Winter cereal production on the Darling Downs dash a comparison of reduced tillage practices

Abstract

Five experiments, 1 of which was continued over 3 years on the same site, were established on non-sloping Darling Downs cracking clays to compare conventional, reduced and zero tillage systems of fallowing for annual wheat production. Average values for soil water storage efficiency (percentage of fallow rainfall stored) were 14.0% for stubble burnt and conventional cultivation with tined implements (TI); 19.8% for stubble retained and conventional cultivation with tined implements (T2); 25.3% for stubble retained and zero tillage with chemical control of fallow weed growth (T3); 21.1% for stubble retained with no tillage but chemical weed control until early March, followed by cultivations with tined implements until sowing (T4); and 21.1% for stubble retained and fallow cultivations with a sweep plough (T6). Nitrogen mineralisation during fallow periods was measured over 3 seasons at the final site. No major treatment differences occurred. A small mean grain yield advantage of 4.6% to T3 over T1 was established in those seasons when improved fallow water storage was obtained with T3. The lack of yield improvement by reduced tillage treatments (T4, T5 and T6) over T1 is attributed largely to above-average crop period rainfall in those seasons when the treatments had resulted in improved presowing water.