Managing soil biological decline during long-fallows in cropping systems

Abstract

No-till farming in Australia has revolutionised the way many farmers crop. Some of the moisture retention advantages of no-till farming have resulted in a reduced reliance of in-crop rain as well as increasing yields and profitability. Less clear is the effect on biological properties. Early results of a survey of the no-till cropping soils of the central west of NSW showed that most no-till cropping areas have lower soil carbon levels and lower microbial activity than nearby uncropped soils. This indicates that many no-till cropping soils may not be as sustainable as first thought. A long-fallow field trial was conducted on "Magomadine" near Coonamble NSW Australia using surface applied amendments (straw, compost, feedlot manure, biochar and zeolite) to investigate their effect on biological, chemical and physical soil properties. Early results are suggesting that the application of 10t/ha of straw can significantly (P < 0.05) increased soil moisture (24%), microbial respiration (50%), microbial biomass (21%), and mean weighted diameter of soil aggregates (75%). This research has highlighted the importance that high stubble residues have in improving these soil properties during a long-fallow.