Effect of different growth stages on rice crop on soil microbial and enzyme activities
N. F. Islam* and Borthakur
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Abstract: The influence of growth stages of rice on soil microbial biomass carbon (MBC), soil microbial biomass nitrogen (MBN) and enzyme activities (amylase, dehydrogenase, alkaline and acid phosphatase) in a sub-tropical rice field has been screened. The above soil parameters were investigated at two soil depth (0-10 and 10-20 cm) and in five growth stages of rice crop, i.e. 30, 60, 90, 120 and 150 days after transplantation (DAT) of rice seedlings. Results shows that, contents of soil organic carbon, total nitrogen, MBC and MBN were highly influenced by the flowering stage (90 DAT) of the rice crop, at both 0-10 cm and 10-20 cm soil depths, but decline gradually when the crop reaches maturity (120 DAT) and late maturity stages (150 DAT). The soil organic carbon and total nitrogen were positively correlated with MBC and MBN. At both the sampling depths soil amylase activity showed a peak value at seedling and flowering stages (30 and 90 DAT) whereas dehydrogenase and phosphatase showed at flowering stage (90 DAT). Both dehydrogenase and phosphatase showed significant correlation with MBC and MBN. Keywords: Oryza sativa - Soil microbial biomass - Soil enzyme activities.
Fig.: Relationships between: A, organic-C and biomass-C; B, organic-C and biomass-N; C, total-N and biomass- C; D, total-N and biomass-N.