Impact of crop rotation in a no-tillage systems trial

Conservation agriculture (no-till) cropping systems have had major benefits for farmers, such as improved soil health, timeliness of sowing, moisture conservation and higher yields. The key components of this system are full crop residue (stubble) retention, diverse rotations and minimal soil disturbance. However, the recommendation for full residue retention is seen as a major constraint for to adoption of no-till by some. Also there is increased use of tillage to combat herbicide resistant weeds. This research is a long term study to determine the impact of crop rotation, residue level and tillage on crop yields and soil quality.

The aim of this Grains Research and Development Corporation (GRDC) funded trial is to determine the long term effect of a high residue, no-tillage system on soil quality, soil water balance, insects, diseases, weeds, crop residue dynamics as well as crop growth, yield and profitability. The main hypotheses are 1) high crop residue levels will outperform low levels (e.g. higher soil organic carbon, increased soil water storage/infiltration, higher yields) and that 2) the most diverse rotation will have less weed, disease and insect pests and increased soil organic matter and wheat yields compared to cereal monoculture.

The trial was started in 2007 on a field at the College of Agriculture Cunderdin. The treatments were based on four different cropping philosophies/rotations: “P1–maximum carbon input” (cereal/cereal/cereal); “P2– maximum diversity” (cereal/legume/brassica); “P3 split into –Continuous wheat and continuous pasture” and “P4–maximum profit” (cereal/cereal/legume). Each phase of the rotation is presented every year. The trial has completed two rotation cycles (three-year cycles) and is currently in the third cycle of the rotation.
The trial is a collaboration between The University of Western Australia (UWA), the Western Australian No-Tillage Farmers Association (WANTFA) and Commonwealth Scientific and Industrial Research Organisation (CSIRO). There is also a number of additional value-adding research projects being undertaken on these plots, including a PhD student at UWA studying the soil carbon and nitrogen dynamics in the continuous cereal and diverse rotations.


  • Western Australian No-Tillage Farmers Association (WANTFA)