Quorum sensing kicks in at 9 or more species. Some recommend as many as 13 species.

When designing a custom cover crop mix, some general rules make it easy. Let’s say you want a three-species blend with 50% Oats, 25% Radish, and 25% Turnip. Take the percentages and multiply it by the full seeding rate of each species to get your pounds per acre of each species. Always increase the full seeding rate by 25% if you plan on broadcasting the seed.^R

For hand-broadcast of the seed you will need to mix the seed together with sterile sand, sawdust, cracked corn, vermiculite, or other similar type of filler material in a sterile pail or garbage can. You will want to mix your seed thoroughly with at least an equal ratio of one or more of the above sterile medias. In many cases additional media can be added to achieve a more even distribution by mixing the seed with enough media to equal a bulk media and seed mix at a rate of 1 to 5 gallons of dry measure for every thousand square feet to be seeded area. Take time to ensure that your seed is mixed thoroughly throughout the media and mix often during the seeding process to insure the heavier seeds do not settle out.^R

Species

Anything can be used as a cover crop. These are only a few that I have considered. Many of these can be bought from the grocery. It is much cheaper to buy a bag of beans or grain from the grocery than it is to buy “seeds” from a supplier. Don’t forget about the spices section!

I plant warm season seed in the last week of April, and cool season seeds in the last week of September.

Warm Season Grasses

Species	Broadcast g/1,000ft2	Drill g/1,000ft2
Browntop Millet	208-260R
Grain Sorghum	313-417R
Sudan grass	260-365R
Corn		688-918 s/kft2

Warm Season Broadleaf

Species	Broadcast g/1,000ft2	Drill g/1,000ft2
Amaranth1	6.8-52R
Buckwheat	729R	521R
Quinoa	94R
Sunflower3		22
Castor Bean		104-146R
Okra		125-160

1. A low 40 to 60 percent emergence rate is not uncommon. Adequate moisture is essential for rapid germination, emergence, and early growth of the small, fragile seedlings.^R
2. Seed may be found in the birdseed section of the grocery store 😉.
3. black oil sunflower are 8000 seeds per lb

Warm Season Legumes

Species	Broadcast g/1,000ft2	Drill g/1,000ft2
Black-eyed pea	729-937	312-520
Fenugreek2	324	290-470
Lablab	260R	208R
Mung bean		186R
Soybean3		520
Tepary beans1	260-312

1. Very drought tolerant
2. Approximately 33,600 seeds per lb.
3. average seed size is 2,800 seeds/pound^R

Cool Season Grasses

Species	Broadcast rate (g/1,000ft2)
Barley (Hordeum vulgare L.)
Cereal rye (Secale cereale L.)
Oat (Avena sativa L.)	1,083-1,354
Spelt (Triticum spelta L.; Triticum aestivum var. spelta(L.) L.H. Bailey)
Wheat (Triticum aestivum L.)	1,250-1,874

Cool Season Broadleaf

Species	Broadcast rate (g/1,000ft2)
Basil	13.9-18.6
Beet (Beta vulgaris)	93.7-104.1R
Carrot (Daucus carota var. sativus L.)	26-59.4R
Coriander	312 (large seed)R, 167 (small seed)
Cumin	111.5-139.4R
Flax (Linum usitatissimum L.)	572.7-624.8R
Kale (Brassica napus L. var. pabularia)
Mustard	104.1-156.2R
Phacelia (Phacelia tanacetifolia Benth.)
Radish1 (Raphanus sativus)	114.5-137.5R

1. Larger varieties i.e. daikon may be more effective at loosening tight soils.

Cool Season Legumes

Species	Broadcast rate (g/1,000ft2)
Chickpea (Cicer arietinum L.)	833.0-1,978.5R
Pea (Pisum satuvum arvense L.)	937.2-1,041.3R
Lentil (Lens culinaris Medik.)	416.5-833.0R
Lupine, Russel	454R
Fava Bean (Vicia faba L.)	2,268-3,402R
Berseem Clover (Trifolium alexandrinum L.)	156.2-260.3R

Links

• Cover Crop Chart
• Summer Cover Crop Use in Arizona Vegetable Production Systems
• Weeds and Why They Grow (fungus:bacteria ratio)