Yes the organic matter will still break down over time, just the same as corn stalks do in the AG world, by terminating the crop the following year. Any type of stem or stalk will decompose into the soil over time.
The nitrogen will mostly be coming from your clover (although the peas will also scavenge N but they are typically long gone as they act as candy to deer). If you kill your clover from the previous year via herbicides the N will be released through the root system and into the soil ..
I hope some of this makes sense...
So basically no till will have the same effects as conventional till(in this seed mix) without the moisture loss and also the improving of overall soil health
A great question that brings up may points I've always pondered on as well.
I agree that in both (til vs no til) cases the crop / organic matter breaks down over time.. Why in the ag world, the first thing that comes through after corn harvest (if full tillage farm) is the ripper / chisel plow, to turn the corn "trash" under to help it break down into the soil more quickly. Or now, many modern farms now use crop devastators to effectively shred and smooth out the trash, so that it can be incorporated more quickly. Some still completely till after this, others just strip til and still others will completely no til - Hence the need for row cleaners on planters, etc..
Some of the nitrogen is in the clover roots, some of the plant itself. Some of the nitrogen is going to be lost to the atmosphere if the clover isn't tilled under?? I think even Dbltree eludes to this in some of his earlier posts.. But it either case, you still get the benefit of the organic matter. Which goes to the next point.. You do lose OM from tillage, typically from erosion, but if your fields are flat... what then? Many in the ag world stick to some form of tillage in flat bottom fields, maybe something there..
Knowing these things, my thoughts are you're likely to build more OM over time with no til (especially on hilly ground) but perhaps not getting the "full" nitrogen credits if not incorporating green manure.. ?? That about brings me to my knowledge limit on agronomics..
Now if you'll excuse me I'm heading to disc up about 2 acres for my fall plots before someone accuses me of being a soil hugger..