The new strategy encompasses cover crop economics and how they can contribute to improving production resilience and beneficial environmental outcomes in maize grain systems.
FAR Maize researcher, David Densley, says cover crops for maize grain require quite a different approach to cover crops for maize silage.
“In maize silage, the function of a cover crop is mostly undertaken by annual ryegrass, which is sown immediately following harvest. However, with maize grain crops establishment is not so easy. Many maize grain crops are not harvested until the end of April, or later, a timing which can make cover crop establishment tricky; and the amount of crop residue remaining following grain harvest presents another establishment challenge.
“However, land that is being used to grow maize for grain has been identified as ‘high risk’ for soil sediment and nitrogen loss over winter, so it’s important to look for ways to incorporate cover crops into maize grain systems to help reduce these risks.”
Benefits of cover crops
Cover crops can provide a number of benefits to maize and other farming systems. These include:
- Nutrient management: Legumes, such as faba beans or clovers, fix nitrogen as they grow and after cover crop termination, this nitrogen becomes available for use by future crops. On the other side of the scale, non-leguminous cover crops can ‘mop up’ nutrients left over from the previous crop, reducing the potential of nutrient losses through the soil profile.
- Reducing soil erosion: Cover crops help hold soil in place, protecting it from wind and rain erosion.
- Soil organic matter: Cover crops contribute to soil organic matter, which helps to improve soil structure, water infiltration, and water-holding and nutrient-supply capacity.
- Soil microbial biodiversity: Non-grass cover crops can contribute additional soil microbial biodiversity where maize grain is grown in a monoculture system (i.e., maize grain following maize grain).
- Soil compaction: Cover crop roots can help to break up compacted soil layers, while the plants themselves can reduce the impact of heavy rains.
- Conserving soil moisture: Cover crop residues increase water infiltration and limit soil water evaporation, helping to reduce moisture stress in the following crop during drought conditions.
- Weed suppression: Cover crops can reduce weed germination and growth during winter and spring, while some can also have an allelopathic effect on weeds.
- Extra feed: Some cover crops can be grazed provided care is taken with the grazing programme or conserved as silage before termination.