Effects of pig manure and biogas residue application on soil fertility, enzyme activities and microbial biomass in tea garden

To study the rational application of pig manure, biogas residue and their effect on the improvement of soil fertility in tea garden, a plot location experiment of applying chemical fertilizer (T1), half-amount pig manure biogas residue (T2), fill amount pig manure biogas residue (T3) and pig manure organic fertilizer (T4) in tea garden soil for three consecutive years was carried out. Soil physicochemical properties, microbial biomass, carbon, nitrogen and phosphorus contents and related enzyme activities were compared among different treatments. The results showed that different pig manure application methods could effectively reduce the acidification degree of tea garden soil, and improve soil organic matter, soil total content and available NPK fertility, among which T4 treatment increased the most significantly. Compared with CK, the contents of soil organic matter, alkali-hydrolyzed nitrogen, available phosphorus and available potassium in T4 treatment were increased by 60.83%, 223.36%, 239.22% and 90.39%, respectively. The contents of carbon, nitrogen and phosphorus in microbial biomass were increased by 44.15%, 98.51% and 121.31%, respectively. Soil sucrase, urease, acid phosphatase, catalase and cellulase activities were increased by 23.00%, 37.69%, 40.24%, 31.53% and 61.07%, respectively. There were significant or extremely significant positive correlations between the activities of five enzymes and the contents of soil organic matter and nutrients. The results showed that soil organic matter and nutrient contents, enzyme activities and microbial biomass were significantly increased under different pig manure application methods, among which the application of pig manure organic fertilizer had the most significant effect. However, it was necessary to pay attention to the problems such as the aggravation of nitrogen and phosphorus loss caused by the high content of soil available nutrients.