Authors: S Muhammad T Müller R G Joergensen
Publish Date: 2006/03/09
Volume: 43, Issue: 1, Pages: 93-101
Abstract
Maize straw and pea straw were added to five Pakistani soils from a gradient in salinity to test the following hypotheses Increasing salinity at high pH decreases proportionally 1 the decomposition of added straw and 2 the resulting net increase in microbial biomass In the nonamended control soils salinity had depressive effects on microbial biomass C biomass N but not on biomass P and ergosterol The ratios microbial biomass CtoN and biomass CtoP decreased consistently with increasing salinity In contrast the ergosteroltomicrobial biomass C ratio was constant in the four soils at pH89 but nearly doubled in the most saline but least alkaline soil pH 82 The addition of the maize and pea straw always increased the contents of microbial biomass C biomass N biomass P and ergosterol but without clear effects of salinity Highest mean contents of microbial biomass C and biomass N were measured at day 0 immediately after the straw was added Straw amendments increased the CO2 evolution rates of all five soils without any effect of salinity The same was true for total C and total N in the two fractions of particulate organic matter POM 63–400 μm and 400 μm Lowest percentage of strawderived CO2C and highest recoveries of POMC and POMN were observed in the maize straw treatment and the reverse in the pea straw treatment Yield coefficients were calculated for maize and pea straw based on the assumption that the balance gap between CO2 and the amount of POM can be fully assigned to microbial products
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