KNOWLEDGE OF SOIL BIOLOGY TO REDUCE NITROGEN LOSS AS N2O FROM SUGARCANE FARMING

CONTEMPORARY CROPPING systems have to combine high yields with environmental sustainability. The conversion of nitrogen (N) fertiliser to forms which are easily lost from soil (as nitrate or gaseous N compounds) is driven by soil biology, specifically the soil microbial community. Although knowledge of soil microbial activity is crucial for minimising N loss, it is not known how soil conditions and associated microbes can best be manipulated through farming practices. We have developed new tools for fingerprinting microbial activities in soil. Our new method quantifies, for the first time, the activities of microbial genes that are switched on or off under certain conditions in the soil. The method links soil parameters and microbial activities by using a new custom-made microarray. The advantage of this novel mRNA-based approach is that it (i) measures of the ‘microbial activity’ rather than the ‘presence’ of specific microbes, (ii) monitors ‘activities’ of many microbial groups simultaneously, (iii) provides insights into whole-system soil biology. We have applied this technique to monitor microbial activities in cane soils with different management histories. Our preliminary results indicate that the method can successfully detect differences in the microbial activities of soils with different fertiliser application and N2O emission rates (Mackay), and different cropping history (Ingham). Ultimately this research will provide information for farmers to effectively manipulate soil biology to reduce N loss and improve productivity.