Impact of alternative methyl bromide technology on soil nutrient and microbial biomass carbon in tomato greenhouse

Four alternative technologies to the use of methyl bromide with ordinary film(MB+PE), metham sodium with ordinary film(MS+PE), MB and MS dosage reduction by virtually impermeable films(VIF) and soil solarization in combination with selected biological control agents(SS+BCA), were chosen for application to an experimental site in Qingzhou, Shandong Province from 2001 to 2003. Soil nutrient indices and microbial biomass C were respectively investigated. Results for 2001～2002 show that soil pH, available P and K and cation exchange capacity(CEC) have no significant difference among the treatment plots. Methyl bromide fumigation measures under PE and VIF prompt release of NH⁺₄-N. Soil microbial biomass C decreases after soil disinfection and has no significant difference among treatments with MB+PE, MB+VIF, MS+PE and MS+VIF. Results for 2002～2003，when organic fertilizers were applied, are similar to that for 2001～2002，except that SS+BCA promotes NH⁺₄-N release and decreases microbial biomass C. In the two years of 2001～2003，microbial biomass C shows significant seasonal variation and application of organic fertilizer accelerates microbial biomass C turnover.