Effects of microbial organic fertilizer and mulch to population and bioactivity of beneficial microorganisms in tea soil in Phu Tho, Viet Nam

Abstract

Currently, tea in Phu Tho is grown in nutrient-poor and acidic soils, with pH_KCl from 3.6 to 4.6, low total and digestible phosphate (P₂O₅); average organic matter (OM), potassium (K₂O) and protein, low CEC (from 3.36 to 4.24 meq/ 100g soil), low Ca and Mg (from 2.75 to 3.27 meq/100g soil). Using microbial organic fertilizer at level of 3.0 tons per hectare influenced significantly both the population and composition of microorganism species in tea soil. Many soil microbes such as Pseudomonas, Bacillus, Azotobacter, Nitrosomonas and Nitrobacter which decompose organic matter, cellulose, insoluble phosphates have appeared in the soil as microbial organic fertilizers were provided. The filamentous fungi which are able to decompose insoluble phosphate, cellulose such as Aspergillus spp., Penicillium spp. Trichoderma spp. and Fusarium spp. have been detected. The total number of bacteria has increased rapidly in a short time as Guot (Gleichenia linearis Clarke) was used as mulch material. The number of bacteria reached to the highest level of 11.30 x 10⁶ CFU/g (soil) after 180 days. Total numbers of actinomycetes have increased significantly. Many newly actinomycetes have appeared in the soil after 90 days of mulching, and continued to increase up to 11.05 x 10⁶ CFU/g after 270 days. Fungi population also grew fast (from 5.35 x 10³ CFU/g to 7.45 x 103 CFU/g) after 90 days of mulching then continue to rise sharply in the next 90 days and stabilized later. When using different materials, the percentage of microorganism groups that have bioactive are also different. Cellulose decomposing bacteria accounted for 40%, while the rate of bacteria that decompose insoluble phosphate made up for 44%.