Reduced tillage increases population density of soil macrofauna in a semiarid environment in central Queensland

The effects of modified tillage practices on population densities of benefi cial and harmful soil macrofauna were investigated Soil-inhabiting macrofau na were sampled during 5 yr in a field experiment on a black Dermasol and V ertisol in semiarid central Queensland. The experimental treatments were 4 tillage practices applied during the fellow periods between grain crops. Re duced frequency and intensity of tillage increased the level of crop residu es providing surface cover. Zero tillage had the highest population of macr ofauna (74/m(2)), followed by reduced tillage (50/m(2)), stubble mulch till age (44/m(2)), and traditional tillage (31/m(2)). Detritivore populations a lso were highest in zero tillage (44/m(2)) followed by reduced tillage (29/ m(2)) stubble mulch tillage (26/m(2)), and traditional tillage (15/m(2)). E arthworm populations were highest in zero tillage (17/m(2)) and lowest in t raditional tillage (5/m(2)). The incidence of termite colonies was higher i n zero tillage (7.0/m(2)) than in reduced tillage (0.9/m(2)), stubble mulch tillage (0.3/m(2)), or traditional tillage (0.2/m(2)). Zero tillage usuall y had the greatest diversity of macrofauna species. Population density of h erbivores, which are generally agricultural pests, was similar in all tilla ge treatments. These results indicate that long-term reduced or zero tillag e will not lead to increased problems with soil insect pests.