To compare an opportunistic break crop against fallow and wheat to better define the pros and cons of fallowing.

In this instance the opportunistic crop of canola in 2011 has proven the more successful rotation. At the beginning of the season, given the rainfall during harvest, the soil had comparable moisture at depth irrespective of the crop in 2011. The weed break given by the canola was significant, very few grass weeds coming through in old canola plots. The management of weeds proved telling in this trial. Much of the potential wheat yield was removed by the brome grass in the wheat on wheat plots.

Wheat on wheat this season achieved approximately 16kg/mm of rainfall. Wheat growing without the competition of weeds on the canola plots achieved in excess of 19kg/mm. Making crude assumptions that wheat on fallow grew at 19kg/mm, and the additional 400kg/ha yield was the result of additional moisture alone, then there was approximately 21mm of additional moisture in the fallow plots. Fallow had more moisture available closer to the surface than the other plots though not significantly more moisture throughout the remainder of the profile.

In 2012 wheat on fallow plots returned $100 more than wheat grown on either wheat or canola residue. This recouped the $40 loss from the 2011 fallow with additional profit. But fallow did not result in the greatest total profit over the two seasons of the trial. The extra production on the fallowed treatments was unable to make up the opportunity cost of not growing a crop in 2011. This is not unexpected given the high crop yields achieved in 2011.