A no-till system using permanent beds, permanent subsurface irrigation and organic mulches grown in situ was implemented as an alternative to conventional production in an experiment conducted in North Queensland, Australia. The system used a tropical legume, Centrosema pubescens 'Cavalcade', or the C 4 grasses Bothriochloa pertusa 'Keppel' or 'Hatch' as cover crops over summer and autumn. Cover crops were killed using glyphosate (1440 g a.i./ha) and residues were left on the soil surface. Vegetable seedlings were then planted through the mulch residues and grown using conventional agronomic techniques. Following harvest, crop residues were macerated and the following cover crop direct sown through the mulch residues. Soil from conventional production areas using polyethylene mulch had significantly lower aggregate stability than all other treatments. Soil aggregates taken from beneath cover crop mulches were more stable than aggregates under polyethylene mulch after one year under the no-till regime. Soil aggregates after three years of treatment showed similar statistical differences between the treatments. Bulk density in permanent beds under C. pubescens mulch was significantly lower than uncultivated bare soil and frequently cultivated polyethylene mulch. Soil under frequent cultivation was significantly more compacted than uncultivated bare soil. There were significantly more earthworms under C. pubescens and B. pertusa mulch than in uncultivated bare topsoil or under polyethylene mulch. No earthworms were found in any sample under polyethylene mulch. The yields of tomatoes after 5 harvests were not significantly different for conventional and no-till production.
