The effect of lead (Pb) treatment on the soil enzymatic activities

soil microbial biomass

rice physiological indices and rice biomass in soil-rice system were studied by pot experiment in a greenhouse. Lead was applied at 0(CK)

100

300

500

700

900 mg/kg levels in two different paddy soils.The results showed that low Pb concentration had a stimulating effect on soil enzymatic activities

microbial biomass car- bon (Cmic) and rice biomass

and an inhibitory influence on most indices when Pb concentration over 500 mg/kg and the influence also restricted by soil properties (e.g.size composition

organic matter content). Rice Chorophyll content increased with Pb level and appeared a peak at 700 mg/kg Pb concentration

then decreased with Pb level in Silty loam

however

no evident difference in Yellowish red soil.Pb was effective in indueing proline accumulation and its toxicity caused oxidative stress on rice plants.Higher soil Cmic with planting rice than with no rice indicated rice growth definite detoxification.On the whole

Soil enzymatic ac- tivities

Cmic and rice physiological indices

therefore

may be sensitive indicators reflecting environmental stress in soil-Pb-rice system.And the correlations among them followed soil types.