Soil organic matter and microbial biomass as influenced by sugar cane (Saccharum hybrid sp.) production practices in Mauritius

摘要

Sugar cane has been grown in Mauritius for over 350 years in a monocropping system. As a result, soil quality could have declined since productivity has been stagnating over the last twenty years in spite of improved agronomic practices and higher-yielding varieties. A study was therefore initiated to determine the effects of sugar cane production practices on the biological quality of the major soil groups of Mauritius. Organic matter (OM) and microbial biomass contents were determined for soils with different cropping histories, namely native vegetation, cropping with sugar cane under manual conditions, and cropping with sugar cane under mechanized conditions. When virgin soil was compared to manually-cropped soil, OM content was found to decrease with cropping in the topsoil, but to increase in the subsoil as a result of soil mixing through tillage. Microbial biomass also decreased in the topsoil as the microbial population had less OM to feed on. When manually-cropped soil was compared to mechanically-cropped soil, both OM and microbial biomass tended to decrease with mechanization as the soil was highly disrupted following land preparation. This decline in soil biological quality will continue if remedial measures are not taken, the latter being trash blanketing, addition of substantial amounts of organic wastes, and the incorporation of leguminous green manures within the cropping cycle, among others.