In order to study the effects of different doses of sweet potato vine and their biochar returning to the field on microbial activity and nutrient contents of dryland red soil

field positioning experiment was conducted. In the experiment

five treatments were set up

which were conventional management (CK)

3 000 kg/hm2 sweet potato vine returning (S1)

6 000 kg/hm2 sweet potato vine returning (S2)

1 000 kg/hm2 sweet potato vine biochar returning (BC1) and 2 000 kg/hm2 sweet potato vine biochar returning (BC2). The results showed that compared with CK

in the 0—10 cm soil layer

soil basal respiration of BC1 increased by 17.93%

while that of S1

S2 and BC2 decreased by 20.33%

10.10% and 2.66%

respectively. In the 10—20 cm soil layer

the soil basal respiration of S2 and BC1 increased by 17.29% and 0.41%

respectively

while that of S1 and BC2 decreased by 13.61% and 16.93%

respectively. In the 20—30 cm soil layer

the basal respiration of S1

S2

BC1 and BC2 increased by 8.26%

48.94%

50.21% and 38.59%

respectively. Compared with CK

the soil microbial biomass carbon of S1

S2

BC1 and BC2 treatment increased about 1.30%

6.09%

28.52% and 39.64% in the 0—10 cm soil layer

respectively. In the 10—20 cm soil layer

soil microbial biomass carbon of S1

S2

BC1 and BC2 increased by 9.76%

16.72%

24.20% and 54.32%

respectively. In the 20—30 cm soil layer

soil microbial biomass carbon of S1

S2

BC1 and BC2 increased by 22.34%

39.27%

54.06% and 84.09%

respectively. It showed that sweet potato vines and their biochar could promote the soil basal respiration and soil microbial biomass carbon content to a certain extent. Sweet potato vine returning promoted the activities of soil FDA hydrolase and soil urease

but had little effect on soil sucrase activity. Returning biochar to the field inhibited the activities of soil FDA hydrolase and soil urease

and promoted soil sucrase activity. Sweet potato vine returning increased the content of soil organic carbon

while biochar returning reduced that. Sweet potato vine and biochar returning both increased the contents of hydrolyzed nitrogen and available phosphorus in the soil. The results showed that the addition of sweet pototo vine and biochar could effectively improve the soil physical and chemical properties and soil microbial activity

which was of great significance to improve the stability of soil ecosystem. The results provided a theoretical basis for the rational return of straw and biomass carbon to the field.