogen content（20.6%-76.8%）, available phosphorus content（11.4%-64.6%）, and available potassium content（78.9%-542.1%）; The organic matter, EC, and nutrient content of the soil in the second year of the same treatment were lower than those in the first year. The application of frass fertilizer increased the activities of soil urease, phosphatase, catalase, and sucrase. The overall soil nutrients and enzyme activity increased with the increase of frass application, with 6% application rate treatment>4% application rate treatment>2% application rate treatment. The application of frass fertilizer promoted the growth of Brassica chinensis. In the first year, the treatment with a 4% application rate resulted in the highest plant height of Brassica chinensis, which was 61.8% higher than CK. There was no significant difference in yield between the 6% application rate and the treatment. However, in the second year, the treatment with a 6% application rate resulted in the highest plant height and yield of Brassica chinensis. In summary, the application of black soldier fly frass can improve soil fertility, promote crop growth, and have strong seasonal and subsequent fertilizer effects.

Key words: black soldier fly, frass, Brassica chinensis, soil, enzymatic activity