The USDA-ARS Northern Great Plains Research Laboratory in North Dakota published this chart a couple years ago. It’s a nice resource for the list of viable cover crops you can utilize. It contains some basic growing and growth characteristics, including the crop’s water needs and it’s rating as a “nitrogen scavenger.” Click here for a copy of that chart.

Below is the list of information the chart has for annual ryegrass.

Annual Ryegrass
Cool Season, grass
• Annual or perennial
• Upright plant architecture
• Major types:
– Annual (Oregon, Italian, Australian, Common)
– Perennial (English)
• Medium water use
• Fair salinity tolerance
• Seeding depth: ¼ – ½ inch
• C:N ratio: 14 – 40
• Will form arbuscular mycorrhizal associations
• Self pollinator (wind)
• Rated ‘very good’ at scavenging nitrogen from