The Mustard Seed

We've all probably heard the Parable of the Mustard Seed but one of my email friends posed this worthy question for today:

"The Brassica comes in many forms but all touted for their value as a cover crop.

The many forms of the Radish and the Turnip are almost obvious. My question is about the Mustard plant. What is it's redeeming qualities? Does our common wild mustard weed have any redeeming features?

We usually see wild mustard growing in a road right of way, equipment yards, or in wheat.

If all are allowed go to seed would they cross resulting in some kind of wild mustard with a humongous root and side spreading, ground shading leaf style?

Would this produce viable seed resulting in a problem feral Brassica?

Maybe a Vegetable version of a mule?"   I must admit I have not played with mustard as a cover crop.  My friends in New Zealand have tried it to some success but I am not aware of any in my neighborhood.   "Mustards are a good cover crop for a variety of reasons. One of the main benefits is that they have high levels of glucosinolates. According to Cornell University …”The practice of using mustard cover crops to manage soil-borne pathogens is known as biofumigation. Biofumigation is simply the suppression of various soil-borne pests and diseases through naturally occurring compounds.

All brassicas such as cabbage, kale, cauliflower, brussel sprouts, broccoli, mustard, and turnips naturally produce glucosinolates, the compounds that make certain brassicas “hot”.   Brassicas sold as cover crops have been identified or specifically developed to contain very high levels of these glucosinolates. The higher the levels of glucosinolates present, the better the biofumigant effect. The process works as so: when plant cells are damaged such as by chopping, glucosinolates are released and come in contact with an enzyme (myrosinase). In the presence of water, the reaction produces the natural gas isothiocyanate (ITC).

ITC is responsible for the suppressive effects of the practice. ITC is similar to the active ingredient in Metham Sodium or the conventional fumigant Vapam (a.i. Methyl ITC). In addition to the soil biofumigation benefits, brassica cover crops are ideal for adding organic matter to the soil and improving many soil health related characteristics due to the large quantity of “green” or fresh biomass produced and incorporated into the system.”  

So far I have had no ill effects from any cover crop I've planted getting out of hand.  One reader is dead set against annual ryegrass because of the threat of Italian ryegrass but I have not seen that either.  Actually, stray vetch, clover, alfalfa, rye, wheat, radish and other once cover crop plants make me smile.  I know I planted it. 

Anyone have comments they would like to send or post about mustard as a cover?  

Thanks, 

 Ed