Dryland Winter Cover Crop?

I need a cover that I can sow in July . July 1-20 is usually when the last cultivation is done to corn in my area. At this intraval there are 3-5 months left in the wet season. I need to establish a cover during this window and have it survive into the dry season. I also need to be able to harvest the cover crop as feed for livestock. I grew a species of vicia known locally as "evo de invierno" last year but, an early frost killed it and made me look like an idiot. I am going to try it again but I'd rather try something that can take the frost and the drought. I have observed a wild species of flower that is winter active and enjoyed by livestock but it seems to grow more one year and less another. I still have no seed sample for this species due to my former ignorance.
This topic is of crutial importance to the Central Mexican Platue and many other areas of the world. What cover to grow and how to get the seeds to the masses. Yet the Gov'nt agricultural athority has done nothing to address the issue. I know it's not exactly permaculture that I'm talking about here but we have to start somewhere right?

I was just studying a listing of Chihuahuan desert plants:

http://museum2.utep.edu/chih/gardens/list/species.htm#A

I wonder if you might be able to find your cover crop among the native legumes?  I'm particularly looking at Purple Prairie Clover Dalea purpurea and White Prairie Clover Dalea candida.  These are both perennials, so I'm not sure they are suitable for your exact use

An excellent book about cover crops is available for free download here:

http://www.sare.org/publications/covercrops/covercrops.pdf

A Mexican farmer told me today that "oats" or "barly" will handle frost but I don't think they would handle the drought. I know wheat is more drought tolorent but I'm not sure if it will take frost in it's later stage of growth.
I will be experimenting with the above crops, lupins and others. I'll be sure to let you all know how it goes.

Here's an update. Napier grass can survive the dry frosty winter here in Puebla though it's not really a ground cover its tall.
Aloe vera
Jade
Opuntia
Vicia cracca (winter vetch)locust resistant
Napier locust resistant
Chayote
Dicon radish
Acanthus mollis
Cana Lilly
Native legume ground vines
All these plants can survive the harsh dry winters here in Puebla without irrigation.

thanks jeff for the harsh dry winter plants.

can you say what kind of temperatures harsh is. and what kind of precipitation dry is.

many thanks. am starting to grow in eastern oregon.

another plant i see they sell at green cover seeds and i plan to use is collards.

also i am planning on using dry land alfala, ladeck or sierra. sierra supposedly comes from mexico. can you find some seed down there?

i am also looking at apios americana, american ground nuts, but am looking at it as people food.

The temperature goes just low enough to get frost minimum -5. Only a few nights a year. From November through February there is usually  almost no rain and grasshoppers eat almost everything that is still green.  The flower in the pic below is highly drought and grasshopper tolerant. It can also survive frost but the leaves can die from severe frost or prolonged cold. If the ground freezes it will probably die. Can anyone identify it and tell me the botanical name for it I know it only as ciento uno or 101. It makes a great fire barrier, chop and drop during all seasons, solid water, and flowers can be sold.

It turns out that the following list of plants though unpalatable to grasshoppers during the summer are consumed during fall and winter when green leaves become scarce.
Jade, acanthus mollis, vicia (visa Evo de invierno), calla lilies

Wheat seems to be unpalatable to grasshoppers even in the dry season. Along with ciento uno, mature opuntia pads, mature loquat leaves, white sapote (not frost tolerant) and fig leaves.

Jeff Hodgins wrote:Can anyone identify it and tell me the botanical name for it I know it only as ciento uno or 101.

Agapanthus

Thank you Tyler. I had finally found the name about a month ago but then I forgot it again. The species is also recommended by the government of New Zealand as fire control. I'm sure they spent a lot more money on determining that than I did. Probably 1000s of times more because I spent about 10 bucks on gasoline to haul the bulky plants that's it.

Ive found that almost nothing can make a green layer over dry ground in the winter in Puebla. Even the opuntia cactus has been a limited success because of bugs. agave and acanthus persist with less work agave being the best plant I have found for staying green but its hardly a cover crop more of a fire brake agapanthus is however a chop and drop but has no food/feed value. There are a a few weeds that I still haven't cultivated to see if I could get a dense enough stand but I dont know the names. I want to start growing other types of cacti among the trees if I cant grow a cover crop at least I can have a better fire brake. summer seeded covers do work until about dec 1st when the ground is completely desiccated until march or april.