Stubble management is a significant issue in Western Australia particularly in the high rainfall zone, where it is not uncommon for cereal yields to reach over 7 t/ha with the resulting stubble loads being up to 10 t/ha. This is a high amount of stubble residue left post harvest and is an increasing concern for local growers due to poor establishment of following crops, nitrogen (N) tie-up, disease carryover issues and seeding operation inefficiencies such as, blockages, hair pinning, poor soil throw and bulldozing. As a result, plant establishment has become increasingly difficult, particularly Canola establishment.

Traditionally, high stubble loads in the region have been removed by burning, however, there has been a move away from burning due to a combination of social license issues, as well as farming system concerns. Burning increases the risk of erosion and nutrient loss and decreases soil moisture.
Growers are also concerned with Nitrogen (N) tie-up from retained crop stubble. Although cereal stubbles contribute very little N to the following crop, stubbles are a source of carbon and N is required from the soil to breakdown this high carbon material.

Previous GRDC research has been conducted to understand the additional N requirements needed to overcome early N immobilisation by stubble, this research suggests that an additional 5-6 kg N/t of cereal residue can help overcome the issues of stubble N immobilisation. Investigation into whether the addition of nutrients, in addition to an enzyme ‘digester’ to stubble in conjunction with mechanical stubble treatments, during the summer fallow period, can increase the rate of stubble breakdown to allow for improved winter crop establishment (especially canola) and reduction in early season nitrogen tie-up. Reduced carryover of stubble-borne diseases could also be explored via observations.

Stubble management is a significant issue in Western Australia particularly in the high rainfall zone, where it is not uncommon for cereal yields to reach over 7 t/ha with the resulting stubble loads being up to 10 t/ha. This is a high amount of stubble residue left post harvest and is an increasing concern for local growers due to poor establishment of following crops, nitrogen (N) tie-up, disease carryover issues and seeding operation inefficiencies such as, blockages, hair pinning, poor soil throw and bulldozing. As a result, plant establishment has become increasingly difficult, particularly Canola establishment.

Traditionally, high stubble loads in the region have been removed by burning, however, there has been a move away from burning due to a combination of social license issues, as well as farming system concerns. Burning increases the risk of erosion and nutrient loss and decreases soil moisture.
Growers are also concerned with Nitrogen (N) tie-up from retained crop stubble. Although cereal stubbles contribute very little N to the following crop, stubbles are a source of carbon and N is required from the soil to breakdown this high carbon material.

Previous GRDC research has been conducted to understand the additional N requirements needed to overcome early N immobilisation by stubble, this research suggests that an additional 5-6 kg N/t of cereal residue can help overcome the issues of stubble N immobilisation. Investigation into whether the addition of nutrients, in addition to an enzyme ‘digester’ to stubble in conjunction with mechanical stubble treatments, during the summer fallow period, can increase the rate of stubble breakdown to allow for improved winter crop establishment (especially canola) and reduction in early season nitrogen tie-up. Reduced carryover of stubble-borne diseases could also be explored via observations.