Choosing cover crops
Define constraints
Crop rotation/Sequence: Avoid pest and disease build up, Brassica cover crops in a brassica rotation, legumes in a Legume rotation etc.
Termination: Winter kill, cultivation, mulch, glyphosate
Method of sowing: Broadcast, specialist harrow, culti-drill, autocast, direct drill, drone
Growth window: Short windows of growth demand quick growing species
Timing of sowing regards water: Small seed generally need less moisture for germination than large, how to preserve moisture
Resource availability: Equipment and human resource when there may be a conflict of interest in sowing main stream crops
Soil type: Light soils easy / heavy soils more of a challenge - less cultivation on higher clay fraction soils
Purpose of cover: Carbon sequestration, nutrient capture, nitrogen fixation or soil structure improvement
Light effect on germination: Some species require light on the seed (Brassicas) some require dark conditions (Phacelia)
Government Regulations: Important to check local rules for cover crop species, especially if part of a environmental subsidy
Ranking the objectives
Maintenance of soil organic matter and/or soil health building: carbon from root material is retained in soil more efficiently than aboveground inputs
Erosion control
Nitrogen release to the following cash crop: mainly from legumes
Nutrient scavenging: mainly from cereals
Weed control: fast growing competitive plant species are best to suppress weeds
Forage production
Improvement of soil structure: focus on rooting system
Pest control